I think I'm using the right word shave/mill to get the compression of my motor higher.

I'm looking to get 10:1 compression. Just wondering, I'm getting the iron Sportsman IIs 64cc heads.

So, would it be worth it to have them shaved to bump the compression a little more?

 

thats kinda high for a street car with iron heads

 

Would require premium gas, but it's not my daily driver any more, so expensive gas isn't a big deal, if it will get me a good amount more HP.

 

I wouldn't recommend it unless you plan on milling your intake as well. you'll also have to worry about getting the right quench height. 64cc with your pistons should give you about 9.5 plus you should be able to use a steel shim head gasket (since its iron) thats only .015. Your final comp won't be all that bad. I'd just leave it be. This way if later on you decide on flat tops or what not you will be able to choose whatever you want. Milling is not reversible!!

 

Yeah, that's what I was thinking in case I stroke the motor later on and get new pistons, if that might raise the compression too high with different pistons, thanks.

 

I would leave them alone. As mentioned above, milling is permanent, and the difference to the finished product so minute as to be unnoticeable. I'd be real surprised if bumping your CR from 9.7:1 to 10.0:1 would make 2 HP of difference.

I would not recommend using the steel shim head gaskets however. They simply do not survive. Every single motor I have ever torn down that had shim stock gaskets, without exception, including factory motors, race motors, and non-automotive engines, had signs of combustion leakage. A 9.7:1 motor with intact head gaskets will outrun a 10.0:1 motor with leaky ones, every time.

Again, the 2 HP max difference isn't worth the aggravation. And, that could even be the difference between being able to use regular gas and requiring premium gas. Something to consider.

 

RB, are you serious about the steel shim? Thats what came factory with the crate motor. I just put them under my 305 heads. .

 

Serious as a heart attack... YMMV

 

YMMV????? Whats the thinnest composite I can get a hold of??

 

I've been doing some searching, so you guys think the 200cc heads won't be too much for my motor. I guess it will be there for later on when I get a bigger cam.

 

Your Mileage May Vary...

I would recommend using a plain old normal Fel-Pro 1010 gasket. IMHO the reliability it gives is worth far more than a couple of tenths of a point of CR.

 

YMMV-I'll have to remember that.

Ok. Well I guess I'll see where these take me for now. When I tear the motor down this summer I'll let ya know what I find.

Thanx

Mark, Those are some of the best heads on the market for their price. There was a magazine who did a test on the top 5 heads and the WP sportsman IIs where the best out of the box head overall (I think all the heads tested were cast iron). I can't remember which mag it was though. Maybe someone else here would know

 

I have used shim gaskets to great success. I've never had one fail. I've taken apart many old running motors with shim gaskets and have not seen a problem with sealing.

Head gasket problems are caused by abnormal running conditions.
Like overheating the motor, detonation, preignition. If a motor is run like this, you WILL have problems with head gaskets and other stuff, reguardless of the thickness.
You have to remember a lot of people are really thick when it comes to their car. Like letting the motor ping and knock while going up a hill or running it on crap gas and or advanceing the timing too far.
You do want to check your head and block for flatness before install as ANY gasket will fail on a warped surface.
By using a shim gasket on a motor that isn't "O decked" you will
improve or maintain the quench action and bump the cr by about 1/2 a cr over a thicker Felpro composite gasket.
Your GM good wrench motor probabily has shim gaskets on it now.
Again as long as you don't abuse the motor as stated above, you can expect these gaskets to last the life of the motor.
If your motor is typical of most Goodwrench motors, the piston deck clearance will be huge (way down the bore).
So switching to a 64 cchead with a .039/.041" felpro gasket
from a 76cc head and a .015" shim gasket would onlly result in a
less than a .5 ratio increase. It will still not be 9:1 ,, That would not be worth it. If you use shim gaskets you cr will be 1 whole cr more than stock.
If it was me building that motor I'd have the 64 cc heads shaved to 58cc, use a shim gasket for final cr of 9.6:1.
Going from barely 8:1 (factory) to 9.6:1 will give a nice performance increase especially with the cam u have. While not being exessive.
When you add up all the little "not worth it's"... it makes all the
difference in the world.

 

So, you think by me going from 76 to 64 cc heads will barely give me 9:1 compression?

 

What I think is not important. What you think ,is.....

and will be the biggest factor in the performance of your car.

You can download a good compression ratio calc for windows
from Performance trends and play with the numbers yourself.

Then tell us what u think.

The piston dish volume is right about 13cc's and the piston deck clearance is typicaly .045"+++

you do the math.....

 

ok thanks.

 

Here's what I got. Tell me if I used the wrong stroke 3.750?

With 76cc heads I have 8.86:1 compression.
With 64cc heads I have 9.95:1.

 

That's funny Mark.....


Try again.

 

Thats a 383. Try 3.48.

 

Sorry, I didn't know, I remember reading 3.750 somewhere, and I did a search and only found that for 383s, wasn't sure if it was for 350s, guess not, as in stroked.

 

9.3:1 That's it.

F-bird, so how much HP would you estimate that I'll pick up? Or be at?

 

World Product's own advertizing literature claims bolt on 30/50hp.
Sounds reasonable to me.

There is potential for more with carefull preparation.
(porting, portmatching, maximizing final cr, selection of supporting components.)

That's up to you.