Technical '57 GMC Pickup Can't get out of it's own way?

This ....[below] start here and don't expect the truck to run interstate speeds.

 

There is a man in AZ that sells 3:55 gears for the '48 - 54 AD 1/2 tons. I think his moniker is "Mother trucker".That will give a bit more highway speed. 50 to 55 MPH with stock gearing is about normal without over revving it. The Jimmy rear in a half ton should be the same as a Chevy. 3/4 ton versions of this truck will top out at around 45 MPH without screaming.

 

Thanks Glenn! In delving deaper, that's exactly what he said. Got to hunt down rear end gears.

 

A stick had 4.11,s and automatics had 3.90’s in 56.

 

Most don’t believe this but a 270 with a small port head is a great street engine done correctly. Yes a 302 with a large port makes bigger power but the 270 from 57 up had a great small chamber that had a shape of its own not like the 228-270 early ones.
Flat top pistons about .010 in the bore or even closer will give the highest compression. The exhaust valves can be 1.50 Chevrolet and the intakes cut down 1.94 or the biggest 283. The key is getting the port work to mimic a venturi and use a big port intake(either old multi or new 4 barrel) and angle taper the first 1/4 to 3/8” of the head with a 45* angle to port match. This venturi effect blended correctly with make the bore and stroke think the head is bigger because it will flow more when the valve first cracks open.
Remember the 270 has a 4” stroke like the 302.
The cam needs to be what the RV cams of the 70-80’s were and advanced 6 to 8 degrees. No way will a piston hit a valve with no pop up which were never available for this chamber design because it wasn’t raced. Most heads can have .075” removed safely and I’ve gone over .100”. I can describe cooling lines if asked. If making custom forged pistons you do it to available rings. As I remember 3- 7/8” is about it but I’d sonic a later block. A1940 270 has enough meat to go 4” but I thinks it’s the only one. A 270 has a stock bore of 3-25/32” so 3-7/8” is doable which is a stock 283 for rings.
Anyway big rant …..Have fun with it.

 

Those sets of 3:55 gears only fit CLOSED DRIVE 48/54 Advance design half ton trucks. They won't help Frankenrodz in the least. The truck he is looking at is open drive and he hasn't said if it is 1/2 or 3/4 ton. The one I mentioned in post 22 was a 3/4 ton that had every bell and whistle that GMC put on a truck in 57 but had been used hard and was a rust bucket to boot. Big window V8 Hydromatic 3/4 ton when it left the factory.

Still we all have our own idea of what "fast enough" is and sometimes we expect far more out of something than it can give but the next guy thinks it is wonderful.

 

A 100 should be a 1/2 ton.
A half ton 6cylinder 57 Jimmy, How bad can it be?
I know it's not Speed Racer but it should be drivable. It's not like it's a covered wagon with a rented mule. If it does run like a crippled rented mule, something is wrong with it.
Can't get out of it's own way...What does that mean? I think that's the point of the whole thread....It's relative. Compared to what? A Maserati?
100 point restoration....What does that mean? Whose points? Cosmetic or mechanical?
A purely cosmetic restoration on a truck pulled out of the bushes could explain a lot.
It sure is pretty but it's only running on 4 cylinders....
I had a 1963 Ford F 250. It had a 292 T984 speed and 4.56 gears. Now that old truck loved 50-55MPH. Let me tell you...It was a Man!
Shifting through the gears was an absolute blast. It could pull anything....Like Hawaii if you had a big enough chain.

Check it out real good. As mentioned it may be just a "cosmetic" restoration.