Honda Prelude Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
105 Posts
Discussion Starter #1 (Edited)
1991 Honda Prelude Si. B21a1 Automatic. Threw a connecting rod and busted the block I am rebuilding and swapping to a 5 speed. I am looking to build a mild street machine thats a daily driver.


Im building a b21. So if i get a b20 block its getting milled to b21 specs.
I need to know all the available Connecting Rods that can be used.
All the available Camshafts that can be used?
How much i can mill off of the head?
If i have to get bigger injectors?
How big you can bore the throttle Body?
What size Pistons i can use? Short or Long?
Depending on Which Connecting Rods I can use?
Which Crankshafts i can use?
Do I Have to Tune or get a new ECU?
Please help me with detailed answers to any of these questions you can. Give me good Connecting Rod/Piston Combos please, with specific detailed number figures please. and thank you


I have all the 5-speed Swap Info Covered. I dont need any help with that. thanks
 

·
Banned
Joined
·
13,157 Posts
we cant tell you any parts we suggest until you tell us what type of setup you want.
all motor, or boost
pump gas, or race gas
stockish compression, high compression, or really high compression
power goals
budget

and theres no such thing as short or long pistons. there are pistons that are made for our motors that work, and there are pistons that are not made for our motors that dont work.

to start you off though, dont bother with a b21 block, get a b20 block. you can use any pistons you want that are made for any 3g motor in a b20 block. to use a b21 block requires getting the block sleeved, which is pointless when you can just use a b20 block

take a gander at one of my 3g's im currently building, and be sure to actually read everything, not just look at pics:

http://www.preludepower.com/forums/s...d.php?t=304416

i'll post some helpful stuff once you can answer the above questions
 

·
Registered
Joined
·
105 Posts
Discussion Starter #4
N/a, Normal Gas, Mild Compression.

i have close to $1000.

I would mainly like to see which connecting rods will fit inside the b20/b21 blocks

and to coincide with the connecting rods, which pistons i should use.

and to go along with this. how much can i mill off of my b21 head.

With all that would i have to change the fuel injectors. and are there more Radical Camshafts that i can use instead of the stock Cams. and How big can the throttle body be?
 

·
Banned
Joined
·
13,157 Posts
$1000 isnt going to get you very far at all.

with what you want to do, $1000 would barely cover just the gaskets, pistons, rods, and tuneable ecu and tuning costs. and thats if you buy the pistons and rods used

oem b21 pistons, and oem h23 rods
h23 rods are the exact same dimensions as b20/b21 rods, but are about twice as strong and only about 20% heavier

read my entire thread. you will learn a LOT just from reading that link
 

·
Registered
Joined
·
105 Posts
Discussion Starter #6
h23 Rods/ b21 Pistons.

okay so i go with that setup on a 2.0L block, Bored out to 2056 cc. which is a 2.1 right? I use my 2.1 crankShaft. with the h23 Rod bearings.

How much can the head be milled off with still using my stock camshafts and Intake Manifold and stock injectors.

And Can my ECU Remain Untouched? Are there other ECU's out there besides AEM EMS's? that i can use that arent as costly?
 

·
Banned
Joined
·
13,157 Posts
h23 Rods/ b21 Pistons.

okay so i go with that setup on a 2.0L block, Bored out to 2056 cc. which is a 2.1 right? I use my 2.1 crankShaft. with the h23 Rod bearings.

How much can the head be milled off with still using my stock camshafts and Intake Manifold and stock injectors.

And Can my ECU Remain Untouched? Are there other ECU's out there besides AEM EMS's? that i can use that arent as costly?
read my thread lol.

having the block bored includes bringing the b20 block and b21 pistons to an automotive machine shop and telling them to bore/hone the cyls for those pistons, with whatever cylinder to wall clearance is correct for the power you'll be making. which in your case is probably going to be about 0.0020" clearance.

you can use a b20 or a b21 crank, they are the same. only difference is the crank pulley bolt size which doesnt matter as long as you have the bolt and the crank pulley too that matches that crank.

h23 rod bearings are the same as b20 rod bearings which are the same as b21 rod bearings.

