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Discussion Starter · #1 · (Edited)
230,000. 1991 Si. Second Owner.
A project thread from beginning to end. Bored FRM .25 over. All Honda Internals going back in.



Yes it leaked some oil and burned some oil. Oil pan gasket was shot also.


Cylinders walls look really good. Cylinders 1 and 4 look the same as these.


There is a ridge at the top of each cylinder. So yes the FRM does wear. Some have stated that the FRM did not wear at all in their engines. Just letting everyone know what I found in mine.


No faults found on crank journals. It will be going back in.


Cams Look fine too.


Keep track of the postition of the rocker arms at disassembly if you are going to re-use them. Always put parts that have been wearing on other parts for long periods back in their original position at reassembly.


Pretty heavy deposits on the exhaust valves and there is a layer of carbon built up inside the intake ports.


Normal wear on bearings. Actually wear was very light. The other two bearing caps and the rods/bearings are with the block and new pistons at the shop. All of the bearings looked like this or better. Some had not even worn through the cladding. Block is being bored 25 over. New Honda pistons and wrist pins have to be pressed on at the shop. All internals going back in are Honda. Ordered through Majestic Honda. http://www.hondaautomotiveparts.com/. Best prices on factory parts I have found.


Piston to Cylinder Measurements
Piston Service Limits:
A 3.2673 in.
B 3.2669 in
Actual Piston Dimension
#1 B 3.2671 OK
#2 A 3.2675 OK
#3 A 3.2675 OK
#4 A 3.2675 OK
Piston to Cylinder Clearance
Service Limit: .0028
Actual:
#1 0.0026 OK
#2 0.0025 OK
#3 0.0022 OK
#4 0.0024 OK

Its kinda amazing to me that after 230,000 miles the Piston to Cylinder Clearances are still within allowable limits.
 

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That's great for a B21 with 230,000 on it. or for a B21 period, Good luck
 

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i thought boring the b21 FRMs was bad....from what ive read only honing should be done.
 

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I think when he meant sleave, he meant ditch the frm and put some Iron sleaves in. But yeah, you can pretty much only hone the frm and it MUST be done correctly. Otherwise you'll eat the rings quickly
 

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Blackludesi said:
I think when he meant sleave, he meant ditch the frm and put some Iron sleaves in. But yeah, you can pretty much only hone the frm and it MUST be done correctly. Otherwise you'll eat the rings quickly

correctly huh, wonder wut exactly that is....you mean use the wrong grade and type of tools to hone it? how would one come about knowing what and how exactly to hone frm walls....
 

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There's nothing wrong with boring anything as long as it is done properly. My B21A1 was bored and honed and it's fine.

--J
 

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Really, i wish i knew i could of got away with boring mine. How far over was it bored? I forget the exact, but honda say it's supposed to be honed with a certain grit stone and at a precise angle. I dunno. i had mine honed with just a standard stone at a 45 degree angle. It seemed fine.
 

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Mine was bored 0.020" which apparently, according to the machine shop, was machine limit. I think that may have been horse shit, though, unless it had been bored before. I don't see the likelihood of that, though. In the big picture, it doesn't really matter 'cause eventually one day I'm going to sleeve the thing.

The machine shop I went to had just done a B21A1 for one of the profs at my school and had done a good job on that apparently, so I figured it was okay to bring my stuff there.

--J
 

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Import_Tuna said:
Mine was bored 0.020" which apparently, according to the machine shop, was machine limit. I think that may have been horse shit, though, unless it had been bored before. I don't see the likelihood of that, though. In the big picture, it doesn't really matter 'cause eventually one day I'm going to sleeve the thing.

The machine shop I went to had just done a B21A1 for one of the profs at my school and had done a good job on that apparently, so I figured it was okay to bring my stuff there.

--J
cant you just hone the damn things and use some moly rings? shafe off the head and doning so proly increase your compression to like 10:1 ?
 

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they should of been able to do more, Like 0.030 or so. The frm isn't that thin. It's strong stuff
 

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scyclone said:
cant you just hone the damn things and use some moly rings? shafe off the head and doning so proly increase your compression to like 10:1 ?
I... guess you could. But if you have it all apart, why not just spend a bit extra and bore the thing? Also, there's no way in hell you could get 10:1 with shaving stuff. You'd never make it, and even if you did, your camshaft timing would go for shit. You would have to correct it with adjustable cam sprockets.

