A20 cam and head help?

[FF37]

I Have an a20 prelude engine i want to put the bisimoto cam in, my question is do i have to go with bigger valves or will the cam work fine in the stock head, i know going with bigger valves is the best way to go but i just wanna know will it work?

[Hail Doom]

The camshaft controls when the valves open and close, and how far they open. The Bisi cam (as well as any cam) will work with stock valves.

[rjudgey]

All depends what mods you have already, what mods your planning and also which cam you are going for!! More details please! :)

[Vanilla Sky]

It will work. Supporting mods always help with a cam, though. My suggestion would be to grab a head from the junkyard and build it as you have time/money. Put the Bisi cam in your current head, and when you have the new ported big valve head, swap it over.

[cygnus x-1]

Which cam are you getting? Don't make the mistake of getting one that's too big for your engine. Anything stage 2 or higher will require supporting mods.

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[FF37]

i am only getting the stage 2 cam they say its the best seller, i have rebuilt the bottom end, boring .020 over, new bearings, new pistons and rings. nothing to the head, im wondering if i should replace the valve springs with the cam?

[rjudgey]

Stock springs are fine for stage 1 and 2, if you were going for something stronger then prelude ET/A18 springs are good for upto 7500rpm, anything more then using springs from ET/A18 exhaust only all round are good for 8500rpm you can use Bisi springs but unless your pulling 8-9k rpm their overkill and will rob you of power from the extra frictional loss not to mention wear out your cam bearings and rocker pads much quicker!! Get a cam gear if anything!! Only other circumstance to use their springs would be for the extra lift on the wilder cams they're are ways round this on stock springs but require machining work on the spring platforms and the head.

[cygnus x-1]

i am only getting the stage 2 cam they say its the best seller, i have rebuilt the bottom end, boring .020 over, new bearings, new pistons and rings. nothing to the head, im wondering if i should replace the valve springs with the cam?


With a stage 2 cam you really need a header and better exhaust system to make the best use of the higher RPM power band. And ideally you would also want to improve the intake and fuel system. Putting on a modified B18 manifold would help, as would converting to OBD1 and doing some tuning (a fair amount of work though). The stock computer is not tuned for the new cam so it won't make the best use of it.

Another option is to switch over to carbs if you don't want to mess with ECU tuning. Tuning carbs is easier in some ways but not as many people are familiar with them anymore.

Really if you don't want to mess around with tuning I would say get a stage 1 cam instead. To make the best use of a stage 2 you really need to improve the airflow in and out of the head, and add more fuel to go with the extra air. You will lose low RPM torque with a stage 2 cam and gain high RPM torque. This is fine as long as the the intake and exhaust system can handle it. If they can't, you get a big surge of torque at 4k-5k RPM and then it chokes.

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[FF37]

Ok thx for the replies, i race on a small asphalt track and the rpms usually get no lower than around 2800 rpms, i am looking into that modidied b18 intake but that will be more air, what about more fuel, the exhaust is basicall 2 1/2 with a cherry bomb no converter or muffler so it wont have any problem getting out, plus it is just a straight pipe that exits behind driver.

[cygnus x-1]

Ok thx for the replies, i race on a small asphalt track and the rpms usually get no lower than around 2800 rpms, i am looking into that modidied b18 intake but that will be more air, what about more fuel, the exhaust is basicall 2 1/2 with a cherry bomb no converter or muffler so it wont have any problem getting out, plus it is just a straight pipe that exits behind driver.


Ooohhh, that changes things then. Your exhaust is probably ok, just make sure the down pipe isn't a restriction. Those things have REALLY thick tubing and are smaller on the inside than you would think, so having 2.5" tubing behind a stock down pipe won't really gain you much. If you don't mind a little extra work try to find a 4-2 exhaust manifold from a 88-89 fuel injected Accord to use. Open up the outlet ports and then have a new 2-1 down pipe made to connect the manifold to the rest of the exhaust. This essentially gets you a 4-2-1 header for fairly cheap.

Anyway on a track that stage 2 should be ok, but it will benefit from more air and fuel. Try to find a B18B intake manifold if you can ('94-'01 non-VTEC Integra). They're simpler to modify than the B18A1 intake, although both will work. Modification involved drilling/enlarging some holes and cutting off the water/EGR ports.

For fuel you can try an adjustable fuel pressure regulator and bump up the pressure. Another trick that might work is to add some resistors in series/parallel with the coolant/air temp sensors. The idea is to fool the ECU into thinking it's colder than it really is, making it add more fuel. If you're going to try these sorts of things it would be useful to get a wide band O2 sensor so you can see what effect your modifications are having. Otherwise you're just shooting in the dark.


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[Vanilla Sky]

You can also move the IAT sensor off of the manifold. That thing heat soaks where it is from the factory. Mounting it on the intake plumbing is a better place for it, IMO.

[FF37]

Ok i couldn't fine the post on the mod manifold, i use the b18 manifold, fuel rail and tb right? Also what about all of the vacuum lines on the existing manifold, i have heard about making or buying a vacuum distribution unit, any info on that?

[Vanilla Sky]

If you're getting that deep into it, you really should consider either OBD1 or MS.

[cygnus x-1]

Ok i couldn't fine the post on the mod manifold,

Here is the HOWTO for modifying a B16 intake. The process for doing a B18 is pretty much the same.

http://www.3geez.com/forum/showthread.php?t=49453




i use the b18 manifold, fuel rail and tb right?

Correct. Use the stock A20 injectors though.



Also what about all of the vacuum lines on the existing manifold, i have heard about making or buying a vacuum distribution unit, any info on that?

On a race car I wouldn't think you would have that many vacuum lines. But if you need more ports than what the B18 intake has you can just use tees, or make a vacuum manifold (basically just a fancier tee with multiple ports).

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[AccordEpicenter]

if you bypass the coolant lines to the throttle body and intake manifold you will pick up a few hp... but deleting vac lines doesnt really give you anything