GMC V6 schemeing

[CTX-SLPR]

Ok, so I don't own one but I think some of ya'll know that I'm a V6 fan for whatever reason. I got a look at the GMC 702 V12 "Twin Six" in the new HRM in the Blastolene B-702. This got me looking into these motors and well I'm also a liker of the oddball and Dare to be Different so these things are really attracting me. Looking over the most basic stuff on an enthusiest site (mainly built around truck stuff) it looks like this thing would be fairly easy to convert to EFI and who'd believe you had a 305 (or larger) V6? Judging by the basic design of the motor it wouldn't be hard to add a turbo (probably a pair) to it either. Anyone have much experience with these things?

[HoosierGTA]

Re: GMC V6 schemeing

So just for clarity ,you talking about the twin six or just the 305 v-6 .

[Freiburger]

Re: GMC V6 schemeing

Isn't the Jimmy V6 basically a 409 minus two cylinders?

[HoosierGTA]

Re: GMC V6 schemeing

You got me . The things are huge ,Saw one in a 67-72 gmc and I thought it was a
V-8 . Till I started counting the plug wires. Don't they come thru the intake or some thing like that? Or maybe just top inside of the head.

[Freiburger]

Re: GMC V6 schemeing

[HoosierGTA]

Re: GMC V6 schemeing

Dave nothing came thru on this end . Check on your end . I'll shake the wire here . Ha Ha .

[Freiburger]

Re: GMC V6 schemeing

Photo shows up fine for me.

http://en.wikipedia.org/wiki/GMC_V6_engine

[HoosierGTA]

Re: GMC V6 schemeing

That worked.

[CTX-SLPR]

Re: GMC V6 schemeing

At 3/4 ton for the engine itself on the V12 "twin six" I don't think thats going to be a very Hot Rod like motor and they are appearantly not very common either. At 800ish lbs for the V6 that's a bit more manageable, I mean my 425 Nailhead weighs near that much.
http://www.6066gmcguy.org/ is the site I've been looking at, all sorts of cool tidbits. Best I can tell, no the V6 does not have a 409 style head since its inline valves like a Buick or Mo'par shaft mounted setup and has the sparkplugs on the valley side.

[CTX-SLPR]

Re: GMC V6 schemeing

Looks like for performance you'd need new pistons with less rings, more compression, and probably less skirt. Also that oil pump looks like a major drain on power and overkill for a street motor. The crank and rods are forged pieces and look like they'd take a beating though not RPM with the mass on the rods. The intake is dry (no water) so that would make fabbing a sheetmetal intake, EFI for me, easier. The transmission would take a Bendsten's unit, no surprise as even my more common Nailhead takes that for anything but an ST300, ST400, or Dynaflow. Looks like it would be an unexpected ton of fun.

[squirrel]

Re: GMC V6 schemeing

409 and the Jimmy V6 are completely unrelated...the only similarity is that both are truck motors from the early 60s.

A friend has a 305 v6 in his mid 60s chevy pickup, with a 3 speed overdrive behind it. Definitely not a performance mill, the engine is way way heavy and doesn't breathe at all.

you got the "ton" part right in "ton of fun"

[CTX-SLPR]

Re: GMC V6 schemeing

Is the air moving problem a head issue or is it more related to the carb and intake?

[squirrel]

Re: GMC V6 schemeing

yes!

[2k3Chevelle468]

Re: GMC V6 schemeing

I had a 68 GMC half ton with a 305V6 and a th400 tranny. The truck had not more than 2 feet of metal without some form of rust and no brakes. The truck sold in less then 2 hours after being posted for sale. The thing was strong and ran like a tank.

[CTX-SLPR]

Re: GMC V6 schemeing

From that site, which seems to be the sole source of information on the web, there were "performance" versions with bigger ports called Magnum versions. Besides, I wonder if the heads are anyworse than a Buick V6 head and turbos fix them up just fine. Their is another commonality between the GMC and the W-motor was the 6 headbolts.