EXACT Stock 3g and b18 Camshaft Specifications

motoxxxman · Jul 11, 2006

ok, so i finally got around to determining the exact specs of our stock camshafts. i accomplished this with the use of an 18 inch moroso degree wheel, a digital micrometer with depth function (clamped to head tightly, spaced with hard cardboard to get the right angle (perfectly parallel to valve)), a strip of exhaust hanger for a pointer bolted to the t-belt cover bolt near the motor mount, my nifty engine stand, a b21 block, a b21 head, b21 crank, and b21 auto flywheel (5spd flywheel wont fit while mounted to the stand.) mounted flywheel so i could perfectly set the pointer to TDC according to the mark on the fly. no pistons or rods were installed, also to decrease rotational friction of the crank. when the crank is being turned so extremely slowly, any amount of unnecessary friction will cause it to bind and jump, instead of turning smoothly at those massively low speeds.

as for the way i set the motor up, i only installed rockers for each cam for the number 1 cylinder. no rockers in any other cyl. means much less resistance for turning the crank. all bearing surfaces were cleaned and oiled with fresh oil, bearings are from a used motor but within specs according to the manual. a few cc's of oil was dripped onto all cam bearing surfaces before caps were put on. a few cc's of oil was dripped onto each cam lobe for cyl 1. timing belt was set extremely tight by pushing very hard on the tensioner as i tightened the tensioner bolt. the 4 rockers were adjusted to 0.0005-0.0010 inches of clearance, to simulate a warmed up motor.

the b20a5 cams have about 80k miles on them
the b21a1 cams have about 117k miles on them

the head has never been shaved at all, block has never been shaved at all, and the block to head clearance (HG thickness) was set to 1.200mm (stock HG thickness when crushed under proper torque). this thickness was achieved by the use of a double layer of make-a-gasket intake gasket material. uncrushed it is 0.8mm thick, doubled up 1.6mm. crushed under proper torque worked out perfectly to 1.2mm.

i determined exact timing at lifts of: 0.010", 0.020", 0.030", 0.040", and the universal 0.050".
i also determined exact lift accurate to within 0.0005" for every 5 degrees between the above lift open and close points
i also determined exact timing of max lift. which is also known as the lobe center.

i did the entire process twice per valve to guarantee no mistakes, or variations in results. 2 cams, 2 valves per cam = 4 valves. twice per valve, means i ran this entire process 8 times. never was there any variations in numbers between any of the 8 processes. so you can be assured all numbers are 100% accurate.

i have all exact lift measurements for each cam in seperate microsoft excel files, along with the original graphs. if anyone would like me to transfer the excel documents containing all the actual numbers and information to them, please pm me through the site, or better yet send me an instant msg through aim/aol yahoo or msn via the little buttons/icons below my name to the left. i would be happy to share all info. putting all of the info in this thread would take quite a while, and take up an aweful lot of space for one post.

pics of the setup mid-progress. notice the sky blue lude without a rear bumper or bumper bracket off to the side? thats my project car, and probably the only pic of it most of you will see for quite a while

:

ok, now on to the part you've all been waiting for, the specs.

ATDC = after top dead center
BTDC = before top dead center
TDC = top dead center
BDC = bottom dead center
all degree numbers are in crank degrees
all measurements were taken in inches

b20a5 cams:
intake cam:
open point: (@ the following lift at the valve)
0.010" 5.5 degrees BTDC
0.020" 8 degrees ATDC
0.030" 13 degrees ATDC
0.040" 16 degrees ATDC
0.050" 19 degrees ATDC

close point: (@ following lift at the valve)
0.010" 241 degrees ATDC
0.020" 222 degrees ATDC
0.030" 217 degrees ATDC
0.040" 213 degrees ATDC
0.050" 210 degrees ATDC

duration (@ following lift at the valve)
0.010" 246.5 degrees
0.020" 214 degrees
0.030" 204 degrees
0.040" 197 degrees
0.050" 191 degrees

max lift:
0.356" @ 118 degrees ATDC
0.209" lobe lift

lobe center:
114.5 degrees ATDC

valve lift @TDC:
0.0135"

exhaust cam:
open point: (@ following lift at the valve)
0.010" 244 degrees BTDC
0.020" 225 degrees BTDC
0.030" 219 degrees BTDC
0.040" 215 degrees BTDC
0.050" 212 degrees BTDC

close point: (@ following lift at the valve)
0.010" 37 degrees ATDC
0.020" 0 degrees, perfect TDC
0.030" 6.5 degrees BTDC
0.040" 10 degrees BTDC
0.050" 13.5 degrees BTDC

duration (@ following lift at the valve)
0.010" 281 degrees
0.020" 225 degrees
0.030" 212.5 degrees
0.040" 205 degrees
0.050" 198.5 degrees

max lift:
0.366" @110 degrees BTDC
0.215" lobe lift

lobe center:
113 degrees BTDC

valve lift @TDC:
0.020"

valve overlap: (@ following lift at the valve)
0.010" 42.5 degrees
0.020" negative 8 degrees
0.030" negative 19.5 degrees
0.040" negative 26 degrees
0.050" NEGATIVE 32.5 degrees!!! (HOLY FRICKIN CRAP MAN!!!! THIS VALVE TIMNG BLOWS MAJOR BUTTHOLE!!!!!)

