Question for Pontiac Engine Guys

I'm going to be building a 400 Pontiac engine......I already have the block, crank, rods, carb and manifold. What I don't have are the heads. I'm not going to buy the Edlebrock or Kaufman heads but rather will be sticking with Pontiac heads. Question is, which heads to stay around 9.5:1 compression ratio?

I've heard that other than the Ram Air heads, which I don't want t spend the money on, the ultimate pontiac heads are the 670 heads. Unaltered, they would have me up around 10:1 or 10.5:1.

Is there any advantage to me spending more money and going with 670 heads and dished pistons to lower the compression ratio or should I just get heads that have the big valves but a little bit larger chamber size? I can get a set of 96 heads with the bigger combustion chambers for $300.00.

Not a Pontiac expert , but I've built more than a few Chevy motors. If ya go with big cubes , 400 or over , stay at 9.5:1 or lower. Gas quality is only gonna get worse and with the old combustion chamber shape , detonation or pinging is gonna happen. Dished pistons allow good flame travel.

Be sure to pick your cam accordingly too. Hi lift , short duration seems to be the pick for street use today.

Ignition system is also something to consider. An MSD unit is probably the way to go. There's probably even better units out today. The old vacuum and centrifugal advance points distributor , while reliable , just don't cut it.

670s will probably be a tad more compression than you want. i'd look for 48 (possibly pricey!), or the secret hidden gem 62. i used to drag race strictly pontiacs, and used the 62 exclusively for nitrous motors. i honestly never saw any measurable difference in them and the 48. the 670 is a great head, too. if you have them, i'd probably go with them, if you can deal with the c/r.

good luck, and post pics!

ed

MaximumLawman said:

I'm going to be building a 400 Pontiac engine......I already have the block, crank, rods, carb and manifold. What I don't have are the heads. I'm not going to buy the Edlebrock or Kaufman heads but rather will be sticking with Pontiac heads. Question is, which heads to stay around 9.5:1 compression ratio?

I've heard that other than the Ram Air heads, which I don't want t spend the money on, the ultimate pontiac heads are the 670 heads. Unaltered, they would have me up around 10:1 or 10.5:1.

Is there any advantage to me spending more money and going with 670 heads and dished pistons to lower the compression ratio or should I just get heads that have the big valves but a little bit larger chamber size? I can get a set of 96 heads with the bigger combustion chambers for $300.00.

Click to expand...

I have a set that came off of my friends 70 GTO. I will see if he will sell if you wont. Shipping sucks. Last set was $135.These are stamped 12.

Compression ratio will be impacted by piston shape, head gasket thickness, etc. I would get a head that has good combustion chamber shape and decent flow at lower RPMs (consistent with the cam grind described above), which would be consistent with most street use; a good quality mid-sized carb, probably not more than 650 CFM (unless you are going with FI), get the heads into good shape, and tweak the CR one you have all the right parts. As noted, gas quality is not likely to get better, and a lower CR is probably going to be a better choice for most uses.

AR: the 670's will absolutely be too high with flat pistons. I'd like to know if there is any advantage to the 670 set up if I dish the pistons to lower compression or if I should just go with heads that already have a bigger chamber. I think the 670's are 72cc's and others that also have the big valves are 88....Do the 670's flow better than other heads, for example?

Doug: I plan on going with the original quadrajet and manifold.

I can get 6x head cheap but those are big chambers and more along the lines of a 455 stroker and I'm considering going with the 400 just because I have the block and crank, etc...

AR: Looks like the 62 and 48 heads are both set up to make 10.5:1 CR without dished pistons. I think I may be better off going with a bigger chamber to start???:

Cylinder Heads

MaximumLawman said:

I'm going to be building a 400 Pontiac engine......I already have the block, crank, rods, carb and manifold. What I don't have are the heads. I'm not going to buy the Edlebrock or Kaufman heads but rather will be sticking with Pontiac heads. Question is, which heads to stay around 9.5:1 compression ratio?

I've heard that other than the Ram Air heads, which I don't want t spend the money on, the ultimate pontiac heads are the 670 heads. Unaltered, they would have me up around 10:1 or 10.5:1.

Is there any advantage to me spending more money and going with 670 heads and dished pistons to lower the compression ratio or should I just get heads that have the big valves but a little bit larger chamber size? I can get a set of 96 heads with the bigger combustion chambers for $300.00.

Click to expand...

While I can't help you with your heads question, I CAN help you with a tripower setup from a 1966 GTO. Mechanical linkage. Three bitty air cleaners. Gooseneck thermostat housing. I sold my last Pontiac 25 years ago so that's how long this rebuild has been sitting in storage. I wanted to make a coffee table out of it with a glass top but my wife doesn't think it's a good idea...

