? about an B20A5 - Honda Prelude Forum

car38 · 01-07-2012, 09:02 AM

I have a 88 prelude with a fresh bottom end. Want to increase hp was told I could change the head to an Acura non vetec, as we cannot have vetec's. If this is true what year and number should I use (b18?). I would appreciate any help with this, just want to go fast

Colfax · 01-07-2012, 08:35 PM

3rd gens handle great, but I guess Honda didn't want to give them a lot of speed for some reason. Sorry, but you can't use any other b-series honda head on these blocks without extensive (and expensive) machining. I've heard of several people who tried, but only one person I know of was successful. And he didn't really give any details about it before he disappeared from the forum.

Your most viable options include swapping engine/transmission to an H or F series, which is probably gonna cost you at least $4000 if you do the work yourself. You'll need engine, transmission, custom axles, custom motor mounts, upgraded wiring, ecu...etc. Swapping to an H22a would give you vtec btw. Or you can turbo the b20a5 for about half that cost, again doing the work yourself. The internals are good for mild boost pressures, as long as you tune it.

car38 · 01-09-2012, 07:57 PM

Thanks Colfax, not what I wanted to hear but par for the course. Next ? any cams or intakes from stock rides. We need more power but it has to be Honda factory, no aftermarket stuff. Thanks for any info

Colfax · 01-10-2012, 08:30 AM

Ah, you're trying to stay within the rules of your race club. I guess I didn't catch that.

There's not a lot you can do unfortunately. Well...one thing that will bump up your compression ratio a little would be to use the combination of a b21a1 block with your b20a5 head. You could use the b21 block or bore your b20a5 out to accept b21a1 pistons. But we're not talking about a big increase here. I forget the numbers off the top of my head, but I think it increases the comp ratio from 9.4 to 1 up to something like 9.9 to 1. At least that's what I remember. Let me dig up that thread for you...
Compression test results on B21 block with B20 head... - Honda Prelude Forum : Honda Prelude Forums

But we're only talking about a 10 hp increase from what they're saying. You'll probably want to advance your timing a couple degrees too if you do this.