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Old 06-25-2013, 08:39 PM
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Pontiac 389, 400 or 455?

Don't know where to start with all this so I'll just start. I've got a 1950 Streamliner in desperate need of some more cubes. I'm looking for a solid Pontiac block to get started and am realizing the 455 I thought I'd use is becoming hard to find. They're out there, just pricey. I'm not in a huge hurry so I can spend a little time to find the right block but was wondering why so few 389's are used for mild performance builds. There seem to be a lot of them. There are a lot of 400's as well and that might be where I go. Still I'm wondering, is a good 389 a bad place to start?

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Old 06-25-2013, 08:51 PM
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It all depends in what you're looking for. For a mild street engine using a lot of factory parts 1hp/ci is a good rule... If you want 389hp then that will work, if you're looking for 450hp then more cubes will make a much easier job of it.
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Old 06-25-2013, 08:52 PM
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I've always had a soft spot for Pontiacs, owned two built '65 GTO tri power 389's, that were bad to the bone.

We have several super Pontiac guys just waiting to fill you in on performance particulars.
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Old 06-25-2013, 08:57 PM
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I'm beginning to develop an interest in the Pontiac......
14 degree valve angle compared to the SBC 23 degree angle....
A 389 is bigger than a 383.....
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Old 06-25-2013, 09:16 PM
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Pontiac 389, 400 or 455?

Hey thanks for the cube to hp rule. That's super encouraging considering the flathead 6 I'm replacing. 389 hp would be a great place to end up. One thing I'm starting to realize is the older Pontiac V8s had higher compression ratios and ran on higher octane leaded fuel. I wonder what limitations I would have with the head selection? Seems like a 9.5:1 is where I want to be from what I'm reading. Do you know if the heads are interchangeable up through the late 70s?
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Old 06-25-2013, 09:32 PM
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Pontiac 389, 400 or 455?

Quote:
Originally Posted by techinspector1 View Post
I'm beginning to develop an interest in the Pontiac......
14 degree valve angle compared to the SBC 23 degree angle....
A 389 is bigger than a 383.....
Seems like I read about this somewhere. I have to admit the physics goes over my head pretty quickly. How is this an advantage? I recall the angle of the exhaust valve effects the quality, or pattern of the detonation in the cylinder chamber but I don't remember exactly how. You've made me curious to go back and find it. Thanks. I wonder if the valve angle feature goes back to the early 389 heads.
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Old 06-25-2013, 09:37 PM
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Thanks, any block codes I should look for? Did you run with a 4-speed or automatic? BTW those tri-powered Pontiacs sound and look incredible.
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Old 06-25-2013, 09:54 PM
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Quote:
Originally Posted by leroycash View Post
BTW those tri-powered Pontiacs sound and look incredible.
I know. In 1966, my friend let me drive his brand-new GTO 389 tri-power 4-speed. It's as close as I ever got to a handful of car back in those days......too busy paying for a house and raising kids.
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Old 06-26-2013, 04:54 AM
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You will be fabricating motor and trans mounts to get the later model V8 in the car so I would suggest picking up a "mock-up" block. 326 to 455 Pontiac blocks are all the same size so, no matter what you end up building (400 block with a turned down 455 crank would be good), you will be able to bolt it in.
The more cubes you use the milder the build can be to get the same amount of power. Torque gets the car moving off the line and that is what Pontiacs make.
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Old 06-26-2013, 07:30 AM
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Quote:
Originally Posted by astroracer View Post
Torque gets the car moving off the line and that is what Pontiacs make.
They don't make torque or power any differently than any other engine, you can slap whatever brand sticker you want on the valve cover- its really meaningless.

If you want a good relatively low cost pontiac (or any other engine) here is a good basic recipe-


Stock rebuilt short block, may need to get it bored and new pistons (cast or hypereutic are probably fine), keep the crank and if you plan on going over 5500rpm or so get aftermarket rods. Pontiac oiling isn't the best, there are a lot of fixes, but the easiest is to just have the machine shop enlarge all the oil galleys and install a ported HV oil pump. If you do that be sure to also smooth all the oil drain back channels. Oil flow is NEVER a bad thing- it can and does cost a little power but it greatly increases longevity.

