B21 rebuild
Moderators: RedRacer, spiffyguido
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3livs
- Prelude Enthusiast
- Posts: 3
- Joined: Sat Feb 04, 2006 7:39 pm
- Location: Richmond, VA
B21 rebuild
I plan to start a rebuild on my 91 B21 and received some great info from synthoova about installing a B20 head, ( thanks synthoova), I also need to find out where the best place would be to buy a rebuild kit. I have read that this engine likes to eat piston rings, so if anyone could point me in the right direction to find better rings I would appreciate that.
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spiffyguido
- Moderator
- Posts: 2196
- Joined: Fri Nov 11, 2005 2:55 am
- Prelude Model: 1991 SE-SR
- Location: Alberta, Canada
- Contact:
3livs, great to hear from you again.
My personal feeling for doing this rebuild would be to stick to all OEM parts. The rings, gaskets, bearings, seals, etc from Honda are very high quality. If I were you, I'd stick to Honda stuff. This is the reason Honda engines last so long in the first place; the components are very well made.
I think that Honda may offer many of the parts that you want for your rebuild in sets. For example, I know that you can buy new rings as a set. This is probably also true for bearings, thrust washers, etc. They're reasonably priced too. I think you can get a complete ring set for one piston for about $30. Just head down to a dealer and ask them about what they offer. I've been able to get gasket sets for the entire engine from them before, so they'll likely have similar packages for other things.
Now, about your rings. It's important to understand why B21A1s 'eat' rings. There's absolutely nothing wrong with the design of the B21 in this regard, it simply comes down to Honda's choice of materials.
When Honda was designing the B21 they wanted to use the exact same block as the B20. To get the extra displacement they had to increase the bore of the B20 a little bit. The boring would have created cylinder sleeves that Honda felt were too thin. As a solution, they had a company develop some special sleeves for the B21 made out of Fiber-Reinforced-Metal, commonly referred to as FRM. The FRM in the B21 sleeves is VERY strong, much stronger than the metal used to make the standard sleeves used in the B20s. FRM sleeves have also been used in the 3.2 litre NSX, to my knowledge.
These FRM sleeves happen to be hard on the softer piston rings, so they wear out a little faster than the rings in the B20s. This isn't such a bad thing, because it's much easier to swap out some rings than to overall both the sleeves and the rings. I'm glad Honda decided to go with the FRM. I've heard some claim that even after 100,000 miles of use, you can still see the factory cross-hatching in the FRM sleeves. Impressive.
The bottom line; Honda rings are great, and I'd stick with them. There's nothing wrong with the design of the B21 that makes it chew up rings, it's just the material that the sleeves are made out of.
Since we're talking about FRM sleeves, I should probably mention that they require a special process in order to be honed. You may not have to hone them at all, depending on the condition. I'm not sure of the exact process, but I think that it involves more of a sanding process rather than sending down a honing bore to deeply crosshatch the surface. If you find you need to hone your B21, post a thread and some people here will likely be able to help you find more information.
Hope that helps you out a little bit. Thanks for visiting; please keep coming back. It's good to have your questions.
Do you have pics of your motor? This is sounding like a sweet project. Putting the B20 head on the B21 is going to create a sweet squish zone. Lovely.
My personal feeling for doing this rebuild would be to stick to all OEM parts. The rings, gaskets, bearings, seals, etc from Honda are very high quality. If I were you, I'd stick to Honda stuff. This is the reason Honda engines last so long in the first place; the components are very well made.
I think that Honda may offer many of the parts that you want for your rebuild in sets. For example, I know that you can buy new rings as a set. This is probably also true for bearings, thrust washers, etc. They're reasonably priced too. I think you can get a complete ring set for one piston for about $30. Just head down to a dealer and ask them about what they offer. I've been able to get gasket sets for the entire engine from them before, so they'll likely have similar packages for other things.
Now, about your rings. It's important to understand why B21A1s 'eat' rings. There's absolutely nothing wrong with the design of the B21 in this regard, it simply comes down to Honda's choice of materials.
When Honda was designing the B21 they wanted to use the exact same block as the B20. To get the extra displacement they had to increase the bore of the B20 a little bit. The boring would have created cylinder sleeves that Honda felt were too thin. As a solution, they had a company develop some special sleeves for the B21 made out of Fiber-Reinforced-Metal, commonly referred to as FRM. The FRM in the B21 sleeves is VERY strong, much stronger than the metal used to make the standard sleeves used in the B20s. FRM sleeves have also been used in the 3.2 litre NSX, to my knowledge.
These FRM sleeves happen to be hard on the softer piston rings, so they wear out a little faster than the rings in the B20s. This isn't such a bad thing, because it's much easier to swap out some rings than to overall both the sleeves and the rings. I'm glad Honda decided to go with the FRM. I've heard some claim that even after 100,000 miles of use, you can still see the factory cross-hatching in the FRM sleeves. Impressive.
The bottom line; Honda rings are great, and I'd stick with them. There's nothing wrong with the design of the B21 that makes it chew up rings, it's just the material that the sleeves are made out of.
Since we're talking about FRM sleeves, I should probably mention that they require a special process in order to be honed. You may not have to hone them at all, depending on the condition. I'm not sure of the exact process, but I think that it involves more of a sanding process rather than sending down a honing bore to deeply crosshatch the surface. If you find you need to hone your B21, post a thread and some people here will likely be able to help you find more information.
Hope that helps you out a little bit. Thanks for visiting; please keep coming back. It's good to have your questions.
Do you have pics of your motor? This is sounding like a sweet project. Putting the B20 head on the B21 is going to create a sweet squish zone. Lovely.
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3livs
- Prelude Enthusiast
- Posts: 3
- Joined: Sat Feb 04, 2006 7:39 pm
- Location: Richmond, VA
thanks again synthoova
the info will be put to good use. I have been doing alot of historical research about the special sleeves in this motor and hopefully when i start, there will be no honing needed but it does have 220k miles. When i start this summer i will share photos and info that i learn along the way with preludedriver. i hope that's not too long to wait, but i have to build a place to work first, i'm kinda tired of working in the driveway.
i am a bit of a rookie in the prelude scene but one thing i can tell everybody is to go out and buy the factory service manuals from helms. these manuals are the best written and illustrated i have ever seen.
i am a bit of a rookie in the prelude scene but one thing i can tell everybody is to go out and buy the factory service manuals from helms. these manuals are the best written and illustrated i have ever seen.
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spiffyguido
- Moderator
- Posts: 2196
- Joined: Fri Nov 11, 2005 2:55 am
- Prelude Model: 1991 SE-SR
- Location: Alberta, Canada
- Contact:
Awesome. Thanks for letting us all know what you're up to. Keep in touch and don't be afraid to ask a multitude of other questions. We're always happy to give you a hand.
Don't worry about being a 'rookie', we've all been there before and we welcome your questions.
Yes, the helms are good. There's also some manuals on the honda.co.uk website. I'll send you some PDF version Honda manuals as well in the next couple of days.
Don't worry about being a 'rookie', we've all been there before and we welcome your questions.
Yes, the helms are good. There's also some manuals on the honda.co.uk website. I'll send you some PDF version Honda manuals as well in the next couple of days.