here are graphs of all data points collected. the concept of these graphs is to as best as possible portray the profile of the cam lobes. again, if you would like the actual microsoft excel documents containing all actual information (tables and graphs) contact me and i'd be happy to send them to you:
the thick horizontal black line is the marker for the universal open/close point at 0.050" lift
left side of each graph is where valve begins to open, right side is where valve closes.
dont mind the negative numbers in the exhaust graph, it's the only way i could get the data to line up properly in the graph.
to the left if the blue TDC line is degrees BTDC, to the right of the blue TDC line is degrees ATDC, for both graphs. 0 degrees = TDC
if you're unable to read it, the red line is "max lift aka lobe center", blue line is "TDC", green line is "BDC"

b21a1 cams:
intake cam:
open point @ following lift at the valve:
0.010" 6 degrees BTDC
0.020" 8 degrees ATDC
0.030" 13 degrees ATDC
0.040" 17 degrees ATDC
0.050" 20 degrees ATDC

close point: @ following lift at the valve
0.010" 236 degrees ATDC
0.020" 220.5 degrees ATDC
0.030" 214 degrees ATDC
0.040" 210.5 degrees ATDC
0.050" 207.5 degrees ATDC

duration: @ following lift at the valve
0.010" 242 degrees
0.020" 212.5 degrees
0.030" 201 degrees
0.040" 193.5 degrees
0.050" 187.5 degrees

max lift:
0.3465" @ 115 degrees ATDC
0.204" lobe lift

lobe center:
114 degrees ATDC

valve lift at TDC:
0.013"

exhaust cam:
open point: @ following lift at the valve
0.010" 242.5 degrees BTDC
0.020" 226.5 degrees BTDC
0.030" 220 degrees BTDC
0.040" 216.5 degrees BTDC
0.050" 213.5 degrees BTDC

close point: @ following lift at the valve
0.010" 34 degrees ATDC
0.020" 4 degrees ATDC
0.030" 3.5 degrees BTDC
0.040" 8 degrees BTDC
0.050" 11.5 degrees BTDC

duration: @ following lift at the valve
0.010" 276.5 degrees
0.020" 230.5 degrees
0.030" 216.5 degrees
0.040" 208.5 degres
0.050" 202 degrees

max lift:
0.3815" @110 degrees BTDC
0.224" lobe lift

lobe center:
112.5 degrees BTDC

valve lift at TDC:
0.024"

valve overlap: (@ following lift at the valve)
0.010" 40 degrees
0.020" 4 degrees
0.030" NEGATIVE 16.5 degrees
0.040" NEGATIVE 25 degrees
0.050" NEGATIVE 31.5 degrees

now for the graphs of the lift of each b21 cam:
the thick horizontal black line is the marker for the universal open/close point at 0.050" lift
left side of each graph is where valve begins to open, right side is where valve closes.
dont mind the negative numbers in the exhaust graph, it's the only way i could get the data to line up properly in the graph.
to the left if the blue TDC line is degrees BTDC, to the right of the blue TDC line is degrees ATDC, for both graphs. 0 degrees = TDC

b18b1 cams:
intake cam:
open point: (@ the following lift at the valve)
0.010" 2 degrees BTDC
0.020" 10 degrees ATDC
0.030" 14.5 degrees ATDC
0.040" 18 degrees ATDC
0.050" 20 degrees ATDC

close point: (@ following lift at the valve)
0.010" 242 degrees ATDC
0.020" 225 degrees ATDC
0.030" 220 degrees ATDC
0.040" 216 degrees ATDC
0.050" 213.5 degrees ATDC

duration (@ following lift at the valve)
0.010" 244 degrees
0.020" 215 degrees
0.030" 205.5 degrees
0.040" 198 degrees
0.050" 193.5 degrees

max lift:
0.388" @ 118 degrees ATDC
0.228" lobe lift

lobe center:
117 degrees ATDC

valve lift @TDC:
0.012"

exhaust cam:
open point: (@ following lift at the valve)
0.010" 259 degrees BTDC
0.020" 225 degrees BTDC
0.030" 219 degrees BTDC
0.040" 215 degrees BTDC
0.050" 212 degrees BTDC

close point: (@ following lift at the valve)
0.010" 15 degrees ATDC
0.020" 6 degrees BTDC
0.030" 12 degrees BTDC
0.040" 15 degrees BTDC
0.050" 18.5 degrees BTDC

duration (@ following lift at the valve)
0.010" 274 degrees
0.020" 219 degrees
0.030" 207 degrees
0.040" 200 degrees
0.050" 193.5 degrees

max lift:
0.3485" @115 degrees BTDC
0.205" lobe lift

lobe center:
115 degrees BTDC

valve lift @TDC:
0.017"

now on to the fun part, the comparison of each cam. the following are graphs on the cams together so you can see the direct relation of one to the other.
notice how the b20a5 intake cam has ever so slightly more lift then the b21a1 cam throughout the duration, but about the same duration time length.
also notice the b21a1 exhaust cam has a decent amount more lift then the b20a5 exhaust cam throughout the duration, and a slightly noticeable longer duration then the b20a5 exhaust cam.
the graph makes it easier to see. and even though it doesnt look like too too much in the graph, in cam terms, the difference performance-wise is fairly considerable.