The next part is the heads, of course some are better than others but you're often stuck with what you have, especially with a relatively rare engine like a Pontaic. The good news is that for a modest 1hp/ci goal almost any of the heads will work- but you need to have a valve job done and I would get them ported too. You may need new valves and guide liners so expect that. You'll then want a good dual plane intake, the typical Performer RPM will work fine if you want to keep a carb, there's also good efi intakes if you want to go that route. Get a good street carb, for street only use a carb in the 600-700 range will be fine, for some track time go with one in the 700-800 range. I like the design of the new Street Demon 625, though I have not used one in the past, Edelbrock carbs are probably the easiest to use. Getting a set of headers will help a LOT but it may be a hard fit. There's a lot of power there though so try to find some that will fit if you can. For a cam, it depends on your final engine and driveline specs but for a mild street engine with 9.5:1 compression 220 degrees @.050" on the intake is about the max you want to go- going with a simple "RV cam" will make a very mild daily driver that will be down on power a little but they work just fine for cruising type cars. 1.65 roller rockers would be a nice addition too, but see what your budget allows.

For 389hp (or thereabouts) you don't need to get crazy on parts, depending on your final selection and tuning following the recommendations I gave you will get you close, perhaps over. Its very easy to spend 2 or 3 times as much and make more power but I don't know how far down that road you want to go.
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Old 06-26-2013, 07:38 AM
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455s are more expensive cores due to the misconception that "bigger is better". Not so. ALL the 3.25" main blocks (including 421 and 455 "HO", but not SD) are "weaker" than 389 and 400 blocks (3" main). Yes, that means the cranks aren't quite as strong. To put that "in perspective", remember, BBC and Hemi have a 2 3/4" main. The 3" main Pontiac is not only "bigger" in the mains, but also about 4" shorter. In short, Pontiac CAST cranks are nearly as strong and tough as Chevy and Dodge FORGED cranks. Vinny Meyeda goes 6.80s over 200 with a nodular Pontiac crank and "stock block" 406. That's about 1,800 HP from CAST parts. He shifts around 8,500, too, so get the idea that a Pontiac CAN'T rev out of your mind. Feed it and oil it, and it will rev as well as ANY American V8.

The 389 is the "forgotten Injun". The short block is very nearly identical to 400 except the final bore size (4.062" vs. 4.120"). Same crankshaft, etc. Using an Eagle "stroker" crank with "custom" pistons makes a VERY strong 458 CID engine.

There are three basic motor mount "systems" from '59-'79. The "two-bolt" mount (pre-'70) is the most common. All the blocks from '70-mid '75 have five mounting holes, supporting both the two-bolt mount AND the three. Later blocks only support the three-bolt mount, and probably should be avoided. The 557 casting (last 3 digits) is the "weak" one. The 988 is much better ('75-up).

As heavy a car as the '50 is, the larger cubes would be desired. If you "lucked upon" a 421, THAT would have "cool factor" beyond any of the others. They're tough to find, though. A 389 block with the 4.25" stroke, the '67-later heads (have the "good" valve angle, where the earlier stuff is 19 degrees) and a '66 TriPower unit on top (all available "new" now), would be the ultimate Pontiac "street rod" arrangement.

NOTE: The "advantage" of a shallower valve angle is a better "approach" to the cylinder through the intake path, providing a straighter "shot" at the center of the cyinder (intake) and "rolls" the exhaust valve over to make a straighter "shot" at the exhaust port. The practice of "angle milling" small block heads stems from the desire to improve both of these issues. It's not as significant for the small block's exhaust, as that port is excellent. The Pontiac needs all the help it can get on the exhaust side.

TH400 is the minimum level of transmission that will "live" behind a high-torque Pontiac. TH200-4R has been known to "take it" if the internals are upgraded. We've seen a lot of trouble with both TH350 and TH700-R4, simply not up to the task.

