Inliners International Forums General Discussion Engines GMC Engine

I have a '51 GMC 620, and am trying to confirm the engine. It's supposed to be a 360". It has block # 2191202.

Questions:

1. Is this really a 360" GMC 6?

2. Are engine rebuild kits available anywhere?

Thanks

Day Radebaugh

I can't identify it based on the casting number but according to my Motors Manual, the 620 did have a 360 cubic inch inline six. 4.125 bore x 4.5 stroke; 6.5:1 compression, 127 HP @ 3000 rpm; 289 ftlb @ 1300 rpm (the later 1955 with 7.25:1 compression had 170 rpm @ 3400 and 318 @ 1100rpm); 35 to 40 psi oil pressure. There is a 6 degree BTDC timing mark on the flywheel; valves are set at 0.012 and 0.018 hot. The wrist pin is 1.124, the rods are 2.374, and the mains are 2.749. I am assuming a four-main crankshaft?

You could check NAPA; they have books going back this far. However, my experience is that parts for these old truck engines seem to be slipping away. Let me know if you find a source.

I really like the big old engines. My brother has a truck with a 602 cubic inch continental. Reminds me of a six cylinder version of a hit and miss engine; big and slow but lots of low end HP. We are currently looking at an old 1500 cubic inch LeRoi inline six. It isn't very practical but it can be had for the price of scrap.

Day, I sold a yellow 41 Willys coupe to Mike Naile in El Dorado a few years back. Did you ever see it. Gary

Dear Mr. Radebaugh;

You could check with Patrick's for the kits. I know used to sell them & probably still can/will.

Good luck.

thanks for the suggestions. the note that there was a version of the engine in 1955 is very helpful: i called egge yesterday, and they had no numbers for a 1951 360", but did have one for 1955. they claimed they could put together a kit. maybe i could even upgrade this thing. i'll also call patrick's.

by the way, what is the motors manual you refer to? i'd better track one down; you've told me all i know about this engine.

i know what you mean about these big 'ol sixes; don't run very fast, but have a lot of bottom end. i also have a 270" gmc in my '44 deuce-and-a-half. these engines are the closest thing to a diesel, but you have a chance of starting them in the winter. that 1500" leroi sounds interesting. what's it out of? before they had all the advanced technology, they just built them big (remember the days they put 2 engines in trucks in various lash-ups?) i'd go for it. parts can always be made, if you have to.

thanks again.

It would be the "truck" manual (green) for the year of your engine.

The blue ones are for passenger cars & red is the labor & parts guide.

Happy trails.

As John said, it is the green manual. They are on ebay all the time for $20 to $25 and are very informative.

The LeRoi was the power unit for a fifties era FWD snow blower. It is at a local vintage truck salvage yard. It was running a few years ago but the manifolds are really in tough shape. There are two of the V12 versions on ebay right now.

thanks; will start looking.

I can't match that number with anything pre '60. Where exactly are you reading that from? There should be a number behind the distributor. They used both 360 and 426 engines depending upon the year/application in the 600 series trucks.

On the back of your glovebox door, and on the driver's doorpost between the hinges, there should be a couple of ID plates. What are the complete numbers indicated on those two plates?

rob......

my confusion here. the number i listed (2191202) is a casting number down on the crankcase, left side. i bought a manual yesterday which told me where to find the engine #. we're getting quite a bit of snow here, but was able to go out and brush off the engine #, where i could make out 360......., so it's definitely a 360. there is no glovebox plate, but from the door post the truck is an HCR 623 4112.

from what i see in the manual, the 360 is a pretty tough old engine. i had it running, and got 100# compression in all cylinders. need to flush out the cooling system (radiator is off, thermostat out), blast 'er off, paint it up and put it back in. it out to be plenty for my needs.

thanks for the help.

Day, were the larger GMC engines four or seven main bearing?

jason....

as i recall from the manual, the 360 at least has 7 main bearings. that was the basis of my comment that the engine seems pretty stout. if you look at the block, you see a big heavy crankcase, with a separately-cast cylinder block on top of that, and on top of that is the head. there's a lot of metal there. this seems to be an engine worth saving and using. i wouldn't be surprised to see that the whole family of those engines were 7-main bearing types.

day

gary....

missed your post, but yes, i've seen mike naile's willys in various parades around town. in fact, he may have a couple of those, as i recall. he has a very large collection of basically hot rods, and brings them out whenever he can.

day

anyone know of a supplier for gaskets & rear main seal for '51 gmc 620 360" 6-cyliner? tried egge, no help, and local auto parts clueless.

apppreciate any help.

Have you tried:

Olson's Gaskets
3059 Opdal Rd E
Port Orchard, WA. 98366
Phone or FAX 360-871-1207

thanks, jason. that reference was a real winner. they didn't have gaskets in stock, but would punch them out from their templates. very nice people to boot.

appreciate the tip.

day radebaugh