Pontiac heads on a 400,what does 7J2 mean?

[Thumprkils]

I have a 400 in the shed with 7J2, or possibly it says 712. sure its 7J2.
What aree they in comparison to the 6x heads,actually do have 3 400s,and 0ne bare 455, the first 400 i spoke of whipped everything on the street, sorry chevys, the other with the 6x ive never used, if the 6xs are better, my 82 TA is gonna rock, thanks for any info.
One more thing the 400 has a preformer intake,with the 7J2 heads, and the 400 with 6X has intake marked with these nubers, under the theromo housing D305,and by the carb hole 486140,can someone tell me a little info bout the last intake and which will will be best thanks.

[TorinoGT69]

The 7j2 heads are small valve heads the 6x would be a better choice. Of course 6x heads are extremely low compression heads so might want to have them milled to bump up the compression a little.

[Thumprkils]

Originally Posted by TorinoGT69

The 7j2 heads are small valve heads the 6x would be a better choice. Of course 6x heads are extremely low compression heads so might want to have them milled to bump up the compression a little.

wow you really think the 6x are better than the others?, the 400 with the 7J2 s rans fannntastic, this other 400 has a lanati 292 cam and i will add the edlebrock, preformer,to go in an 82 TA, what do you think this 400, preformer,and 292 will do?

[sixt8bird]

Originally Posted by Thumprkils

wow you really think the 6x are better than the others?, the 400 with the 7J2 s rans fannntastic, this other 400 has a lanati 292 cam and i will add the edlebrock, preformer,to go in an 82 TA, what do you think this 400, preformer,and 292 will do?

The heads are 1972 400 200HP 1.96/1.77 8.4cr . They have pressed in studs and are not very good for performance heads, unless a ton of work is done to them. You are better off with the 6X #4s they were on the 1976-1978 engines. The floor is raised on the 6 X heads which give a better cylinder charge.They also have screw in rocker studs and 2.11 1.66 valves.The best ones are the ones from the 350s and the 4 sp 400s. They have a smaller chamber and will give 8.2 compared to 8.0 . If you really want good performance then go with the 1968-1970 heads that came on the performance 400s. These will have 72-76 cc chambers and big valves, they will also boost compression to about 10-1 which can still be run on Premium gas. here are some numbers to look for. 16,62,48,12,13,670 to name a few. I run a mid 12 sec car with stock #16 heads on a 400 built stock and run Arco gas. If you get a set of these heads I would also recommend a cam that is in the 224-234 with a 114 deg LSA for a broad power band. What is the 292 Lunati cam specs at .50 lift. Isnt that around 244 degs ? If it is, you are missing alot of power that can be gained raising the compression. This cam is built for 10-1 and up engines. High stall speed etc.

[TorinoGT69]

I agree with sixt8bird, also on the cam I would go with a split pattern design with more duration on the exhaust side.

[Thumprkils]

guys your knowledge is way out of my league, probably your wallets to, thanks for your help,
I have 4 - 400s , one 455 blk, 2 preformer intakes, 2 apparently stock 4 bbl intakes, the lanati cam is on a 400 with 6xs-stock 4bbl, have a 400 w a set of 4xs- preformer,400-6x-stock int, then another
with 7J2s and preformer, which combo is best, just a po boy type mech, thanx

[TorinoGT69]

455 with the lunati cam, the performer intake, and 6x heads. Thats your best option with the parts you have.

[sixt8bird]

Originally Posted by TorinoGT69

455 with the lunati cam, the performer intake, and 6x heads. Thats your best option with the parts you have.

Ditch the heads on the 455 and put on the 6X from the 400. I am not really to thrilled with the Performer intake. It flows about the same as the stock 1968-1972 stock ones which do actually work pretty good but a Torker II or an RPM with a Holley 850 DP and some good 4 tube headers would be the best choice. Thats if you open up the 6 X s up some. That cam is crying for some head porting to make it come to life and a 3.55 with a 2600-3000 stall would be a road terror!!! Pontiacs do like a split duration cam shaft unless the heads have been port modified to get the intake and exhaust ratio to work right with the cams that are ground straight up.