You should consider getting Jim Hand's "How to Build Max-performance Pontiac V8s" published by SA Designs. The original work was done in '04. There's a "rewrite" available (not by Jim, himself) but none of the principles were contacted for that. More "tractor motor" crowd stuff, rather than embracing the present (stuck in 1979...). Though a bit dated today, it still has many good pieces of information and history of the Pontiac. The old HO Racing and Pete McCarthy books are okay, but WAY obsolete.

Feel free to add questions here, or if you have trouble finding things, PM me. I'll point you to the right people. Pontiacs show more "cool factor" than most other American cars, and a Pontiac-powered Pontiac street rod is among the COOLEST!

Jim
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Old 06-26-2013, 07:42 AM
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For a daily driver, a 455 engine and a stock Q-jet manifold is obviously the best choice, if you can find a 455 engine that is still rebuildable. Good 455 Pontiac engines and cranks are becoming difficult to find but they can be found with some diligent searching. The drag racing crowd has grabbed those engines. Do not use 1965-1970 heads on a 455 CI engine if you want to use pump gas. Any of the 1972-1979 Pontiac heads will produce a compression ratio that will work well with 93 octane pump gas and will still make good torque and horsepower up to 4000 RPM.

Option #2. Step down to a 389/400 engine if a good 455 cannot be located but be advised, it is difficult to use production Pontiac heads on 389/400 engines. The 1967-1979 Pontiac heads that are available will either have too high compression for pump gas or too low compression ratio for good power. The best option with a 389/400 engine is to use 1967-1979 heads with factory screw-in rocker studs with hypereutectic dished pistons. The 1965-1966 heads will work but are kinda "left-handed" heads since they have small valves and pressed-in rocker studs and should be left for the restorers.

Do not use a 326 or 350 CI Pontiac engine under any circumstances. .

The only thing that will make more horsepower and torque than cubic inches is rectangular money.
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Old 06-26-2013, 08:00 AM
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I was typing when AP72 posted. A couple things he says need addressing.

Due to the length of the intake track, the shape of the port (a true "venturi") and the "long" connecting rod, the Pontiac makes more torque at a lower RPM than most American V8s. What makes the Pontiac "different" than the Olds and Buick (the only ones that make that level of torque) is the ability of the Pontiac to accept modifications. Not unlike a Chevy, when you add perfornace parts to the Pontiac, it responds well. Think of it sorta like a small block on steriods. But rest assured, ALL engines are different when it comes to the approach to making power. This concept "one is the same as another" is what got Pontiacs the negative reputation in the '60s, when small block guys left in droves as GTO stomped everything on the street. They would try to make power at a high rev and ignore the torque. This led to the feelings that Pontiacs don't "run" and blow up. And it's true. If you approach it like a small block, this IS what happens. Approach it from the correct angle, and you get the engine that powered GTO. And never forget, GTO didn't get a reputation for LOSING... No other muscle car has a mystique around it like GTO. In '64, add slicks and run 12s all day... Smokey said regarding the Pontiac, "Don't rev it up, GEAR it up..." Today, we do both...

The Pontiac oiling system is excellent, just misunderstood. The only change we make is to restrict the oil (at the lifter bore) when using a solid lifter. Like the Chevys, this prevents "filling" the valve covers and starving the mains. The 60 lb. oil pump is the true "high volume" pump, regardless of what is said in various catelogs. The 80 lb. pump is the "high pressure" version. I PROMISE you, Melling knows more about oil pumps than Summit.

Demon carbs should be avoided. The company no longer exists. It was never anything more than a genuine immitation Holley anyway. Rochester Q-Jet is among the better carbs for the Pontiac (single 4-bbl), and of course, 2GCs on the TriPower. Once the "need" for more than 800 CFM arrises, we use AED Holleys.

Don't mean to step on everything he said, but he's propegating erroneous mythology. Having built literally hundreds of Pontiacs AND Chevys (including record holders and track champs), I am in a good position to know of which I speak.

PAX

Jim
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Old 06-26-2013, 08:23 AM
How fast is fast enough?
 
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Quote:
Originally Posted by Mr. P-Body View Post
I was typing when AP72 posted. A couple things he says need addressing.