If you want the compression, do it with pistons or with a B20A head. Or both! Honing the walls and putting in new rings might restore a bit of lost compression, but getting the thing bored, I think, is the best option. I'm sure you could get away with honing it, but how long will it be before you have to take it apart again and bore it anyway?

I think FRM is a great idea, but if you want to get any kind of performance out of a B21 and you're serious about it, I think sleeves are the way to go. That way, you can hang out at 7,000 all day long and the only thing you'll have to worry about is hucking a rod!

--J
 

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Discussion Starter · #13 · (Edited)
Honda specs allow for one bore of 25 over. That is also the only oversize piston Honda has available for the B21 that I see. I've opted to put all Honda internals back in. For me sleeving wasn't worth the expense for how I intend to drive it. I got a quote for $600 for sleeving. I'm not going for mega power. I'm satisfied with the power the B21 puts out as it is. Don't get me wrong. Im for all the power I can get. I'm just not willing to spend that kind of cash right now (Turbo etc). I'm also not convinced the FRM is as bad as alot of people believe. It just has to be handled properly.
 

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Discussion Starter · #14 · (Edited)
Ridge Reamer

The only reason I mention the ridges at the top of the cylinders is because somebody in an earlier thread said the FRM cylinder walls are so hard that they show virtually no signs of wear even after 200,000 miles on them. I just wanted to let it be known what I found when I opened mine up. Thats all.

Got the block, head, and piston assemblies back from the shop yesterday. Everything looks good so far. Will post pics soon
:)
 

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Discussion Starter · #16 · (Edited)
:huh2: Well my main goal is to get an engine back to factory specs that doesn't burn oil. I can always get it sleeved later if I want a bigger bore or get another engine to really build up for power. I could have just gone ahead and had it bored to whatever size there are after market pistons for but I chose to use all Honda internals. The point of this thread is not to build a powerhouse. It's to show that the B21 with its FRM is not as scary, unreliable or worthless to rebuild as a lot of people want to believe.
:tounge:
 

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Discussion Starter · #17 · (Edited)
:grin: Got the block and head back from Dave's HondaHaven


Going to port match and polish the ports
All of the exhaust valve guides were replaced. They told me the intake valve guides looked good and didn't need to be replaced and usually don't go bad because they are not exposed to the high heat like the exhaust guides are.


Crosshatch of FRM after Boring and Honing


All Honda internals going back in


Block shown in boring config. with #1 #5 main bearing caps and girdle installed. These had to be installed to anchor the block for boring. Rubber tubing was put on the two oil pan studs before I took it in to keep them from getting trashed


The suspension kit I bought off of Ebay for $350.00


Fronts assembled



Thats about as far as I've gotten so far. Have a lightened flywheel on the way.:cool:
 

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B21a1 212,000

Hey diamond,

I rebuilt my my B21A1 at 212,000. I was getting low compression on number 3 cylinder,(135 lbs), the others were 190 lbs.
I was using oil at 1qt every couple weeks. I couldn't see it smoking, but it was using it.

I found the piston ring lands cracked on all four pistons. The number 3 piston had several cracks. Miraculously, the cylinder bores were not damaged. I was able to push every piston up and out of the block by hand...no ridge at all.
I had the block (FRM cylinder walls) checked by three machinists....alll three told me it did not need boring/sleeving. All I did was rough the walls up with 400 grit sand paper....by hand.

I went with all Honda parts.

Pay attention to the position of the main/rod bearings...each half is color coded. Get the same color and use it in the same piston/cylinder as the original.

The after market kits didn't mention this at all....one kit fits all.

I had the head redone and assembled the motor myself.

I've got 23,000 miles on the rebuild so far and use no oil at all. I'm getting 30 MPG combination town/hwy.

Good Luck,

Keep us posted on your progress.

Forgot to mention ....pay particular attention to the intake manifold during assembly. That's the only problem I had. After 3,000 miles the gasket started sucking air from the bottom of two ports.

I had to pull the intake and replace the gasket. I guess I either pinched the gasket or didn't torque the nuts evenly.

Also, my compression on each cylinder runs 190-194 lbs right now.

Later.
 

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Discussion Starter · #20 · (Edited)
zolemite said:
How much did it cost you to have them hone the block?
To answer your question on cost:


Hey Boxer1, Its good to see someone else that has gotten into this engine. I wonder how your piston ring lands got cracked? I've seen that before on a V8 that was had a pre-igintion problem. I would have liked to have taken the route you did. Mine was so close to being able to do that. :thumbs-up:
 
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