head work

[efreeman]

i am looking to build a 600 hp 7 bolt out of a 98 gst... i have a stage 2 kit from built4g63 rotating assembly all standard size(bearing, bore ect). My question is with a port and polish job on the head with the standard valves suffice or will i need to bump up to oversized valves with more porting and polishing? i will be running gsc power division cams (274/274) with the gsc beehive springs

 

[BIRDCLAWTSi]

Oversized valves will help, But are not a necessity to reach that goal.

Put the money somewhere else,

Intake manifold and turbine housing will make a much bigger difference.

Porting and polishing helps too, But don't go hogging out the head, Mild porting is all that is needed, And Port matching.

What parts do you currently have?

 

[mercaholik]

I am not a fan of this whole gasket matching thing. Making all the ports the same size is a good idea, I used a snap gauge and dial caliper. But gasket matching the 1g head is making a big intake port even bigger, and even on 2g head you are making the first inch or so bigger and now you have messed with ports taper. I'm not sure but I think there may be some kind of ideal ratio like area to radius ratio on a turbo. But obviously not exactly like that but you get my drift right? Just looking out, all you need is to clean up the casing flash and smooth out some spots. I agree with you bird claw tsi, plus I have read a ton of info on head porting, both on tuners and many other sites, books and I have barely scratched the surface.

 

[efreeman]

all i have now is the rotating assembly....i am getting ready to take my head to the machine shop to get it pressure checked and ported and polished...if i dont need to go bigger on the vlaves to achieve my goal will the standard valves hold up if everything checks out on the them running that setup with the cams and springs or should i go for a better set?....if not i havent ordered the cams yet i wanted to make sure the head was in order berfore i did so

 

[BogusSVO]

The first inch or so into the runner will not do much for flow gains maybe 1-2% at most.

The best gains are in the bowl for air flow and the combustion chamber to reduce predet.

Oversized valves can end up flowing worse that a std valve if they are not installed correctly

 

[BIRDCLAWTSi]

I am not a fan of this whole gasket matching thing. Making all the ports the same size is a good idea, I used a snap gauge and dial caliper. But gasket matching the 1g head is making a big intake port even bigger, and even on 2g head you are making the first inch or so bigger and now you have messed with ports taper. I'm not sure but I think there may be some kind of ideal ratio like area to radius ratio on a turbo. But obviously not exactly like that but you get my drift right? Just looking out, all you need is to clean up the casing flash and smooth out some spots. I agree with you bird claw tsi, plus I have read a ton of info on head porting, both on tuners and many other sites, books and I have barely scratched the surface.

I would not recommend gasket matching, That will make the ports huge, Just port matching, Like the intake manifold to the head. I should have stated that, Thanks!

 

[fastfred]

I had my machinist leave the intake ports unpolished and when we talked about oversized valves it just didnt seem cost effective for what i was doing with the car. Also like stated above can hurt you if not done right