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Old 01-27-2004, 06:42 PM
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Rebuilding Pontiac 389

I recently purchased a 1966 GTO and want to redo the 389 engine. I want to try to obtain around 400 HP with pump gas and maybe some additive. One suggestion was to drop down to 10:1 compression pistons, some porting of the Heads, Install the larger valves, roller rockers, stock factory spec Ram Air lV camshaft, ram air lV exhaust manifolds, Edlebrock Performer Intake manifold, Holley Carb, & MSD Ignition. I have a stock Tri-Power set up ready to go but don't know if the nostalgia of this will hurt the performance of the Tri-Power vs. the Edlebrock/Holley set up? My trans is a performance Turbo-400 with 2000 stall converter and an Eaton posi 3:55 gear (10 Bolt). I want performance for the street and an occasional strip run. Any and all suggestions are welcome.

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Old 01-27-2004, 07:11 PM
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Hey Ron,
It sounds like you have it pretty well thought out. The only things I would change would be the cam, intake and exhaust manifolds. I would step up to a good dual pattern cam. The old Ram Air grind is just that... old. Todays grinds improve on drivability and performance in leaps and bounds so it's something you should look into.
I would recommend the Edelbrock RPM intake in place of the Performer and a good set of headers will make quite a difference once you get your 389 breathing better. There has been enough testing on the Pontiacs lately that proves headers do make a difference that I wouldn't waste the money on the Ram Air
manifolds.
Just something to think about with your tri-power intake. The reason GM stopped using them was beacause the single Quadrajet out performed them and was much easier to maintain.
Mark
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Old 01-27-2004, 10:22 PM
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Those factory cams didn't have much lift,not long ago I finished a friends 400,he had 70 ram air 3 heads,flat tops, a factory try power intake that we port matched with Rochester carbs,I chose a summit catalog 224/234-.465 .488 hydraulic cam and he is still bragging about how fast it is. I never put it on a dyno,but Im a pretty close guesser and its real close to 400hp with gobs of torque. His is a 4 speed,but it pulls from near the ground up,so your converter should be fine. His came out to 10.25 but never pings on 92. He wanted the factory look,but he did go with headers.
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Old 01-27-2004, 11:05 PM
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There have been published tests lately putting the factory cast iron manifolds against good headers, and the headers performed much better. Even the reproduction cast headers with the larger 2.5" outlet came in a distant second place.

I would rather see you stay under a true 9.5:1 for a mostly street driven engine. If you have to retard the timing to get it to run right, then you would have been better off starting with a little lower compression. I haven't seen any octane boosters really help, and they greatly increase the operating cost per mile. Mixing race gas works great, but there again, the cost goes up. In our area, we only have 91 octane, and sometimes this number is a stretch of the station's imagination.

I'd also stay with the tri-power if you have it. Set up properly, it won't be a detriment to your performance (probably won't help either). I've seen many goats at the races that successfully run them. It just takes much more patience to get them right.
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Old 01-28-2004, 12:45 PM
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From what I've read (I've never used one), the ram air IV cam doesn't do well with lower compression (below 10:1) 389's and 400's. 11:1 would be better for that cam. You can make strong hp with the 041 cam, but off idle and low speed power will be less than desireable for a street driven car. If it was me I'd keep the compression at 9.5:1 for the street and you might want to try another cam like the Crower 60916 (221/229,112LCA). Your Tripower can be made to perform very well. Talk to Paul spotts at Spotts Performance. He's a great guy to deal with and will performance rebuild your tripower. And let's face it, there aint nothing like the sound of a tripower at WOT!

www.spottsperformance.com
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Old 01-12-2005, 01:41 AM
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the 041 cam

i have a 69 gto with a 30 over 400 with 62 heads 211 177 vavles a crane 041 cam its 230/240@50 with 469 lift with the stock rockers and springs a set of flowtech hedders and 2.5 inch ehaust pipes and flowmasters with a torker 2 intake and a holly 750 vacum secondiary carb with a turbo 400 tranny and a 2800 to 3200 stall with488 12 bolt rearend and it runs 7.55 in the 1/8 a mile and the car ran some 8.20s with the 3.23 single traction rearend the 041 has a rouch idle and idles at 650 rpms and out performs the comp cams 292 501 magnum cam i had in it and also the lunti special purpose cam 320/540 cam i had in it the 041 dont require no special springs or rocker arms and you cantorque the rockers at 20 pounds and it has tire smoking lowend power and pulls good to 5800 rpms you can get the cam and lifters from jegs for $115.00 ps its the best cam i ever used in a pontiac and has a rocgh idle and good vacum for my power brakes so give it a try youll love it i do
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Old 12-19-2005, 06:36 PM
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389 Rebuild

