B21A1 head on B20A5 block?
Moderators: RedRacer, spiffyguido
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tprelude
- Lude Dude
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B21A1 head on B20A5 block?
I have a B21A1 engine in my lude right now, but unfortunately I've had the head rebuild, and the engine still burns oil like nobody's business. Was wondering if anyone has swapped the block out and put in a B20A5 engine block? From what I can tell, they are exactly the same accept for the bore stroke. Does anyone know if this is possible and if there is anything else that needs to be changed, or is it a straight hook-up?
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spiffyguido
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- Prelude Model: 1991 SE-SR
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Re: B21A1 head on B20A5 block?
It is possible to do the swap.
The ECU is different between the B21A1 and the B20A5, but mechanically, they are very similar. You won't have to worry about getting new axles or anything like that. Even the trannies are interchangeable.
If your B21A1 is burning oil, why don't you just change the piston rings?
The ECU is different between the B21A1 and the B20A5, but mechanically, they are very similar. You won't have to worry about getting new axles or anything like that. Even the trannies are interchangeable.
If your B21A1 is burning oil, why don't you just change the piston rings?
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team123luder
- Prelude Enthusiast
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Re: B21A1 head on B20A5 block?
The issue with the B21 burning oil is simply the piston rings hate the FRM sleeves.
The B21 head will bolt right onto the B20A block with no issues. The only difference is the bore size. The B21 has a larger combustion chamber because of the larger bore size as opposed to the B20 setup.
Which will then mean you'll have a lower compression ratio and less power.
Personally I'd get a complete B20A and just interchange intake and exhaust manifolds.
The B21 head will bolt right onto the B20A block with no issues. The only difference is the bore size. The B21 has a larger combustion chamber because of the larger bore size as opposed to the B20 setup.
Which will then mean you'll have a lower compression ratio and less power.
Personally I'd get a complete B20A and just interchange intake and exhaust manifolds.
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tprelude
- Lude Dude
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Re: B21A1 head on B20A5 block?
Personally I would prefer not to put a complete B20A in as I just had the head rebuilt in the B21A. 
I have come across another forum that says that the you can have the B21A resleeved with iron sleeves. Does anyone here know if this is possible or know of someone who has had this done? http://www.preludepower.com/forums/show ... p?t=184486
I'm trying to weight all my options here before I go putting any more money into the car or decide to sell as is.
I have come across another forum that says that the you can have the B21A resleeved with iron sleeves. Does anyone here know if this is possible or know of someone who has had this done? http://www.preludepower.com/forums/show ... p?t=184486
I'm trying to weight all my options here before I go putting any more money into the car or decide to sell as is.
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spiffyguido
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Re: B21A1 head on B20A5 block?
I'm sure that you can have your B21A1 resleeved with Iron sleeves, but this is going to be a lot more expensive than just changing the piston rings on your existing setup. The FRM sleeves in a B21 are incredibly strong, so they'll be fine. If you change your rings, your oil burning problem should disappear. Changing the rings is far easier than resleeving the engine. You don't have to pull the engine to do it, and new rings aren't that pricey.