Re: GMC 478

	GMC 478 March 18, 2013 03:50AM
bp4455	anybody know if the 478 GMC diesel pistons were flattop or dished? Reply Quote

	Re: GMC 478 March 18, 2013 05:17AM
Toro Flow	The 478 V6 Toro Flow diesel? I actually put one in a chevy 3/4 ton pickup in 1974 with a torqueflite automatic transmission! I think they were flat, but I can't imagine a diesel with flat pistons unless the chamber was in the heads. They were high compression--they were also hard on cranks! I will have to look through some of my old pictures and see if I have a picture of the pistons. Reply Quote

	Re: GMC 478 March 18, 2013 05:21AM
ppmengineering Registered: 03/15/2010 Posts: 158	Reply Quote

	Re: GMC 478 March 18, 2013 05:23AM
ppmengineering Registered: 03/15/2010 Posts: 158	sorry that is the gas engine Reply Quote

	Re: GMC 478 March 18, 2013 11:23AM
bp4455	forgot to add, anybody know where to find GMC v-6 pistons? Reply Quote

	Re: GMC 478 March 18, 2013 02:24PM
Wondering clone	So, are we actually talking about the GM Detroit diesel that would actually be a 4-71 ??????? Reply Quote

	Re: GMC 478 March 19, 2013 05:43AM
S'no Farmer Registered: 04/04/2008 Posts: 630	Wasn't the V-12 two V-6 engines mated together? I had a coworker years ago that had driven a semi that he said was the V-12 but was made by joining two of the V-6 engines together. Is that fact of fiction? S'no Farmer Reply Quote

	Re: GMC 478 March 19, 2013 06:06AM
ppmengineering Registered: 03/15/2010 Posts: 158	Looks to me like it has only one block, but four heads and two intakes? Reply Quote

	Re: GMC 478 March 19, 2013 09:41AM
S'no Farmer Registered: 04/04/2008 Posts: 630	I always thought that engine would be cool in a Rat Rod truck. S'no Farmer Reply Quote

	Re: GMC 478 December 30, 2013 07:02AM
HeavyD	Anybody know a source for Head Gaskets for the 478M, seems no longer made. thanks for any leads FelPro HS8164S-1 McCord VG6561-2 Victor HS3328X Reply Quote

Re: GMC 478 March 20, 2013 03:19AM

Charlie Jones

Todd,
Like one of the earlier posts said, the V-12 702 GMC had one block, four heads, two intakes and carbs. It had a common crankshaft and camshaft. Many of the componets were common with the 351 V-6 GMC. It had a weird distributor with two 6 cylinder distributor caps. One cap was for the left bank (odd cylinders) and the other for the right bank (even cylinders). Only bad things I heard about the 702's were that they only got about 4 MPG and the phase of the weird distributors could cause problems with harmonics on the crankshaft if they weren't kept in phase with each other. I've got a few of the 702's and have thought also about building a rat rod using one of the Willys cabs I've got. One other problem is you can't find main bearings anymore since they went out of production unless you get lucky enough to find some NOS.

Charlie Jones.

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Re: GMC 478 April 23, 2014 04:15AM

Anderson Thomas

My brother is a retired halibuton international machanic. Back in the day he called the turo flow a "gargage truck engine" We have several trucks and pickups with the gas 305 and 351 engines still running in retired units out on the farm. We still have the machanics books on trucks with the GM diesel sections including the V6 eingine series. Long ago dad worked for a regional dairy that used numerous turo flows in delivery van trucks. Many of those vans ran from the 60ties untill the dairy closed out in the early 19 eighties.
No body seemed to love those eingines but aparently they got excellent fuel milage and if taken care of ran quite awhile. I was looking to find a running turo flow to put in a 1965 GMC 3/4 ton 4x4. it is equiped with a good 305 gasoline. A long time Mormon farmer rancher had a tandom axel farm truck with one. He was proud of hauling loads of cattle over the Big Horn Mountians with extremely low fuel consumption. He gave me the numbers but I forgot what it was. If you have ever been over the Big Horns you will understand how empressive that can be. I have hundreds of gallons of reclaimed cooking oil bio diesel. So I am thinking of a lot of cheap driving with a turo flow. The turo flow will bolt up to the bell housing clutch and transmission of the standard gas truck. reducing conversion issues. The issue is finding one cheap in good condition. Hopefully the turo flow fuel pump can handle the vegi oil with out thinning. Fortunalty one of my old high school lady friends is married to the local diesel pump repairman. He runs bio fuel and fixes all kinds of diesel pumps. so everything I need to find out is available.

thats what I know.

