350 Motor differences
 

So my own truck is a 98 K 2500 GMC and the lower end of the motor started going and last drain there was a decent amount of metal in the oil so it was time for a motor.. I had a motor i pulled last year from a 97 Tahoe 1500 4wd and as i got my motor out i noticed some differences starting with the truck motor has an extra threaded hole at the top of the bellhousing... is there a difference between these two motors mechanically? ( i also had a HD oil cooler on mine and mine was purchased as a municipality truck)

Re: 350 Motor differences
 

the 2500 had a beefed up motor compared to the 1500.

The 2500 has 4 bolt mains, forged crank, hypereutectic pistons where the 1500 has 2 bolt mains, cast crank, and cast pistons. Compression and cam specs are essentially the same. You can swap it in but know that it's designed for lighter use.

Re: 350 Motor differences
 

Huh, I never knew that.

Re: 350 Motor differences
 

The heads are different on my 93. Not sure if they are on those though.

Re: 350 Motor differences
 

Not a true statement. Not trying to be a d*ck, but I have pulled SEVERAL 350's from GMT400 2500's and most have been 2 bolt cast crank motors, but to be sure, pull the pan. Now if you get a 3500, then YES it will most likely be a 4blt block, but still no guarantee it will have a forged crank.

Re: 350 Motor differences
 

It should be a 4 bolt for anything over 8600 GVWR according to what I've been reading. Under 8600 it would likely be a 2 bolt.

Re: 350 Motor differences
 

There’s a difference in the heads too, the heavy duty motor uses different valve seats too if I remember correctly. I don’t believe it’s cut and dry based on GVW but I do agree 8600+ Is more likely to have the HD motor.

Re: 350 Motor differences
 

i can find out. need to replace the motor in my yukon, got one from a crew cab short box C2500. It was the light duty, had the 14 bolt semi float. Looked up casting number and says 2 or 4 bolt. I need to replace the oil pan.