I have AFR 195 heads with the 74cc chambers. Can I get away with milling them down to 64 cc's without having any problems with the intake ports and bolt holes lining up? I am considering getting the zz383 and with 74cc heads, the compression ratio is gonna be around 7:1 .

 

sounds like you're asking 2 differant questions about 2 differant parts, or maybe i'm confused again. .030 is about the limit of milling without problems. there's a formula around here for amount milled to what cc it removes ,but i can't find it right now. i don't think milling is going to help get your compression anywhere near 7:1

 

certain shops can weld your heads to change the chamber volume. I forgot the name of this process, but a local shop does it for a reasonable price. other than that I ask why did you get 74cc heads? those chambers are huge. 7:1 comp is great for a blown or turbo car though

 

I got the 74 cc heads because they where $1,000 brand new on ebay. They are the L98 style heads.
You guys still didnt answer my question though. Will my intake bolt up to the heads if I have them milled down from 74 to 64cc? The ZZ383 will produce 9.1:1 with 64cc heads and 8.4:1 with 72cc heads. With that being said, that is why I ask my question. If I leave my heads alone, the CR will be very low.

 

new pistons.... about the only way your going to get your compression up to where you want it to be.

and as for your intake bolting up after having your heads milled, give your shop your heads and intake, after milling the heads, they will shave the intake as well to make sure it all bolts up.

 

Will I even be able to from 10 cc's on these heads or is that too much to mill? If it seems like i am gonna be screwed for comrpssion in the ballpark where I want it (10:1) then I may have to cancel the nitrous setup and focus on a blower. what do ya think

 

Holy ****, 7:1!!!

You can run like 50 psi without missing a beat, hope your ignition system can fire a B2 rocket!!!

I would find some pistons to up that CR, check out SRP, good pistions and great prices...

I just creeped over to their website. They list domed pistons that with a 70cc yield either 11.7 w/ 5.7 rods or 12.0 w/ 6.0 rods. Either could be knocked down some to lower your CR, I don't know by how much because I don't know how much material could be removed. I would make some calls and see.

Yeah, I know that is just what you want to do to a brand new engine!

 

i think people are missing what you said. it is actually better that you got the 74 cc AFR heads and are milling them down to 64cc. it will help to unshroud the valves. to answer your other question about the intake will have to be milled also. when you go to have your heads milled give the machine shop your intake also and they will match the parts up. a lot of people on this board swear by buying the bigger chamber AFR heads and having them milled down, so i think you may have done yourself a favor.

 

demon, thanks for the imput. IM gonna see what I can come up with from SDPC on the pistons that are in the block. How much can I bump up the compression by switching head gaskets?

 

With an open chamber (about 4" in diameter), each 0.010" milled off the the heads equals 2.0 cc's. So 0.050" will give you your 10 cc.

BUT

You will only increase your compression to no more than 8:1.

Sounds like you have inverted domes in that engine. If you want 10:1, you need at least flat tops or maybe domes with 74 cc heads.

 

you saying that I will get no higher then 8:1 with the 74cc chanmber or the 64cc chamber? I dont want to swap pistons on a brand new engine.

 

a73camaro, what are you talking about, im not sure i followed what you said. with the zz383 shortblock, 64cc heads will yield a very streetable 9.3:1 compression ratio. i think itll make for a nice engine.

 

true but can you mill enough to achieve 64 cc?? i personally would aim for 10:1 maybe a TAD higher, and i dont think you can mill enough to get that, and i wouldn't want to put pistons in a new engine either, so i would...

A) start looking at a different engine
B) think about a blower instead of nitrous (if 70cc = 8.4 then 74cc should equal around 8.0-8.2 not 7:1)
C) you got a great deal on your heads... couldnt you sell em for oh say $1300, and buy a set of 64cc's for that same $1300? (i would think you could anyways)

 

Let me ask, what makes you believe that your engine has 7:1 compression and is it at 7.0:1?

If you decrease the combustion chamber 10 cc in a 7.0:1 engine (from a 74 cc head to 64 cc head) you will only improve your compression at most a unit.

 

Is the block zero decked? since this will also effect overall compression. If your going to have them milled, spend the little extra change and have them angle milled, definately more bang for the buck since this will change the valve position and inherent a better flow characteristic as well as warrant better flow and a more effiecent quench. if you went with a .015 shim head gasket it's almost universally accepted you only gainaround .5 in compression which might be okay as a last ditch effort but make sure the heads and block are perfectly smooth since clamping/sealing needs to be spot on with such a thin gasket that wont soak up minor imperfections.

 

well with all this being said, it seems that I may have a few issues. I bought the ZZ383 is zero decked too. Maybe I can opt for the ZZ4 and try and find the loss hp somewhere else. Ill do some searches and see what guys have done with head cc sizes and the zz4 short block.

 

Bottled,

I am just curious why you are buying a new engine. I thought your engine was pretty new? Were you the guy that was having the problem with rings sealing?

 

Yes I am the guy that had a ring sealing problrem ona brand new GM crate engine. It got to the point where the dip stick was being blown up into the hood and the oil pan gasket was leaking severly. I have to tear it down to fix it so I might as well make some changes. I am not buying a new engine now. I just found a nice local machine shop that is gonna take care of my needs.

 

wait, why exactly cant the 74 cc heads be milled to 64 cc?

 

They can be. It would take 0.050" of material removal from an open combustion chamber.