ZZ4 86 Z28

iTrader: (1)

I was planning to get my heads milled down as my next performance upgrade. What are the pros and cons of doing this. Also, what should i ask for, like, what is angle milled? Also, what compression should I go to to stay on pump gas, I am at 9.8 right now. If someone could just give me a couple scenarios of like what i can mill it to, and how it will change the compression, gas mileage, power, etc.
I am running a pretty much stock zz1 motor. It has the aluminum l98 heads, performer rpm, 700 double pumper, msd 6al, headers, no cat, flowmaster, etc. I just wanna know what to expect by doing this mod, and what kind of changes I can expect. Thank you.

Sonix

iTrader: (1)

I wouldn't bother.
Your possible HP increase is outweighed by the cost and risk.

What is your deck height and what gasket are you using now? You could always move to a shim gasket to up the CR for less $.
Lots of other good mods to consider before milling the heads.

ZZ4 86 Z28

iTrader: (1)

I have no idea what the deck height is or what kinda gaskets are in there.
What kinds of other things were you thinking of that I could do before this?

Guest

Milling heads shouldnt be considered a mod or should it be done for any type of power increase on a small block chevy. If your compression isnt what you want it to be, either you have the wrong pistons or wrong gaskets. Also going from 9.8 to maybe 10.3 isnt going to help any, at least not for all the work involved in doing that. You'd be better off porting the heads or replacing them if you're going to take them off.

F-BIRD'88

The compression ratio (9.8:1) of your engine as it is now is not holding you back. A higher compression ratio increases the likleyhood of engine damaging ping at detonation at WOT unless a higher octane fuel is used.
if you want to improve your engines performance you want to do things to improve the engines ability to pump air. Intake , exhaust system air flow, cylinder head port airflow (cfm) and camshaft valve timing and lift.
Work on these areas first.

The engines compression ratio is coordinated with the camshaft valve timing to maximize the in cylinder compression pressure. but there are real world practical limitiation on how far you can go increasing compression ratio (even with a big cam) until you exceed the knock limit of pump gas. Its a slipperly slope. A little too much, is a lot too much.

You want to avoid riding the edge of that cliff as your engine octane knock limitation will change from day to day and as the engine ages and the weather conditions change. We won't even get into variances on actual pump gas tested octane performance.
You have lots of real world room to improve the engines performance without increasing the engines compression ratio. What works on the dyno for a few seconds test under controled conditions, does not work on the street were real world "as installed" conditions change rapidly.

ZZ4 86 Z28

iTrader: (1)

ok, well i guess i heard wrong from my friend.
what would you guy suggest i do first. I am purposely not spending all my savings for this summer on my camaro so I can get another car. This way I can do much more serious stuff to the camaro and not have to use it as a daily. I am just not really sure where to start.

doc221978

Milling the heads is not as much of an improvement as most people think. If you are looking at that much time and effort, a cam swap looks like a good idea. You would benefit more from that. That along with porting the heads 400 hp would be very feasible.

I am running 10.2 compression with vortec heads, and a xr 282 cam. It's over 400 hp, but i have to run premium with octane boost.

F-BIRD'88

You need to reasearch much further (than asking your friend) into the workings of an internal combustion engine and how the performance is effected by modifications including the compression ratio before digging in.

http://en.wikipedia.org/wiki/Harry_Ricardo

http://www.ricardo.com/ricardoStore/...t.asp?P_ID=149

required reading. There will be a test.

Sonix

iTrader: (1)

Grab some aluminum carbide burs and do some work on the ports and bowls.

ZZ4 86 Z28

iTrader: (1)

ok, so one of you is telling me to read more before i make decisions, and the other is telling me to go out and start porting my heads all by myself, lol. the only reason i listen to my friend is because he built his 85 sport coupe to run high 8s in the quarter all by himself. he built the suspension, motor, rear, (not the trans), and just about everything else you can think of. He is really old school though and doesnt always know what hes talking about, but when he gets his hands on things, he knows exactly what to do. thanks for the tips. im pretty sure if i got a cam with more lift i would need better springs too, but what else will i need? will i need lifters too? rockers?