[pjdutton]

I have a pair of 94 heads off a 71 350.I also have a pair of 6x8 heads.Both sets need a rebuild.Which heads are the better to rebuild and why?

[P@blo]

The #94's will have the small intake valve so I would go with the 6X but don't get rid of the 94's. You can install larger intake valves down the road if you want to use them and I think the CC volume on either head will be similar. I think the 6X is better but doubt you would notice the difference between the two with both having the 2.11" intake valve.

http://www.wallaceracing.com/head1.htm

[form406]

depends what your using them on as well...

[pontorquer]

Go with the 6X's ! They have hardened valve seats and screw-in studs and are excellent heads ! Valves sizes are 2:11 intake and 1:66 exhaust...inches.
Pontorquer=PONTIAC=TORQUE MONSTERS !!!

[74Grandville]

I would not go with either if this is for a 350. 6X-8 heads will give you really low compression i'm guessing 7.6:1. Find some heads with a chamber of 72-80cc's

[b-man]

Originally Posted by pjdutton

I have a pair of 94 heads off a 71 350.I also have a pair of 6x8 heads.Both sets need a rebuild.Which heads are the better to rebuild and why?

Hard question to answer without knowing what size engine they're going on. Also need to know what you're expecting out of the engine, intended use is a factor as well. A bit more info would be very helpful.

[INJUNTOM]

i agree, you can't run those particular 6Xs on a 350...you'll need the 350 version.

if you are building a 400, those 6Xs would be perfect.

if you are building a stock driver 350, then those 94s would be perfect.

if you are building a performance 350, then you'll want the 350 version of the 6X, or just put bigger valves, and screw in studs in the 94s with some port work to take advantage of the larger valves.

[pjdutton]

Sorry for lack of info.I want to fit these to a 400.Machine work is not a problem.Over here in the uk you use whatever you can get your hands on.THE studs on the 94 heads have been pulled and I was thinking of fitting B/block chevy studs.These 94 heads have smaller combustion chambers so I will up the compression a bit but I don`t know if the ports are better or worse than the 6x heads.

[b-man]

The 6X-8 heads would give you about 3/4 to 1 point less compression on a 400 (about 8:1) than the #94 heads (about 8.75:1 to 9:1).

Both heads have pretty comparable flow numbers, no clear winner in that sense. I would suggest upgrading the #94 heads to 2.11"/1.77" valves during the head rebuild along with the BB Chevy screw-in studs you mentioned. The new larger diameter seats will be cut into 'new' material, putting the valves where they should be in the chambers and not sunken in like heads with a few valve jobs.

For a 400 engine the #94 head is a better choice since it will put your compression ratio up where it needs to be for best performance. If you were building a 455 the 6X-8 would be a good choice, save them for the future when you might decide to add a stroker crank to the 400 to up the cubes to 455 and beyond.

[INJUNTOM]

Originally Posted by pjdutton

Sorry for lack of info.I want to fit these to a 400.Machine work is not a problem.Over here in the uk you use whatever you can get your hands on.THE studs on the 94 heads have been pulled and I was thinking of fitting B/block chevy studs.These 94 heads have smaller combustion chambers so I will up the compression a bit but I don`t know if the ports are better or worse than the 6x heads.

use the 6X with BBC studs...the studs will screw right in.

Pontiac used a 7/16" for the lower section, and tapered to 3/8" at the top.

[pjdutton]

Many thanks to all who replied to my post.It makes life a lot easier.

[Ron H]

Shave the 6x heads down to increase CR.

[RicksGTO]

I have a nice set of 94's I'm going to use on a 428. They have had the 2.11/1.77 valves and Arp screw in studs installed and some mild port work. I cc'ed 3 of the chambers on them and got 87cc's on each, these had only had a mild cleanup cut on the deck.(the 96cc rating for the 94's on most Pontiac sites is in error I think) That would be a good size to get your 400 into the 9.00-9.25 range with no significant milling. The 6X-8's with 100+ cc chamber will need to have quite a bit removed to get you in that range. Rick

[blaktopr]

I don't know if you are doing the work yourself but here is something else to think about. The small valve head can flow too, without switching to the bigger valve. I dont remember flowing a 94 but other small valve heads, after 1970 flow just as well as a street ported 6x, 5c and the like and with more velocity. You don't even have to open up the inlet, yes stock. Most of the work, and not alot is through the runner into the bowl. 220 cfm is no problem. So far I see 250cfm in a mild ported "small valve" head. 220ish and good velocity is enough to make a nice 350 to 400hp street motor.