removed the old comparison graphs, and added these new ones that include all 3 cams in each graph. i think the graphs speak for themselves. enjoy!!!

b18a1 cams:

today i got all the same data on b18a1 cams. i got a few basic specs on the b18a1 exhaust cam and it is almost identical to the b20a5 exhaust cam, so it would be pointless to get all data and graph it and compare it and everything else. and at the cost to modify a b18 exhaust cam to fit our motors, it's really pointless. so no major data was collected for the b18a1 exhaust cam, and no graphs were created.
the b18a1 intake cam is 99.9% identical to the b18b1 intake cam, except the fact that the entire lobe is shifted about 5 degrees. in other words, all duration and lift specs are identical between the b18a1 and b18b1 intake cam, but the b18b1 intake cam is advanced 5 crank degrees more than the b18a1 intake cam.
this means that you can use a b18a1 or a b18b1 intake cam in your 3g and get about the same results. if you get a b18a1 intake cam, it would be a good idea to get adjustable cam gears to advance it to get it even with a b18b1 cam, or advance it further to aim towards a little more overlap. aka not so far into the negatives lmao. to get the b18a1 cam even with the b18b1 cam as far as exact timing, you would set the cam gear to +2.5, because 2.5 cam degrees equals 5 crank degrees.

here is a comparison graph of the b18a1 and b18b1 intake cams to display the exact specs on both cams. i think the graph is pretty self explanatory.

b20a cams:

today i was able to get all the usual data on a set of jdm b20a cams, thanks to secluded luder for providing them for testing. i was shocked when i looked over the results, and especially shocked when i graphed them. well, kind of a mix between seeing what i expected for one, and something totally unexpected for the other. due to the graphic nature of this program viewer discretion is advised lmao! actually, due to the results of the data collected, im not going to bother posting the actual info on them as i have for the above other cams. to sum it up, the jdm b20a intake cam is 100% identical to the USDM b20a5 intake cam. the jdm b20a exhaust cam is similar to the b20a5 exhaust cam, but a bit worse. to further explain and see the similarities, simply lok at the following graphs; they show all:
sorry to disappoint you guys lol

b20a5 overlap:
(@ following lift at the valve)
0.010": 42.5 degrees
0.020": negative 8 degrees
0.030": negative 19.5 degrees
0.040": negative 26 degrees
0.050":negative 32.5 degrees

b20a5 overlap with gears set to +4/-4:
(@ following lift at the valve)
0.010": 58.5 degrees
0.020": 8 degrees
0.030": negative3.5 degrees
0.040": negative10 degrees
0.050":negative 16.5 degrees

b21a1 overlap:
(@ following lift at the valve)
0.010": 40 degrees
0.020": 4 degrees
0.030": negative 16.5 degrees
0.040": negative 25 degrees
0.050": negative 31.5 degrees

b21a1 overlap with gears set to +4/-4:
(@ following lift at the valve)
0.010": 56 degrees
0.020": 20 degrees
0.030": negative 0.5 degrees
0.040": negative 9 degrees
0.050": negative 15.5 degrees

b21 ex b20a5 int overlap:
(@ following lift at the valve)
0.010": 39.5 degrees
0.020": negative 4 degrees
0.030": negative 16.5 degrees
0.040": negative 24 degrees
0.050": negative 30.5 degrees

b21 ex b20a5 int overlap with gears set to +4/-4:
(@ following lift at the valve)
0.010": 55 degrees
0.020": 12 degrees
0.030": negative 0.5 degrees
0.040": negative 8 degrees
0.050": negative 14.5 degrees

b21 ex b18b int overlap:
@the following lifts at the valve:
0.010": 32 degrees
0.020": negative 6 degrees
0.030": negative 18 degrees
0.040": negative 26 degrees
0.050": negative 31.5 degrees

b21 ex b18b int overlap with gears set to +4/-4 in/ex:
@the following lifts at the valve:
0.010": 48 degrees
0.020": 10 degrees
0.030": negative 2 degrees
0.040": negative 10 degrees
0.050": negative 15.5 degrees

b21 ex b18a int overlap:
@the following lifts at the valve:
0.010": 36 degrees
0.020": negative 10 degrees
0.030": negative 22 degrees
0.040": negative 30 degrees
0.050": negative 36 degrees

b21 ex b18a int overlap with gears set to +4/-4 in/ex:
@the following lifts at the valve:
0.010": 52 degrees
0.020": 6 degrees
0.030": negative 6 degrees
0.040": negative 14 degrees
0.050": negative 20 degrees

