[Cmseabee24]

I acquired a 62 389 engine out of a 62 Bonneville. The engine had only 88,000 miles when pulled and ran. It was pulled for a rear main seal leak. I paid $250 total for engine and transmission. I want to rebuild the engine a bit while I have it a part. Nothing to crazy just looking to squeeze maybe 350hp out of it. Looking for advice on a good cam and what year heads would get me there. I am new to Pontiac all I have ever worked on on diesel such as Mack, Cummins, cat, and Detroit. What is a good compression ratio for these engines? Any help on this build so I can get started would be appreciated.

[tom s]

Get rid of the heads and get a set of later heads along with the timing cover.Tom

[Cmseabee24]

What later year heads? What cc would be good to stick around? Also aren’t the later year heads have different valve relief? I am new to all this with Pontiac. I’d like to stick to somewhat of a budget build. Also I do want to throw a new cam in it. Do I stick with the flat tapper or go to rollers?

[Cmseabee24]

I acquired a 62 389 engine out of a 62 Bonneville. The engine had only 88,000 miles when pulled and ran. It was pulled for a rear main seal leak. I paid $250 total for engine and transmission. I want to rebuild the engine a bit while I have it a part. Nothing to crazy just looking to squeeze maybe 350 out of it. Looking for advice on a good cam and what year heads would get me there. I am new to Pontiac so I am looking to learn from some guys who are more knowledgeable. I know the heads in the later years have different valve relief. So I am looking for someone who knows these engines inside and out to help me plan out a build. I
Like I said I’d like to see anywhere from 350-400hp. Would like to stay to somewhat of a budget but not complete necessary. I appreciate any input.

[tom s]

Later heads would require new pistons which you would want to do anyway.If me on a budget build i would get a set of later cast rods(I know everyone will fall back in horror)but I used them in my 421 HO build.For what you want any head like a 68-69-70 with screwin studs will work,a set of custom pistons to get you too about 9.5 CR will be good and a 068 tripower clone cam will be fine.Tom

[77 TRASHCAN]

It would help to know at least, what vehicle you are thinking about using the engine in. The vehicle weight and what type of gasoline you have available to use, intended use of vehicle. Do you want to use the original intake and carb? Which carb?
There’s a few things about these older engines that you will need info on, depending upon the direction you go, none of which I have knowledge of.
There are any here that CAN help you, though!

[Cmseabee24]

I want to use the original carb it is a Carter. I’m not sure yet what I am going to be throwing this in. Probably a trans am of firebird. I’d love to throw it in a GTO but just too costly unless I come across a deal. I have access to pretty much any fuel E85, 87-93, etc. I was looking for a fun street build. Nothing to crazy though. I’d love to go E85 but I’m sure that’s a pain in the ass with a carb set up as the fuel weight is way different.

[Sirrotica]

If you're thinking of using it in a Firebird or T/A I assume you'd be looking at a second gen. (1970-1981). The first problem you're going to run into is the motor mounts are incompatible. The only chassis that a 62 would fit into would be a first gen, 1967-1969.

There are motor mount adapters sold so you could transplant it into the later chassis, just be aware that Pontiac changed the mount system in 1970, and early engines have to be adapted to be used in the later chassis.

If you bore it 060 over you could run 400 pistons in it and also use the later (post 1966) cylinder heads. These heads are much better engineered that the earlier heads are, many have screw in studs, which none of the 66 and earlier heads have. You'd be able to reach 350 HP quite easily in a street driven car with the later heads, and still have a mild cam in it.

The late heads can be used on a 389 block, but only if you keep the valve lift below .450. You won't have piston to valve interference with a low lift cam.

Just some of the subtleties I can think of off the top of my head.

[steve25]

If you stick with those 1962 heads with there 1.88" and 1.60" valves they will need some serious porting work to make 350 hp without race Caming and compression, no less making 400 hp!

Without knowing what your budget is I would first try to pick up a used set of 1968 to 70 D port heads that have been ported to to 225 to 240 cfm.

Hopefully these would be already to go and be a drop on with nothing more then a valve spring change if they had been set up for racing.

If this search fails and you have the bucks then either of the two aftermarket D port Aluminum heads would be a drop on 400 hp with a 9.2 to 9.5 compression.

[61-63]

Get #16 heads they are big valve open chamber heads with factory screw in studs. There are others and people will surely chime in.

[leeklm]

I recently helped with a 1966 389 build. .030 over, custom dished pistons, stock heads with new valves, no porting. Butler 218/224 roller cam. End result on the dyno was 340hp, so very close to the factory published 335hp.

To Steve's point, you will need more head flow , etc to push 400hp.

Another example was a stockish 455 build with mostly untouched 1975 7k3 heads, similar cam as above (under cammed for a 455). That engine made 409hp.

Sent from my SM-G965U using Tapatalk

[steve25]

Here’s a option for getting early blocks into 70 and later cars.

[steve25]

Here's some 389 build info that can still be applied.

[77 TRASHCAN]

A possible deal breaker (experts tell me, if I’m wrong).
64 is the earliest that block mounted starters were used. I don’t believe there’s a good option, unless you run a standard trans?

[Cmseabee24]

Originally Posted by 77 TRASHCAN

A possible deal breaker (experts tell me, if I’m wrong).
64 is the earliest that block mounted starters were used. I don’t believe there’s a good option, unless you run a standard trans?

No they make an adapter kit to mount up to a th350 or th400 although I think they range from $600-$1,000.

[Cmseabee24]

Would I be able to use a set of maybe 11 heads off of a 350. 85 cc should be about good to keep compression ratio 9:1 right?

[Radman]

If you go to the later heads you will also need to get a new intake manifold. The 62 heads have a 12 bolt intake 6 per head. The newer style has a 10 bolt pattern 5 per head.

[Stuart]

A good reference for building Pontiac engines would be a copy of Rocky Rotella's book: https://www.amazon.com/How-Build-Max.../dp/1613254741 There's also an updated version of the book, although I suspect the older one would be adequate for a mild build: https://www.amazon.com/How-Rebuild-P.../dp/1613255632

[steve25]

Yes, just as posted above it will be best to build it then with stock Bore 4.120" Pistons for a 400 .

It would also be best to install screw in rocker studs into any head that has pressed in studs.

[tom s]

65-66AFB intakes are cheap.Won’t have to spend much money and a roller cam is out for a budget build.Tom