[Tim66]

Hi guys,I know that you guys know everything so here goes.I have a tri-power that I want to put on my 400 .My question is,what size heads would I use? Thanks for any help for a novice like me.Tim.

[b-man]

As long as you have a '65 or '66 Tri- Power intake you can use any '65 or later heads of your choice.

Keep in mind that Tri-Power came on '66 and earlier 389 and 421 engines, the early heads weren't all that spectacular in comparison to the '67 and later heads.

[Tim66]

Thanks,B-Man,I have to look and see what I have,then I'll get back to you.Tim.

[Tim66]

My tri-pwr is supposed to be a 66 and my heads say 7H1 in the middle and 4 on the rt side
.What do you think? Thanks again ,Tim.

[Doug]

7H1 is from a 1972 350ci engine, low (8.0 or less) compression, pressed in studs, "small" valved, etc.

Assuming you are going to "freshen the heads", I suggest you do some research and find a "better" set of heads and "freshen" them, looking for the highest compression suitable for street gas.

A somewhat maligned set of heads that would work good for you is the 1973 7K3 heads.
Big valves, 96cc chambers, screwed in studs, decent compression. The complaint about the 7K3 is that the ends of the exhaust manifolds don't have bolts because the heads are not drilled on the ends. This is a fairly easy fix, either by drilling holes in the head or by using a set of aftermarket "clamps" that hold the ends of the manifolds. Another nice thing about the 7K3 is ideally suited for use on a 455 engine (later on).

I think that using the 7H1 with tri-power would be a case of over-carburetion.

[Tim66]

Thanks Doug for the good info,I got excited for a moment,thought I was going to get away cheap.Oh well,thats what happens when you want something that you have to have.I will continue to save my pennies.Tim.

[Doug]

Originally Posted by Tim66

Thanks Doug for the good info,I got excited for a moment,thought I was going to get away cheap.Oh well,thats what happens when you want something that you have to have.I will continue to save my pennies.Tim.

I mistakenly said the 7K3 were 1973's. They are 1972 models.

I looked up the "brackets" I mentioned and they run about $65-$75 for a complete set.

I had a 72 Safari wagon with a 400ci/Q-Jet/7K3 engine rated at 250hp and that engine was a strong engine when you are whipping around a 5,000lb vehicle. I suspect that type setup with tri-power and a good cam would be quite stout in a much lighter vehicle.

Good luck!

[b-man]

The 7H1 350 heads aren't really a performance head, however they're every bit as good as or better than the heads any Tri-Power engine ever came with.

None of the Tri-Power 389s or 421s had valves bigger than 1.92" intake or 1.66 exhaust, all of them had press-in rocker studs as well. The 7H1 heads have 1.96" intake valves and 1.66" exhaust and better ports than the earlier 389/421 heads believe it or not.

Granted there are better heads available, but there is nothing wrong with using the 7H1 heads on a Tri-Power 400 engine. The main drawback, like with every 1972 head, are the lack of outer exhaust bolt holes.

[Tim66]

Thanks B-Man for your info,I'll have to start looking around.Have a good day.Tim.

[Tim66]

B-Man,were you talking about the 7K3 heads or 7H1 heads.I have 7H1 heads on the car now,with bolt on exhaust.Thanks,Tim.I think I UNDERSTAND NOW AFTER RE reading the posts.

[b-man]

The funny thing about the more common Pontiac heads is the port size is pretty much identical between the large and small-valve heads. Once you convert the small valve heads to large valves you have an equivalent head, with a bonus of not having to deal with worn out or sunken valve seats on old used large-valve heads.

On a mild street build valve size isn't really all that important, the 7K3 big-valve heads won't run that much better than the 7H1 heads. The only drawback is the press-in rocker studs on the 7H1 heads, but with low-lift stock performance cams (like the 068 Tri-Power cam) they'll work okay.

If your 400 is already running with the 7H1 heads, just bolt on the Tri-Power (taking care to mate up the center exhaust crossover properly, '71 and earlier vs. '72 and later designs) and have fun.

[Tim66]

Thanks again b-man,i'm excitedall over again, can't wait to bolt her in.Alot of great info again,I thank you.Tim.

[GTO JOHN]

One other thing to consider is the later heads such as 4X, 6X, etc. have the heat crossover ports that do not match up with the tripower intake. You will end up with an exhaust leak at the intake crossover.

[b-man]

Originally Posted by GTO JOHN

One other thing to consider is the later heads such as 4X, 6X, etc. have the heat crossover ports that do not match up with the tripower intake. You will end up with an exhaust leak at the intake crossover.

How to overcome the mismatch issue between '71 and earlier intakes and '72 and later heads:
http://www.wallaceracing.com/intake-crossover.html

[GTO JOHN]

Originally Posted by b-man

How to overcome the mismatch issue between '71 and earlier intakes and '72 and later heads:
http://www.wallaceracing.com/intake-crossover.html

Ahh good info there. Wish I had that knowledge back in 1988 when I put a 3x2 setup on my 455 with 6X heads....

[Doug]

Originally Posted by Tim66

Hi guys,I know that you guys know everything so here goes.I have a tri-power that I want to put on my 400 .My question is,what size heads would I use? Thanks for any help for a novice like me.Tim.

Tim, While driving down the road thinking about your post, another couple of items came to mind for you to consider.

It seems that you have a sort of hodgepodge of pieces/parts from various production years so some of it may or may not be directly compatible with others.

1. Please be aware that the underside of 65-66 tripower manifold will not clear the valley pan of some other production year engines. I don't recall which years will fit but you can research it and hopefully someone can chirp in and answer that for you.

2. Also, the "water neck" on the 65-66 manifolds will not clear the timing covers on some other production year engines. (The "correct" timing covers will have a proper sized "dimple" in its design to allow fitment of the water neck.) Again, I don't recall which years will fit but you can research it and hopefully someone can chirp in and answer that for you too. (Although the various year timing covers may "appear" to be similar, they are different!)

You seem unclear as to whether your tripower is a 65 or 66 unit. Do an easy search by looking at Pontiac tripowers on Ebay and you can see the differences in the pics.

Good luck!

[Tim66]

Thanks Doug,alot of great info to check on.I have to finish welding the trunk floor and replace gas tank,before I get to the motor.Hope to be on the road someday.Tim.

[b-man]

Good points Doug.

A '65 - '67 valley pan is required, '68 and later won't clear the bottom of the intake.

Timing covers with the dimple to clear the water neck were used up until 1974 so you may already be okay. Minor clearancing of the back upper bolt boss on the cover is required for water neck (or thermostat housing) and thermostat installation and removal.