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Old December 7th, 2021, 04:15 PM
Prowbar Prowbar is offline
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Default The fuel efficient GMC V6

Here's something I've been tinkering with for a while. I've been reading that old post from James Cleary and he mentions outstanding fuel economy from an engineering standpoint. Well, as we know, these V6's are anything but fuel-efficient.

Which got me wondering, is it possible to improve the mileage on these V6's? I believe so, by reducing the internal friction that these have. The main advantage we already have is 2 cylinders less than a V8, meaning less friction.

Some ideas I had: (which apply to a 305E)
1. Custom (longer) connecting rods and the use of 4.250" big block Chevy pistons with thin, low tension, piston rings. Modern materials make this possible. This would reduce the massive friction of the thick piston rings and the large piston skirts.
The longer connecting rods are needed because of the higher wrist pin location.

Does anything know what length the stock rods are, and what the deck height is?

2. Another advantage is the compression gain, with a flattop or even a slight dome design. Up to 9.5-10:1 static. Maybe even higher, given the rod ratio.

The disadvantage would be to have everything rebalanced.

Of course, the mains and rod diameters are larger on a V6 than a comparable engine, adding to the friction, which is a given. But I have a hunch this (different piston) will improve the efficiency of the engine significantly.

Reducing additional friction could be done by the switch to a roller camshaft.

Another idea is to change the intake manifold, but I'm not sure how good or bad these are. Optimized and equal fuel distribution to all cylinders is the idea.

I'm no engine builder, just a student on the subject, but I'd love to hear your ideas. It is not my idea to write off the base design, just some thoughts to improve on it.

Last edited by Prowbar; December 7th, 2021 at 05:11 PM.
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