The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post

**THI** · 09-29-2021, 10:37 AM

This to keep in mind of Big Block Chevy's:

Somewhere around 1980 they went from Series Cooling to Parallel Cooling - Parallel Cooling is better, if you get a block that is Series Cooling you can add the additional holes to the deck to change to parallel cooling, you need to use a later head gasket if you do that, one that has the proper holes and block offs for Parallel Cooling.

Depending on the engine, somewhere between 1977 and 1979 the Large Oval Ports were replaced by Peanut Port heads. I have a 1978 C20 with Large Oval Port heads and a 1979 C3500 with Peanut Port heads - The Large Oval have about 1,000 RPM more operating range than the Peanut Port in stock form.

Stay away from Gen V Big Blocks (1991-1995) as they can only use Gen V or Gen VI heads, and they are still a flat cam block. If you do not mind the flat cam block, you can bolt a set of Gen VI L29 heads on a Gen V block (7400 Vortec heads) and the Gen V's have a better oiling system than the Mark IV blocks, but Gen V blocks usually come with 156 casting Peanut Port heads - the smallest and least desirable Peanut Port heads.

Gen VI blocks have factory roller cam capability, Priority oiling system and usually come with Vortec heads - flat-top pistons with the Vortec heads yields around 9.3:1 compression and works with low octane fuel. However, most have no mechanical fuel pump pad except a few replacement and crate engine blocks. I stumbled across one of those "few" a couple of years ago, I will be putting that in my 1978 C20 when the time comes to restore the truck.

09-29-2021, 10:37 AM	#6
THI Active Member Join Date: Jan 2017 Location: Traverse City, MI Posts: 173	Re: Wtb 454 This to keep in mind of Big Block Chevy's: Somewhere around 1980 they went from Series Cooling to Parallel Cooling - Parallel Cooling is better, if you get a block that is Series Cooling you can add the additional holes to the deck to change to parallel cooling, you need to use a later head gasket if you do that, one that has the proper holes and block offs for Parallel Cooling. Depending on the engine, somewhere between 1977 and 1979 the Large Oval Ports were replaced by Peanut Port heads. I have a 1978 C20 with Large Oval Port heads and a 1979 C3500 with Peanut Port heads - The Large Oval have about 1,000 RPM more operating range than the Peanut Port in stock form. Stay away from Gen V Big Blocks (1991-1995) as they can only use Gen V or Gen VI heads, and they are still a flat cam block. If you do not mind the flat cam block, you can bolt a set of Gen VI L29 heads on a Gen V block (7400 Vortec heads) and the Gen V's have a better oiling system than the Mark IV blocks, but Gen V blocks usually come with 156 casting Peanut Port heads - the smallest and least desirable Peanut Port heads. Gen VI blocks have factory roller cam capability, Priority oiling system and usually come with Vortec heads - flat-top pistons with the Vortec heads yields around 9.3:1 compression and works with low octane fuel. However, most have no mechanical fuel pump pad except a few replacement and crate engine blocks. I stumbled across one of those "few" a couple of years ago, I will be putting that in my 1978 C20 when the time comes to restore the truck.