[Givindabird]

I'm in the process(as money allows),of putting together the parts for the edelbrock perf. rpm combo for the 400 in my'78 T/A.It will be a long time before I can afford aluminum heads.I have the 6x heads,but I've come across some #16 heads 2:11,1:77,72cc,I can afford.My questions are; what octane of gas will I need to run with the #16's,would I be better off spending the money on shaving the 6x heads to a desired comp. ratio?Also, do I need to have an adj. valvetrain with the perf. rpm camshaft and what's the best way to go about that.I'm finally out of questions for today(I hear the sighs)LOL.I'd also like to thank you all for contributing to the love of Pontiacs that I also have felt for a long time,even though I'm a new guy here.Thanks Al

[Givindabird]

I'm in the process(as money allows),of putting together the parts for the edelbrock perf. rpm combo for the 400 in my'78 T/A.It will be a long time before I can afford aluminum heads.I have the 6x heads,but I've come across some #16 heads 2:11,1:77,72cc,I can afford.My questions are; what octane of gas will I need to run with the #16's,would I be better off spending the money on shaving the 6x heads to a desired comp. ratio?Also, do I need to have an adj. valvetrain with the perf. rpm camshaft and what's the best way to go about that.I'm finally out of questions for today(I hear the sighs)LOL.I'd also like to thank you all for contributing to the love of Pontiacs that I also have felt for a long time,even though I'm a new guy here.Thanks Al

[dyingbreed]

6X #4 or 6X #8 heads? Just curious!

db

[Givindabird]

I didn't know there were different 6x heads, how do you tell the difference?(probably dumb question,right?)They are off a w72 engine if that tells anything.

[Skip Fix]

The #4 are smaller chambers than the #8s and off 350s or TA6.6 motors. The stamp is on th boss near the valve cover urface like the AC bracket bosses.

#16 will definitely push the limit for pump gas and compression, expect some pinging or octane booster/race gas.

[Brian Baker]

I'd go with the 6x-4 head, shave it .030" which will bring the cc's down to about 86. This will yield a pump gas friendly 9.0-9.5:1 compression ratio.

Install 7/16" rocker studs. Whichever rocker you decide to run, make sure you have a "polylock" nut so you can adjust lash on it for the Performer cam.

[Givindabird]

Dying breed they're #4 6x's,Skip Fix thanks for your help again(like when you helped me with my disc rearend swap)Brian Baker thanks for your much valued help.I knew I could count on a bunch of PONTIAC guys!GB

[Brian Baker]

Just be sure to have the machinist shave the same amount off of the intake mounting surface of the head. Otherwise you'll have intake manifold alignment issues.

[dyingbreed]

GIVENDABIRD,
Not to contradict Brian Baker and others, who has alot better knowledge of the 400, but from what I've heard and read the #16 heads would give you approximately 9.0 - 9.5:1 CR without milling the heads. To get this CR from the 6x-4 heads you would have to shave them along with the intake as Brian stated. You may be able to save $ by using the #16 heads, since you wouldn't have to machine both parts (heads & intake). I've heard positive feedback from people using the #16 heads on 450+ hp motors and using 92 octane pump gas. However, I've been told that the #16 heads are not tapped for the power steering bracket, but this problen is an easy fix. If you decide to go with your 6X-4 heads, they are more desirable to work with than the 6X-8. This info is just something to think about.... when in doubt, I'd listen to others who have more experience than me!!

db

PS- I am facing this same frustrating dilemma at the current time !!!

[Givindabird]

db,thanks for the added info.It's a hard decision to make.I use my T/A as a weekend street cruiser,so if I had to run higher octane it would be o.k.,I just want to make sure that '79 Camaro in the neighborhood doesn't pass me up in the h.p. department.I love givin' him a weekly whoopin'!Thanx again gb.

[Brian Baker]

#16 d-port on a .030" overbore 400 is definately at 10:1, maybe a little higher. Might be ok on pump gas (92 octane or higher) but why risk it when the 6X heads are plentiful and still cheap in the junkyard. Most junkyards view heads from the 70's as "smog heads", so they're priced cheap accordingly.

[Givindabird]

Thanks again for all the help and info. guys.Like happens alot with me I took too long deciding what to do and the guy sold the #16 heads.Looks like decision made.Machine shop here I come,ready or not,with my 6x #4 heads.Maybe I can talk them into replacing the 1:66 with 1:77's.Hmmmmmm.....then shave them to 72c.c.'s,then use pure nitromethane,then pay up life insurance for wife and kid.Thanx gb