did any of you check gas milage before/after using 1.7's or 1.6's? I really want to put a set on my 5.9 but know it'll hurt the milage, but my question is how much? And arent the 1.6's a stock ratio? maybe that is the way to go...

 

I am not sure on the milage....though the 1.6 is the stock size. The 1.7s will give you good gains but is to large to be used with a cam. If you just go with 1.6s you will not see as good of gains with out the cam being swapped out as well

 

I would say to do a cam swap. It may cost more but the change will be more of what you're looking for. Not sure if you know, but to get the numbers using the 1.7 rockers, simply divide the cam specs by 1.6 (current rocker ratio) and then multiply them by 1.7 (new rocker spec)

eg.

0.410 intake lift / 1.6 rocker ratio = 0.25625X1.7 new ratio = 0.436 approx.

.026 will make a difference, but this number goes down with a smaller cam.

And fo course something like that will change the mileage, for the worse. Can't give ya numbers cause I don't know!

I'm new, if that's rambeling let me know and I'll stop.

 

Problem with a cam swap is it's not CA legal (sucks living here sometimes) and I don't want to do anything major that I'll have to undo for smog. I know the crower rollers have a CARB EO# so I'm safe there, but a cam would not be practical (however I would probably do it in a heartbeat if I could get away with it... screw the mpg... lol) But, I'm in the middle of trying an experiment to improve gas milage & just wanted to know how much the 1.7's would set me back. Should be done by the end of the weekend (really, it should only take 1 evening if I got my *** in gear).

I was under the impression that it was a 1.5 ratio, glad I posted this... so the 1.6's are suppose to give up to 8hp an aweful expensive 8 hp...

 

If all you need to do is improve gas mileage, add one of those "turbo" air thingys. They sit between the air filter and the throttle body or before the air filter, I can't remember. My cousin had one on his Silverado and said it made a decent difference. Another tip, make sure that your O2 sensors are working correctly. By default, if they fail the truck will run rich, meaning more fuel. Clean air filter or even a K&N will help too. I think even using synthetic oil would help. Less internal resistance equals power and mileage.

 

Already have K&N, gibson headers, synthetic oil (mobil 1) and 2 new O2's. Replacing the o2's helped some, the plugs were getting soaked w/gas before I swapped them. Now they are firing good, but the mpg's did not change that much, maybe .5 mpg. Also should mention that I'm running BFG AT's (285's). Those "turbo" air thingys dont work on the dodge. The design of the intake would prevent any benifits since it has long runners for each cylinder, it seems like it is just an air box for the heads. The M1 manifold may see some benifit because of it's straight runner design (from the TB to the head), but I wouldn't count on it.