Transam461

EDITED VERSION

Are the chamber volume sizes that are usually quoted, typically correct, or do they normally measure larger or smaller? I know on Pontiac stuff, alot of the time, the chamber volume will actually measure larger than what is normally quoted, but I wasn't sure about Oldsmobile. The heads I have a 1969 "C" heads, and people usually quote them as being 80cc. They are currently at the machine shop, but I will measure them when I get them back to be sure, but in the meantime I was just wondering.

1970greensupreme

ball park but remember, surfacing them will make chamber vol smaller, valve job could make them larger so better off checking them.

Doug Carner

ive heard they range from 80-82cc's. I just got my 69 442 C heads cc'd today and they are 80.

OLDSter Ralph

Published where ? Who is "they" ? 80 cc's sound about right for "as manufactured" and volume observed by others with original cylinder heads.

Fun71

Exactly what my thoughts were. I have a set of G heads that measured in the 82-85cc range and "supposedly" they are 80cc as-cast.

Transam461

Just about everywhere, doing a quick search on google, most Olds websites list the 67-69 Oldsmobile "C" Head as having an 80cc Chamber, in FACTORY form. Thats what I was refering too...

OLDSter Ralph

#1. Your thread specifically says "Factory published". That says to me.......Oldsmobile factory/engineering. Googling "Olds websites" would be excluded.
#2. If you are using web sites as a standard, that would point to a measured "observation". Something posted on the internet isn't always accurate.
#3. What if I told you Oldsmobile published head volume spec's for (455) 1968, 1969 H/O and 1970 W-30 as being 69.75 cc's ? I can just about bet you none ever came from the factory with those numbers.
#4. The 80 cc's you are quoting is merely an observation of heads as manufactured. You only need to remove .005" from a 455 head to change the volume 1 cc.
I hope I helped clear things up.

Transam461

No kidding, I know exactly how all of this stuff works. I guess I shouldn't have said "Factory Published". I was simply asking if the Oldsmobile heads were usually close to the normal 80cc that is "quoted" for the factory "C" head, or if they had a reputation of being either "Larger" or "Smaller" than what is normally "quoted". I am huge into Pontiacs, this is my first Olds, and the normal for Pontiacs, are most head chambers measure "Larger" than what is normally quoted, depending on which head is in question. I didn't realize I would start such a big stink over something so simple. The Olds crowd sure is a lot tougher than the Pontiac crowd Lol.

Transam461

I fixed the Title as well as the description, so that future people don't get confused. Thanks to everyone who has replied.

OLDSter Ralph

I wasn't trying to be harsh. When people come here saying "I heard", "on another website", "on Facebook", etc. they are quoting things that may or may not be accurate. "Quoted" is an observation from someone. A valve job can increase volume as Fun71 pointed out and reduced if the heads are resurfaced (milled). How much variance are you talking about ?
I am sure Pontiac published head cc and other specs that varied from what is observed on parts people have.

Transam461

That's ok, it's all good. Emotion is undetectable on forums and text messaging, and sometimes people take things the wrong way, like I did above. Sorry about that. I do understand the valve job can gain a cc or two, and also the rule of losing 1 cc for every .005" of head milling is usually pretty accurate. The last sentence that you included above, is essentially why I ask this question, except I was asking if what Olds Published was accurate, compared to what people actually observed them at, in factory form of course, no milling, no valve job.

VC455

Heads generally have larger volume than published to make sure the compression ratio doesn't exceed rating AFTER the heads (and/or block) are milled during a rebuild. This is not just a Pontiac/Oldsmobile thing.

During the horsepower wars of the 1960s, people milled the heads severely to get to the factory volume in order to improve their quarter-mile times. During teardowns, NHRA checked chamber volume to ensure it wasn't below factory specs.

Transam461

Thank You

OLDSter Ralph

Excellent information.

83hurstguy

My D heads CC'd at 82cc even though Olds published the volume at 69.75.

64Rocket

pretty much all the heads i have dealt with , they all measured 84 to 85 CC's. Of course i did not do any "D" or "F" heads. But B's, C's, E's, G's and Ga head were all at least 84 CC's.
I just machined .025 off a set of "E"'s and they are now 80CC's
I'm sure there are exceptions, but that is what I have found.

Gene

Transam461

Thanks. I just got my 1968 "C" heads back from the machine shop, and measured them with my CC kit. They previously had ".020" stamped in the deck of each head(before taking them to the machine shop). I had the machine shop do a valve job on them and resurface them to clean them up to make sure they were flat. I measured them and they now come in at 76.5 CC. I'm not sure how much the machine shop took off them, but I know it was just enough to clean them up, so not much.

Fun71

I would be very happy with those numbers.

Transam461

Most definitely happy. They will have right at 10.0-1 on the 455 we are building with the 18cc Speed Pro piston, block Zero Decked, and the .039" Felpro gasket. The heads have mild pocket porting, and will be running the Erson TQ50 camshaft and matching Springs that I bought from Mark, so it should make some decent power on pump gas Im hoping

joe_padavano

This comes up a lot. First, the chamber volume for mass produced heads will vary, typically by 2-4 cc, just due to manufacturing tolerances. Second, the numbers published in the NHRA blueprint specs are the minimum allowed chamber volumes for stock-class cars based on submitted manufacturer's design data. These numbers, which are the ones typically quoted in books and other resources, are not as-cast, and are definitely not what you would have seen had you pulled the heads from a brand new motor and checked them. These are the minimum volume you were allowed to mill the head to and still qualify as "stock". Olds heads as delivered were nearly always larger than the blueprint numbers. This was done intentionally - in a mass production environment you want to be sure that a part made at the extremes of the allowable tolerances would still function. Heads with larger than blueprint chambers would work just fine on a production car, but if the heads were too small, the engine would be subject to pinging and thus warranty repair work. Also, after half a century, you have no idea if one head that you have in your hands has ever been worked on. Has it been milled? Have the valves ever been cut? Unless you took delivery of that car from the factory, you don't know what was done to it. Any post-delivery engine work could have changed the chamber volumes somehow.