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	Re: GMC 478 January 26, 2020 11:09AM
Ohio Case	We had a V-12 gasser in a GMC single axle semi tractor. It did have a common block and crank, however 4 heads, 2 distributors 2 carbs. 4 exhaust manifolds. The thing was a torque MONSTER, we broke a rear axle bringing 800 bushels of wet corn out of a field once when someone stood on the throttle tooo quick...….. Reply Quote

	Re: GMC 478 August 06, 2020 05:53AM
GW7ky	need parts for toro flow dh478 call1-540-400-0624 Reply Quote

Re: GMC 478 March 19, 2013 01:36AM

Toro Flow

The 478 was called a Toro Flow. It was a V-6, available in both a gas version and a diesel version. The diesel had a reputation for breaking cranks, probably because of the high compression. The gas crank would fit right in, but was not "Tufftrided" from the factory, and would not hold up at all in the deisel. Also, if someone hurt the diesel crank, and had it turned even to .010 - .010, it was likely to fail soon after installing it, due to removing the hard surface on the diesel crank. The were good starters, and good on fuel mileage. They were a 4 cycle diesel, not a 2 cycle like the Detroit series. Also--they were a lightweight engine--the front of the 3/4 ton chev. pickup I put it in had no problem with the weight. I have not found pictures of the pistons. There's got to be an old timer out there that worked on these things. They were fairly easy to find in junk yards due to their reputation for weak cranks. I guess farmers and contractors re-powered their trucks with a heavier duty diesel. I bought 2 complete engines for less than $500!

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Re: GMC 478 March 19, 2013 01:57AM

swamp gas

This series of GMC truck engines was similar in design and construction to the 348 and 409 Chevrolet V8. I believe there were three of the gas V6 engines, the smallest being around 305 ci, the middle one being 350 something, and then one larger whose displacement I cannot recall. If memory serves, this series also included an extremely large V8 and maybe even a V12 for medium and heavy trucks. Don't quote me on this, because I haven't seen any of them in years. I do recall the head being flat on the valve side, much like a conventional diesel head, with the dish in the piston providing the combustion chamber. Gobs of torque, not much of a runner out on the road, and they weren't anybody's favorite because they had a lot of problems. Many simply got swapped out for a small or big block V8 when said problems happened because parts have been obsolete and difficult to find for years.

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Re: GMC 478 March 19, 2013 04:44AM

Old Mod Puller

First off,, GMC built several versions of the 60 degree 4 cycle engines. Of the gas versions, there were the 305, 351, 379, 401 and 478 cu. in. V-6's. There were also a gas 637 cu. in. V-8 and a 702 Cu. in. V-12. The Toro Flows came in three different cu. in. configurations. The 351 was only built the first few years after the Toro Flow's release. The 478 cu. in. V-6 and 637 cu. in. V-8 were built up until production was ceased on the Toro Flow's. A side note here is that New Idea used the GMC gas and diesel V-6's as power plants in the Uni-Harvester power units. I've not seen many of the New Idea GMC V-6 diesel power units here in the states, but a friend of mine in Canada says there were quite a few of the Toro Flow powered ones up his way. My brother-in-law has a New Idea Power unit on his "Super Chopper", it's a GMC 401 V-6. I'm sure quite sure where the 348/409 came in to play, as there were few if any similarities between the Chevrolet 348/409 and GMC 60 degree engines. I actually own two 351 V-6 Toro Flows and three V-12 702 GMC's. I don't claim to be an expert, but I have done quite a bit of research on them.

