This question is of great interest to me since I also have a '76 Corvette two-bolt, so I did some "look-see" research at nearby "Joe's Machine Shop" in Ashland, VA. The proprieter is Mr. Joe Butler who showed me a shelf full of track trophies which he said is only half of his trophies for circle track racing with the rest at home and he says he would not run a four-bolt block on the 1/2 mile tracks he races on (running a 5.34 rear gear!). Then he showed me two blocks in his shop where it was clear that the outer bolts of the four-bolt tap through the block webbing at the bottom of the cylinders while the two-bolt blocks are solid there and I was able to look at both examples there in the shop, the two-bolt was being bored/honed at the time and I could see down into the cylinders. I wish I had a picture to show, perhaps someone else has a good picture of this? Of course it is clear from comments on this Forum, magazines and conversations with racers that there are variations on this belief and others and I do not know what class Joe runs in, but he said he is running a two-bolt 377 with a 5.34 rear gear for the 1/2 mile tracks. That's good enough for me to just rebuild my two-bolt 350 and that is what I plan to do. If anyone else has a picture of the bottom of the SBC cylinders that would show this point clearly. I was surprised due to my dinosaur experience limited to flatheads where the cylinders go straight down with no webbing at all, but I can see how the webbing at the bottom of the cylinders in the SBC add strength and the added holes could weaken this, but this means to me that it is OK for my intended motor at no more than 300-320 H.P. As Streets said, for the street there is probably little difference, but to me this means that the two-bolt is OK and according to Joe Butler, the two-bolt is actually better, so I will go ahead with a mild two-bolt 350. If you plan to use a blower or push 400 H.P. or more that is your call to use/not use a two-bolt, but surely if 1/2 mile racing is OK with a two-bolt that is a comfortable cushion for the two-bolt on the street? It would be interesting to hear from a drag racer who has used say up to 250 H.P. from nitrous, but maybe all of this is relative to the rods as a weaker part. Maybe the main caps are much less of a problem than the stock rods and Joe Butler encouraged me to purchase new rods rather than recondition the old ones. As usual I talk too much and it amazes me how some of you can say so much in a few words, John Wayne/Gary Cooper genes?

Don Shillady
Retired Scientist/teen rodder