Technical Pontiac Gurus: Need some help

I've been trying to do some reading on the topic, but just not finding quite what I'm looking for. Here is what I want to do:

I'd like to take a late 60s - early 70s Pontiac short block (400 probably) and marry it up with a set of early heads. The reason I think I want to do this is so that I can avoid a pricey adapter (or rare bellhousing) in order to run a decent standard trans, but still be able to run a cool old, as yet undetermined, intake.

I'd like to take this combination of parts, finish it of with the appropriate pistons, cam, etc. and end up around 350hp. Nothing too radical, it's going in a Model A Coupe. I'd also like it to run on pump gas.

If you were starting from nothing, what parts would you recommend putting together?

 

If you have a 65 and up V-8 Pontiac, manual bellhousings are fairly easy to find. Dual quad intakes are available new and plenty of used ones floating around. Tri powers are a bit more rare but you can still score a 65, 66 tripower iron manifold for 400 or so. No need to do an early head swap.

If you have a 64 and under, intakes are about as plentiful and tripowers you can get new from Offenhouser. Bellhousings are out there, but starter placement can be an issue.

Any of the V-8 Pontiacs are gonna haul that Model A around with a quickness, so shop your local junkyards and craigslist and find a good one.

Also, check out performanceyears.com for all things Pontiac.

Good luck, -Abone.

 

Thanks for the input. On the intake, I should have been more specific. I'll probably regret this later, but I'd really like to try to run a 6x2 setup - which I don't believe is workable with later heads?

 

I am doing exactly this in order to use a '62 tripower imtake I got cheap. Yes to early heads (pre 64) on a late block. It's the water passages thst are different
Factory Pontiac made 350hp all day, so careful assembly and don't get crazy with the cam. Torque is what matters on the street.
posted via smoke signals made with a Mexican blanket

 

I had the same plan on a Pontiac I was building a while back. I had a freshly rebuilt late 60's 400 and was planning to run pre-64 heads to run one of the 6x2 setups I had. Good question and I understand struggling to find all the information you are looking for.

 

one thing you have to check is the valve angle on the heads as in 67 they changed the valve angle and the eyebrows in the pistons will not match if you go with a .400 lift cam at the valve ( standard is .409) and you can smack the piston tops . they did make a double eyebrow piston for the 400 to remedy the situation , don't know if they are made anymore .

and 350 hp is easy with a Pontiac . keep it sane on the cam ( more of the highperformance 60's cams ) and make loads of torque ,the 066 cam will do it easily ,

 

Thanks for the responses so far. Stimpy, that's definitely helpful. I remember reading something about valve train geometry issues, but I wasn't sure what the issue was.

Any particular guidance on what heads I should look for? I see lots of info out there about the better late model castings, but what about good (non SD) early castings for a street motor?

 

One thing i would do is if you do run an early head is have the machine shop drill and pin the rocker studs. The old heads have the studs pressed in not screwed in. While your at it just gently grind the top of the rocker studs smooth, this way you can use poly locks on the rockers and when you tighten the center allen screw it will bite solid and hold and on a pontiac i always run poly locks and adjust for almost zero valve lash even with hydralic cams. Its amazing how well pontiacs respond to that mod, you will notice a difference.

 

basically any big car head after 1973 will work but make sure you check the CC's on them you do not want to run a 114 or larger cc head ( they were only designed for 455's ) on a 400 as the compression will drop off also you have to be aware of some later model heads ( post 70) are minus the end bolt holes which can cause problems with headers , as for post 67 any 16 head and some 96 heads are good flowers , and if you have money a set of 48's are nice, one thing we tell people is basically is if it has push in studs .take the head to a machine shop and have 7/16 threaded ones put in , but you only need that if you want a adjustable or non stock ( roller) valvetrain as the studs are bottlenecked and non adjustable and are not needed for under 450 lift .the wallace racing website has a list of heads and the cc's and applications and how to properly ID them . a easy rule of thumb is pre 67 is closed chamber ( and different valve angle ) post is open .

 

Yeah using the poly locks allows them to be adjustable.
Ok if your set on using early, pre 65, heads one option you have and what i would do. Using those heads, i would bore 30 over on the block, go with 60 over 389 pistons( stock 400 is a 30 over 389, 428 is a 30 over 421). These 389 pistons will put the valve reliefs in the proper location for early heads then you can run a good performance cam and not have to worry bout valve clearance ( within reason of course).
If you want some free power, match intake and head ports, pin the rocker studs, poly locks with zero lash and i like the older comp cams with around 450 lift and 230 to 235 duration at 50 lift and a 110 to 112 centerline. Run a split spec cam, pontiac old heads dont breath as good on the exhaust so you can help it with the split cam.. i wouldnt use a factory cam technology have come along way in cams since the 60's. Only thing to remember is its not a sb chevy and many shops build em like they are.

 

you cannot use poly locks with a factory rocker stud as the stud is bottlenecked ( the base is larger than the threaded section ) you have to change the stud out completely .

 

......I would suggest you get a book called "How to Build Max-Performance Pontiac V-8s "..I paid $24 for it and it was well worth it,.... www.car-techbooks.com has it...I have a 1971 455ci Pontiac with a 1966 cast iron 3-2s intake,running stock heads 114cc,mild cam,flat pistons,in a 1931 pick up with a muncie 4 speed and the truck has far more power then I will ever need,....which ever combo you go with get the 1 piece oil pan gasket and the special rear main seal,...A few things I found out was Pontiac parts are not cheap,...the pontiac clutch FORK is not the same as chevy,..... Miller

 

Yes you can use the poly locks, poly locks are not just a nut, they are a long threaded tube design just for bottle neck studs, they have an allen wrench set screw in the middle that lock down against the top of the stud and keep them from backing off. They work excellent, i have used them on every pontiac i have built since 1982. Used em on a couple sbc too. Mr.gasket calls em poly locks although i dont feel their name (poly locks) fits their design.