only shave the head the bare minimum for a straight surface, dont shave it for higher compression, you'll hate yourself later for it if you warp the head and can't mill it any more and have to buy a whole new head.
an unmilled b21 head, with b21 pistons, with still give you the stock compression of a b21 which is 9.4:1.
a b20 head though, used with the b21 pistons, will bring the compression to 10.0:1, and its a direct bolt on

just remember, you need to use a b21 head gasket when using b21 pistons or b21 head or both

yes your ecu can remain untouched. but any amount of engine work that actually provides more power than stock will require you to use 89 octane at all times instead of 87. especially if you use a b20 head. if you use a b20 head, you'll need to use 89 octane and retard the timing 1-2 degrees from stock

there are a lot of different tuneable ecu's you can use, notice my sig below, my main side business is selling all forms of tuneable ecu's, and tuning

for your setup, all you'd need is a basic chipped ecu tuneable with crome or ectune. and its a direct bolt-in/plug-in part in your car, with no modding or conversions needed at all. $200 shipped from me, with a custom basemap made to your specific setup

im serious, read my entire thread, its very similar to what you seem to want to do to yours, except mine will end up with a turbo
 

·
Registered
Joined
·
105 Posts
Discussion Starter #8
Yeah . Im a 17 year old. My dad is helping me with this build I know alot for my age but he knows alot more. lol

But I have your thread saved on a side tab im going to read it in the morning! Thanks for all your help man!
 

·
Registered
Joined
·
3 Posts
camshaft choice

I see a suggestion for the B18 intake cam. I have also heard that the B21 exhaust cam is the way to go. Any opinions on this? My situation would be ultimately a stock scenario, yet a 2.0 longblock swapped into and 2.1. Looking for mild upgrades that will increase HP at higher RPMS and not be noticed by ear. Racing in a stock class, yet the engine runs very little risk of being checked internally unless suspicions are raised by it idling funny. Any injector mods that you would suggest? No need for street considerations, just a HP focus. Thanks in advance.
 

·
Banned
Joined
·
13,157 Posts
I see a suggestion for the B18 intake cam. I have also heard that the B21 exhaust cam is the way to go. Any opinions on this? My situation would be ultimately a stock scenario, yet a 2.0 longblock swapped into and 2.1. Looking for mild upgrades that will increase HP at higher RPMS and not be noticed by ear. Racing in a stock class, yet the engine runs very little risk of being checked internally unless suspicions are raised by it idling funny. Any injector mods that you would suggest? No need for street considerations, just a HP focus. Thanks in advance.
best is the b21 exhaust cam and b18b intake cam. just remember the b18 cam needs to be modified a bit to fit properly.
combine that with a good flowing exhaust, and you'll gain some nice chunks of power in higher rpms.
the b21 exhaust cam is a minor bump in power pretty much everywhere. our intake cams suck though, and the b18b intake cam really helps enlighten the top end into its glory, but only if the exhaust flows well enough to keep up.

check out the link in my sig below for my 3g turbo build thread. the first couple pages of that thread are actually when it was n/a when i did a bunch of dyno comparisons and such with different exhausts and different cams, and without tuning and with tuning
 

·
Registered
Joined
·
9,584 Posts
I built my B20a5 with B21 pistons and H23 rods. It's about together just need to drop it in.

Also, buy some cams. B18a intake and B21 exhaust will do you good. Then get adjustable cam gears. That should make you a happy lude owner.
 

·
Registered
Joined
·
11 Posts
so for this all you need is the b21 block, and b20 head? would it make a difference as to which b20 head was used(a, a3, a5)? also if the jdm b21a block instead of the b21a1 were used?
 

·
Registered
Joined
·
9,584 Posts
so for this all you need is the b21 block, and b20 head? would it make a difference as to which b20 head was used(a, a3, a5)? also if the jdm b21a block instead of the b21a1 were used?
Well, it's more reliable to use a B20a5 block bored out to 83mm to fit stock B21 pistons. B20a head and B20a5 head are good for the fuel injection. B20a3 head is only good for SOHC dual carbs.
 

·
Needs Sensitivity Train'n
Joined
·
2,142 Posts
Really you are safe going to 83mm just the same as 81.5. 83mm just allows alot more power potential. There is an old saying that goes like this "There's no replacement for cubic displacement." This is somewhat true with our engines but in my opinion if you plan on going boost just bore it to 81.5 because there is a better choice of off the shelf pistons available at this bore plus it allows for resurfacing down the road. If you are going NA and want an ultra high compression engine without having to buy custom pistons then stick to 81.5mm. If you are like most of us and just want to make the car perform better without spending several thousand dollars then bore it to 83mm, use the H23 rods, b18 intake and b21 exhaust cams, put a good exhaust and CAI on it, and throw an MSD ignition on it, and don't forget the ECU and have fun driving your new toy.
 
1 - 20 of 26 Posts
Top