I have a 68 400 engine with "C" cylinder heads. What are the really desireable cylinder heads for the 400 engine and is the type 'C' a good design and what is recomended to improve it. Thanks all!

 

Put the 400 G block in a corner covered in grease then take the C-Heads and all the 400 internals, buy a 455 block for $100, & re-build it. That's the best & cheapest way to improve it.

 

what would you gain by doing that? just curious because i have a 1968 442 also. thanks.

 

Sadly, the G-block 400 was apparently designed by the accountants. In earlier years, Olds used the same crank as the 425 in the 400 motor. This short stroke forged crank yielded a nearly square 400 motor (4.000" bore, 3.980" stroke) that was a very nice performance motor. Unfortunately when the 425 grew to the 455 in 1968, Olds again used the existing BBO crank with it's now 4.25" stroke to save money. To meet the GM-imposed 400 cu in limit on the A-body cars, the bore was reduced to 3.870". This long stroke, small bore motor has one of the worst bore/stroke ratios of any US-built motor. A 455 short block is definitely the easiest way to improve the situation, as Olds proved on the 68 H/O.