389 in 3900# 55 Truck. Best heads, torque cam, and gear ratio?
 

I’ve finally found a good ‘59 389 block and crank locally that’ll bolt up to the Hydra-Matic in my 55.2 GMC 100. So I’ve resisted the urge to LS swap it so far, but man these old poncho’s are different animals completely.
I’m wanting to rebuild the engine for dependability and torque since it’s in a truck and give it more guts than the original 316. I’m also going to swap out the banjo rearend for an O/P 9.3” I’ve acquired for better choices in gearing.
Other upgrades I will be adding are power brakes and a Holley Sniper or TBI retrofit at the least.
Since I’m starting with just a block and crank, I’m trying to figure out what combo to build.
What heads, cam, and gear ratio would be ideal for a driver that’s a fun to drive with lots of low end power and instant throttle response, BUT still able to pull a utility trailer loaded with building supplies and most importantly, dependable?
The gear ratios in my hydramatic are: 4.08:1, 2.63:1, 1.55:1, and 1.00:1 if that helps. I will be running approximately a 29” tire. Those tranny gears should allow me to have a taller ratio for decent infrequent highway cruising.
In terms of camshaft, I will spring for a hyd roller for durability with focus on low end and midrange power and excellent throttle response. Good vacuum and easy on valve springs. Are a must.
Anybody have a good suggestions or build something similar to this back in the day? All advice is appreciated.

Well to start with you can’t run the original heads.
I would try to turn up a set of #62 casting since with a .030” overbore your compression will be good for pump fuel.

Cam wise since you want as much torque as possible you then want a cam with .450” to .470” lift.

I don’t understand why you want to blow so much money on a FI set up though.

What is a fair price for #62’s? Would I use the stock replacement style pistons for that 59? I’m guessing a factory flat top?
As for the sniper EFI, I know nothing about carbs. The only other carb vehicle I’ve ever had was an 86 z28 with an electric quadrajet. I I don’t have anyone left that knows the wizardry of carbs to teach me. I grew up on EFI and fair to say that I’m spoiled to it. Just get in and turn the key. For people like me, who don’t know carbs you can’t beat the dependability of a simple EFI setup. Now that port fuel injection is all the rage, I could probably find a GM TBI setup for nothing. The quadrajet sniper system is an option. I see them on marketplace for reasonable prices.
I’m moving the gas tank out of the cab so I have to redo fuel lines and what not. Whichever I do, it will still have a traditional air cleaner.

If you want torque then I would get a stroker kit with a 4.25 stroke
https://butlerperformance.com/i-2459...tegory:1234862

If your going with a hyd roller cam then I think the Lunati Voodoo 262/270 20510710 would be perfect works with a stock converter and would make great power
https://www.lunatipower.com/voodoo-r...8-262-270.html.
I would go with a gear ratio of 3.23 with your 29 inch tires

I did score a running 60k mile 287 the other day that has a 4 barrel Carter on it. I’m contemplating putting it on the 316 while I build the 389. If that Carter dies, I reckon I’ll buy one of those edelbrock carbs that are supposedly good out of the box. If it surprises me, I’m not against keeping it. But if it’s as cold natured as the Stromberg on my truck…it’ll get sold ASAP.

The stroker kit is a bit out of my budget. Plus, with the truck being so light in the rear IIm afraid that would be overkill for me. My trans doesn’t have a torque converter. It has what’s called a torus. I don’t know much about them, but I am not willing to pull it out hence why I’m stuck to a 59 or 60 389. IDK how sensitive hydramatics are to cams. But I do like wat the descriptions say about that cam.
I’m just trying to build what I have without butchering the truck or doing anything that can’t be easily undone to it. Otherwise I’d set it down on the c20 frame in my way and slap my L92 or 418 stroker LS and 6L90 I have laying around in it. But this ain’t really the kind of truck to do that to.

From what I’m reading, I’ll probably have to have this bored to use 400 pistons. Or buy custom pistons unless I want to use cast pistons. I wish they made the 4032 Forged Mahle’s for these or 400’s. I’ve got to buy rods and pistons regardless so custom isn’t out of the question. I’m thinking that would open up my choices of cylinder head availability. I have no idea of what heads were good for pontiacs. Because of rarity some are outrageous because of collector desirability. I want to avoid those. So far I’m hearing #62’s. Any other good candidates?