Due to the length of the intake track, the shape of the port (a true "venturi") and the "long" connecting rod, the Pontiac makes more torque at a lower RPM than most American V8s. What makes the Pontiac "different" than the Olds and Buick (the only ones that make that level of torque) is the ability of the Pontiac to accept modifications. Not unlike a Chevy, when you add perfornace parts to the Pontiac, it responds well. Think of it sorta like a small block on steriods. But rest assured, ALL engines are different when it comes to the approach to making power. This concept "one is the same as another" is what got Pontiacs the negative reputation in the '60s, when small block guys left in droves as GTO stomped everything on the street. They would try to make power at a high rev and ignore the torque. This led to the feelings that Pontiacs don't "run" and blow up. And it's true. If you approach it like a small block, this IS what happens. Approach it from the correct angle, and you get the engine that powered GTO. And never forget, GTO didn't get a reputation for LOSING... No other muscle car has a mystique around it like GTO. In '64, add slicks and run 12s all day... Smokey said regarding the Pontiac, "Don't rev it up, GEAR it up..." Today, we do both...

The Pontiac oiling system is excellent, just misunderstood. The only change we make is to restrict the oil (at the lifter bore) when using a solid lifter. Like the Chevys, this prevents "filling" the valve covers and starving the mains. The 60 lb. oil pump is the true "high volume" pump, regardless of what is said in various catelogs. The 80 lb. pump is the "high pressure" version. I PROMISE you, Melling knows more about oil pumps than Summit.

Demon carbs should be avoided. The company no longer exists. It was never anything more than a genuine immitation Holley anyway. Rochester Q-Jet is among the better carbs for the Pontiac (single 4-bbl), and of course, 2GCs on the TriPower. Once the "need" for more than 800 CFM arrises, we use AED Holleys.

Don't mean to step on everything he said, but he's propegating erroneous mythology. Having built literally hundreds of Pontiacs AND Chevys (including record holders and track champs), I am in a good position to know of which I speak.

PAX

Jim
****************

The brand on the valve cover is irrelavent and pontiacs runners are NOT "true venturis" You can build either a chey 383, a Chrysler 383, or a pontiac 389 and if you do everything right end up with almost the same exact power. As for torque- well torque is a made up meaningless number, what matters is the average power but to the ground, regardless if your engine is buzzing at 5,000 rpm or 10,000 rpm.

Restricting the oiling is one method of oil control, supplying more is the other, enlarged galleys and a HV pump will take care of supplying more- regardless of what pressure you chose (60lbs should be adequate). fixing the oil drain back and emptying the valve covers is an entirely separate issue and should be addressed as such, there are many way to increase the drain back.

As for Demon, the company certianly is still around, you can contact them here: Demon Fuel Systems - Sales & Product Support Contact



40 years ago when not much was widely known about engine design your recommendations would have been spot on, but in the past 40 years a lot was learned and improvements have been made.

Last edited by 68NovaSS; 06-26-2013 at 01:24 PM. Reason: Profanity, demeaning comment
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Old 06-26-2013, 03:09 PM
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I have addressed ap72's "issue" with me on a personal basis. Perhaps someone here (with more local "credibility", as I guess being a professional engine builder isn't enough) can explain the dynamics of runner length, cross section and velocity to him, so he understands they are NOT "all the same". And, at least for a street engine, torque is hardly meaningless. In fact, it's EVERYTHING. Torque is "the ability to do work", involving the "twisting force". Horsepower is a measure of power spread over a given distance and in a certain time frame. Torque is what "moves" cars.

Barry Grant ("designer" of Demon) died last year and his company went under. I was unaware there was another using the name and marketing the carb. Doesn't matter, still a genuine immitation...

I apologize for any "ruffled" feathers, but the man came here looking for accurate information. Attempting to discredit that because it doesn't "match" one's personal opinion (based on myth and ancient information) serves only to confuse the OP. I "shipped" three Pontiacs last month, including one 700 HP pump gas streeter. A couple small blocks and an Olds snuck out at the same time... (:-

If something is merely my opinion, it WILL be stated as such. If it's not "qualified" as an opinion, you can take it to the bank.

Jim
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