350 Motor differences - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**old Rusty C10** · 06-22-2021, 03:44 PM

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)

sntrym95 · 06-22-2021, 05:09 PM

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.

**special-K** · 06-23-2021, 05:41 AM

Huh, I never knew that.

Just call me Sean · 06-23-2021, 12:31 PM

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

manimal · 06-23-2021, 02:42 PM

Quote:

Originally Posted by sntrym95

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.

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.

sntrym95 · 06-25-2021, 01:24 PM

Quote:

Originally Posted by manimal

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.

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.

57taskforce · 06-26-2021, 01:26 AM

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.

b454rat · 06-26-2021, 07:28 AM

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.

06-22-2021, 03:44 PM	#1
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,261	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) Attached Images __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

06-22-2021, 05:09 PM	#2
sntrym95 Registered User Join Date: Jan 2006 Location: Big Pine Key, FL Posts: 745	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. __________________ Mike

06-23-2021, 05:41 AM	#3
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,863	Re: 350 Motor differences Huh, I never knew that. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

06-26-2021, 01:26 AM	#7
57taskforce All about them K’s Join Date: Jun 2014 Location: Farmington, New Mexico Posts: 6,231	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. __________________ Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 315/75/16's ‘87 IROC-Z all original 50K mile survivor TPI 305 IROC Blue ‘10 Camaro 2SS/RS Aqua Blue Metallic #93 -version 2.0

06-26-2021, 07:28 AM	#8
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,453	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.



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