Oversize valves - 4age?

[jezza323]

Just wondering if anyone has tried the 4age valves in a 4e/5e head?

They are pretty much exactly 1.0mm oversize, but would require the stem to be shortened, and new collet grooves machined.

[ivan]

4e/5e heads dont have alot of room for oversized valves. Personally i dont see there being a requirement for it, and think better the money go into a good porting job and some more aggressive cams.

Ivan

[HardcoreEP]

There are several guys here that have done it. According to them the valves are pretty much the same with the exception of the diameter. I have a head with a port and polish, 3 angle valve job, with the 4age valves in it I'll post later. The problem experienced is that you have to be running a lot of boost because the air velocity at low rpms isn't there anymore. I'm not sure what this would do for an NA engine because you can't alter cam timing to make up for that.

I do agree with Ivan here. Its not worth it unless you're looking for every last hp.

[jezza323]

did you have to replace the valve seats? or were they able to be cut out large enough to suit the 4a valves? for interests sake :)

[ivan]

HardcoreEP, you can alter cam timing... its not the most ideal way however i have an adjustabel cam gear on my car.

Ivan

[HardcoreEP]

You'd need to adjust them independently. The overlap would make up for the drop in air velocity. Since this is fixed in the FE head I don't see where adjusting it would bring back the low end flow.