Heads for 1969 Pontiac 400 CID ??

[j5ball]

I am starting to rebuild a 1969 Pontiac 400 CID block. I only bought the block and crankshaft. I will be replacing the crankshaft with the steel crankshaft that comes with the stroker kit I will be installing in the engine.

I really cannot afford $2k+ new heads from summit or jegs. So I need to buy some heads I can rebuild. I found some 6x heads for $325. Here are the details on the heads

DATE CODE 1166 which is 11month(NOV) 6th day 1976. They were removed from a pontiac 400 motor. I believe these are 101cc chamber heads with 2.11 intake and 1.66 exhaust valves. These heads are drilled and tapped for screw in rocker studs. They have been cleaned and checked for cracks and straightness Guides have been replaced. Work done by BAKER ENGINEERING.

2 questions:

1) I am trying to drive as much RPM with the new engine as I can (I WANT THE CAR TO DRIVE LIKE A SCALDED CAT.) Do I care if these are 6x4 or 6x6 or 6x8 heads. From what I have read the 6x6 head drives more RPMs than 6x4. Does this mean a 6x8 head will drive more RPMs than a 6x6 head.

2) I thought the smaller the chamber size drives higher combustion which drives higher RPMs. The heads I am thinking about buying are 101cc chamber size. I see summit and jegs sell heads with 85cc chamber size. Do I want smaller or larger chamber size?

Help educate me. I have read my Pontiac book and looked online. These are not helping me.

Thanks.

 

[melsg5]

When you say as much RPM as possible you may already be aware that a stock Pontiac block is not a high reving engine. The typcial engine should not go past 5,500 RPM. The exception would be something like the Ram Air IV which uses a steel crank amoung other changes. So unless you are doing something more to the block concerning the oiling characteristics you still should not safely go past 5,500 RPM. Small chamber size generates higher compression which produces more power but the brains in any engine as far as potential RPM is the camshaft. That potential RPM is then limited by air restrictions caused by the intake and exhaust systems. Once you can reach that potential RPM you then have to look into will the crank, rods, etc. survive at that RPM. Concerning head flow, read the link below where they did a comparison of all the popular heads and list pro's and con's. I also recommend if you havent already seen it the book below. The next link explains the difference between 6x-4 and 6x-8, the 6x-4 having a higher compression since it is smaller chambered. Generally any of the 6X seem to be problematic with regards to being able to generate a decent amount of compression and you may want to look elsewhere as suggested in the last link.

http://www.wallaceracing.com/ultimatehead.htm

https://play.google.com/store/books...SEM&utm_campaign=PLA&pcampaignid=MKTAD0930BO1


http://www.pontiacstreetperformance.com/psp/6XheadID.html

http://www.hotrodders.com/forum/1978-trans-am-se-400-220hp-4spd-cam-upgrade-138543.html

 

[Too Fast]

Lots of reading from Mels links, but some great reading on Pontiac heads/engines.

Great links as usual, Mel!