LT1 head flow

I am buying a set of late model LT1 heads and I have the option of punching out the valves from 1.94 to 2.05 intake and 1.50 to 1.60 exhaust. Is it worth the extra cash to convert it or should i leave it stock? How much power can i expect to gain if i go through with this? I have a fairly hot cam shaft and 8 to 1 compresstion pistons. I plan on using a TPI intake also.

You have a few problems. Stock LT1s had 10:1 compression or higher. It was still compatible with 87 octane through the accuracy of EFI and careful timing advance curves.

Running 8 to 1 with a cam any more than about stock will make a real dog out of it.

Your other problem is that the TPI intake will not fit on LT1 heads at all. LT1 heads are reverse flow heads and the bolt patterns, water passages, and accessory bolts are different. Even if you matched up the odd head bolts you would have massive water leaks since the gaskets and holes don't line up.

Larger valves will help a little, but they really show their ability in overbored applications or where the port flow has been increased (ported). The gains will be modest on a stock head or a stock bore.

Didn't we have this conversation before ? :)

http://www.automotiveforums.com/vbulletin/showthread.php?t=327325&page=1&pp=15

http://www.automotiverebuilder.com/ar/ar99928.htm

Here is a tech page for LT1s that verbally explains the differences between classic 350 stuff and LT1 350 stuff.

Thank you for the information. turns out you where right. the machine shop said the heads would fit when i asked them, but that is becouse they thought i was using a LT1 block. And no we had'nt had that conversation before, i simply wanted to know if i would gain much horsepower if i punched out the heads. but becouse those heads are out of the question that does not matter. I do want to thank you, your advise made me double check what i was about to purchase, you saved me about $180.

You bet. Six years ago I made this exact mistake :) I was able to resell the heads for the same money, but I felt like a dope :D