I bought a set of GTP ported heads and the port matched intake from a guy a couple of weeks back. The heads were advertised as being milled to 52.5 cc and the intake had been milled accordingly to match. I thought, no big deal then. My static compression would have fallen into the 11.5 range and the dynamic in the 8.2-8.3 range. Now, here the trouble begins.
I get the heads and right off I can tell that they look to have been milled a lot. The valve ridge is actually sitting up out of the seat. I am sure that they seal, but there is a very good visable ridge there. I took the heads to my local machinist and had them cc'd. The result came back as 47cc. I wasn't even aware that stock castings could be milled this much. Other than this the heads look fine. However, this blows my dynamic compression way out of range to above 9.1 I use this as a street/strip car and I don't see it running on pump gas. The guy I got them from swears that he ran his 383, flat top car on 93 octane all the time with these heads, even on nitrous without any problems at all.
I just need some insight from some of the more knowledgeable guys on here regarding the milling on these heads. Are the maxed out at this point? Should I even attempt to run them? Also, my compression is calculated with the CC306 in mind. Could I correct the dynamic number with a custom cam? Bret??
The guys is basically refusing to take them back even though they aren't what they were supposed to be. I could probably get my money back from mastercard if I really push the issue though. Thanks in advance.
Josh

 

The ported LT4 heads I'm using with 2.05 valve are the same what you discribed, and these are not the only set I've sean like this. Don't think you could go this samll with straight milling with a 23* head. I aslo couldn't see how they cc'ed the cambers with the valves higher than the deck, the plastic plate will not sit flush on the head deck.

 

i had my heads milled down to 48cc,also i used 0.29 head gaskets and i run 93 octane all the time with no problem.

 

Josh,
I was just wondering what cc piston you are running and is that 0 deck?

 

The block has not yet been decked. I have a set of -4 cc flat top Probe forged pistons. I am just worried that the compression is going to be too high on this setup. I had everything purchased with the 52.5 cc head in mind. I am going to get some pics of the heads up tomorrow morning so I can hopefully get some more opinions from the forum.