Anatomy of a dinosaur... Inside a gmc v6

There has been plenty of threads on here asking about these old beasts, and I got my paws on one and am building it up to see what I can do with it. I know, I'm crazy. Everything is huge in this engine and it's going to be a torque monster that will likely never see above 4000 rpm. Well, I thought I would share some pics from after I tore the beast down.

 

One of the biggest gas hogs ever made, but can't ware them out.

 

OK, so i forgot the pics

 

Looks like you could shove an old oil can down those cylinders.

 

Those old GMC V6's were plenty tough, very well built motors for the time. However they are pretty thirsty motors.

 

Cool project, man those Pistons look like they could have come out of an air Compressor!

 

Are those 4 ring pistons?

 

I wonder how it would respond to fuel injection?

 

that looks like a little 305? The 478 is where the action is

 

Back in the day I use to rebuild those boat anchors. I worked as a school bus mechanic and we had several of them in GMC school buses and one in a old cab over short wheelbase GMC wrecker that was used to tow school buses. It wasn't fast, but it would pull anything we put behind it.

 

That engine is really clean inside, someone took good care of it.

 

A 4-71 would look nice on top of that beast!

 

Like dadstoy2 I also worked in the local school districts bus barn during the summers. Tuned up and changed the oil in many of those in GMC school busses, don't ever remember tearing into on. The first real job I had we had an GMC Tractor trailer with one in it. The driver was sitting on the scales at the Louisiana/Texas border and threw a rod out when leaving the scales. Dumped all of the oil on the scales. I had to go get him, the highway patrol was pissed.

 

I think you will be lucky to get 4000 rpm out of it. There are essentially zero performance parts for it. At best you might be able to regrind the cam for a slightly more performance oriented lobe. The stock engine is just as stated, low rpm torque. Very heavy, thirsty, and not a base for performance.

I have to say, that this is an example of just because you can does not necessarily mean you should.

 

Stump puller, low RPM engines. I had one in a GMC p/u that pulled my friends semi tractor out of a mud hole. MAKE sure you have the heads magnafluxed !!!!!!
I cracked three heads before swapping it out for a 400 SB. Never ran it hot!
IF you want to boost its power the only thing available would be a supercharger, have fun finding the manifold. An old truck junkyard may have it.......

 

GM actually put them in their pickup trucks in the early 60's,
an older fellow in my neighborhood hadd one. The front/rear weight percentage may have favored the nose a bit....

There may be more powerful V/6's but none heavier.

 

I've got a 305 in a 2 ton truck, little on the slow side, but she'll get about 10 to 12 MPG.
If a pickup engine I don't know why they wouldn't turn 4000 we ha d a64 GMC with a 305 also, I believe the pickups are e series and the truck is a c series.
Look on the GMC 6066 pages there is quite a bit on them there.

 

If you know where to look and have the money (not unreasonable) any cam grind you want is available. High compression pistons are also available. I am sure valve springs can be located and large stainless valves installed in these heads for the same money as any other head. A dual point distributer can be purchased I think. This is an odd fire V6? Header flanges need to be made as would any intake. Just not an engine for someone who builds his engines out of a catalog.

 

i like your title

 

get the later model Magnum heads and manifolds off a big displacement engine

 

I had a set of factory GMC PLAID valve covers for one of these. GMC had a Suburban called a Thermos Edition. Plaid everywhere, even the valve covers.
They were cool garage art, wish I kept em.

 

Saw one of those big v6s. Big ass fire truck go over the auction block. Was told they have a 400+ displacement? It was a 2ton cab over truck with a 2 spd rear.
Im slowley stripping an old GMC 2 ton that has a 5 spd. Id like to replace the 4spd in my 62 K20 pickup. The GMC is 50 mi away, will it bolt up to my bell? The engine and bell is gone out of the GMC truck. My truck is a 235 4 spd.

 

I am putting one of those 5 spd.s in my 65 c 10, only thing I have to do is enlarge the circle in the belhousing at a machine shop, bolt pattern and the clutch disc fit.

 

Sweet thanx for the info jonz!

 

http://www.6066gmcguy.org/
/\ this site has all sorts of info on the gmc v6, and a message board dealing only with the v6.
http://www.thunderv12.com/
/\ this site is some guys hotrodding the 702 gmc v12, they should have a 4bbl manifold, header flanges, and maybe some trick heads available.

 

According to my old truck manual GMC coupled two of them together to make a V12. I always thought that would be interesting to have. I'm thinking that if you had a tanker truck you could carry enough fuel to get across town.

 

the V12 is a single block, single crank, it has 4 heads, two intake manifolds, and 4 exhaust manifolds.

 

HaHa on the tanker truck! Will the PTO off the 4spd fit the 5spd?

 

drove one of the v12s in a B model chevy , a trip from Gary Indiana to Lawrencville Il required a fill up when you got there and you had to fill up when you got home , the trucks got about 2 mpg tops and 2 100 gallon tanks , but they had power !

and squirell is right single block but 4 heads .