 

Here you go , now they call them sure locks along with poly locks. Note 3/8 stud with clearance for 608 shank.
http://pitstopusa.com/i-5058903-mr-...hed-nuts-have-3-8-stud-and-603-shank-o-d.html

 

Thanks, I'll pick that up.

Can you describe in a little more detail what I would be looking for with the 1 piece oil pan gasket and "special" rear main seal? Are these stock (later?) OEM apps or?

Nothing is quite as cheap as small block chevy stuff, but I was previously considering an early hemi. The good news is that anything seems cheaper than hemi stuff.

I'm glad you mentioned that. I'm betting that would have had me scratching my head for a while because I have a few chevy bells and clutch setups laying around the shop.[/QUOTE]

 

My dad wrote that book on Pontiac's so maybe I can help some.

For a pan gasket, any of the Felpro kits will work just fine, I haven't used the one piece, but never really had a problem with the others.

For a rear main seal, Best Gasket Company, the only one to use if you want it to seal.

For a camshaft, smooth idle, good torque, Summit Racing #2800. Pretty close to the Pontiac #9779067 stock camshaft.

For better performance and rougher idle, Summit Racing #2801. This is similar to the #9779068 GTO and Ram Air cams. This is really good all around cam that pulls hard up to 5500 rpm and still idles with good vacuum. The Ram Air III #9779041 is a really big cam for a 400. When the factory installed them, the car had to have a 3.90 - 4.10 gear and four speeds. A/C was out, this is also a .470" lift cam.

ARP #290-7201 rocker studs are 1/2-13 on the bottom and 7/16-24 on top. You can tap the stud holes fairly easy at home with a simple fixture and a sharp tap and cutting oil. This eliminates the pinning and small 3/8" hollow studs.

Check here for casting numbers, http://www.wallaceracing.com/head1.htm .

The old heads use a shorter length pushrod so check the rocker arm geometry really close when assembling the valve train. If you use stock rocker studs, any small block Chevrolet lock nut will work, poly-locks are optional.

 

...

[/QUOTE]
....Take a look at www.bopengineering.com you will see the pan gasket and the rear main seal,...these are not cheap but I have them on the motor for 2 years now and no leaks...I will try to post a pic of the clutch fork...Miller

 

....Take a look at www.bopengineering.com you will see the pan gasket and the rear main seal,...these are not cheap but I have them on the motor for 2 years now and no leaks...I will try to post a pic of the clutch fork...Miller[/QUOTE]
....pontiac clutch fork pics...

 

I went the other way with my Pontiac build. I used late heads [#96 1973 GTO 400 heads] for their big valves, hard seats,screw-in studs and pushrod guide plates. They have big [96-98 CC] chambers to work with my old Jahns pop-up pistons.
The short block is based on a 57 block bored .125 to 370 cu. in. I tapped and plugged the old oil port in the block's deck that use to feed the oil galley in the original 57 heads that fed the hollow rocker studs. It now feeds oil through the pushrods. I used chevy big-block 7/16ths rocker studs and poly locs.
During assembly I checked valve to piston clearance and it's more than 1/4 inch. Used play-doh to check but I found my stock Pontiac valve retainers hit the PC valve seals on the intake side at full valve lift. [.490 lift cam] I had to remove each retainer and grind the bottoms to clear the seals + .050". Don't let the keepers hang out the bottom.
I used a Lunati grind cam with 230 degrees at .050 and a 110 LSA.
It's a little lumpy at idle but it's being used in a light car with a 4 speed and quick change rear.
Can't remember if I used early or late pushrods but on testing, they have great geometry through the cycle.
IMHO, the onliest guys who will know the difference between early and late Pontiac intake bolt pattern will be real pontiac guys who also know the advantages of running late heads.
BTW, my fell-pro head gaskets say they fit 1958-1979 Pontiac engines. I checked the differences between my original '57gaskets and the fel-pros and found no extra holes [including the rocker-feed hole] or differences between the 2 with the obvious exception of the bore holes. Parts interchangeability on Pontiacs is almost as good as the chevy S.B.
EDIT. .... I also used the Best rear main seal [rope type] and had the old front cover machined for a modern seal. No leaks after running the engine on my stand for break-in. I used an old original 58-60 stick bellhousing [1959 ambulance] and have an extra 57 GMC pickup housing if you need one. Mounts the starter upside down from the passenger car housing. I also have the starter and flywheel that fits the bellhousing. Works on '55 to 1960 pontiac engines.
I see no advantage in running a one-piece pan gasket. If you need to remove the front cover for any reason, you run the risk of ruining that gasket at the front cover/oil pan point. You'd have to cut the gasket and install the front 1/4 piece of a conventional gasket. Just sayin.

 

Actually, stock 400 bore is .055 greater than a stock 389 bore. .030 makes about 395 CI.

So if your 400 will clean up with .005 or so then .030 over 389 pistons will go in there and because they cross from 59 to 66 they're made with reliefs for both valve angles.

Valve train geometry is key, lots of running changes as the motors grew; you probably want to stay with 59-60 heads or 61-64 heads for the build, depending on what intake you end up with.

You can also change the front cover back and forth if you want the older look, but the 4-bolt water pump is tougher to come by (more $$$) than the later ones.

 

For a variety of reasons, it seems like the later heads would be easier to live with. Just to be clear, this isn't an effort to fool the traditional police into believing that I have a legit 1958 motor in the car.
I'm not 100% sold on anything yet, but just how difficult would it be to mate an early 6x2 intake to a set of later heads? I've read some different things ranging from flat out won't work to difficult/expensive.