NMP, thanks but you'd probably be better off selling it on ebay....I don't think I'm going to go with trips....My project has been sitting for 25 years too. I initially got it to keep me OUT of the bar but with all the "fun" I've been having with it, it's actually driving me (metaphorically speaking) TO the bar! Here are some before and afters of the frame along my journey...

I didn't go with the normal engine build when I built my big block 396 with 325hp. I used a two bolt main block with the 9.5 stock positions. I had cut the oval port heads .010" to make sure they were flat. I installed the complete 375 hp valve train along with the solid lifter oil pump. I ported and matched the ports myself. I did cut and snitch the block were the exhaust valve is so it can flow better than with the square edge. I went with the electrical 180 degree intake with a 780 Holley carb stagger jetted to the big block book. With a 1" carb spacer under them carb. Then i installed the oil pan windage tray and the oil baffle to keep the hot oil off the bottom of the intake manifold.

Proper tuning is the key. I took the point distributor and removed the brass bushing that limits the rotors advance. Then I put in the heavy weights with the lightest springs. Using the vacumne hose on the carb for advancing the distributor I adjusted the idle timing till I got 50 degrees of total advance @ 2,000rpm. With the accel points, gapped at .017" and the champion spark plugs gapped at .032"'.

I installed it in a 63 s/s impala with a super t 10 4 speed and 4:88 in the rear. At the strip she ran 12.85 the first time out. I even forgot to turn on the electric fuel pump so she couldn't rev past 5,000 rpm and she still ran in the 12s... on the full body car dune I had 299hp at 6,800 rpm and about 400hp under the hood that's not too shabby for a 325hp stock engine with the small port heads.

Note; I went thru the traps at 3,500rpm so if I had 5:38s in the rear and wired my electric fuel pump to the ign key she would of broke into the 11 seconds no problem. But my older brother who love fast cars
Haunted me to sell it before I got hurt in it I guess he was right.

We also built a pontiac 400 ci by installing a ram air cam I it. It was in a 64 gto convertible. We won lots of $$ drag racing this sleeper too.
It had 4:30s in the rear with a 400th tranny.

But it's all in the proper tuning and big blocks love a lot of total timing. Setting it at 50 degrees seems to be it's sweet spot with any big bore engine. Bigbill

Btw; I suggest cutting the heads .010" to make sure there flat and tune it correctly.

I do regret missing my calling as an engine builder and tuner but I did get to build dirkbike engines.

Thanks Bill..

You know that cubic inches is cubic inches so any big bore block will respond to proper tuning. Just stay tuning and adjusting it till it's right. That's the fun of doing it.

MaximumLawman--I`m guessing you`ve been on Performance Years website. Everything you would ever want to know about Pontiac engines has been discussed there. A good reference book is "How to Build Max-Performance Pontiac V-8s, by Jim Hand. In the back of it there`s recipies for mild to wild.

Hey DH, I'm reading the Hands book now and am looking at Chapter 11 with various build "recipes". I've heard of the Central Virginia Machine Service on several pontiac forums and they come highly recommended. I'm leaning toward 96 heads, I think, OR buying THIS bad boy if the prices to do my 400 is close...This guy is an easy drive from my house....maybe he'd knock $400.00 off if I picked it up....
http://www.ebay.com/itm/160998552824?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

If I go with my current block, I have to decide if I want to be strokin' or not.....The Eagle stroker rotating assembly is about $1500.00 and would work with the relatively inexpensive 6x heads......And 461 does sound cooler than 400....

That combination from "Jeff" is almost identical to one I put together about 6 years ago, except my cam was a lot more radical. Still idled good and had enough vacuum for power brakes though. It was the 1st engine I`d done in 20 years and it came out really well. Went into a 68 Firebird with a reworked THM-400. It always pulled like a freight train all the way through the rpm range. That looks like a good combination he has there.

DH, specifically which one are you referring to? Recipe "A" from Virginia machine with the 400 block and stroked crank and 6x heads? The very first one in the series of builds? .....and who is "Jeff"??

I had a 69 GTO with a 400 and 2 4 barrels back in 1978. Paid 750.00 for the car, got married in 78, blew the motor in 79, put a 389 in it and sold it for 200.00! When the carbs were set up right and the progressive linkage was working correctly it was pretty fast!

Hmm, "when the carbs were set up right" indeed.....That's why I'm leaning toward one carb....That's enough for me to try to figure out, let alone three of them....

Is that a 64 or 65 Tempest body?

ralph7 said:

Is that a 64 or 65 Tempest body?

Click to expand...

'65 GTO. Post (sedan) body.

MaximumLawman said:

DH, specifically which one are you referring to? Recipe "A" from Virginia machine with the 400 block and stroked crank and 6x heads? The very first one in the series of builds? .....and who is "Jeff"??

Click to expand...

The e-barf ad.