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cayoterun

1964 Gmc 702 V-12 Irrigation Motor

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The V-6/V12s were built by GMC from '60-'66. I went to work for the guy that put this engine in service in 1964. I came out of the Army and started taking care of it in Feb. '65. Decided I wanted to do something besides old cars/travel trailers. The engines are almost all gone to the scrape pile. Found this in a neighbors barn. Was reunited with her after 42 yrs. She's up and running now, and am wanting to put her on a 1-ton truck frame and suspension/w a '62 GMC cab and front clip. Have a video of her first start and run on Utube.

Cayoterun

Edited by Cayoterun

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I looked at the video of the engine running.I have worked on those engines years ago when they were used in the trucks.I see it is on propane and i wander if there is still a problem with the rings seating when on propane. When i worked propane engines we most the time could break them in on gasoline but if we could not there was special procedure to build one that was going to start up on propane. I have seen good results out of propane and natural gas when done right.

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I looked at the video of the engine running.I have worked on those engines years ago when they were used in the trucks.I see it is on propane and i wander if there is still a problem with the rings seating when on propane. When i worked propane engines we most the time could break them in on gasoline but if we could not there was special procedure to build one that was going to start up on propane. I have seen good results out of propane and natural gas when done right.

All this engine has known is natural gas. It ran stationary on a 10" water pump from '64 thru '85. I tore it all down, and cleaned all the gunk out I could. Put a used head and two used pistons in and it runs pretty good now. Of course, new parts are history. It has .30 over propane pistons, and standard bearings. The engine has the equievelent of 5.5 million miles on it. That's stationary, 24/7 for about 6 mo. a year for 21 yrs. No telling how many times it was overhauled, at least one bore job. All engines run a long time on the pumps. Must be the constant temp, lube, & rpm. The farmers loved these and V-6s both. The sure burned lots of fuel. It smoked pretty bad on first start up, but changed one head and piston, and it runs pretty clean now. It will always use some oil tho. A neighbor had one, burned propane while natural gas line was being worked on. It used 22 gal an hour on propane.

They are a simple and easy old engine to work on, aren't they? I'm enjoying trying to get it up and running in something. Feel like I'm saving a piece of GMC history.

Cayoterun

Edited by Cayoterun

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All this engine has known is natural gas. It ran stationary on a 10" water pump from '64 thru '85. I tore it all down, and cleaned all the gunk out I could. Put a used head and two used pistons in and it runs pretty good now. Of course, new parts are history. It has .30 over propane pistons, and standard bearings. The engine has the equievelent of 5.5 million miles on it. That's stationary, 24/7 for about 6 mo. a year for 21 yrs. No telling how many times it was overhauled, at least one bore job. All engines run a long time on the pumps. Must be the constant temp, lube, & rpm. The farmers loved these and V-6s both. The sure burned lots of fuel. It smoked pretty bad on first start up, but changed one head and piston, and it runs pretty clean now. It will always use some oil tho. A neighbor had one, burned propane while natural gas line was being worked on. It used 22 gal an hour on propane.

They are a simple and easy old engine to work on, aren't they? I'm enjoying trying to get it up and running in something. Feel like I'm saving a piece of GMC history.

Cayoterun

Is there any of those old cummins engines that burn diesel and natural gas still out there in the field?

I have not been out there in a long time .

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Is there any of those old cummins engines that burn diesel and natural gas still out there in the field?

I have not been out there in a long time .

They're still using alot of natural gas coverted cummins, Minneapolis-Molines here. Many of them have changed to straight diesel engines now. For awhile, they could burn diesel cheaper than natural gas from wells on their own land. Don't make sense, but the gas companies that produce them had them bound by contract. Many foreign diesel motors, Dawoos, etc. are used now too. Won't be many years 'til irrigation will be history here. Water table falling, hence weaker wells, high fuel costs, etc. We never did drill wells on our place, and glad we didn't.

Cayoterun

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They're still using alot of natural gas coverted cummins, Minneapolis-Molines here. Many of them have changed to straight diesel engines now. For awhile, they could burn diesel cheaper than natural gas from wells on their own land. Don't make sense, but the gas companies that produce them had them bound by contract. Many foreign diesel motors, Dawoos, etc. are used now too. Won't be many years 'til irrigation will be history here. Water table falling, hence weaker wells, high fuel costs, etc. We never did drill wells on our place, and glad we didn't.

Cayoterun

A facility that I used to maintain the standby power generation at has an 855 Cummins engine that runs on natural gas. That is the only genset that when exercised, I would put plugs in my ears, and hand towels in my earmuffs! That engine is louder than the F-4's I deployed with in the Navy!

