Motor isn't what I expected

[Alberta Newbie]

Hi everyone, can you help me out with ID-ing this motor? I've been trying to figure out the horsepower, and now I'm not even sure I know the size.

It's in a 1972 GMC 3/4 ton, which I was told was original and only had 45,000 miles on it. But now that I started looking I found a plate that says it was rebuilt.

Model XC120087
Serial X31791
Bore 040
M 01 T 01
Engine Rebuilders Ltd.

The VIN says TCE2421522076 and the SE (?) is FT0705638. The plate in the glove box just says 350 CID V8.

Any help greatly appreciated...

[BCOWANWHEELS]

Well Its Bored .040 Over

[Alberta Newbie]

I'm pretty new at this, guess I should have googled it. I was hoping the numbers would help me figure out what the horsepower of the motor (and maybe the compression) would be?

[Ole Blue 68]

Hey Newb,

Do you have a casting number?

[quickpm]

You can figure out if it is really a 350 block if you get the casting number off the back of the block. The numbers are easy to see, they are about 1/2" tall. You can get stock head specs with the casting number on the heads. If it's been rebuilt, the sky's the limit. Heads could have been worked on, different size valves put in, ported, etc. Depending on the combustion chambers, head gasket thickness, and whatever kind of pistons they used (flat top, dished or domed) makes the compression ratio. The cam also greatly determines the power band. You may either have to dyno it or call Engine Builders, ltd to see what kind of motor they built.

I've been burned a couple times on a "350" that turned out to be a 305. You think I'd have learned the 2nd time. You can't tell from the outside. You have to run the numbers (with a book or google) or you have to pull a head and measure the bore size. It is really aggravating. I honestly think the 2nd guy didn't really know what he had (he was taken by someone else), but still.

[Ole Blue 68]

Follow quickpm's advice and then you can look up the casting number at http://www.mortec.com/castnum.htm

[Alberta Newbie]

I couldn't find it, so I thought they covered it with the rebuild plate. But a little work with a wire brush and I found it

K0312T4U

P.S. Thanks for all the help, I'm off to mortec!

[72armyswbtruck]

Welcome Newbie

[quickpm]

Originally Posted by Alberta Newbie

I couldn't find it, so I thought they covered it with the rebuild plate. But a little work with a wire brush and I found it

K0312T4U

P.S. Thanks for all the help, I'm off to mortec!

I'm pretty sure casting codes are all numbers. Look here (hopefully this works):



It is on the driver's side rear on top. 460776 for this one. 305 POS. If you do have letters, I haven't seen that before. (Of course I'm not the de facto expert, either).

[brak]

Originally Posted by quickpm

I'm pretty sure casting codes are all numbers...
It is on the driver's side rear on top. 460776 for this one. 305 POS. If you do have letters, I haven't seen that before. (Of course I'm not the de facto expert, either).

The code on the rear of the engine is all numbers, but if you look at the front of the block (passenger side, directly above the waterpump), there is a flat pad which has an engine code, and a partial vin. this Code always starts with a letter, and the code works as follows...

Engine ID Code Example: V0107CLJ - (V = Plant, 01 = January, 07 = 7th Day, CLJ = Engine Suffix Code)



Newbie, are you sure the last three in the code is T4U? I can't find that code (although my resources are limited) but i see a TAU which would be:
TAU = 1970 350 m/t 255hp 4bolt C-10

EDIT--> I forgot to mention, i usually look engines up using the info on NastyZ28.com. Mortec's site gives me a headache, and i can't ever find what i'm looking for

[quickpm]

Originally Posted by brak

The code on the rear of the engine is all numbers, but if you look at the front of the block (passenger side, directly above the waterpump), there is a flat pad which has an engine code, and a partial vin. this Code always starts with a letter, and the code works as follows...

Engine ID Code Example: V0107CLJ - (V = Plant, 01 = January, 07 = 7th Day, CLJ = Engine Suffix Code)



Newbie, are you sure the last three in the code is T4U? I can't find that code (although my resources are limited) but i see a TAU which would be:
TAU = 1970 350 m/t 255hp 4bolt C-10

EDIT--> I forgot to mention, i usually look engines up using the info on NastyZ28.com. Mortec's site gives me a headache, and i can't ever find what i'm looking for

Sorry, I all but forgot about that pad. The place I always buy my shortblocks always scratches that off clean.

[WorkinLonghorn]

Sorry, I all but forgot about that pad. The place I always buy my shortblocks always scratches that off clean.

Mine too,but I think that happens when they "deck" the blocks (?).

[Alberta Newbie]

Thanks everyone!

Yes, I found the number on the passenger side on the front of the block. I could barely read the numbers, so I'll bet it was an "A"; I'll double check tonight.

[Ole Blue 68]

Originally Posted by WorkinLonghorn

Mine too,but I think that happens when they "deck" the blocks (?).

Definitely a possibility since this engine was rebuilt.