motoxxxman before posting the b21 results and comparisons said:
my comments:
STOCK B20A5 CAMS SUCK THE BIG FAT HAIRY NASTY THING!!! durations of 191 intake and 198.5 exhaust at the universal lift of 0.050"?? thats horrible!!!!!! NEGATIVE 32.5 degres of valve overlap??? WTF IS THAT SHIT?!?!?! it's no wonder adjusting cam gears to +4/-4 in/ex increases low and mid range power so much. 4 degrees of cam timing = 8 degrees of crank timing. that cam gear setting creates 16 crank degrees more valve overlap. but when the stock overlap is negative 32.5 degrees, it still doesnt create any overlap at all. even with those cam gear settings, it still has negative 16.5 degrees of overlap (@ the universal 0.050"). negative 16.5 is better better then negative 32.5, but still; you want to have between 2-8 degrees of positive valve overlap.

for reference, less valve overlap is better for low rpm power (still has to have at least some positive overlap though). shorter/less duration is better for low rpm power; as long as the intake valve still closes at or after BDC, and exhaust valve still opens at or before BDC.
more valve overlap is better for higher rpm power (to an extent. too much overlap and you're just blowing gas and air out the exhaust). longer/more duration is better for higher rpm power.

the reason noone seems to be able to get any higher end power out of stock cams with adjustable cam gears, is because the stock cams simply suck!! when you advance the intake and retard the exhaust cams far enough to at least get half the negative overlap, (still not positive, but closer to it) it causes the intake cam to close earlier and the exhaust valve to open later. both of which are bad for higher rpm power. and with such short duration cams, just makes it even that much worse for higher rpm power.

now, comments, suggestions, opinions, additions, thank you's, donations of actual money via paypal to me or the site ( ), feedback of any kind....

added july 12 2006, updated july 15 2006:

suggested cam specs for regrinds:
keep in mind these figures are given with the lift point being at the valves, not at the cams. so these are not a direct translation to simply hand over to a re-grinder.
i will translate them into specs that you CAN simply hand to a re-grinder sometime in the near future i hope.

stage 0.5:
b20a5 intake cam
b21a1 exhaust cam

stage 0.9:
in: 193.5 degrees duration @ 0.050" valve lift, 0.388" max lift (b18b intake cam, uncertain for now)
ex: 202 degrees duration @ 0.050" valve lift, 0.382" max lift (b21a1 exhaust cam)

stage 1:
in: 201 degrees duration @ 0.050" valve lift, 0.400" max lift
ex: 202 degrees duration @ 0.050" valve lift, 0.382" max lift (b21a1 exhaust cam)

stage 2:
in: 198 degrees duration @ 0.050" valve lift, 0.415" max lift
ex: 203 degrees duration @ 0.050" valve lift, 0.405" max lift

stage 3:
in: 204 degrees duration @ 0.050" valve lift, 0.430" max lift
ex: 204 degrees duration @ 0.050" valve lift, 0.420" max lift

stage 4:
in: 208 degrees duration @ 0.050" valve lift, 0.440" max lift
ex: 206 degrees duration @ 0.050" valve lift, 0.430" max lift

i could create a stage 5 if anyone wants to know

turbo cams (any type of turbo setup):
in: 205 degrees duration @ 0.050" valve lift, 0.465" max lift
ex: 202 degrees duration @ 0.050" valve lift, 0.465" max lift

stage 2 is recommended for street and strip and various speed track racing.
stage 3 is suggested for all out racing (mostly higher speed track, and drag), but can be used on the street with some minor discomfort in typical driving situations at lower rpms, and may not idle at stock idle speeds. crap power below 3k, decent 3k-4500, great/wicked power 4500-7200
stage 4 is full out 100% race only; high speed only track racing, and all out drag. basically meaning that with stage 4 the engine will be tough to start initially, and it WILL NOT IDLE below 1500-2k or so; and you will have crap for power below 4500, good power 4500-~5800, and wicked power 5800-7200

i have officially determined max allowable lift at the valves with the stock valvetrain; aka springs and retainers.
maxed out at: 0.487"
my recommended max limit: 0.450"
my recommended max SAFE limit: 0.440"

so basically, if you want to go with more then 0.440" of lift i highly suggest you get aftermarket springs and retainers that will allow that much lift. if you want to go more then 0.450" of lift, you will NEED to get aftermarket springs and retainers that will allow that lift.

update: 1/04/08:
jdm b21a cams are practically identical to the usdm b21a1 cams i previously measured.

ludasaurus was kind enough to ship me a set of jdm b21a cams to spec.

im not gonna bother making charts and diagrams and everything for them cuz they are almost 100% identical to the usdm b21a1 cams. like 0.001" difference in valve lift at a couple random points, thats about the only difference, which is nothing, more than that could happen just from wear and/or user error

update 05/12/08:
i specc'ed and charted secluded luder's crower regrinds for the 3g prelude, which were discontinued a few years back. but here they are:

exhaust cam compared to b20a5 and b21a1 exhaust cams, all 3 spec'ed with stock cam gears:

crower regrind intake cam compared to b20a5 intake cam and b18b intake cam, all spec'd with stock cam gears:

crower regrind intake cam retarded 2.5 cam degrees (5 crank degrees), compared to b20a5 intake cam and b18b intake cam both with stock cam gears (stock timing).

