[BattlestarOne]

I'm doing a sort of "restomod" for a guy on a 67 Bonneville Convertible (yeah, I know, it's a barge...)

It has the original 400 4bbl THM400 in it. He wants to bump it up a little so I suggested he get a 455 to start with for a little more bottom end. He picked up a complete '75 455, all stock/original.

The question is since it will need a total rebuild is there any advantage to using the '67 heads over the '75 heads. I'm guessing they'll interchange, but my knowledge of Pontiacs is minimal.

What we're looking for here is some big bottom end grunt to move the barge, but if there is something to be gained at the other end with possibly better heads??????

He's willing to go with a bit of gear to help, somewhere around a 3.70 or so.

Also, the exhaust manifolds on this thing look pretty pathetic. Any chance GTO headers might work (maybe with some mods) on the big car chassis? Or are there any "H.O." manifolds available that aren't "collector's items"?

Before you tell me to forget it, the guy wanted to take the 400 and "Cam It Up and Put Dual Quads On It" so I'm just trying to save him from himself and put a decent motor combo together.

Thanks for any thoughts.....Greg

[6567GTO]

Cool car to do up!

Tough choice. The heads will definately interchange. What 455 head is it? What 400 heads are they - 061's? If they're the later 061 thay have a chamber design similar to a RA IV head. But they have pressed in studs, which is a minor issue - just have the machine shop drill and tap the heads for threaded studs. The real problem with running those heads is that the compression will be at around 11:1 Ive got 670's on my 455 which is the same cc as the 061 and it needs a 50/50 mix of 110 octane Cam 2 and 93 unleaded pump gas to not ping. Make sure he gets forged pistons.

As far as headers go I've heard that 67-69 Firebird headers will work. I've never done this so don't take my word for it. Try and find a cheap set for a trial fit. From what I understand long branch Ram air exhaust manifolds won't work due the interferences.

[BattlestarOne]

I'm looking at the number that's on the center exhaust port. It's 143. Is that the number I'm looking for or is it somewhere else on the head?

I don't have the 455 here yet, but I'll get the number as soon as I can.

[astroracer]

Be careful with the 400 heads on a 455. You need to figure out what you've got because they can push the compression ratio way higher then he'll need and still be able to run pump gas. If you do use them they'll need hardened seats installed before you go to far...
Do a search for Pontiac info. Kaufman, Butler, Nunzi, etc. there is a bunch of info out there.
Look here for a junkyard build Car Craft did.
http://www.carcraft.com/techarticles/116_0306_pont/
You could also consider swapping the tranny to an auto O.D. A built 200 R4 will help get the "barge" moving and the .67 O.D. will help the mileage and reduce engine wear... best of both worlds.
Mark

[6567GTO]

Yup, that's the number of the heads - 143. They also have pressed in studs and are around 72-75 cc. Find out what the heads are on the 455 and we'll go from there. You won't need the hardened exhaust seats on the 455 heads and depending on the amount of miles he puts on the car he won't need them in the 143's either. Those old Pontiac heads are tough. It's a nice precaution though.

[BattlestarOne]

Thanks, Guys.

This car won't be driven all that much. The guy is a total Pontiac nut and he also has a '57 Star Chief Convertible and a '67 GTO Hardtop that he bought new, 41,000 miles.

Seeing as this will be the "new" car this summer it will get run, but after that it will be a 3 way split......couple thousand a year tops....

I'll get the 455 head #s and meantime I'll check out some of the "big guy" sites mentioned above.

[Jared]

in 75 they only had one head # from what i can tell. they are large chamber smog heads. i think they are # 51's I would look for some early heads like the ones you have and put hardened seats in and possibly bigger valves if they are not large valve heads already and run dished pistons. Im building my 455 up with 6x heads. they seem to be good heads, fairly common too. on the topic how good are 5c heads? I have a set on my 75 400. thanks and good luck ponchos rule.

[lust4speed]

The stock 5C head is not really a bad choice. It comes stock with 101 cc chambers that give the engine a true 9:1 compression ratio. A cleanup cut will raise this to possibly 9.2:1 which is the territory you want to be with pump gas. Some replace the smaller 1.66" valves with the larger 1.77", but the money might be better spent on gasket matching and a little port and bowl cleanup. I think that the 6X's have slightly more port volume. I would use the earlier '67 intake manifold and a Pontiac 068 cam. Either the stock long branch cast iron manifolds or the Firebird headers should fit with only a minimal amount of fitting. A different oil filter adapter needs to be used, and I believe there is slight contact with the steering box.

[jimfulco]

Ram Air Restoration has factory-type high-performance iron exhaust manifolds. They list pn LB-1 & SLB-1 to fit 62-69 B-body cars.

http://www.ramairrestoration.com/catalog/index.htm
(scroll down about half-way for D-ports)

www.pontiacstreetperformance.com (more good Pontiac stuff)

[Mr. Green]

If you can spend a little extra money I would go with dougs header's, they have a awsome fit great finish and they are easy to install here's a link for there pontiac header's http://www.dougsheaders.com/applicat...turer.cfm?id=7

[lust4speed]

The Doug's require about half the time my old Super Comps did to install. But hey, it's a Pontiac and you still have to stand on your head to get them on. The difference is that Doug's give you more room around the bolt holes which makes a tremendous difference when you are upside down trying to get a bolt started. Doug's moved recently to their new manufacturing facility in Riverside, CA and it has become just way too convenient for me to hop on the freeway and spend money there. They do produce a superior product, and the extra cost polished ceramic coating looks like satin chrome.

The long branch cast headers (either the original or the reproductions) were down in power compared to headers on dyno tests, but they are much better than the stock log manifolds. The oil filter adapter was original equipment with the cast headers, and a reproduction is available from a couple of the aftermarket suppliers - but it does add on another $70 to $80 dollars to the final price of the cast units.

[6567GTO]

The difference is that Doug's give you more room around the bolt holes which makes a tremendous difference when you are upside down trying to get a bolt started.

Amen! to that! My Hookers are a nightmare. Especially the rear bolt on the drivers side center port.

[55mole]

The rear that is already in the bonneville could have 3:70's in it . I am restoring a 65 bonnevile & thats what's in it . Along w/a 3 X 2 , 4 spd & posi from the factory. "Ames" will have just about every part you need inside & out . 55mole

[BattlestarOne]

Yeah, 55mole, I was hoping for a decent gear but it's somewhere in the 3.0 or taller range.....

Your 65 probably came with a decent gear as part of the performance oriented tri-power 4 speed combo.

There's a guy locally that has a 65 Grand Prix 421 Tri-Power Automatic that he bought new. Still a nice original car with around 60K on it.

It'll probably take some talkin' to get the guy to go with headers, but he'll get at least the HiPo manifolds for sure.....

I just looked on the Doug's web site......Those Babies are NICE!!!!! Says they won't work with the column shift, though. I'll do some checking and see if reasonable mods can be made.

$505.00!

[turbo67bird]

The 72cc heads on a 455 with a flat top piston is not a good choice for a street driven car. 670's have a closed chamber in 67 with a good intake port but the 68 and 69's open chamber design swirl better. If you can find a set of 6x's that would be a good start.

Here is a link to a good source for decoding pontiac heads

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

Shoot for a street comp around 9.5 to 1 and you'll be safe on pump gas.

Here is another link to a build with pump gas that is pretty amazing. 500hp and 500 lb tq.

http://www.pontiaczone.com/forum/showthread.php?t=21895