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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old September 25th, 2020, 05:39 PM
Autodoc Autodoc is offline
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Default Racing efforts with 478 v6

Does anyone here know what the fastest jimmy v6 is and what kind of build it has?
I just recently started studying the engine format, and it looks really appealing for making a very strong drag race engine. Just looking at the stock bore size and the head port design it looks like it has the potential to run at least the same power per cubic inch as a good inline valve head small block chevy or any big block chevy with regular 24-26° heads
Has anyone gone all out on one of these? With roller cam, big cam core with roller bearings lightweight pistons and valves, and a good porting and fabricated intake and headers, NA or supercharged/turbocharged?
What is the limiting factor, other than head flow?

There are a lot of specs listed in various places, but I never found the actual bore center spacing. Anyone got that, or can you measure a block or head gasket for cylinder spacing just from the front edge of one cylinder to the front edge of the next will do.

I remember reading somewhere that the middle cylinder might be offset for some reason, as in it does not perfectly line up with the other cylinders. It would seem odd when there is so much space between them already. No need to stagger them for extra room for coolant to circulate or whatever.

if the stock block and heads are not suitable for this kind of build(900hp NA) or maybe boasted around 1800-2500, then it certainly would be feasible to build a billet block or even new aluminum castings with even bigger bores on the same architecture, even the heads could be made to be pro stock levels of flow and combustion efficiency while retaining stock valve arrangement if the ports are moved around a little and the high camshaft and relatively short pushrods should be great for spinning it up to high rpm. I think the engine architecture itself is probably good enough to surpass all but the biggest big block chevies and hemis in potential power if the bore sizes that are achievable with that huge bore spacing can still function well at the rpms necessary.
Anyone built a nitro V6.
Myself, I would like to explore the potential of stock blocks and heads first, starting with a good head porting, offset grinding the crank for smaller rod bearings and a little more stroke, as big a cam bearing and cam core as will fit in the stock block, custom rockers and springs on taller, titanium valves and a sheet metal intake and long fat headers and see how high it will spin up. I would try and address any strength issues with the block that are evident from analyzing the design and maybe looking for what has failed in the past, and do any reinforcement possible, then if the heads seem like they work pretty well, try and see what kind of boost it will handle with a big turbo, then 2 big turbos, then maybe try some nitro.
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Old February 17th, 2022, 02:13 PM
Gwhizzard Gwhizzard is offline
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Default Re: Racing efforts with 478 v6

if you have any updates i interested on reading more on this topic. Ive read ll the why nots now id like to see someone just do it lol
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  #3  
Old February 17th, 2022, 09:40 PM
Prowbar Prowbar is offline
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Default Re: Racing efforts with 478 v6

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Originally Posted by Gwhizzard View Post
if you have any updates i interested on reading more on this topic. Ive read ll the why nots now id like to see someone just do it lol
Sadly most of these projects just seem to die. People realize that they are heavy, low revving truck motors, not suitable for any performance of racing use.

Not that they are bad engines; they are not suitable for hot rodding. If they were I'd bet they'd be a lot more popular now.
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Old February 18th, 2022, 07:55 PM
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Default Re: Racing efforts with 478 v6

I think with some work you could get 60 MPH in the 1/4 mile.
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Old February 19th, 2022, 04:18 PM
POWERSTROKE POWERSTROKE is offline
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Default Re: Racing efforts with 478 v6

MY 1979 WHITE Road-Boss 2 would run 67 mph up a surprisingly steep hill about half a block long. It had a 320 hp 903 Cummins V-8 and 6-speed Spicer Trans, with 2600 rpm and 4.44 gears and 11.00x22.5 drive tires it only ran 67 mph anywhere. Bare tractor weighed about 14,000#. Most nights climbing that hill I was getting pretty low on fuel, probably only 20-30 gallons in a 150 gallon tank.
With a 478 gas V-6 high rpm and close gear splits would be a big advantage. I drove a 1978 FLEETSTAR IH with a 478 gas V-8, straight 5-speed, what little I bob-tailed with it, it seemed reasonably quick up to 65 mph. Biggest problem was the rough ride and lack of weight on the drive tires.
Seriously, I watch a show, ENGINE MASTERS a lot! Their favorite engine above ALL others is the big block Chevy V-8, the bigger the better. Anything over 500 Cid or as big as your bank account can handle will be good. OR a Ford GAA WW#2 tank engine, 1100 Cid all aluminum DOHC V-8, 500 hp @ 2600 rpm and 1050 #/ft torque @2200 rpm, and only 1470 pounds dry weight.
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Old February 24th, 2022, 01:03 AM
BillT BillT is offline
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Default Re: Racing efforts with 478 v6

Quote:
Originally Posted by Prowbar View Post
People realize that they are heavy, low revving truck motors, not suitable for any performance of racing use.

Not that they are bad engines; they are not suitable for hot rodding. If they were I'd bet they'd be a lot more popular now.
I had a 478 in my '62 GMC 6500. It would go 62 MPH. But as mentioned above "they are heavy, low revving truck motors, not suitable for any performance of racing use".

Slow revving with a whole lot of torque. Hot Rodding one would be like Hot Rodding a 673 Mack. They just weren't built for speed and trying to make one go fast would take a whole lot of money, if even possible.

But as indicated they sure would pull. I moved a completely loaded railroad freight car once with mine. It didn't even whimper.
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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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Old February 24th, 2022, 05:47 PM
Prowbar Prowbar is offline
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Default Re: Racing efforts with 478 v6

Quote:
Originally Posted by BillT View Post
I had a 478 in my '62 GMC 6500. It would go 62 MPH. But as mentioned above "they are heavy, low revving truck motors, not suitable for any performance of racing use".

Slow revving with a whole lot of torque. Hot Rodding one would be like Hot Rodding a 673 Mack. They just weren't built for speed and trying to make one go fast would take a whole lot of money, if even possible.

But as indicated they sure would pull. I moved a completely loaded railroad freight car once with mine. It didn't even whimper.
Oh yeah, pulling power is what these engines do best. Would love to compete in a 'slower' tractor pulling class with a 478 V6... Maybe someday. or a V12...

Here's a tractor with a GMC V12: https://www.youtube.com/watch?v=qr3QdLDJfsU
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  #8  
Old March 8th, 2022, 03:12 PM
Gwhizzard Gwhizzard is offline
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Default Re: Racing efforts with 478 v6

But still if it could be done. It would be fun to see!! Tractor pulls would be fun to watch it as well.!! Any info on building these would be good to have in a file on here
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