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Old 12-23-2013, 01:01 PM   #1
Skip's Avatar
Join Date: Dec 2013
Location: OR/CA
Posts: 53
Year: 1989
Coachwork: Thomas
Chassis: GMC
Engine: 366 6.0L V8
Rated Cap: 72
How do I find out what engine I have?

Yes, I am a newbie ( to this forum and this is my first bus ).

So, I just bought a 1989 gmc thomas, and when I bought it I was told it had a big block 366, and of course I had no reason not to believe the guy at the dealership who sold it to me. But when I went today to get a smog check on it, I was told it was a 454.

When I got home I looked at it my self and the sticker in the air filter says 6.0 l. And I checked the VIN online and it told me I have a 89 gmc s6000 b6p042, which Wikipedia says it would have a 366..

..and I'm pretty sure the only other owners were me, and international dealership, and a school district. So I wouldn't think the engine was swapped.

I think the smog check guy (who informed me that this was the first time he had ever seen a bus pull into his shop) was wrong and it is unfortunately a 366, not a 454

Any suggestions?
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Old 12-23-2013, 02:02 PM   #2
Bus Geek
Join Date: Aug 2011
Location: Stony Plain Alberta Canada
Posts: 2,939
Year: 1992
Coachwork: Bluebird
Chassis: TC2000 FE
Engine: 190hp 5.9 Cummins
Rated Cap: 72
Re: How do I find out what engine I have?

Welcome to the skoolie sickness.

Engine swaps by school districts on gas buses are more likely than a model with a good diesel engine (5.9 and 8.3 Cummins, DT 360 and 466). The gas jobs are just not up to pulling around that kind of weight.

I would Google the two engines that you think it may be. The outside of the block is the same. Only internals are different.. The 366 was used years before the 454. Due to the year of the bus, it's most likely a 454.

This is from wiki

Commercial applications

Mark IV engines saw extensive application in Chevrolet and GMC medium duty trucks, as well as in Blue Bird Corporation All American and TC/2000 transit buses (the latter up until 1995, using a purpose-built, carbureted 427). In addition to the 427, a 366-cubic inch (6.0 liter) version was produced for the commercial market. Both the 366 and 427 commercial versions were built with a raised deck, four bolt main bearing cap cylinder to accommodate an extra oil control ring on the pistons. Unfortunately, the raised deck design complicated the use of the block in racing applications, as standard intake manifolds required spacers for proper fit. Distributors with adjustable collars that allowed adjustments to the length of the distributor shaft also had to be used with 366 and 427 truck blocks.

"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."

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Old 12-23-2013, 02:41 PM   #3
Skip's Avatar
Join Date: Dec 2013
Location: OR/CA
Posts: 53
Year: 1989
Coachwork: Thomas
Chassis: GMC
Engine: 366 6.0L V8
Rated Cap: 72
Re: How do I find out what engine I have?

Well the block is casted "gm 6.0l" and since chevy only made one 6.0 liter big block during the late 80's, it's gotta be a 366.
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Old 01-03-2014, 10:19 AM   #4
Bus Nut
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Join Date: Apr 2011
Location: Cleburne TX
Posts: 606
Year: 1983
Coachwork: Ward
Chassis: GMC
Engine: 366 Gasser
Rated Cap: 66
Re: How do I find out what engine I have?

Theres nothing wrong with the engine you have. They used it in a LOT of medium truck application. Would a 5.9 or other diesel engine do a better job... sure. But for all the ups there is a down. That usually is cost for a repair.

I have no regrets when I bought my bus with the same engine as your as I am a gas engine guy so I can take care of most of what happens with it. All be it this bus is kind of a guinea pig to find out what I want and don't want.

ask your self what you want it to do..... and see if your want and its ability to do can be one and the same.
Here is my school bus conversion thread

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