Rob

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Guys, I am really curious - what kind of power did the GMC V-12 pump engines develop?

And did it develop the same power on gasoline as on natural gas or propane?

Looks like a neat project - just saving it from the scrap yard is a good thing!

Thanks,

Paul Van Scott

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Guys, I am really curious - what kind of power did the GMC V-12 pump engines develop?

And did it develop the same power on gasoline as on natural gas or propane?

Looks like a neat project - just saving it from the scrap yard is a good thing!

Thanks,

Paul Van Scott

These #s are from my factory maintenance manual:

Cubic In. 702.4

Bore: 4.56

Stroke: 3.58

Comp. ratio: 7.5

S.A.E. hp 99.80

Gross Brake hp @ 2400rpm 275 Max recommended rpm 2400

Gross torque 630 @ 2400

Net torque 585 @ 2400 Torque #s aren't a typo. The motors are luggers.

Since natural gas and propane doesn't develope the same as gasoline, I know that when they needed to be bored, they had a

propane/hi-altitude slightly domed piston they used which are in the engine I have.

I don't understand GMCs hp ratings, as it seems they should be rated higher.

I really like to hear them start and run. They have a sound all their own. and LOUD.

Hope this is helpful and not too long winded.

Cayoterun

Edited by Cayoterun

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Sounds like a good candidate for a truck project - Good Idea!

Sure is big torque at 630 ft.lbs. - more than our old Mack diesels, and at a pretty low

RPM for a gas engine.

275 bhp is no slouch either.

And I'm surprised at the short stroke. I would have guessed at a higher rev limit because of it.

It's a cool old motor. Thanks for the info.

Paul Van Scott

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http://www.youtube.com/haystack155

Anyone interested, You can hear her run on utube. I've changed the head and one piston on the right front bank since. The vapor coming out of the water jacket is just warm air. It was pretty cold in the shop and had no water in it. It was only run the 2 1/2 minutes.

We, also, wear ear plugs.

Cayoterun

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http://www.youtube.com/haystack155

Anyone interested, You can hear her run on utube. I've changed the head and one piston on the right front bank since. The vapor coming out of the water jacket is just warm air. It was pretty cold in the shop and had no water in it. It was only run the 2 1/2 minutes.

We, also, wear ear plugs.

Cayoterun

This is probably one of those storys that is only funny if you were there....

My very first job was at a gas/service station, (remember those)?, and the small oil distributor that filled the tanks had a 66 GMC tanker with the V-12 GMC gas engine. It had a different sound. His bulk plant was about three blocks away as the crow flies, and about seven blocks by street route. In a weeks time, we would get three deliveries of 500 gallons of gasoline, a barrel of straight 30wt. oil, and a bulk load of 10W30, or 10W40 depending on season.

This GMC tanker did not have a fuel tank that was used, it had a fuel line that was run to the tank on the back. Every time my boss would pay for gasoline he had to complain about paying for 500 gallons, but getting only 490 because that truck was sucking down his gas and it couldn't be proven otherwise!

I once asked about gas mileage on that truck and if I remember correctly; Three to three and a half is what it typically acheived.

That truck was finally retired in 1974. It still exists, but hasn't been ran in as many years due to the passing of the owner.

Rob

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This is probably one of those storys that is only funny if you were there....

My very first job was at a gas/service station, (remember those)?, and the small oil distributor that filled the tanks had a 66 GMC tanker with the V-12 GMC gas engine. It had a different sound. His bulk plant was about three blocks away as the crow flies, and about seven blocks by street route. In a weeks time, we would get three deliveries of 500 gallons of gasoline, a barrel of straight 30wt. oil, and a bulk load of 10W30, or 10W40 depending on season.

This GMC tanker did not have a fuel tank that was used, it had a fuel line that was run to the tank on the back. Every time my boss would pay for gasoline he had to complain about paying for 500 gallons, but getting only 490 because that truck was sucking down his gas and it couldn't be proven otherwise!

I once asked about gas mileage on that truck and if I remember correctly; Three to three and a half is what it typically acheived.

That truck was finally retired in 1974. It still exists, but hasn't been ran in as many years due to the passing of the owner.

Rob

Your story matchs one here. One of our bulk distributors put a V-12 road tractor under his bulk semi tank truck he hauled from the refinery down state. His mileage was right on target with yours. Didn't take him long to trade for a diesel.

I don't think he had a gas line to the trailer tho.

Cayoterun

Edited by Cayoterun

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