I had an Oldsmobile 55 years ago with that Hydramatic and an Olds 371 CI engine. I put an Isky E-2 camshaft (HFT) in that engine and it really woke it up in the lower/midrange RPM area. The Hydramatic handles it all very well. In fact, B&M transmissions in Calif used those older (pre 1958) Hydramatic's to start their company. Their reman B&M trans were popular in the NHRA gasser classes, even the classes using blowers and solid roller cams on the engines. If your trans is in good shape it should not have any problem with that mild Lunati cam. Of course with any cam swap, you'll need new lifters and valve springs. Looks like you'll have a great nostalgia project, go for it!

The only thing wrong with '59-'64 heads is it may limit your intake choice a little.
Ideally, a 1960 timing cover which would retain the front mount but use a standard cooling config would be great for 1965+ heads and pretty much your choice of intake.
Any mild build would result in at least 425ft/lbs of torque. How much ya need??

Make SURE that you read and understand the "interchangeability" section of Larry Gorden's page in the link below before you try to attach the '59 crankshaft to the HydraMatic's flywheel.

https://www.pontiacsafari.com/L1Gara...eID/index.html

Read further down into that section and follow the link to find out why you can't put '60 or later heads on a '59 or earlier block.

And as long as you are tearing into the '59 engine, take a look at this https://www.pontiacsafari.com/L1Gara...ealUpgrade.pdf
article I wrote about upgrading the front seal. If you decide to do it I'm still loaning out my alignment tool ($100 deposit cheerfully returned when I get the tool back, you pay the freight both ways).

If you use it, you will be the 14th "customer" without a complaint yet.

Great to know about the timing cover!

Thanks Bill, I’ll definitely do that Bill.

I know a lot of folks don’t like the Edelbrock carbs but I like them. Sure a properly prepared Quadrajet is a “better” carb as far as performance but after owning a few Edelbrocks they are easy to tune & stay in tune with minimal fuss. If you don’t know carbs it’s a good place to start IMO. Plus, with all of the information available here & Youtube as well as books you could learn how to run any carb out there.

Everyone else has covered your engine. I'll mention rear end choices. I built a 1961 Chevy PU with a 1965 389 , Turbo 400 and used the 3.08 that was in the car I got the 389 from. I welded the brackets from the truck's rear end to the car rear end and it worked great. The 3.08's worked very well with the power available from the 4bbl 389. Also like was mentioned the trans is not a direct bolt up to the later engine. Be careful to use the correct parts to join them.

That’s solid gold info Bill. Thank you!

Thank Larry. He's the one that gathered all this early V8 info.

Glad to hear you'll be keeping the GMC Pontiac-powered!
Although mine isn't a 389, the '58 car engine is now 382 c.i. (4.127" bore). So my truck is very similar to what you are building. I'm using a HydroMotive HydroStick (built in a '55 Pontiac housing) which has manual control of all four gears, and a fluid coupling brazed and cut for 3,200 stall. I use a '57 Chevy car rearend with Posi and 3.08 gears. Instead of slapper bars, I designed a center torque arm (think late Firebird). With the 4.08 1st gear, rear housing control is a must! My tires aren't as tall as yours, but the 3.08 rear is perfect- I've run 75 mph for hours towing my lakester on a trailer.
I redesigned the '58 combustion chambers, eliminating the bathtub shape and reducing valve shrouding, and used KB hypereutectic pistons with D-shaped reliefs to get 9.05:1 which is happy on 87 octane.
As for carburetors, I love the simplicity of 2-barrels. My GMC has Tri-Power, but I've used a single 2-barrel (the huge Rochester 2GC from big Pontiacs) on other Pontiac-swap vehicles with milder cams than my GMC. It wouldn't surprise me if you'd be happy with a single big 2-barrel.

My hard learned experience with 59 389 crank shaft and 55 hydromatic. The 59 389 crank has a little extra material above where the stock 55 flywheel bolts on. However this extra material causes the flywheel to wobble taking out the hydros front pump. The stock 55 flywheel can be machined to work. I found this out the hard way in about 1969 when I swapped the 59 389 into my 55 Pontiac. I like the 6X heads.

If you have a complete '59 engine then keep it together. Once you start swapping part years you run into unforeseen inchangeability problems. You need to figure out your compression ratio and reduce it to something like 9:1 or less if you're going to be towing. For the price Pontiacs 067 or 068 cam would give you the power and throttle response you want. Find a vintage 4bbl intake and use a Edelbrock carb to get the car running and driving before you spend the big bucks on EFI.