as you can see, the exhaust cam is best left at stock timing. either by using a stock cam gear, or by keeping the adjustable cam gear at zero.
the intake cam however i feel is best when set to -2.5 (2.5 cam degrees retarded, aka 5 crank degrees retarded).
the exhaust cam i feel has too much lift though for the duration it has, as well as too much lift for being used with the intake cam.
if the exhaust cam had a bit less lift, while everything else stayed the same, these would be a great true stage 1 type cam. very streetable with a very good idle at 1000 rpms, yet a good noticeable increase in power.
for those that dont know, i did a full street tune on secluded's stock b20a with these cams and a b21 intake manifold and pacesetter header and exhaust, and it pulled very well with awesome throttle response. not balls to the wall power, but a heck of a noticeable increase from stock cams

specs:
intake:
duration:
233 degrees @ 0.010" valve lift
222 degrees @ 0.020" valve lift
213.5 @ 0.030"
207 @ 0.040"
200 @ 0.050"
peak lift: 0.410" at 108 degrees ATDC
exhaust:
duration:
257 degrees @ 0.010" valve lift
243.5 @ 0.020"
231 @ 0.030"
222 @ 0.040"
215 @ 0.050"
peak lift: 0.438" at 108 degrees BTDC

and heres some charts as requested by secluded luder of the overlap period. it is being compared to a b21 exhaust cam and a b20a5 intake cam. first pic is with the crowers both at 0, the second is with the crowers at -2.5/0 in/ex as previously reccommended according to the entire profile of the cams:

within 2 weeks, i'll be speccing and posting charts and measurements for Web Cams's grind #13 for the 3g lude. i have the cams in hand, just need to find the time to spec them and enter the info in excel. keep an eye out for them!

cidgrad130 · Jul 11, 2006

Questions:

1. Where is your pointer for your degree wheel...don't see it in the pics?

2. Was your test motor ever rebuilt...has there been any material decked from the block or milled from the head?

3. Do you have a set of B20A cams to compare to your USDM cams?

Cheers!

OMega · Jul 11, 2006

Good job! Research like this helps us make more power. It better then the shot gun approach. This information also back why cam gears help so much on a stock setup. With my stuck setup I was able to shave off .2 off my track times after adjusting my cam gears.

valenburg · Jul 11, 2006

so at this point new cams are def. must. How are these cam specs compared to the b18b cams or any other cross transferable cams.

David Mansfield · Jul 11, 2006

sweet man this is awsome info!! I cant wait to see the B21 cam info. Mabe you can do the same for the B20 JDM motors?

motoxxxman · Jul 11, 2006

cidgrad130 said:
Questions:

1. Where is your pointer for your degree wheel...don't see it in the pics?

2. Was your test motor ever rebuilt...has there been any material decked from the block or milled from the head?

3. Do you have a set of B20A cams to compare to your USDM cams?

Cheers!

i know it's a long thread, but had you read it all you would have found the answers to the first 2 questions. for the third, no i dont have a set of jdm b20a cams to do the same to.

if anyone wants to donate a set of jdm b20a cams for me to get info on, im sure it'd be helpful to know. or if you need the cams but can part with them for a week or two, you could always ship them to me along with some form of payment to ship them back to you as soon as im done with them. for anyone willing to do this though, please be from the U.S. makes it quicker and easier to ship back and forth

OMega said:
Good job! Research like this helps us make more power. It better then the shot gun approach. This information also back why cam gears help so much on a stock setup. With my stuck setup I was able to shave off .2 off my track times after adjusting my cam gears.

sounds about right. now imagine what you could do to your times if you could get longer duration regrinds with even a bit more overlap then the stock cams with adj gears allow lol.

this is the main reason i decided to get all this info in the first place; so i have a base platform to get reground. so i know what the cams are originally, so i could figure out what i want changed, and to provide the grider with the information so he knows what and how much to grind off where to get the new specs i provide. other reason for doin it was cuz i really want to know the exact diference between b20a5 and b21a1 cams. third reason is cuz i know all of you that are serious about your motors could sure use the knowledge lol, and the ones that dont need to know would at least like to know and appreciate the info haha

valenburg said:
so at this point new cams are def. must. How are these cam specs compared to the b18b cams or any other cross transferable cams.

i'm really not sure. i dont have much for specs on stock b18b cams.

