1960 GMC 370 rocket Vs. Real olds rocket engines: what is the difference

So i went in to my favorite shopping center today, and lo and behold there sat a 1960 GMC Thomas built school bus. The engine in it is totally complete, BUT after tomorrow it will be crushed.
IS it worth my time to pull it? from what I read, it should be a 370 and of the same family as the Oldsmobile rockets and that it wasn't used in any olds.
But how similar is it really? Will aftermarket intakes/ cams etc. fit it? is there anything undesirable about it that will make it impossible for me to use or to sell?
It is coupled to a straight drive and the hood, emblems, headlight trim and grille are all good, anybody need anything while i am frantically pulling parts?

Olds experts: what would you do?

 

Why ask? Pull it, unless it's set up and full of rust. Then at least nab the valve covers, since you can always sell them to some ratrodder and make some of your investment back. It's a tall deck 371 the same as an Olds car motor most likely. Same block. The only oddball GMC motor I'm aware of is a 331 that was a Pontiac block with a smaller bore, and that's the only real difference in the motor.

For that matter take the bell/clutch/flywheel, I'm sure it's connected to some kind of manual transmission, the trans itself not usable in a car but the bell can be modified to take a car trans I'm sure.

Lot of sellable bus stuff, grille, cluster, a lot of the lights and things are worth saving.

 

U sure that isn't a Pontiac 370 engine? Look for the two small hoses from the water pump to each cylinder head. If so you have a Pontiac engine, not an Olds.

 

I went and started pulling parts. I am pulling some of the tin- hood, grille headlight buckets etc. as well as the steering wheel. The motor has a two barrel, a Gmc sticker and oil fill in the valve cover. the intake has a seperate tin pan over the lifter valley, and the water pump DOES have a hose to each head.
I am going to pull the sucker out, but more info on the beast would be great.

I will try to get some picture up soon.

Thanks guys!

 

Pull it, same base was used for the Nascar 370 back in the day
Larger crank than the 371 olds.

 

post pics!

 

ok Guys, I have pictures.
BUT i think i have a Pontiac not an olds. Pulled the intake and a head today and it has a 3.76-3.8ish bore so i am thinking it is a 287. I was thinking of selling it, but my buddy has me about convinced to make a Chevy eater out of it. What do you think??

 

Dude, that is the official school bus from hell.

Good find!

 

Probably a 336, same mains and stroke as a 389, small bore. Not a bad motor but an oddball.

I could probably use that bell if you don't have plans -

 

Absolutly a Pontiac. Pontiacs are good. A 455 in my Vega went 208 in 94. fastest I ever went. I fooled around with one old PMD head and cut the exhaust ports back to before they started to bend down. Then ground the remaining port straight. The next move would have been to make a aluminum or steel piece that would bolt to the new port face and be held down with the head bolts that would continue the exhaust port up and out. Should breath a lot better. But I never finished it. If your going to race the Pontiac and want to take a chance with the heads PM me.

 

when you go to sell the body parts, they're 58-59, not 60.

if it has a tach in it, get that too

 

A friend of mine years ago had a mid 50s Pontiac hearse, a 56 I believe. When he rebuilt the engine the only odd bit that he ran into, that I recall, was main bearings. The diameters were the same but I'm thinking his had a wider rear main bearing. A local machine shop recalled that GMC used a Pontiac based motor during these years and sure enough, the GMC bearing set was sized like the original part for the rear main bearing.

IIRC, Pontiac designated the engine as a 287 while GMC listings showed it as a 288. I guess since the hearse was a commercial chassis it got what might have been a slightly beefed up GMC engine. There might have been some other pieces like stronger pistons and steel timing gears and roller chain but nothing else drastically different that I can remember.

Don't remember seeing any GMC decals or logos anywhere else on the engine, and it all appeared to be original when it came apart.

 

That is a reverse flow pontiac engine i have one in my 55 gmc pk. a 1959 389 will bolt up to your flywheel and bellhousing. and any gm chev trans will fit the bell. OldWolf

 

If that bus has a 'GMC 370' badge on it... it's for the chassis, not the engine size.
370 was a chassis series number used for buses and large trucks.

 

Well it sure doesn't look like a reverse flow engine from the location of the carb and exhaust manifolds in the pictures, or are we getting our legs pulled a bit here? It so hard to tell sometimes here on this internet thing.

You're not referring to that odd GMC 305 (and larger) V-6 that had the spark plugs located on the intake side of the heads, are you?

GMC V-6 Engine

 

two small radiator hoses going from water pump to each head means reverse coolant flow. You can see one of the hoses in one of the pics.

 

Well DUH! Hadn't thought about the coolant flow being reversed. Saw the previous mention about the hoses in the front of the head but figured they were just rerouting things, not changing the direction of coolant flow.

Carry on!

 

gee whiz...I knew rustynewyorker & squirrel would be on sum-n like this...the looks of that yard it's in, good effort Bro... GET IT... pm me...

 

I originally though it was a 370 because it is cast into the base of the distributor, and i thought it was an Olds out of ignorance, Which would have made it a 370. But there are no badges that say anything other than gmc and V8.

as Far as the displacement, i was figuring it might be a 336 (once i realized that it was a Pontiac) but now that it is in the shop i am starting to believe that the block and heads were swapped out for a 287 from a 55 Pontiac car. The intake, valve covers and brackets are all painted orange, but the heads are light blue and the block is metallic blue green. That and the bore is 3.76ish- too small for it to be a 336.

Rusty, you will be the first to know if that bell housing is available, but right now i am pretending that i could afford to build it.

If it is a 55 car block it should have 2.5 inch mains, and a 3.25 stroke. I am thinking that i might be able to take a 57 crank, with a 3.5625 stroke and 2.623 mains and have it offset ground for a old fasion, forged stroker crank.
Between that and a .040 over bore i should have 400ish Ci.

Am i being foolish to think that that should work?
I haven't pulled the pan and taken any mesurements so I am yet to see if there are any differences that would be unreasonable to overcome.

 

I don't feel much like doing the math, but you are sure not going from 287 to 400 inches that way. Did you mean 300?

 

Talk to Steve Barcak aka Applekrate here on the board, he knows all about modding early Pontiac blocks.

 

whoops- yeah my math was off. I was adding the .040 over as .40
After correcting that it looks like a healthy 326 should be possible.
I will Pm Applekrate tonight about it.

Thanks for all the help guys!