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GMC V6 and V12 Engines Engine repair and rebuilding

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  #11  
Old June 17th, 2020, 01:10 AM
POWERSTROKE POWERSTROKE is offline
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Default Re: 401 vs 432 torque ratings???

BILL - I haven't had a DEF diesel but I drove a '96 F250 with 7.3L PSD for 23-24 years, and 304,000 miles. I gave it to my Son, he traded his Cummins for his mid-life crisis, a new '18 Mustang GT. He fixed a lot of things that needed done to that truck, and it's completely reliable again, at 315,000 miles.
But I bought a gasoline pickup. Hard to justify a diesel when I only drive 2500-3000 miles a year now.
I'm surprised your 637 V-8 got 5-7 mpg. I drove a late '70's IH FleetStar single axle tractor 478 V8 and straight 5 spd, ran 62-65 mph between the Mississippi River and Des Moines 5 nights a week and got between 3-4 mpg grossing about that same 45,000-50,000. 13--1/2 ft tall 45 ft trailer caught a LOT of wind. The '81 or '82 F700 Ford tractor I drove for 6 months before the FleetStar had a 8.2L Detroit Fuel Pincher diesel, I got an honest 7-8 mpg pulling the exact same trailer hauling the exact same loads. But every couple months it needed a tune-up, troublesome fuel system. Drove a single axle dump truck two summers in college, C65 Chevy's with 366 V8 and 5+2. I really can't say what they got for mpg, no gallon counter on the gas barrel at work, but if I ran hard enough hauling rock out of the quarry I had to put some gas in for the last load. I was the only hired help summer of '74, I put a LOT of miles on a brand new C65 that summer. It had much better rear gears for road work than the '67 C65 366, 5+2 did it replaced, but the '67 spanked the '74 bad plowing snow.
The thing I see guys have the most problem with on old gas powered trucks is keeping the brakes working reliably. Second biggest problem seems to be finding rebuilt carbs and fuel pumps.
When I was a kid Dad drove for a couple livestock haulers, think they all had GMC Big V6 powered trucks. Livestock hauling was the last segment of trucking to start using diesel tractors. Lots of old farmers thought the diesel exhaust hurt their livestock, tainted the meat just before butchering.
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  #12  
Old June 17th, 2020, 01:44 AM
BobBray BobBray is offline
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Default Re: 401 vs 432 torque ratings???

The renewed interest in gasoline engines for medium trucks is due to the high purchase cost and maintenance/repair expenses of the new DPF/SCR diesels, The overall ownership costs for diesels are higher than gasoline engines in many situations, particularly low mileage/speed operations that utilities and municipalities experience. This trend has been a long time coming, in fact GM was trying to capitalize on it back in 2008 when they were the only manufacturer of gasoline powered medium trucks. When GM dropped their medium trucks in 2009 it left a hole in the market that Ford was able to exploit in 2011 when they began offering their 6.8L V-10 in the F-650.
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  #13  
Old June 17th, 2020, 10:08 PM
BillT BillT is offline
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Default Re: 401 vs 432 torque ratings???

Quote:
Originally Posted by POWERSTROKE View Post
The thing I see guys have the most problem with on old gas powered trucks is keeping the brakes working reliably.
Both my trucks had Air Brakes, the '62 6500 and, of course, the '71 9500. Only, I found out somewhat after I quit driving it that the '62 only had Rear Brakes!!

Still had no trouble stopping and don't remember the mechanic changing the Brakes that often.

The 9500 with Full Air had the well liked Maxi Brake (Spring Brakes). The old Dashboard E-Brake in the 6500 didn't hold very well. Had to cut the truck off and put it in gear many times to help it.

Parking on a hill with a full load grossing out at 32,000 was pretty impossible, lol. There is nothing like a Maxi Brake.
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Drove and owned many, but some of the more interesting ones were:

-'60 GMC 2500 Dump, 305 V-6
-'62 GMC 4000 Flatbed, 305 V-6
-'62 GMC 6500 Flatbed Dump, 478 V-6
-'67 GMC 7500 Box, 6V-53 Detroit
-'71 GMC 9500 Flatbed Dump, 637 V-8
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  #14  
Old June 18th, 2020, 08:08 AM
BobBray BobBray is offline
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Default Re: 401 vs 432 torque ratings???

I was excited about the new Ford 7.3L when I first heard about it and have been following it closely. It is the first gasoline engine designed primarily for commercial trucks in many many years and it's output figures are good all things considered. Have to say after seeing the 7.3L in person and having a good look at its internals I am not that impressed. It seems to borrow a lot from the GM LS engines, which is good, but other features look questionable. For instance, one of the features of the GMC V-6 was its wide cylinder bore centers. This allowed bores up to 5.125" (478) and still have plenty of water passage between the cylinders. It also provided for wider crank bearings and a lot of block deck surface for a good head gasket seal. The Ford 7.3L has a siamesed bore block and one of the thinnest deck areas between cylinders I have ever seen. In addition, Ford saw cut a cooling passage between the cylinders open to the deck, further compromising the head gasket sealing surface. The block coolant passages are largely open to the deck. I guess with current head gasket technology this will not be a problem in service but I suspect this block might be 'throw-away' come rebuild time and you probably shouldn't consider super- or turbo- charging it with any meaningful boost. No roller timing chain, the 7.3L gets by with old style silent chain and a plastic tensioner, and also has a small separate chain and sprocket driving a shaft turning a rear mount variable displacement oil pump that is actually part of a large aluminum cast windage tray. Really kind of clever but a lot of extra parts. Engine has variable cam timing, but it appears all VVT components are behind the timing cover, not accessible behind the water pump like an LS. Cylinder heads look pretty good port and valve angle wise, but do not appear to have much coolant flow through them. The head bolts are large and threaded deep into the block, but the block casting looks to be very light. The whole engine is only slightly larger than an LS. Overall, I might consider a 7.3L in a Super Duty pickup but I think I like the new GM L8T 6.6L direct injection gas V-8 better. It makes a little less power but I hear the fuel economy is better and you just can't beat an LS/LT for toughness and long life.
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