I am also starting to get a parts list together for my 66 GTO 389 rebuild. I want to run pump gas as well. I was told to go down to 8.5:1 on the compression to run the pump gas. Get Ross dish pistons, cast rings, Clevite bearings, Felpro gasket set, vitron rear main seal, teflon valve seals, roller rockers, stainless steel valves, harden the seats, port heads, new springs, keepers, and such.

I have the original 4V YS engine and am looking to put on a tri-power and keep the AFB on the shelf. Anyone not using one want to get rid of let me know.

Anyhow, I am still baffled on what cam to put in my car as well. Car has TH400 with mild shift kit and 2K stall and 3.23 posi. Stock exhaust manifolds on car as well. Will be starting from stop mostly and shifting at 5500 RPM when rocking and rolling. I do not want to go wild with rough idle. Just enough roughness to let people wonder what is under the hood. I too have P/B vacuum to be concerned with.

What are the best headers to replace the stock exhaust manifolds?

Sounds like we have the same project going on.
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Old 12-19-2005, 08:31 PM
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The Crower 60916 sounds about right. We are pulling the 421 out of my son's '65 2+2 over the holidays for a cam, intake and carb swap; and I have just about decided on that cam. The car runs pretty strong on what is probably a 204/214 @ .050 cam, but we have recently installed Doug's Headers and a Pypes 2.5" exhaust and it's time for the next improvement. The car is driven daily and I have become a firm believer in not going over 230 @.050 for a vehicle with power brakes.

I cheated on my goat and went larger on the cam, but have to remember to not pump the brakes on a stop because there isn't enough vacuum left for the second push. Not really something I want to stick other members of the family with.

There's also that fine line where too big of cam with mild compression will kill off so much torque that the little possible extra horsepower on top end just isn't worth it. If someone gets 5 car lengths on you while your engine is trying to climb up on it's power curve, the party's over. It's much more fun with the 8.8:1 engine and the 221/230 cam running a full 34 degrees with the A/C on and seeing the temp gauge running at 180.
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Old 01-21-2006, 07:37 PM
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As far as the 389's go alot of the Pontiac builders are boring for a 400 piston and then dishing it to achieve around 9.5 compression. As far as the tri-power by all means use it. Contact Jim Taylor (his address escapes me right now) to set up the carbs for you. The RAIV manifolds will not bolt to the standard D-port heads as even though I'm a big fan of the 041 (RAIV) cam I feel the 744 H-O (or RAIII) cam would work very well as most 389 tri powers had the 067 cam in them. If you want an aftermarket cam contact Bullet Cams as they are now the supplier for the Ultradyne cams, noted to be some of the best cams available for Pontiac engines. If you want more lift from the standard .407 from the 744 have your pushrod holes elongagated for use of 1.65 ratio rockers, this should bring your lift up to .447. If you do decide to go with an 041 grind (RAIV) then go with the one available from Melling as they were the original grinder for factory Pontiac cams. The Melling cam is highly recommended by Jim Hand over the aftermarket grinds. I have used the Crane myself in the past and yes it was a good performer but it needs some really good heads with 2.11 inch intakes to really perform good. Jim Hands new book How to build Max Performance Pontiacs is one of the best available today. I hope this helps as I haven't been around for awhile and was going back through some of the older posts on Pontiacs.
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Old 01-22-2006, 05:05 AM
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Whilst you've got the heads off dividing the centre ports can help. RA 4/5 heads are like rocking horse dung here, same there?
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Old 03-15-2006, 12:02 AM
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389 re

