the things that make this truck a poor fuel mileage truck is , it doesn't has a mass air flow meeter/sensor, low compression ratio, low operating temperature. i just try to get it as efficient as possible, i am not crazy, just to try save money.

 

it is those thing that make these engines so reliable. the old slant 6 that is almost impossible to kill ran a compression ratio of 7.5:1. sure they could have shaved 11/410 inch or so from the head surface and increase compression while loosing about 5 pounds of cast iron but it would not as reliable and bullet proof as they are.

 

Well I mean no offense, if you can squeeze better mpgs out of your truck than great!

If not, don't be too let down...

 

How does a double roller get you better power/mpgs? Isn't the main benefit they don't stretch as much, or do they actually "roll" better?

 

I want a stereo in my 76.
I am going to do the timing chain soon, provided I get the cash. E-fan, yeah, it's on the list...the long list....along with the HS1.7's.
They don't stretch as much and I think consequently there is less drag on the engine BECAUSE it doesn't stretch.

 

Might try headers. Seems like if the exhaust can escape easier, it might help MPGs. Im sure someone will disagree, but its a thought.

 

Yeah buddy, rock it ole'-school! Same with mine. My truck has no idea if I unhooked the battery since the last time it was run or not.

 

Some say they don't stretch as much, I can't comment on that as I have a fairly stretched double roller in my '72 d100's 318, but the main benefits in my opinion are 1) replacing the old worn and stretched timing chain with a new tight one, and 2) it is much lighter to turn and creates far less friction.

To explain a bit better. The original timing chain in your truck is going to be stretched, guaranteed. It just happens over time with miles. Since everything having to do with an engine eventually wears out, I wouldn't try to say that a double roller timing chain will never stretch. So, double roller or not, a new timing chain will tighten up the relationship between crank and cam, causing the valves to open and close at precisely the right time, where they may have used to be a bit inaccurate with the old looser chain. So that's benefit #1 of replacing it, and that benefit would be acheived whether one used an original "morse" style chain or a double roller.

Benefit #2 is the friction reduction. There is less contact between the gear teeth and the chain with a double roller set, resulting in less friction. The contact that does exist is also more optimized by design of the chain/teeth, so it creates the least amount of drag possible. The morse chain is also significantly heavier than the double roller. Weight multiplies when rotated at speed, so as engine rpms increase, more rotating weight makes more drag, hindering quicker revs and horsepower.

In the case of removing extra load from an engine, you would see an mpg gain along with the extra power.

 

+1 for a very informative post.


What is your take on advancing the cam timing with a 3-keyway timing set?

 

^ I like the characteristics of the motor in stock form. If I wanted to change valve timing I would do so with an aftermarket cam. I don't think that changing the degree of a stock cam by 3 degrees in a stock electronically controlled engine would make any beneficial difference whatsoever, so I left it stock.