I have 2 sources and each say something different.

Talking 5 heads one says they have 64 cc's and the other says 68 cc's

Which one is right?

Also the CR of the 350 in 1968 was 8.5:1 and the 403 in 1979 was also 8.5:1, but with major head cc differences. They had to use dished pistions at one point, how big is the dish?

Also what exactly is the "deck height" I know it's the mounting surface for the heads, with a gasket between them of course, but what is the deck height number?

I'm looking to buy a reman bottom end in a few years. I was kicking around 350 or 403, but I'm going to stick with the 350. I plan on using 5 heads and a .028 gasket from Mondello to bump up the CR. I also plan on swapping out the cam for the Edelbrock top end kit which makes 400 hp /397 ft lbs with "their" heads which are 77cc's along with 1 3/4 dump headers a 1406 edelbrock 750 CFM carb the 7111 manifold, and the cam (7112) which is a .496/.520 lift and either 110* or 112* lope.

I'm also going to swap the rocker arms, but in time, I like to 'build up' the car and I know that roller rockers free up some HP.

I plan on doing the work myself

 

According to wiki,68 350 had 64 cc combustion chamber either 9.5 or 10-1 comp depending on std or perf engine.

 

The distance between the crankshaft centerline and the head surface.

"Blueprint" is 9.330" ± .005" for the short deck vs 10.625" ± .005" for the tall deck.

All #5 heads were 68 cc ±.

The misinformation originated at 442.com and the Oldsmobile wiki has not yet been corrected.

Norm

 

I thought I read that someplace else, but figured I remembered wrong. Thanks for the correction.

 

Let's all remember that there are really three different combustion chamber volume numbers that get thrown around. There is the advertised number, the as-cast number, and the NHRA stock blueprint number. The as-cast numbers typically run a couple of CCs larger than the advertised number, and the blueprint number is usually smaller than the advertised.

 

Since "as cast" means before machining, the term (and the spec) is useless to anyone outside the foundry. After they were machined, they would meet the same "blueprint" specs that were given to NHRA.

What "advertised" number are you referring to?

Norm

 

Yeah I thought my Mondello book was correct, but somebody else told my 5's were 64 cc's too

 

I'm going to disagree here, Norm. I've seen what I call "advertised" numbers, which are the generally accepted chamber sizes. I define "as-cast" as the chamber volume of a new, factory-delivered fully-machined head. In my experience, the chamber volume on these "as-cast" heads tends to run a couple of CCs higher than the generally accepted numbers (ie, while BBO heads are generally accepted to have 80 CC chambers, I've found most heads to be a couple of CCs larger than that). Yes, the actual chamber volume is a function of how (and how well) the valves have been cut, etc. I assume that the reason for this "oversizing" was to allow for both production tolerances and to allow the heads to be resurfaced in the course of normal rebuilding without causing a large increase in CR. The NHRA published numbers run smaller than even the advertised numbers. For example, the D heads are usually referenced at 72 CC chambers, but NHRA lists them at 69.5 CCs.

 

Odds are, your "somebody" got that number from 442.com.

Free information, is only worth what you pay for it.

Norm

 

Have a set with 64 cc, had the same question years ago so we filled em, released each one and measured using water method. not like it makes areal hill of difference though get a valve job and you have less valve taking up space, not to mention the original head gasket was like .018 vs .044 for the felpro blue gaskets we buy these days. Every little thing makes a difference, alot of calculations if you want to know your exact compression. I believe the biggest issue with all this head confusion are the different programs they had going on back in those days. I have parts from the Ram Rod motor, and they are different from the regular engine.
Remember all this crap we are trying to decipher came from the advertising dept at Olds.
Wanna hear a wierd one?
The first car i ever owned was a 67 olds, it took me many a conversation with many a retired GM assembly line worker to figure out how the motor I had in my car came to be. The Motor was 425 two barel with a solid lifter cam! That thing would smoke the tires for miles! After alot of research and talking with people who worked in motor assembly plant at that time, i was told that basically anything you could want in a car or motor could be ordered special, it depended upon the level of senority the sales person had. As it turns out if your sales guy had the clout the sky was the limit. The car was a one owner car when i purchased it, and after the confusion i had about the motor i contact the old man who had sold it to me, and he verified that the motor had never been opened, He ordered the car with the motor built as such because he need to have a family car, and be able to tow a horse trailer with the car. So I know for a fact that quite a few facts and figures about these cars are not always 100% accurate.

 

What I call? Generally accepted? I define?

Not terms that are normally used in a production environment. Also not used in "blueprints".

I would expect any "over the counter" part to be well within all tolerances, as outlined in the "blueprints", that were used during its fabrication.

You found what you found. The reason you found it, might be open to discussion.

Your "etc" would include the head surface and any variations in the casting, which are also among the dimensions "called out" in the "blueprints".

If all the involved tolerances were stacked toward a bigger chamber (highly unlikely) I doubt you would pick up half of that "couple of CCs".

Is that an "engineering" term?

An "assumption" is only as accurate as the premise it is based on.

Fabrication is always done to nominal "blueprint" dimensions. Tolerances are included to define the maximum deviations allowed, due to tool/tooling wear. If one dimension, is not within those limits, the entire part will be rejected by quality control.

Production iron heads seldom need resurfacing during their lifetime. Those that do, should not need more than 2 or 3 thousandths to clean up.

Normal rebuilding would include valve grinding, which would compensate for that 2 or 3 thou.

NHRA is/was given the factory numbers, at the outset. The numbers they use, have nothing to do with the "real world". Does the term "red herring" sound familiar?

From my previous post:

Horsepower and torque were "advertised" for sales purposes, and manipulated for a variety of reasons. They could do it because dyno readings are not absolute measurements.

Chamber volumes, however, are actual production values that cannot be manipulated in the same manner.

Norm

 

 

The biggest issue, is people talking about things they do not know about.

This has been common knowledge, since the beginning.

Nothing in this discussion has anything to do with advertising.

Any Salesperson, at your local dealer, would have been happy to give you the details.

Hard to get a solid cam, lifters, and adjustable rocker assembly, when they do not exist.

If that is what you were "told" you were lied to. "Special" had nothing to do with anything.

For a buyer who chose to order, from the factory, his/her choice was limited to the boxes on the order form. If one wanted something else, it was common practice for a dealer to "install" items from its parts counter.

Not so common were the "dealer installed" aftermarket parts, that started this 50 year old myth.

If you wish to start your own thread, we can discuss it further.

Norm