Modifying a 20v Head

**Dom-AE71** · 12-03-2006, 01:55 PM

Im buying another head to do a bit of work on, i dont want it to be all out and crazy with massive cams and the like becasue i still want the car to have decent street drivability but i would like to improve the performance of the engine a little bit.

i know theres been alot of talk about port sizes recently, would there be any benifit in increasing the size of the exhaust and intake ports for better flow? or perhaps jsut have them polished up and any rough egdes smoothed out.

will there be any advantage in using heavy duty valve springs?

i want to get the head shave, only a little bit, how much can i go without being close to causing damage to any parts of the motor? would it be more benifit to run a thiner metal head gasket instead?

the car is currently NA but MAY down the track i might wack a turbo on when i feel rich and want to blow it up for fun but its probably unlikely that i will go down that path without building a proper motor.

the car is controlled by a microtech ltx8.

how much benifit are adjustable cam gears?

what about getting the standard cams reground?

**ira11y** · 12-03-2006, 06:16 PM

Compared to a 16V head there isnt a lot of port area to play with, also IMHO the head is reasonably designed enough allready to get benefit from mild cams etc without playing with too much other than port matching and the like.

If you are going to bigger cams then HD valve springs for me would be part of the package, remeber that when you goto bigger cams the VVT will be thrown out the window.

Shaving of the head is a personal choice, talk to your engine builder as to waht they think you can get away with.. some say 10thou others say 40thou or even higher depending on your components.

If you are running an aftermarket computer then adj cam gears are a definite advantage, considering that you will probhably loose the VVT then the CPU with Adjustables gears can go some way to compensating that loss.

**Dimitri** · 12-03-2006, 10:38 PM

we've run 20vs on the dyno. with it on, it made more torque everywhere. I.E i wouldnt be too worried about losing VVT. it has more to do with emisions.

**Dom-AE71** · 12-03-2006, 11:34 PM

well the microtech was going to be running the VVT would i be better off not running it with the microtech and jsut have it tuned on a good map?

i thought the microtech could control the vvt reasonably well?

(i know its off my original topic but i couldnt be arsed making a new thread)

**ira11y** · 13-03-2006, 05:11 PM

with it on

sorry im having a stupid brain day ... with what on?

**Dom-AE71** · 13-03-2006, 05:17 PM

m pretty sure he means with the VVT turned on

**AE86slut** · 13-03-2006, 05:28 PM

Most people I've spoken to who have spent a fair bit of time on the silvertop head reckon they take them out to black top specs and don't bother with much more. Apparently this is the way to go for velocity, flow, filling etc...

**Dimitri** · 14-03-2006, 01:46 PM

with the vvt activated.

**adamaw11** · 14-03-2006, 05:18 PM

Originally Posted by Dimitri

we've run 20vs on the dyno. with it on, it made more torque everywhere. I.E i wouldnt be too worried about losing VVT. it has more to do with emisions.

More torque above ~7500 rpm even? With the factory computer it actually turns the vvt off again up there somewhere round 7000rpm

i thought the microtech could control the vvt reasonably well?

All it has to do to control it is either turn it on or off based on rpm and throttle position.

Its just that when you start upgrading cams and adjusting cam gears the effect of the vvt improving drivability will be diminished

**Dom-AE71** · 14-03-2006, 05:21 PM

ok well cams and cam gears will remain standard for now and yes the VVT turns off and the cams kick in, the idea of VVT is to increase the power in the mid range of the engine unlike VTEC