Doug Carner

Does anyone know the cc specs on a C head?

Fun71

I measured mine at 82 to 84 cc.

Doug Carner

I've heard that they run somewhere between 79-80 but wasn't sure. I want to build a 455 and set my numbers matching 400 block aside. I want to use my C heads and maintain the factory 10.50 to 1 compression

70W-32

You'll need to have your hads cc'd and then build you engine accordingly ie piston dish cc, piston to deck height, head gasket thickness, and head cc.

matt69olds

The “blueprint” volume is 80cc. In reality, as someone already mentioned it’s 82-84cc. Only way to know for sure is to measure.

OLDSter Ralph

80 cc's would be the "as manufactured" number. At one time the "maximum legal compression ratio" used a figure of 69.75 cc head volume, .017" head gasket thickness, .002" below deck piston, pistons with 13 or 15 cc dish. .005" needs to be removed for each cc. Generally, that means .050" milled from each head.

cutlassefi

The factory comp numbers are a little happy. It’s actually less than 10.25:1 in most cases.
And on today’s gas I’m not sure I’d go above that.
Just an FYI.

ajr2820

FWIW. My C's measured 82cc. They were untouched when I got them. I use the Wiseco pistons (15.0cc dish), the Cometic .027 head gasket, and had the deck cut .005" and am right at 9.97:1.

Doug Carner

I am trying to get the compression ration at or near factory for that year. I am trying to calculate it but I now need the deck height. Anyone know the deck height of a 1973 455F block?

cutlassefi

Right about 10.630.
Not sure why you would try to do yesteryear compression ratio when you don’t have yesteryear fuel available. But that’s obviously your call.

jensenracing77

What are your end goal for HP and Torque? What are you using it for? There can be more than one way to get to your end goal but you need to factor in today's gas and oil. I built a 70 455 with less compression than stock (9.8:1) because of modern fuel and run a roller cam and rockers because of modern oil. Also used Wiseco pistons and a cam that cutlassefi recommended to hit my goals of 500 torque and 400 HP with A/C, power brakes, stock intake and exhaust. The engine ran on the dyno at 512 torque and 425 HP. I would not go over 10 compression. I am a purist nut on a restoration and still would not go with original compression

ajr2820

Also, my combination above with an Erson TQ40, mildly reworked small valve C heads, Torker intake and a Holley 750CFM Ultra Double Pumper made 400HP/513TQ on 93 octane pump gas...and that was hurt from having too little clearance on the mains. Likely would have made more had I not messed up.