66 389 Rebuild

Gents -

I am going to be rebuilding my 389 soon, but would like some more HP out of it. This is what I have currently. I am looking for a good reliable engine with some balls, no drag racing. Nothing lopey and run on pump gas, somewhere in the 375-400 hp range.

XE Block bored 40 over. Not going to bore anymore. Cylinder walls are good.
Crank is good, ground .010
Stock cam.
Edelbrock Performer Intake
1405 Edelbrock carb, manually choke.
Electric fuel pump, Holley Blue, with adjustable regulator
Relocated oil filter.
Hooker Comp Headers.
093 Heads
3.23 Safe-t-Track rear
4spd M21 Transmission

Piston suggestions?
Cam suggestions?
Head suggestions?
Intake suggestions?
Carb suggestions?

I appreciate the feedback.

- Tony

Tony, you need to get advice from a speed shop or a high performance engine rebuilder. If you live in or near any large city there will be enough old time mechanics and engine rebuilders out there to help you.
You will find on this site plenty of "experts" with a number of opinions, some good, and some goofy.
If it is an original 389 GTO engine and you want blazing speed, just add headers and change your rear end to a 355 or a 390 with positraction.
This might be an easier solution to your "problem".

carb throw your edelbrock carb in the can there junk get a new demon or a new holly 5150 .easy to tune and keep tuned .also has a 1 peace top so you can take the lide off with 4 bolts and see your floats A good raceing card .cam i would go a 272 H isky or comp cam not solid they float at high rpm's piston's forged TRW or seald power flat tops w/4 valve ,to drop the compression a tenth.allways chrome molly ring's or pontiac'c total seal rings are awsome but spendy heads 6X heads or some 16 heads if you can find a set 6x heads will flow bettter for the 389 & 350s or a set of ram air heads #31 48 13 will work just as well
intake stay with the performer or the RPM air gap dont get the vapor lock like older manifolds.. the 272 cam will run on pump fuel will give you the low end & mid range torque your looking for and high horse power at low RPM around 2200 to 3000 rpms it kicks in at. go with roller lifters & rockers comp cams make a nice roller set.the rollers will give you extra 10% hps and less wear
also wont float at high RPM's cloys true dbl roller timeing chain or a pete jackson gear drive will give you the most acurate timeing and is easyer to retard and advance also not good for all out drag raceing but great for street and every day use Travis Williams @EdWilliamsMachine boardman,oreogn hope this help's this is what i like to use..(2) 68 gto's one RAM AIR ho the other convert,



travis williams

and i forgot the older block have a 2 bolt motor mount 67 and newer are 3 bolt pattern so some thing to think about Travis



travis williams

There is a lot of meat in the cylinder walls. I took a 66 out .165 and that gave me 421. With twin 4 barrels, headers and cam it was a fierce unit. But now I have a 65 with a 455 in it. As powerfull or better and has nice manners



David W Davies

Somebody correct me if I'm wrong but although a set of 6x, 16, 13, or anyother head made for 67 and up 400, 428, etc...., they will bolt onto any 65 or 66 389, 421. The problem with doing this is if you run a high lift camshaft you will have problems with valve to piston clearence. If I were to rebuild a 389 I think I would use my stock heads have them ported and polished and have them bench flowed. I know the 389 heads have smaller valves than the 400's but I would talk to someone such as Paul Spotts @ Spotts Performance and see what he could do to get every inch of power out of a set of 389 heads.

you can run 421 head's and X6 heads are from around 63 and up & older,My many set's of X6 heads came off older grand prixs and some on other big car's I think they even came on GTO;s in 64 I have to look and make sure but,they a big valve;d head if I Remember correctly like the #16 #13 head's, I know the X6 head's flow the best on 350's..So hope this help's Lift from cam has some worry,just let you'r machinest know what you'r intension's are.BEST BET..He'll be able to help any good Machinest could!!!
travisWilliams@EdWilliamsMachine,boardman,oregon,



travis williams

I wanted to comment on Scott Sheeder's comment, in 67 the valve dia. was increased as most all of you know but whats important to remember is that the valve to bore centerline was changed as well. This is why 67 on up pistons have a bigger valve relief in them, basically to accommodate the valve dia. increase and angle change. Another important thing to remember is that the "valve to valve" centerline was changed too (the larger the valves, the wider distance from valve stem to valve stem) check for exhaust valve and cylinder wall clearance, the larger exhaust valve can come in contact with the cyl. wall. 67 on up heads can be ran on a 65-66 engine if you choose to bore the cylinders and use 67 on up pistons... i hope this info. helps......Joe

Hi Tony,

I am new to the pontiac forum however I was reading your question on a pontiac 389 rebuild. I rebuilt a Pontiac 389 for a 65 Pontiac GTO and used the following.
Ramair 3 camshaft
6x heads
The block was bored .040 over and I used the stock pistons (new of course) the heads had a 3 angle valve job and the exhaust ports were releived. along with 3 tube headers. It also had the Tripower intake and Carbs one other small thing that a few folks miss is installing a curve kit in the distirbuter it makes a major differance as it allows the timing to advance faster than the stock unit.
The ramair 3 cam has rough idle to it but it sure is sweet sounding at the exhaust and it does perform well However if you want a smooth idler engine wise I would recomend a cam for a 360 horse 400 and yes it will fit a 389 block. One other thing that a friend of mine did to a pair of 6x heads was swirl polish the valves. they were installed on a 428 pontiac engine that had the same things done to it that I had done to mine as for camshaft and carberation and headers the only other differance was the he used rhoads lifters on the cam to tone down the rough idle (they were sure noisey) however they worked very well.

I hope this helps you in your rebuild of the 389 as it is an excellent engine.
Wally G.

Rhads lifter's are great,I use them all the time but they don't make the tone of the rough idle go down,, THAT HAS TO DO WITH THE SIZE OF CAM YOU HAVE FOR IT BEING RUFF CHOPY Lumpyetc.bigger the cam the ruffer the idle
And retarding & advanceing of
the Dist,has some to play with that also. not Intirely correct..
the lifter's you use have nothing to do with it.
Rhoads lifter's are mostly Hydraulic and don't float at high RPM's on big cam'd motor's,as solid lifter's ..not good for big cam'd motor's..they float @ high RPM
TravisWilliams@EdWilliams Machine,,Ive been building motor and machineing motor's for over 23year's my dad has been do'ing it for over 50...P.S I'am at the track every weekend watching bracket's QTR miler's we sponser
I just thought you would like to know not knocking you.......Travis
The Pontiac Guy



travis williams