David Mansfield said:
sweet man this is awsome info!! I cant wait to see the B21 cam info. Mabe you can do the same for the B20 JDM motors?

thanks, same here. as for the jdm cams, scroll up...

mhughes165 · Jul 11, 2006

this information will help greatly....makes me wonder if i should ahve used the b21a1 cams when i did the head instead of the b20a5......i guess we will find out how different they really are here shortly

motoxxxman · Jul 11, 2006

on my way outside right now to install the b21a1 cams and get the info for them. i'll add it to the first post once completed. bout 2 or 3 hours from now should have the info in here.

wow, i just realised how dedicated i am to this site haha. i got exactly 3 hours sleep last night (this morning lol) just so i could get up early enough to get this info for the b21 cams lol. well, not sure yet actually if its my dedication to the site, or just my wicked anxious curiosity to see the outcome of the b21 cams compared to the b20a5 cams

cidgrad130 · Jul 11, 2006

motoxxxman said:
i know it's a long thread, but had you read it all you would have found the answers to the first 2 questions. for the third, no i dont have a set of jdm b20a cams to do the same to.

...

Now is where I have to admit that I didn't read the setup portion of your thread too closely...just skipped ahead to the results- :crazy:

I'm sure you have never done anything like that on this site...open mouth, insert foot!

Cheers!

OMega · Jul 11, 2006

Well, if you want to do it moto, I have some b18a cams in the garage you can play with.

scyclone · Jul 11, 2006

finally, now some things should be easyer on all of us .

Thanks 'steve'

motoxxxman · Jul 11, 2006

DAMNIT. I HEARD THUNDER COMING AND SAW DARK CLOUDS SO I FINISHED THE INTAKE CAM AND PACKED UP AND PUT EVERYTHING AWAY. SURE ENOUGH, AS SOON AS I CLOSED THE GARAGE DOOR, TERRENTIAL DOWNPOUR. SIIIGH, AT LEAST I DIDNT GET ANYTHING WET. BUT NOW I GOTTA WAIT TIL IT CLEARS UP TO DO THE EXHAUST CAM.
OOOooooooOOOooOOOooOOO! CAN YOU FEEL THE SUSPENSE? HAHA, I KNOW YOU'RE ALL WAITING TO SEE THE B21A1 CAMS COMPARED TO THE B20A5 CAMS.

IMMA RUN TO THE BANK WHILE IT'S CRAPPY OUT. IF ITS STILL RAINING WHEN I GET BACK, I'LL POST UP AT LEAST THE INTAKE CAM RESULTS WITH GRAPH. MIGHT EVEN DO AN OVERLAY GRAPH FOR BOTH INTAKE CAMS

SORRY FOR CAPS, DIDNT NOTICE TIL I WAS HALFWAY DONE TYPING HAHA

cidgrad130 said:
Now is where I have to admit that I didn't read the setup portion of your thread too closely...just skipped ahead to the results- :crazy:

I'm sure you have never done anything like that on this site...open mouth, insert foot!

Cheers!

moron. nooooo, neveeeeeeeerrrrrrr hahahaha. j/k. no worries, figured thats what happened. im sure 90% of the people that check this thread out for the first time went straight to the results lol. then maybe half of em, or at least the ones that cared to know went back to read everything else lol

OMega said:
Well, if you want to do it moto, I have some b18a cams in the garage you can play with.

if they'll fit directly into my b21a1 head without modification, sure thing. send em my way. if you want em back though, you'll have to send me some kind of payment for the return shipping.

when i say fit directly into my b21 head without modification, i simply mean head and cam caps and rockers only. i dont care about the end cuz im not mounting distributor or cam sensor or anything.

sobelazy · Jul 11, 2006

thanks bud. thats deffinitely bad for power but its make more sense to me if i knew more bout cams. keep up the good work.

Guest · Jul 11, 2006

so you took all these measurements but what does it all mean...why is it bad to have .050 overlap at 35 degrees?

motoxxxman · Jul 11, 2006

im headin outside to finish getting the exhaust numbers for the b21 cams. i'll post the results up when im done. then after that i'll go into an explanation of everything for those of you who dont fully understand what all the numbers mean, and their relation to engine power and such.

LoVeMYHoNDa · Jul 11, 2006

I have a b18b exhaust cam you can have to play with too.
You can have it for free, just need you to pay the shipping. I have no use for it since I'm getting rid of my 3rd gen.

motoxxxman · Jul 12, 2006

b21 specs and graphs, plus valve overlap graphs for each, plus comparison graphs for each added to first post on first page.

check em out. comment, do what you will. very useful info here.

mod please sticky this thread or add to FAQ or whatever

owners of prelude3.com and prelude3g.com please add to your sites. this is deffinitely sought after info, and kinda required for custom regrinds to be done properly and to spec how the owner wants them

car_boy_16 · Jul 12, 2006

So...I have never done much research on camshaft dynamics and their respective specifictions. Can you tell us exactly what we're looking at? It seems like the B20A5 intake cam mated with the B21A1 exhaust cam would be the ideal pairing of OEM cams. Would you agree? Also, if so, when you have the b20a5 intake and b21a1 exhaust cam in your motor, what might be a good cam gear setting to further enhance overall power (not just high rpm power)? Thanks moto, I knew you'd come through

Remember when you got pissed at me cuz I said you would never actually do this? Hehe...

