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Old 12-10-2005, 09:19 PM
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Pontiac 389 Rebuild

I have a 66 goat and am going to rebuild the engine. I have never attempted this myself as of yet but assisted others in their rebuilds many years ago. A little intimidating / scary for the first solo.

The goat is going to be driven on weekends, special occasions, and nice weather. Not a daily driver. Car has the original 389 4V, TH400 with shift kit & 2K stall, original 3.23 posi rear end.

I want to build the engine to run on pump gas. Things i know is to put in stainless steel 1 piece valves, harden seats, lower compression to 9.5:1 to run the pump gas.

The problem I have is what parts to buy such as cast or forged pistons, what manufacturer or type of rings, bearings, water pump, oil pump, gasket kit, brass or steel freeze plugs, etc.... What cam to get so i can still use my power brakes. Want a little rump on idle to hear cam but don't want to be rocking and rolling while idling. 2-6K range on cam i believe is the power range.

I know what parts to replace but am inquiring on what specific items and manufacturer is best. Is there a list of what needs to be replaced when rebuilding?

Go to Westbay, NAPA, Summitt Racing, Schucks, or??? to buy the parts.

Any input and suggestions are GREATLY appreciated. Want to start buying parts late January to February to rebuild in the spring. (NO heat or room in small garage)

Thank you for your assistance and guidance on this subject.

Larry

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Old 12-10-2005, 10:04 PM
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Quote:
Originally Posted by GTOLVR
I want to build the engine to run on pump gas. Things i know is to put in stainless steel 1 piece valves, harden seats, lower compression to 9.5:1 to run the pump gas.
You could save a few bux by re-using the stock valves. Stainless valves are great, but not necessary at this level. If your machinist tells you that your valves are loose and the guides should have work done, just have them replaced. Don't do the more common "knurling" of the guides. Pontiac guides don't seem to hold up for long if they've been "knurled."

Pontiac pistons are pretty easy to find, so I might suggest something. The stock 093 heads on that 389 were never wonderful. I might suggest some 6X heads from a later 400. They flow better than almost all other Pontiac stock heads. There were also 6X heads on the 455, but they had a bit bigger chambers that would be tough to get the 9.5:1 you desire. The small chamber 6X heads have the big valves. The exhaust is 1.66" and there is a bigger 1.77", but its not beneficial at all. Too much shrouding. Mill the heads for the compression you want on the pistons you want.

Quote:
The problem I have is what parts to buy such as cast or forged pistons, what manufacturer or type of rings, bearings, water pump, oil pump, gasket kit, brass or steel freeze plugs, etc.... What cam to get so i can still use my power brakes. Want a little rump on idle to hear cam but don't want to be rocking and rolling while idling. 2-6K range on cam i believe is the power range.
I would use hypereutectic pistons. Cast pistons are strong, but brittle. Forged pistons are stronger, but "soft". For street use like you're planning without nitrous or forced induction, hypereutectic is the best choice. I suggest getting rings, bearings, and other internal parts from Federal Mogul. Just good stuff. Nothing special, just consistent quality stuff. Pistons you should use whatever manufacturer makes your desired compression in hypereutectic. Ross, Mahle, Speed Pro, Fed Mog, and other recognizable names are all fine piston manufacturers. Fel Pro makes a complete kit for your Poncho that will work fine. The finer points of what sealant (if any) to use on what gasket can be discussed later when you get to that point.

Quote:
Go to Westbay, NAPA, Summitt Racing, Schucks, or??? to buy the parts.
I would use PAW, Summit, or Jegs. Everything you need is there and it can be delivered at a cheap price in one box.

Have fun and good luck.
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Old 12-10-2005, 11:48 PM
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where abouts are you in WA state?
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Old 12-11-2005, 12:40 AM
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when did pontiac change the head design?

i was in your same shoes about 6 years ago, i rebuilt a 65 389 with stock 75 heads. unfortunatley for us the 389 is one of the expensive engines to build
i ordered a .030 rebuild kit from PAW with forged slugs. ive had hyper****ic pistons break on me at the wrist pin and left me with a pile of junk so i went with the strongest. i reused the valves and valvesprings, just had a full work over on it. lucky for me my 389 lived life as a demo engine at my highschool and had never been touched by a machine and had less than 200 hours on it.

a th400 went behind it for the first 3 years of DAILY abuse, and when i say abuse, i mean everytime i got in that car i turned into a maniac and couldnt help myself but to leave thick black marks everywhere, usually in a sideways manner.

for the last 3 years it has underwent a couple of diffrent transplants into diffrent cars, i dropped it in my 68 tempest at first, then into a 42 pontiac, and then almost went into a 65 falcon untill the 400 in my 68 tempest blew up . now i drive it on occasion when im tired of the whimpy lill import i got.
she starts up every time, usually on the 3rd rotation of the crank, and thats after me letting it sit for a week or two.

the only problem i ever had with this engine is that i put 389 pistons in.
which limited me to the use of 65 or earlier heads. but 1966 may be included.
so talk to your machine shop about opening up the valve reliefs in the slugs, or just order the "400" style pistons. pontiacs all used flat tops so compression was as simple as a choice of heads.
ive ran 72cc chamber heads on 91 octane with a MSD ignition and had little problems with detonation.

in my 389 right now im running a 234/242 dur cam (@.050) this is probally what your lookin for. gives it a nice idle and with my 3" exhaust and 2 chamber flows, i rattle pictures when i come home. no problems with my brakes.
one of the 2 best investments i bought was a set of crane stamped roller tipped 1.5 rockers for 175 its well worth it!
and the other being a MSD 6AL, so much nicer on cold mornings, hot days, and those times you have to put **** fuel in!!

all my speed parts come from summit , OEM parts come from performance years, OPGI, and AMES. only have bought a hand full of things from PAW, their parts were right on but shipping was a probelm.
warrior racing has the eliete stuff for the pontiacs.

for 19 dollars, you can go to a book store and pick up"jim hand's guide on how to build max performance pontiacs, he shows ya all the lill tricks to do it the right way.

hope thats of some help!
B
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