6 mpg... please help

[piecesparts]

Originally Posted by nekkidhillbilly

be cheaper honestly to find a 700r4 used you can get em for like 200 bucks all day long here

With the 2.73 geared rear end, I believe that you will be going the wrong way by going to a OD tranny. You will kill off the 6 MPG with the lugging on your drive train (been there, done that). Changing gears is about an $800.00 project (If you have someone do it for you) Changing rear ends is about the same, if you look for a good one (especially if you upgrade to a posi unit) and pay someone to do it. A complete rear end is something that you could do in your garage if you have air impact tools for the spring u-bolts and a way to handle the complete assembly under the truck frame. Rear ends with lower gear ratios can be found everywhere, especially ones W/O posi. Remember to rebuild the brakes when you do the rear end and look into getting the tranny's speedo gears updated for the rear end gearing change.

NOTE: An OD tranny is still a good idea, but do it as a combination, not just one thing and expect the best of results.

[truckincurt]

id check timing and then recheck it lol

[bitchin85]

I thought I mentioned it already.. But if I didn't I already changed out the rear end. I found a 3.42 open diff out of a low mileage suburban complete for 75 bucks and the brakes on it are like brand new and they're a lot bigger then the 1/2 ones that I took off it. Today I put a new coil in it, fixed all the arcing problems (I think) and set my plug gap to .045. Helped a lot. Its getting about 9-10 right now on mid grade but I still think it could do better. And I just put a new tranny in it a couple months ago so the 700r4 is out of the question for a while lol. I still think my harmonic balancer is out of whack because I set it at ten degrees acording to the balancer and tab with a timing light and it ran crappy but had someone tweak it by ear and had it run a lot better but the timing acording to the balancer was way off.. So I'm going to check that out tomorow. Also when I first bought the truck I had an edelbrock streetmaster intake (like the torker single plane) laying around and being young and dumb I threw it on. Now that I know a little more about this stuff, would a performer or any dual plane intake help me out any?

[68 TT]

Originally Posted by *****in85

I thought I mentioned it already.. But if I didn't I already changed out the rear end. I found a 3.42 open diff out of a low mileage suburban complete for 75 bucks and the brakes on it are like brand new and they're a lot bigger then the 1/2 ones that I took off it. Today I put a new coil in it, fixed all the arcing problems (I think) and set my plug gap to .045. Helped a lot. Its getting about 9-10 right now on mid grade but I still think it could do better. And I just put a new tranny in it a couple months ago so the 700r4 is out of the question for a while lol. I still think my harmonic balancer is out of whack because I set it at ten degrees acording to the balancer and tab with a timing light and it ran crappy but had someone tweak it by ear and had it run a lot better but the timing acording to the balancer was way off.. So I'm going to check that out tomorow. Also when I first bought the truck I had an edelbrock streetmaster intake (like the torker single plane) laying around and being young and dumb I threw it on. Now that I know a little more about this stuff, would a performer or any dual plane intake help me out any?

The single plane intake is not helping your gas mileage any by making you get on the throttle more to get moving. What the Performer intake will do is lower your power band and with an engine like yours with a small cam that pulls 21 inches of vacuum you would benefit from that lower RPM power band.

That intake is older than your truck, it was new around 1974. Intake technology has come a long way since then.

[bitchin85]

I'm going to start looking for a used performer. Would that give me any power gains over what I have now? Or mpg gains?

[68 TT]

Originally Posted by *****in85

I'm going to start looking for a used performer. Would that give me any power gains over what I have now? Or mpg gains?

It should give you both by moving your power band lower and increasing low to mid range torque.

[bitchin85]

Ok well that will probably be the next thing I do to it. Another thing I was wondering about is would a carb spacer help me any? I have a e inch four hole spacer wittin around and I wondered if it would help with mileage or power..

[68 TT]

Originally Posted by *****in85

Ok well that will probably be the next thing I do to it. Another thing I was wondering about is would a carb spacer help me any? I have a e inch four hole spacer wittin around and I wondered if it would help with mileage or power..

Every motor acts differently. The only way to know is to give it a try.

[piecesparts]

Do you have a tach on the truck? If so, what are your RPMs at highway speeds? With your present tranny and rear end combo, can you gain there? Look at your tire setup, to see what you have and will get from any possible changes.

[bitchin85]

no my tachs broke. im looking for a new one but anyways i put the 2 inch four hole spacer on and took the one inch open spacer off and it takes off alot harder out of the hole but i can tell it dont have as much balls in the higer rpms. i think im going to put the one inch under the four hole. and yes i know this is probably a sad redneck excuse for a righrise lol but other then that i put new accell short u-groove header plugs in and gapped them at .045 and they actually seemed to help a bit over the autolites. and most important no more arcing! but with all the tweaks ive ben making and the 195 degree thermostat(which helped alot) im getting about 10-12 if i baby it. so problem mostly solved... for now lol thanks everyone for the help

[truckincurt]

single plane intakes are for high rpm motors (motors that start makin power around 4 g).. dual plane is for low rpm torque if your motor is stock you want a dual better power and slightly better mpg