boblasek · Jul 12, 2006

I concur with car boy, i might just go to the junkers and try to find me a B21A1 ex cam.

motoxxxman · Jul 12, 2006

car_boy_16 said:
So...I have never done much research on camshaft dynamics and their respective specifictions. Can you tell us exactly what we're looking at? It seems like the B20A5 intake cam mated with the B21A1 exhaust cam would be the ideal pairing of OEM cams. Would you agree? Also, if so, when you have the b20a5 intake and b21a1 exhaust cam in your motor, what might be a good cam gear setting to further enhance overall power (not just high rpm power)? Thanks moto, I knew you'd come through Remember when you got pissed at me cuz I said you would never actually do this? Hehe...

yes, i remember you pretending to be mad at me for saying i'll do this with you thinking i never will. i dont remember your exact words, but it was somehting along the lines of "so many people are all talk, but when it comes down to it, noone actually follows through" or something mildly related to that haha. and you came back sayin you were talkin smack like that to try to motivate me to do it sooner haha. i do remember you saying something stupidly funny though about it haha. i told you i would do it eventually lol

i agree. b20a5 intake cam, b21a1 exhaust cam is the best combination.

as for ideal cam gear settings with any of the stock cams, to be honest, it's really hard to judge because the cams have such short durations. just going by my knowledge (dyno would be much much better to determine it exactly) i would say you want about 3 degrees of valve overlap in crank degrees at 0.050" lift. and personally, i would want the intake cam to stay open as long as possible after TDC. so, i would say you'd want the intake cam to have 0.050" lift at 1 degree BTDC, and the exhaust cam to have 0.050" lift at 2 degrees ATDC, both in crank degrees. remember, 1 cam degree = 2 crank degrees. cam gears are labelled in cam degrees, not crank degrees. so always double the number on the cam gear and that is how much it is actually changing the valve timing in crank degrees.
we'll use the b20a5 intake and b21a1 exhaust cam for this demo. now, to achieve these numbers, look at the timing of the intake cam for where it has 0.050" lift: 19 degrees ATDC. that means you need to advance the intake cam 20 crank degrees, or 10 cam degrees lmao. thats a lot haha. i dont even think theres any cam gears that go that far, is there?
now look at the b21 exhaust cam timing at 0.050" lift: 11.5 degrees BTDC. thats a lot better to work with. thats a difference of 13.5 crank degrees, or roughly just shy of 7 cam degrees. some gears may be capable of this.
so you would set the cam gears to +10/-7 in/ex if that is even possible with your cam gears.

now lies the problem though. for those of you that know the concept of cam duration, you want shorter duration for lower rpm power, and longer duration for higher rpm power. to an extent for both of course, 90% solely dependant on what rpm you consider low end and high end power. when you advance the intake cam gear 10 cam degrees (20 crank degrees) you are causing the intake valve to close 10 cam degrees (20 crank degrees) sooner. which is bad for mid and high end power. especially with out stock duration which is already really frickin low. b20a5 intake cam closes to 0.050" at 210 crank degrees ATDC. with the 10 cam degree advancement, you are now causing the intake valves to close at 190 crank degrees ATDC. this is the closing point you want for max power at approximately 2k rpms ROFL!!! sorry, but that is such a joke. if you want the most power possible in the broadest rpm range, you want the intake valve to open at about 1 degree BTDC and close at around 235 (we'll say 234 to make it an even number) degrees ATDC. considering stock duration at 0.050" lift is 198.5 degrees, that means even the b20a5 intake cam needs a duration increase of about 36.5 degrees. 234 +1 = 235. 235 - 198.5 = 36.5.

the above is a demonstration on how to adjust cam gears for overlap, which is the main purpose of cam gears to begin with. less overlap for lower rpm power, more overlap for higher rpm power. but you do deffinitely want positive overlap no matter what, even for the lowest imaginable running rpm. the above is not my actual recommendation for cam gear settings, as it will severely throw off the closing point of the intake valves and opening point of the exhaust valves, greatly affecting higher rpm power.

thats the problem with our cams. horrible overlap timing, plus horrible durations, equals practically no tuneability whatsoever by using the stock cams. by properly tuning the overlap, you greatly affect the other end of the valve timing in the worst way. by tuning for close point of the intake, and open point of the exhaust, you greatly affect the overlap, which is even worse the the previous stated possibility. our overlap timing is already the worst i've ever seen. creating even more negative overlap then we already have will give you much much better gas mileage, but will absolutely rob the motor of any possible power at all in every rpm range due to the extremely wicked high negative overlap.

my suggestion? get custom regrinds with as close to stock profile as possible, but with 25-50 degree longer duration, and ever so slightly more max/overall lift, with max lift at the exact same point as stock. then get adjustable cam gears to fine tune the overlap period.

for example. b20a5 intake opens at 19 ATDC and closes at 210 ATDC. if you get cams with 36 degrees more duration, with max lift (lobe center) at the same point, that will add 18 degrees to both ends. causing the intake to open at 1 ATDC and close at 228 ATDC. which is pretty damn close to where you want both numbers. then use a cam gear to advance the intake cam 2 crank degrees to cause it to open at 1 degree BTDC. so you'd set the cam gear to +1 (1 cam degree = 2 crank degrees). now the intake valves will open at 1 BTDC, and close at 226 ATDC.

