[rad400]

4X 7H heads what is the cc's roughly and what would the compression be on a 400? If they are 98cc's what would the compression be?

[1qikta]

Originally Posted by rad400

4X 7H heads what is the cc's roughly and what would the compression be on a 400?

Conrad,

Most have 100-102 cc's stock. Depending on if you cut the heads look for around 8.0 -8.5. If you take 60 thou off you can get them to 92 cc's or so..

Good Luck.

I plan to sell a set this winter sometime...

[Craig Hendrickson]

4X-7H are 400 4bbl with auto trans, 98cc, 2.11/1.66" and screw-in studs. Roughly 8.0:1CR on a 400.

I found this on John Wallace's website: WallaceRacing.com That's a good place to look first for stuff like this.

[1qikta]

98'ccs is the "listed" CC but after testing a few sets you will think different.

[71 Ventura II]

"ALL" of the Pontiac iron cylinder heads were built with larger than advertised chambers. As an average "Add" +- 4-8cc's to the claimed size. Among other explanations it gives a cushion for serviceablitity of the product. Perfect example: My current 1968 #16's are/were rated @72cc but measured 78cc. Do a search and you will see the small chamber d-ports measure between 76-82+ cc's from the factory.

[gtoformula]

Here's another Pontiac cylinder head website.
http://www.angelfire.com/on/geebjen/heads.html

[David Holmberg]

Originally Posted by 1qikta

98'ccs is the "listed" CC but after testing a few sets you will think different.

Jay, you do know who "OriginalHO" is, right?

I suspect he's checked more than a few sets, among other things.

[Craig Hendrickson]

If one asks a simple question, one receives a simple answer. Note the use of the word "roughly" in the original question.

No offense taken to a more extensive answer.

So, what is the HP/TQ difference between 102CC and 92CC? It is about 10-12 increase (~5% for -10CC), everything else being equal. In other words, for every CC decrease, you will gain about 1HP/TQ (0.5%). You have to decide if all the other aggravations (shorter pushrods, milling intake surface, etc). are worth that relatively small amount compared to other changes like cam, headers, porting, etc.

I personally do not think so unless you have a NHRA Stock or SS class car and are looking for the last ounce of power.

Also, why not just change heads rather than throw $$$ at a set of 4Xs?

One more point: I happen to have a set of 4X 7Hs (1973 400 +0.030) on my 1976 TurboForce Firebird. Turbocharging it to 6-8 psi is worth about +200 HP/TQ (+80%) on the street. Supercharging would produce about the same increase. The last thing one would want to do with 'charging is INCREASE the CR.

[1qikta]

Originally Posted by David Holmberg

Jay, you do know who "OriginalHO" is, right?

I suspect he's checked more than a few sets, among other things.

David,

I understand. Since I am forced to run 4x's I have checked bout 15-20 sets(3h and 7h)...still have not found a 98cc set.

Sorry, Mr. H I wasnt paying attention...I still reference your book even today..Had it since the 80's

[David Holmberg]

Jay, I was just kidding with ya.

Craig, Jay runs the FAST class, and is doing a very good job.