[pastry_chef]

Originally Posted by 455'73inElCamino

I have been getting 13-14 MPG.

This must be city driving?

Years ago we measured a buddies, the car was perfectly tuned.
80 Firebird, full weight.
463 with ported 310 Eheads, 10.2 compression. 110 LSA cam
3.42 rear / 2004R, 10 inch PTC - 3200 stall.
Just over 20 Miles/Gallon on the highway with lockup used most of the time. (56 Miles/ 10.2 Liters of gas)

[66beaumont]

Originally Posted by 455'73inElCamino

I have been running 3.73 gears and due to some rear end vibration, will have the opportunity to change gears.

Anyone swap from 3.73 to 3.08 and wish that they didn't?

I did just that in my beaumont(454 with tko5spd) and was the best thing I ever did especially since first gear was so deep. Would do 70 at about 2000 rpm. On a trip to Calgary averaged 22 mpg

[455'73inElCamino]

My 2004R also has a non lockup converter, with a 2000 rpm stall (i.e. same as a stock OEM converter).

My 13-14 mpg is not city driving but mixed.

also engine is 400 based engine at 440 cu.in. with 530 hp.

[455'73inElCamino]

I recently installed a holley sniper without timing control.

idle: AFR set to 13.5
cruise: AFR set to 14.0
WOT: AFR set to 12.5.
mileage: TBD

vs quadrajetmy basic setup was as follows)
idle: AFR setup approx 14.0
cruise: AFR setup approx 15:0
WOT: AFR setup approx 12.5
mileage: 13-14 mpg

both setups with aftermarket distributor 30 degrees advance max, 12 initial, 10 vacuum.

[JLMounce]

Does your mileage calculation take into account your incorrect speedometer, which would also effect your odometer reading?

I do 13-16 in a KRE headed 455 with a non OD transmission, 3.73's and short 26" tall tires.

Your idle and cruise AFR's should be able to be dipped even lower I would think.

[ta man]

Originally Posted by footjoy

I am curious to know what gas mileage your getting with 3.73 and your 2004r?

My 400 2004r with 3.73 get 11 mpg.

Greg

My car gets 16mpg with 3.08 gears no overdrive and 28 inch tall tires.
Approx 600 hp high 10 sec street car.

[455'73inElCamino]

This is great feedback on mileage results. It is great to be able to benchmark against what others are achieving.

Originally Posted by JLMounce

Does your mileage calculation take into account your incorrect speedometer, which would also effect your odometer reading?

Considering that my speedometer is saying I am going faster/further than I really am, it means my mileage is actually worse than my calculation.

Originally Posted by JLMounce

Your idle and cruise AFR's should be able to be dipped even lower I would think.

You mean idle could be > 14 and cruise could be > 15?

[JLMounce]

Originally Posted by 455'73inElCamino

This is great feedback on mileage results. It is great to be able to benchmark against what others are achieving.



Considering that my speedometer is saying I am going faster/further than I really am, it means my mileage is actually worse than my calculation.



You mean idle could be > 14 and cruise could be > 15?

"Could" be yes. But you'd have to road tune it to see what it likes. The sniper is tuned just like you would tune a carb, only difference is that you're doing it via a handheld controller vs screw drivers, jets and rods.

My setup isn't an exact copy of yours, but my cam is similar to the stump puller and given our cubic inch differences, may act a bit similarly.

I found highest vacuum at idle for my car was 14.1:1. The car cruises best between 14.6-14.9:1, but will tolerate into the 15:1 range as well.

Again though every engine is going to want something a bit differently. I'd start with your idle fueling. Get out a trusted vacuum gauge and make changes to the commanded AFR in small increments. If vacuum rises by leaning the mixture, keep going in that direction until it no longer rises, or falls, then back in off from that spot to your highest vacuum reading. Just like you'd do with the idle screws on the carb.

cruise afr is a little bit harder because the weight of the car and it's inertia keeps the engine going fairly steadily even if the engine isn't really liking the fueling it's receiving. Having a passenger monitoring the vacuum readings from the handheld as you drive at steady cruise is helpful, and again make changes in small increments, all the while listening for detonation, feeling if the car is nosing over, paying attention to throttle position needs for steady cruise etc.

If I had to take a stab at a guess I would bet that your engine will want to be in the 13.8-14.2 AFR range at idle and will probably cruise well right at 14.7:1

Tuning your WOT AFR is best done on a dyno, but you can also do it with a stopwatch and a second gear pull. Make changes to the AFR and do a timed run. Make another change and compare the times. Go in the direction that the car is getting faster until it stops getting faster.

[455'73inElCamino]

Originally Posted by JLMounce

"Could" be yes. But you'd have to road tune it to see what it likes. The sniper is tuned just like you would tune a carb, only difference is that you're doing it via a handheld controller vs screw drivers, jets and rods.

My setup isn't an exact copy of yours, but my cam is similar to the stump puller and given our cubic inch differences, may act a bit similarly.

I found highest vacuum at idle for my car was 14.1:1. The car cruises best between 14.6-14.9:1, but will tolerate into the 15:1 range as well.

Again though every engine is going to want something a bit differently. I'd start with your idle fueling. Get out a trusted vacuum gauge and make changes to the commanded AFR in small increments. If vacuum rises by leaning the mixture, keep going in that direction until it no longer rises, or falls, then back in off from that spot to your highest vacuum reading. Just like you'd do with the idle screws on the carb.

cruise afr is a little bit harder because the weight of the car and it's inertia keeps the engine going fairly steadily even if the engine isn't really liking the fueling it's receiving. Having a passenger monitoring the vacuum readings from the handheld as you drive at steady cruise is helpful, and again make changes in small increments, all the while listening for detonation, feeling if the car is nosing over, paying attention to throttle position needs for steady cruise etc.

If I had to take a stab at a guess I would bet that your engine will want to be in the 13.8-14.2 AFR range at idle and will probably cruise well right at 14.7:1

Tuning your WOT AFR is best done on a dyno, but you can also do it with a stopwatch and a second gear pull. Make changes to the AFR and do a timed run. Make another change and compare the times. Go in the direction that the car is getting faster until it stops getting faster.

Thanks for this! It will be much easier now that I can change the numbers as opposed to tuning the carb.

[71 Goatman]

My new combo in my signature below will pull down a consistent 15 + mpg @ 75 mph.

[footjoy]

Where can I get a 2004R dust cover?

Thanks
Greg

[455'73inElCamino]

Originally Posted by 71 Goatman

My new combo in my signature below will pull down a consistent 15 + mpg @ 75 mph.

Is your converter a NON lockup?