The GMC CCKW

I'm sure this topic has come up before, but I could not find it in the search.

What is the effects of unleaded gasoline on these old engines? I heard from a mechanic friend that it will wreck the valve guides. Do I need to get a lead additive?

Anyone know if the 10% Ethanol gas good/bad?

Thanks,
Daniel

This question could be a standing Headline in every Classic vehicle group, cars, trucks, tractors, engines, etc.

I do not believe there is a concrete answer to this at the present time. There is much conjecture and a lot of unsubstantiated "expert" opinion. The good-bad is also greatly influenced by politics and the position of the writer on the Global Warming --- strike that --- Climate change issue.

Finally somebody is going after the facts.

See links below

http://www.americanfuels.info/2008/08/s ... hanol.html

http://kettering.edu/visitors/storydeta ... rynum=2779

I am sure where opinions and emotion are involved the issue will not be settled. But facts will come forward.

What I do know is is that Ethanol laced fuel goes bad alot quicker that it's predecessor and that my purchase of Stabil has increased exponentially to keep the gas in all the internal combustion toys in my possession from going stale.

Bill

From my experience, driving the underpowered CCKW many thousands of miles, that the unleaded gas appeared to have no negative affects. I ran over 10,000 miles on my original 270 in my cargo truck w/o problems. Then I had the head modified for the Chev 350 (cid) valves and hardened ex seats. I actually think it ran worse after that

I ran the engine that way for more thousands of miles till I finally replaced it with the civy 302 it now has.

It is my understanding, as Bill pointed out that the new gas is not too good for storage even for relatively short periods of time like over the winter. There is also evidence that the new gas can deteriorate the rubber parts in the fuel system. Having had a fuel pump diaphram failure my Jeep that loaded the crankcase with gas, most all my HMVs have electric fuel pumps so that cannot happen.

My $0.02

Hi

According to all information I have read, the engines were designed to run on 64 + octane fuel. Since Europe and most other mid-east countries in the 30's and 40's did not have leaded fuel, the engines were designed for unlead fuel of very low octane.

When the engine head was removed from my truck, it already had hardened seats and guides.

Lee

Even though tetra-ethyl lead is a deadly poison, you can/could (last time I looked) buy it online!

The stuff you buy locally "lead substitute" is sodium based and is NOT lead