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	Re: GMC 478 April 20, 2014 06:41AM
Mike Wilson	Would you be interested in selling the two 351 toro flow's? Contact me at 520-560-5783. Thx Mike Reply Quote

	Re: GMC 478 October 10, 2018 12:53PM
John griffin	I have a pair (2) DH478 cal.heads.They have been rebuilt, surfaced,springs,etc.If interested call me at 231 350 3002.DEont leave a message if I dont answer, just keep trying until I do. Reply Quote

	Re: GMC 478 March 20, 2013 03:26AM
bp4455	i did just find a picture of the pistons. they were dished with a spike in the dish just like many of the ag diesels had. Reply Quote

Re: GMC 478 April 20, 2014 07:12AM

Banker

I have a 1969 GMC with the 305. Tons of straight trucks and school busses had the 351. Rock auto and Northern Auto Parts both still seem to have toms of parts for them. It is only 7.75:1 compression. Pull the choke, pump it full of gas and it will start in about 3 seconds when it is 20 below zero. Not a highway runner, but it will lug down under a load and keep on chugging. They are big and heavy. Takes up the entire engine compartment in that 69. It make a 454 look small. Big and heavy. I can drive down tight logging roads in 3rd gear at about 5mph. It will idle down and stay running and you can't even hear it running. There are some youtube videos of them running. They have a sound of their own. It was my Grandpas truck. When I was little I remember my mom going to town to get parts for it and she would have to argue with them that it was a 305 v6 and they would say not it is 305 v8.

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	Re: GMC 478 September 10, 2017 03:05AM
MattA Registered: 01/11/2012 Posts: 66	Does anyone on this thread have any parts for the Toroflow? Know where the dataplate is on the engine? Not even sure of the CI yet .A friend has one in an old uni system, and has a dead cylinder. Either need to find a parts source or would someone be interested in the engine if it had to be repowered? Thanks much! Reply Quote

Re: GMC 478 September 11, 2017 01:25AM

One Sick Puppy

Registered: 04/23/2008
Posts: 114

Seems to me I remember the engine model and serial number is located on the deck of the block at the front of the right bank. This information will give you the cu. in. version you're dealing with (first three numbers followed by a letter). The following numbers will be the serial number. Uni-Systems used the a 478 cu. in. GMC Toro-Flo engine. The early model 478's used the American Bosch Model PSB pump (early model version of their Model 100 pump). The later versions used the an inline Bosch A-pump. Before getting into the engine very deep, I'd check the fuel system including the injectors. Has this engine sat for a long period of time without being run? Parts for these engines are almost impossible to find now. Some people have had luck finding some NOS parts through AGCO dealers.

Charlie Jones
AKA One Sick Puppy

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	Re: GMC 478 September 28, 2017 03:40AM
One Sick Puppy Registered: 04/23/2008 Posts: 114	Hey Chris B. Could you please send me a better photo of the GMC V-12 702 powered 2WD from your posting above? I like the 702's, in fact I've got three of them. Thanks, Charlie AKA One Sick Puppy Reply Quote

	Re: GMC 478 any one help with details on injector pump dh478 diiesel July 24, 2018 08:25PM
John forrest	Looking for a injector pump for dh 478 please Reply Quote

	Re: GMC 478 any one help with details on injector pump dh478 diiesel July 25, 2018 12:47AM
rdl1953 Registered: 07/22/2008 Posts: 116	I have a pump core,715-308-2163 Reply Quote

	Re: GMC 478 any one help with details on injector pump dh478 diiesel June 19, 2019 07:04AM
Kytrainer Registered: 01/15/2018 Posts: 9	Is the “one sick puppy tractor” still pulling? Reply Quote

	Re: GMC 478 any one help with details on injector pump dh478 diiesel June 20, 2019 01:59AM
One Sick Puppy Registered: 04/23/2008 Posts: 114	Kytrainer, yes, last I knew of it's still running on the Single Engine Modified class over in Ohio. One heck of a great chassis!!!!! Edited 1 time(s). Last edit at 06/21/2019 08:02AM by One Sick Puppy. Reply Quote

	Re: GMC 478 September 27, 2017 09:10AM
Chris B	This helps nothing with the question at hand, but beings it's a pulling forum and we are on the subject of these GMC motors, I thought this pic would go good with this post. This guy is running the gas 702, lots of custom work obviously. Reply Quote

	Re: GMC 478 July 25, 2018 08:07AM
One Sick Puppy Registered: 04/23/2008 Posts: 114	Wish I could have seen the photo you posted. Reply Quote

	Re: GMC 478 January 26, 2020 08:44AM
gary burton	they had a combustion chamber in the piston Reply Quote

	Re: GMC 478 August 06, 2020 05:32AM
GW7ky	the pistons have two indents for the valves opening and a combustion chamber 1 1/2'' with a pointer in the middle of the chamber Reply Quote

	Re: GMC 478 August 06, 2020 05:56AM
GW7ky	need parts for toroflow dh478 call1-540-400-0624 Reply Quote