Basically I agree with ever one else. Trypower doesnot have it . They sound good when the rear one opens up. If its not the ram air engine forget it. The size and shape don't lend themselves to enough grinding metal to mate the different shape heads, besides that the really do much either. I leave the details to the others. It will come a part on you, under 6000 rpm or you are asking for trouble. I never crossed 6500 more than a few times, and that wasn't intentional . Are you tring to lift the front end. You can't get enough tire under it istock to do that. I would start with the stuff you have here, when thats finished start asking questions again. A 455 is another story.
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Old 03-15-2006, 09:08 AM
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madamstn my 71 GTO pulls the front wheels with a 10.5 in slick under it with a 3.55 open rearend. All depends on how the suspension is set up. Several years ago Jim Taylor did a comparasion of a tripower setup vs. a four barrel on a 68 GTO that had a 428 in it and it was quicker by over two tenths with the tripower. The tripower has shorter runners so the mixture doesn't have as far to go as compared to the single four barrel setup. Somewhere I have the old issue of High Performance Pontiac that this comparasion was done in. When setup properly the tripower is one of the best induction systems ever designed and used. If the 041 (RAIV) cam is used for a strictly street engine use Rhoads lifters to help restore some of the bottom end that this cam loses. Also when using the 389 heads you have to remember that the valve sixe and inclination is different than the later model D-port heads. The Crower 60916 would be the better cam to use over a RAIV as it will give you better bottom end power and torque.
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Old 03-16-2006, 06:43 PM
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389- 428 -455 don't 421

That should sum it up. I been out of circulation for a while. After 65, in 65, there were some things changed in production. At least the 428 had a larger center carb, Maybe we could have the 421 in 65. The front carb should start at 65 percent and the rear some where in there, I would have to go look it up. But the end was that all were full open at full throttle. That's they way I set them up. Tha'st not very scientific. I wasn't go find a dyno ever time I turned a screw. I would have to go find the things and look at them. The bolt pattern changed slightly and I would have go look at them to see what I have, but they always sounded best when the rear one opened up. later Mark
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Old 04-04-2006, 07:55 PM
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power transfer

That'spretty good. I was really thinking about the early models. Are you streetable without rattling your teeth or getting buried in every pot hole, my pickup's are just about without shocks on the farm-soft- get you killed on the highway. It's a fifteen thousand pound tractor drop off 4 inches in the front and you need to check your crowns to make sure you didn't crack them. I really would like to know what you suspension is like in that body style. I love the three duece set up mine is with the larger center carb' I have had it so long I don't remember where I got it. m
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Old 08-23-2010, 05:42 AM
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Quote:
Originally Posted by gto67ron
I recently purchased a 1966 GTO and want to redo the 389 engine. I want to try to obtain around 400 HP with pump gas and maybe some additive. One suggestion was to drop down to 10:1 compression pistons, some porting of the Heads, Install the larger valves, roller rockers, stock factory spec Ram Air lV camshaft, ram air lV exhaust manifolds, Edlebrock Performer Intake manifold, Holley Carb, & MSD Ignition. I have a stock Tri-Power set up ready to go but don't know if the nostalgia of this will hurt the performance of the Tri-Power vs. the Edlebrock/Holley set up? My trans is a performance Turbo-400 with 2000 stall converter and an Eaton posi 3:55 gear (10 Bolt). I want performance for the street and an occasional strip run. Any and all suggestions are welcome.

Old thread but worth reviving- you'd have to drop the CR down below 10:1

9.25 CR would be more like it with today's fuel

the factory 068 cam, or Comp 268 cam will work fine- slight lope on the Comp cam, increased duration @ .050" and more lift, but still driveable and decent mileage and vacuum at idle.

A single 4 bbl is better than tri-power, the original cast iron 1967-72 Qjet carb/intake is very good. Imagine rebuilding 3 carbs every few years, and replacing 3 needles/seats, and 3 accelerator pumps- and in the end the airflow is less than an 800 cfm Qjet, unless you get the 1966 tripower, in that case it's only 20 cfm more, not worth it.

You don't really need the stall converter, they slip and get terrible gas mileage.

I'd ditch the exhaust manifolds and get 4-tube headers

a RA IV cam has lower manifold vacuum, rougher idle, and is dead below 3000 rpm in a 400, I ran one for years in a Firebird w/3.70 rear gears, even those gears were not low enough, it really needed a 3.90 gear. If you're running 3.55's use a milder cam.
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