Ok, so the head is finally off, and i need to find a machine shop. But first i want to know some things before i dive into this process. Cylinder one had low compression, and it has to be a valve problem. Im not around to look at the head right now because im up at school, but my uncle says that 1 or 2 of the valves look like they might be some what bent. I have 120k on the car, when i take it to the machine shop should i expect to replace all the valves? i talked to sean1.8 before about lightweight stuff, and i know its not necessary for me. But will i be needing new oem exhaust and intake valves for everything, should i expect the shop to take care of it or should i order off ecstuning.com etc??
Also, i should expect to have the head decked? if thats the right term, and what should i know about it?

Finally, i wouldnt mind to have the head ported and polished, but am i wrong to think that 1) its hard to find a shop that does it 2) ill need different valves then oem replacements 3) it will affect my tuning, and or ill need to change my tuning?

Any help would be great.

 

I would just replace the bent valves if there are any. It could be a bad piston ring(s), with that many miles it, thatwould be more likely. Not to mention you should see imprints on the piston if the valve(s) did make contact. New rings and having the cylinders honed would make a world of differnce. Wouldnt worry about having the head ported/polished unless you plan on high 300whp or more. It just wont be worth the money. Not to mention a AEB head would still outflow it and cost less. Plus you would need a AEB intake manifold to go with it if you did have it ported/swapped. Tunning would need to be changed to optimize the head, but gains would still be shown with a standerd tune. Unitronics would tune for it if interested.

 

don't let the shops buy the valves. they'll charge you worse than the stealership. you should ask them if they'll do the work if you bought the parts.

 

If you dont specify that you want the valves replaced, they may not do it. Theyll pretty much do what you tell them too. Personally if the mating surface is flat i wouldnt deck the head. That can change your compression ratio which probably wont cause any problems, but you never know. It can be difficult to find a shop the will port heads because theres a chance they can take off to much metal and hit a coolant or oil passage. Personally i wouldnt even worry about porting and polishing as its less of an issue on a turbo motor than on a naturally aspirated one. If you do get the heads ported and polished, you wont need different valves. Tuning shouldnt change either as the airflow gains should be minimal. IMO not really worth the $ and posible trouble.

 

Green = Large port
Brown = small port


Green= Stock AEB head
Yellow= Ported AEB head
Intake flows up top, exhaust below


Little more than you think. Not to mention make rather big gains on stock vs stock on gt30+ size turbos.

 

Ok so decking shouldnt be important. And i should replace the valves? or is there a way to have the refurbed? Im looking at this place here, it should link to there performance page. They seem to have different types of porting, different angles etc, can you guys shed some light on that?
http://www.enginelaboftampa.com/machineshop.html

 

inspect the valves and they are bent, just replace them. But ask your uncle if there is marks on the pistons, there will be if they made contact. If there isnt, i doubt they are bent. Leave the head be.... please

 

They leave pretty marks like this

 

Thanks for the graphs cincy, again i talked to sean1.8 before and i guess i can make a decision on the head based on this:

I want to go big turbo, gt28rs, something that wont be boosting at low rpms cause i hate how my ko4 acts. I have fwd[:'(]but no choice because i am a student. Basically is there any point in doing performance crap to head when i will reach my performance limits just with the turbo and the strength of the bottom end. Sean said i would find the limit with a new turbo before i find a performance head usefull. Agree?

 

Thats pretty much what i said twice. Leave the head be, stock valves and all. Unless there is marks on the pistons, im guessing you valves are fine, but then again, im not looking at them.