BBC-Aluminum heads?

[xx_ED_xx]

If you would of got the 119 heads it would be 10-1

[Bandit]

These pistons have a dome +38cc according to Wiseco's website. Which yields 11:1:1 CR with 110 cc chambers according to them. Which makes my CR with Brodix RR heads with 115cc chambers ????

A local engine shop put my engine together years ago, so unfortunately I don't really know what they had to do to install the roller cam. From what I understand there's not much difference other than it costs about 5X more, and break-in is much less finicky.

[Bandit]

If you would of got the 119 heads it would be 10-1

Umm...that's not good news!
I was looking for around 9:5:1 CR, or at least some CR that I can live with on the street. I think 10:5 is way too high for 92 octane, am I right? Should I call Summit and tell them to get me the 119 cc heads instead?

[xx_ED_xx]

Not sure how long ago you ordered them but i would

[Bandit]

Not sure how long ago you ordered them but i would

OK I'm confused though. Right now my CR is fine with my factory heads for 92 octane. I don't know exactly what it is but below 10:1 for sure. My chamber size is supposed to be 113 cc. So with 115 cc heads my CR should be lower.
Where are you getting these numbers from if I may ask?

[JChristian1835]

I always thought a smaller chamber raised compression and a bigger cc lowered it...

[xx_ED_xx]

http://car.race-cars.net/calculators...alculator.html

If you dont know the cc of your heads then the arguement is m00t.

The too big cam helps a bunch with bleeding off cylinder pressure.

Get hard facts to make a comparison its alot easier that way. i am just taking the info you feed me tryin to help you out.

[Bandit]

http://car.race-cars.net/calculators...alculator.html

If you dont know the cc of your heads then the arguement is m00t.

The too big cam helps a bunch with bleeding off cylinder pressure.

Get hard facts to make a comparison its alot easier that way. i am just taking the info you feed me tryin to help you out.

Please, I am not trying to argue with you, just trying to figure out
A: What is the combustion chamber cc for BB chevy heads casting # 336781.
B: What will my final CR be with Wiseco piston 5039H6 (+38cc dome) using Brodix Race rite 115cc chamber heads.
If this info is totally unobtainable without CC'ing the heads then that is what I will do, but it will take time that I really don't have because I have to get the old heads off and have them CC'd. It would be nice if I could figure out what I am going to end up with in advance.

[xx_ED_xx]

Its cool...
But you have to understand you need all the info to make a correct choice
I just went thru this recently i thought the closed chamber heads on my 454 were 100 cc ended up being 110 cc so the compression i thought i had i didnt. so when i got my pistons i knew what my compression was going to be since i want to put a blower on it. and i want around 9-1 comp to do that.
Also the cam was humongous especially for 8.5-1 compression
so it was a dog til about 4000 rpm then it wasnt too bad. needless to say find out what you have. You are chagning the heads right? If your old heads happen to be 119 cc and you get this other set of heads your kinda doing opposite of what you were tryin to accomplish right. With that being said i have run 11-1 on the street with pump gas as well. Hell alot of the new cars do too so...

[Bandit]

Thanks for all the tech help, I see now that I will definitely need to get my current heads cc'd to find out where I'll be at with these new ones. (I guess that's what you've been trying to tell me all along)



After researching these GM heads on other sites, most sources say they are 113 cc chambers but some guys have reported up to 120 cc. And my heads have been shaved a time or 2 so who knows what they are at this point. Now I wish my pistons didn't have the +38 dome.
But I am not planning on boost anytime in the near future, so maybe a 10-11:1 CR might be ok after all.

Thanks again to all who helped me science this out!