now for lovely pictures

look at my timing wheel. it's meant for engines that turn clockwise (ours turn counterclockwise), so picture everything backwards.
notice the areas labelled intake open, intake close, exhaust open, exhaust close. i'm not sure yet what lift numbers these areas are supposed to be used for, but i would guess 0.020" or 0.030". but you get the idea.
btw, in this pic, the crank and cams are at perfect TDC. if you look closely, you can see my exhaust hanger strip i used for a pointer, and it lines up perfectly with the TDC mark on the degree wheel.
because our motors are lower rpm motors, you want to keep the exhaust opening time and intake closing time closer to BDC in the suggested areas, and the exhaust closing time and intake opening time closer to TDC in the suggested areas. now look at the angles of each section and get a picture in your head of proper cam timing.
when looking at this wheel, go counter-clockwise around the wheel to follow the timing events....

this wheel has to be setup using open/close points of 0.010" or 0.020" lift, cuz the ranges are really far off from where they would be at 0.050" lift. i guess you gotta know a decent amount about cams to understand that if you dont by now.
anyways, compare the open/close points of our stock cams at 0.010" (on first page in this thread) and you'll notice that even at 0.010" times, the points dont even touch the areas on the wheel still.

i'll add more to this simplifying/explaning cam specs for those of you that dont understand the concept of it all, even after reading all my gearhead talk. it's 5:47am here, and im just gonna stay up all night/morning. havent slept yet, and im still wide awake haha. gonna toss a movie in soon here, then i'll add explanations. unless i decide id rather do that before the movie.

Cheers!! (copying cidgrad's typical post ending hehe. is that copyright infringement? i hope he doesnt have that response copyrighted lmao) damn i've been up too long staring at this computer.

edit/addition: b20a5 intake cam is a bit better, b21a1 exhaust cam is considerably better. both still blow in comparison to what would be ideal even for a very very mild cam, but these are my recommendations for the common swapper person that wants the best combination in the cheapest easiest way possible. best way would be to get custom regrinds with much longer duration, and cam gears to fine tune the overlap period.

if i were to recommend cam gear settings for any of the stock cam combinations, i would say stick with the previous recommended +4/-4 in/ex. as it brings the overlap closer to zero from the wicked negative number it is stock, but wont hugely affect the other end of the cam timing destroying all possible power capability above 2k rpms.

when i get a general idea for recommended n/a regrind specs, i'll be sure to add it to this thread. i gotta talk to some devoted cam specialists before i officially recommend anything in that department. i have a pretty good idea of what i recommend, i just dont want to have someone get all pissed at me cause its too much or still not enough, and the person wasted $250-$400 on custom regrinds that could be better

Nugz · Jul 12, 2006

I have both PK2 and PK3 complete heads here for my build.
So taking the PK2 intake cam and PK3 exhaust, would be awsome.

Thanks moto.

BUT, out at my junk yard there is about 5 B18A1's with the head still on them, if I'm going to swap the intake cam I'd like to know how much better the B18 intake cam is vs the B20A5.

Next up moto, is the B18 intake cam

...

Great work man.

Peace, Nugz

motoxxxman · Jul 12, 2006

well, lovemyhonda offered to give me a b18 intake cam to get specs on, and said i could keep it, but said that i would have to pay the shipping to me. i have no use for a b18 intake cam, as i am just gonna get regrinds to my specs once i determine exactly what i want. sooo, im not really willing to pay shipping for something i'm not actually going to use myself.
if someone would like to pay the shipping cost to lovemyhonda to have him send me the cam, i'd be more then happy to get the specs on it. and then if that person wants the cam, they can just pay me shipping from me to them.

Prelude4ws13 · Jul 12, 2006

Great work Steve, :emthup:

Like i was telling Sobelazy, "thank the almighty that Steve lives close to both of us!"

motoxxxman · Jul 12, 2006

CADster · Jul 12, 2006

its settled....

the red lude is getting the b21 exhaust cam

great info

+1

miko · Oct 1, 2009

b18 intake and B21 Ex on a JDM B20 with adj cam gears

ok i did this i notice a bit more power, but there some backfire on decel at low speeds, intake cam is stock and the EX is set at -2 degree,i had it at plus 2 intake and stock for ex, it all top end speed(highway),does the the -4 and +4 intake good,is there anyone who mess around on the dyno with this set up,what the best all round cam setting

eludethis · Jul 12, 2006

CADster said:
its settled....

the red lude is getting the b21 exhaust cam

great info

+1

hey Cadster aren't you glad you got a B21A1 head for free? let me know what the results are. until AZ gets the mounts out. i might just go dig out the EX cam from my cuz's dead lude. he's got the B21A1 also. his car overheated and blew the head gasket among other things.

EXACT Stock 3g and b18 Camshaft Specifications

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