Hom much should I have milled on a set of gt-40 with a 64-65cc and a NA 306?

[bjl95mustang]

I'm doing a budget build with a stock rebuilt 302 .30 over pistions an performer intake and a set of 351 gt-40 heads with a 64-65cc chamber (i just checked them) and a tfs 1 cam and 24 lb injectors. I'm going to stay NA for a while and i'm trying to deciede on how much to get milled off of the heads to get a decent cr. Any help would be great.

 

[Joes95GT]

If the pistons are supposed to retain the stock compression and the heads indeed are 64cc, you are looking at something like a 8.8:1.

Without having the heads checked, I'd mill 'em 0.030". Anything more than that, you are running into intake manifold sealing problems, and possibly weakening the head, which could lead to head gasket sealing problems.

Ideally, you could run a 54cc (and probably smaller) chamber and still run safely on pump gas.

Joe

 

[blksn955.o]

well I had mine shaved 35 and then found out when thumper did them that they already were shaved befor that and I now have a total of 60 shaved . I am going to have my lower intake shaved now so I have a good matched surface. I need to go over my shave and piston as I fig. with the 35 I would be close to 10:1 but now am lookint at more like 10.5+:1 at least. Surface still looks good, and I did not have any issues with the heads sealing as I did run the heads on the block with the shave some 3k miles before I sent them to thumper (he shaved them 4-5 more to make sure they were flat).

Another thing I want to have looked at is I heard that some gt40 heads (on cobras mostly) were shaved from the factory since the gt40 had a larger chamber than the e7 and made less comp. and that is were they get the cc for the cobra heads (I have a set of a 95 cobra, so its kinda important to me). This also my explain some of the extra shave on the heads, as I know the guy that had the heads befor me and he never had more than a 5 shave done.