Guys my machine shop sold me some liberty alluminum heads for my 68 396 L78 block. Bought some manley head bolts but it seems the new heads are a half inch higher in size so the bolts go in only a half inch into the block. Machine shop said don't worry about it but at the end this will be a 500HP 450 Ft Lbs torque engine...should I be worried? Just seems they should go in deeper no?

Sam,
Are all of the bolts too short, or just the ones across the exhaust side ?? Some of the aftermarket aluminum heads need 4 longer bolts at the exhaust ports. Personally I think that 1/2" is pushing your luck. Have you measured the heads ? How about the Manley bolts ? Compare them to the original heads and bolts ? I think I might have a set of ARP bolts at the shop I can measure on Friday, I will try to remember.

The minimum length of any threads should be 1 1/2 times the diameter of the bolt. 1/2 inch bolt would need 3/4 inch of threads. I was a tool and die maker for 42 years.
fasteddies68

Take a look at how many threads you have on the block. The top of the block where the head bolts go into the water jacket is not very thick on some that I've looked at. Ideally, I like to have enough threads on the bolt/stud to take advantage of the threads available in the block.
Does anyone have information on the thickness of the top the block on a given casting number?
Squido

OK I am going to see the difference on the old heads and the new ones and report back thanks guys.