SO who came up with the GMC V6's???

[Dave Boboltz]

Big Block V6, that is a great question and I don't know the answer to that. I did send Cleary an email so maybe I can learn more. Or there is another guy who lives nearby who has some amount of historical information (Don Meyer).

I suspect that the tooling went somewhere that would be capable of making service parts. It would be interesting to know where that tooling is now.

Dave Boboltz, Waterford, MI

[bigblockv6]

It would be interesting to know what became of the tooling. From what it looks like in the email, Cleary was no longer in the V6 development sometime in 1960. He was not aware of the 379,432 and 637 engines.

[TJ's GMC]

So here's a question....anybody know why a small single barrel and then two barrel carb were used on these engines? I'm assuming for low end power and fuel mileage? Might be a dumb question, but with the large bore I would have thought a bigger carb would have been used.

[bigblockv6]

The one barrel did not work out well with the 305 engine by 1961 the 305D 2bbl engine came in to replace the 305A even though it was still available. 125 net horsepower to carry around that much weight was really underpowered for the 305. The 2bbl brought it up to 142 net horsepower then with more improvements for 1966 to 157 horsepower. Possibly mileage may have been why a 1bbl was used. Originally the prototype trucks used were lighter 1958-59 trucks and the 1bbl version was more than adequate.

[TJ's GMC]

Originally Posted by bigblockv6

The one barrel did not work out well with the 305 engine by 1961 the 305D 2bbl engine came in to replace the 305A even though it was still available. 125 net horsepower to carry around that much weight was really underpowered for the 305. The 2bbl brought it up to 142 net horsepower then with more improvements for 1966 to 157 horsepower. Possibly mileage may have been why a 1bbl was used. Originally the prototype trucks used were lighter 1958-59 trucks and the 1bbl version was more than adequate.

Ah, Ok. I watched a video of a 305A running...man you could hear that thing Breath. lol I was like yeah....that carb is a bit small. You know what improvements were made in 66? I remember running the numbers on mine with a fellow forum member, and my 305 in my 64 looked to be a 67 series engine. Did the 305E ever come in medium duty trucks? Cause mine had the governed dizzy on it.

[bigblockv6]

A new cam along with different count timing chain and sprockets were some of the changes, at some point up to 66 larger valves were used on the 305 engines as well. Medium duty trucks used 305 engines from their beginning in 1960 all the way up to the very last in 1974

[bigblockv6]

I should have included this in my previous response. Yes 305E engines they were used in 3500, 4000 and 4500 series medium duty trucks.

[bigblockv6]

Light duty trucks too were available with governors.

[TJ's GMC]

Originally Posted by bigblockv6

A new cam along with different count timing chain and sprockets were some of the changes, at some point up to 66 larger valves were used on the 305 engines as well. Medium duty trucks used 305 engines from their beginning in 1960 all the way up to the very last in 1974

Originally Posted by bigblockv6

I should have included this in my previous response. Yes 305E engines they were used in 3500, 4000 and 4500 series medium duty trucks.

Originally Posted by bigblockv6

Light duty trucks too were available with governors.

Ah ok, yeah....I had to get a new dizzy cause the old was was frozen up....the governed vacuum pump was seized or something. Here's another question....any particular reason why the compression was made so low?

[bigblockv6]

I'm not absolutely sure but from what I recall The idea of having low compression was for achieving low end torque.