plakia

I'm putting in a b20a in place of my b21a1 that drank too much oil. I have a question on intake manifolds. I want to use the intake from the car (b21a1 intake) Although it bolts up just fine the intake shape is slightly different from the head shape. There is a bottom lip on the head about 1/8 of an inch. I don't want this to cause turbulance thus reducing power or fuel mileage but I also want to get this done as quickly as possible. Any help would be greatly appreciated.

Colfax

This swap is pretty common among 3rd gens. Unfortunately, you're pretty limited as far as intake manifolds go. You can either use the b20a5 or b21a1 for bolt on. Anything else will require significant modification. You could try and port match the b21 manifold to the b20a head, just don't remove too much or you will actually make less power than if you'd left it alone. Or run it like it is. One other thing you can do is use the b21a1 head on the b20a5 block, as it bolts right on. This will lower your compression ratio a little, so it's better suited for a turbo application. You just need to make sure to use a b21a1 head gasket.

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89 Prelude 2.0Si 4WS
91 Prelude Si - SOLD

plakia

Thank you for your help it is very much appreciated.

89turbolude

Why do all these preludes have b20a's and b21' in them why does mine have a a18a? and i cant find hardly any parts for this damn motor so i built a turbo setup for it and i had to hand build everything!

Colfax

Your 3rd gen has an a18a? It's either a second gen prelude or it's been swapped. Please post pics. It's not really a swap that would make sense. It SOHC dual carb'd, and smaller displacement. It's rated the same as the b20a3 as far as hp goes.

Depending on your model and what country they were sold in, all 3rd gen preludes came from Honda with a b20a/3/4 (dual carb), b20a/5/7/9, or b21a/1. None came with an a series engine.

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89 Prelude 2.0Si 4WS
91 Prelude Si - SOLD

89turbolude

it doesnt have a any carbs on it. Its fuel injected. and its pretty fast it just as fast as a stock 5.0 mustang the older style.

89turbolude

the motor has been swapped but its was swapped with the same motor that came out of it.

Colfax

Please post pics of this. No 3rd gen prelude came with the a18a engine.

__________________
89 Prelude 2.0Si 4WS
91 Prelude Si - SOLD

89turbolude

i dont have any pics right now. We're in the middle of a snow storm! There is so much snow!

jdmhonda91

actually preludes did come stock with a 1.8 it was the destroked b20. the first version b20. it leaned towards front not back. google it. prelude wiki. as far as intakes when i put a b21a1 into my 89si i used everything from the 89si just 91 block and head everything went together fine. and it got over 30mpg. now swapping the carbed intake would be interesting on dohc. technicly u would be bypassing ecu and all of its functions.

Colfax

Re-read what I said. I didn't say that Preludes never came with a 1.8, I said 3rd gens never came with 1.8. All 3rd gen engines were either 2.0 or 2.1 liter and slant towards the rear.

Don't believe everything you read on wiki. It's usually pretty accurate, but since anyone can edit the pages (fact by committee) you're bound to get people who post inaccurate information.

There is actually quite a bit of information out there for doing a carb to fuel injection swap (S to Si) on a 3rd gen. You don't bypass the ecu, you replace the wiring harness, ecu, and vacuum system with the Si parts, along with the fuel tank because they have different baffling, run another fuel line, and of course the engine and manifolds. Transmission would be optional.

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89 Prelude 2.0Si 4WS
91 Prelude Si - SOLD