GMC V6 (305-351-401-478) resources

[IowaOffRoad]

https://irate4x4.com/resources/gmc-v6-repair-manual.37/

Posted this to the resources page for any who want it.

Also, anybody hot-rod one of these? Friend of mine wants to find a 478 and use it for a bush pull "stock" 4x4 truck pulling engine.

Crank pin on these is huge, lends itself to offset grind, but cutting off way too much material for anything long-lived using a conventional automotive rod.

Lemme know what you know...

 

[total newb]

I clicked your link and there is nothing there.

 

[IowaOffRoad]

I clicked your link and there is nothing there.

You have to hid download

Let me know if it doesn’t work and I’ll hit up Austin

 

[total newb]

Ok.

 

[Lowrollin70gmc]

I had their cousin, a 478 ToroFlow diesel, in my Burb before the Cummins. Very narrow for a huge V6, 60 degree V if I remember right.

Pretty sure I have an old manual for it in my collection, should scan it sometime.

Loved it except for parts availability, no preheat apparatus, and weight. Front end came up an inch or two when the 12 valve went in.

The gas V6s seem to have better repair support as they were in light duty and MDT trucks.

I'm sure you've seen it, but there's a ton of stock info on 6066gmcguy.com

 

[350TacoZilla]

The heads are the big limiting factor, the "magnum" heads flow the best but are hens teeth. Even the smallest one 305 uses same bore as a 427\454 so with playing with the rods\pistons you could probably come up with an off the shelf setup where you just buy for a v8 and have 2 spares. The blocks are all physically the same for things like bore centers and such so in theory you could bore the common 305 out to accept the 478 piston but your looking at 5.125 so custom pistons required.
Personally for a puller I would run the shorter 3.58 stroke crank like the 305,351,401 uses (since again you can actually find cores) and offset grind it to take something with a common rod diameter. then bore to a "common" off the shelf 4.6-4.625" bore. You could end up in 450+ cu.in pretty easy with parts that are available rather than max cubes with all custom parts.

 

[arse_sidewards]

Good luck. The GMC big block V6 is on my short list of old gas engines I wanna run in something.

I think the only way you'll make those heads flow respectable amounts of air is by force feeding them with a turbo but if your class allows turbos you are going to get your ass handed to you by someone who dropped a modern V6 into something so....

Old engines are cool but the amount of time, money and effort it takes to make them make substantially more power than they left the factory with just isn't worth it.