oversized valves?

[itzdave]

ive got a spare head kickin around that i wanna have built up. BIG P+P, larger valves, bisi springs, etc...
question is, who's got oversized valves for us(or what other engine are they swappable from), should i have the p+p done before i get the bigger valves, will the bisi springs work with those other valves, etc.
thanks in advance...

[Strugglebucket]

You should look up rjudgey posts. He's gone into extreme detail about head work and oversized valves many times on this site.

If I remember right he did an A20 head with stock exhaust valves machined down to use as intake valves, and custom exhaust valves.

[2ndGenGuy]

There's also a thread... somewhere on PreludePower that someone had put some serious detailed info into building up the head, what valves, etc. It's not very old either so the info should be pretty relevant.

[2drSE-i]

Heres that thread baby girl ;)

http://www.preludepower.com/forums/showthread.php?t=332536&highlight=oversize+valve

Good info on 31mm Valves for the intake side

[2oodoor]

DOHC yo dog "its been done":blah:

those are two excellent references though...

[rjudgey]

You can also got those valves in 32mm flavour which would be more benefitial and still fit on a stock seat!!
For some off reason 32mm fits on A20 and 33mm can just about squeeze onto a A18 head. I have big valve conversions on both types but I've not yet had a chance to test the A18 with the higher compression and larger exhaust valves, the previous version just had larger intake valves and stock exhaust which caused a bit of a bottleneck!! Also if you go down this route you will need a custom exhaust manifold and at least 2.25" exhaust system mandrel bent or 2.5" system if running a cam bigger than 272 degrees.