[PONTIAC LARRY]

SO just curious on the 59 336 is supposed to be a small bore but same 3.75" stroke as the first 389 same tear so assuming also 3.0" main. Any chance the cylinder wall is just super thick then?

Is it a less bored out same casting 389 (very thick wall)

versus a

Different 59 casting with water jacket / cyl wall thickness to stay way under a 4 inch bore (3.78) ?

[tom s]

I thought the 336 was a 58 engine?Tom

[PONTIAC LARRY]

Originally Posted by tom s

I thought the 336 was a 58 engine?Tom

Supposed to be two different ones and the 58 336 was based off a small bore 370 with the same mains as the 370 same stroke and the 59 the 336 was now a smaller bore than the 58 and matching the longer stroke of the 389 at 3.75" and I suppose 3 inch mains. I think since posting this I found 59 336 casting number 350046 vs the 59 389 is 532000 3.78 bore so if as robust as the 389 perhaps at the least the 59 336 could literally use a STD 350 Pont piston in a rebuild bore .100 over makes it salvage able and stick later model 68 up 350 or 65/66 389 heads on it.

[Bill Hanlon]

All the GMC (Pontiac) V8 engines had serial number starting with the displacement. So both a '58 and '59 engine's serial number would start with 336. Remaining serial number would tell the rest. '59 (389 based) engines are serial number 33635001 or higher, while the '58 (370 based) is lower. The serial number is on the passenger's side of the block.

In 58 the GMC block was bored to 3.875" giving a 336.1 cubic inch engine instead of Pontiac's 370. In 59 the GMC block was bored to 3.78" giving 336.9 cubic inches instead of Pontiac's 389. Crankshafts for both years had different part numbers that Pontiac. Maybe because of smaller (lighter) pistons???

Given a different casting number, I wouldn't depend on the '59 GMC 336 block being a 389 block that just wasn't bored as far.

[Murf]

I have a 59 gmc block setting in the garage. I could take a pic of the bores if it helps ya. It looks like a lot of room but IDK

[tom s]

Confirm 3in mains!Tom

[694.1]

It always seemed odd to me that GMC putzed with the displacement.
The only thing that makes sense to me is if motor carriers were taxed on displacement?
If it were a HP thing, it would be much easier to trim the HP. Heck, they used the Olds 370 too.
That would result in many more part #s than the Pontiac 370!!
But engineers do things for a reason...

[b-man]

In some of the European markets road tax was determined by bore size so perhaps the GMC brand was being positioned to take better advantage of that.

Lots of early 4-bangers and V8s made for transport use (think Ford flathead) had extremely small bores and relatively long strokes to have lower taxable horsepower.

[CATBIRD]

and so.....which was the infamous 1963 326/336???

[b-man]

Originally Posted by CATBIRD

and so.....which was the infamous 1963 326/336???

It was the 1963 Tempest 326.

Those first year 326s had the 3.78” bore for 336 cubes. The next year they fixed it with a 3.72” bore for 326 cubes. GM corporate edict related to 10 pounds car weight to 1 cube of engine displacement, 336 was too much engine displacement I guess.

So it wasn’t a GMC truck V8 336.

[blueghoast]

Can you bore a 4-cylinder to a .030 400 piston size?
I've got four good pistons from a earlier motor that
I would like to use in this 4-cyl build. Thanks for any info

GT

[PONTIAC LARRY]

Originally Posted by blueghoast

Can you bore a 4-cylinder to a .030 400 piston size?
I've got four good pistons from a earlier motor that
I would like to use in this 4-cyl build. Thanks for any info

GT

I believe the extra thick 4 cyl block could go 090 over but the common regular one I would stop at a STD 400 piston at 060 over

Dave Johnson 63 Banshee can give more details on that