Awful gas milage.

[Obwonkonobe]

Your better off stabbing your eyes out than thinking about the Holley Sniper. Biggest POS ever made. Do your research.

REALLY? I’ve always heard it’s the way to go for full tun-ability, not the case?

 

[Big Chip]

What’s milage?

 

[DoubleDingo]

I remember seeing somewhere that you will achieve your best mpg when your engine is at its peak torque. True or not, I can't confirm.

I have also heard that to achieve the best mpg, you want you engine to turn the rpm where max vacuum happens. Hook up a vacuum gauge and go for a cruise. You may actually be lugging the engine at 1800 rpm. Check and see what your vacuum is at 1800 rpm, and then drop it into drive and see what you get for vacuum at 2200, 2500, maybe even 2800 rpm. If you get max vacuum at 2500 rpm, that is where you will get max rpm because your engine is hardly working to maintain that rpm, even though if it 700 rpms higher.

Yep, peak torque is where it's at. I recall when I got a new gear set for my Cherokee, it had 3.55's in it and I wanted 3.73's, but I also wanted to run down the highway at the same rpm it was running with the tiny tires they had on there from the factory. So I got out my calculator and an old 4wheeler magazine that had a tire size/rpm formula, and then made a list of various tire diameters with the 3.73's, and I achieved my goal. Same mpg's and same mph at the same rpms.

In my '65 I get 12-14 cruising at 2,600 which it running at the same speed as the cars around us. I think it's around 75 mph (I disconnected the speedometer). Of course that is with the overdrive engaged, otherwise we'd be cruising 55 at 3,000 rpms. Those 4.57's aren't good for highway speeds, but engage the overdrive and those 4.57's become 3.19's. Yes it is a 30% overdrive, pretty steep!

Exhaust pipe sizes also make a difference. Too big and it doesn't flow as well. I've heard it time and time again, your engine is just an air pump, and it needs to be pumping air as efficient as it possibly can. So from the air intake to the exhaust, it has to be efficient. Any restrictions in the air flow and it won't be running at its peak.

 

[4WDKC]

Well, I see I am not the only person with this confusion.

I have a '74 with a .030 over 350 high nickel content block, full rebuild, HEI, long tube headers, 650 Edlebrock on an Air Gap running 14°, 268H CAM, no AC, and a new 700r4 with corvette internals and no lock up. I cruise at 60/1800 rpm on 30" tires and a 3:73 gear set.

Before I started the build, I had a clapped out 350 and TH350. I got 12+ MPG. With the new setup, I was hoping for 14-15 and get between 8-10 on a good day. Confusion reigns.

I was told that the Air Gap cools the mixture for more HP at higher RPMs at the cost of lower mileage due to less atomization in the colder mixture. I am at a point where I am considering a F.I. conversion kit and replacing the Edlebrock 650/Air Gap combo. . .

My neighbor gets 24 MPG cruising with his 10 year old F350 4x4. . . now that's a pisser! I am not sure what part, or parts, of my combo are wrong, but 8-10 MPG wipes the smiles off my face every time I fill up and looking at it sitting in the driveway while I drive the '98 Silverado. . . well, that's just as bad.

you are not using lock up the torque convertor is still slipping and is not being efficient costing you mpg.

Honestly if you go fuel injection I’m starting to think I should’ve gone with a factory tbi setup, and built that out. Or the Holley sniper, you have WAY more control over those sniper units. But for simplicity you can’t beat the msd atomic

stock tbi systems are great for stock engines, once you start modifying them it becomes a pita to tune and this is with the latest upgrades. Tuning them like they had to back in the 90's was terrible 1 in 3 chips you burned actually burned the files to it and the hardware was expensive. Modern efi systems are much better, I cant speak to the Sniper system but I have an old holley efi system that works much better than the stock systems but still archaic by todays standards.

 

[CSFJ]

What’s milage?

Isn't that when a municipality asks for a tax increase for a special reason?

 

[shiftpro]

I cruise at 60/1800 rpm on 30" tires and a 3:73 gear set..

I have to agree with Greenscotty... 1800 a bit low for highway @60 mph.

 

[Big Chip]

Isn't that when a municipality asks for a tax increase for a special reason?

Close. You’re thinking millage. Ironically, millage autocorrects to mileage.

 

[Super-Dave]

Your better off stabbing your eyes out than thinking about the Holley Sniper. Biggest POS ever made. Do your research.

Been looking at the FiTech. They (or their people) are supposed to have a long history of making fuel systems for OEM.

Seems every one of these aftermarket kits tell a good story and there is at least one person on youtube who swears by their choice. Guess it's nothing but a crap shoot anymore.

 

[Super-Dave]

I remember seeing somewhere that you will achieve your best mpg when your engine is at its peak torque. True or not, I can't confirm.

I have also heard that to achieve the best mpg, you want you engine to turn the rpm where max vacuum happens. Hook up a vacuum gauge and go for a cruise. You may actually be lugging the engine at 1800 rpm. Check and see what your vacuum is at 1800 rpm, and then drop it into drive and see what you get for vacuum at 2200, 2500, maybe even 2800 rpm. If you get max vacuum at 2500 rpm, that is where you will get max rpm because your engine is hardly working to maintain that rpm, even though if it 700 rpms higher.[/QUOTE

you are not using lock up the torque convertor is still slipping and is not being efficient costing you mpg.

The shop that built my 700r4 was a racing shop and the owner advised to bypass the lock up. He died from a heart attack in the bathroom a few months ago. . . so I have been asking around for another source and was directed to a shop about 25 miles away. Had them work on my '98 Silverado. Owner is also into racing and has 40 years experience, so I will be taking the '74 out to his shop for a once over and we will chat about the lock up.

My tire and wheel selection kept the overall height of the OEM wheels (=/_ no more than .5 inches.) Guess I can look for the sweet spot for RPM/MPG but it's somewhat dependent on how the clowns around me drive. All these Hybrid, Rice-Burner Imports and even the "American" Fossil Fuel cars seem to think that they are the designated speed control nazis. . . getting any reasonable sustained speed is an exercise in futility.

The hard part to swallow is cruising the I-5 corridor at 10 MPG. . .

 

[SquareRoot]

The shop that built my 700r4 was a racing shop and the owner advised to bypass the lock up. He died from a heart attack in the bathroom a few months ago. . . so I have been asking around for another source and was directed to a shop about 25 miles away. Had them work on my '98 Silverado. Owner is also into racing and has 40 years experience, so I will be taking the '74 out to his shop for a once over and we will chat about the lock up.

My tire and wheel selection kept the overall height of the OEM wheels (=/_ no more than .5 inches.) Guess I can look for the sweet spot for RPM/MPG but it's somewhat dependent on how the clowns around me drive. All these Hybrid, Rice-Burner Imports and even the "American" Fossil Fuel cars seem to think that they are the designated speed control nazis. . . getting any reasonable sustained speed is an exercise in futility.

The hard part to swallow is cruising the I-5 corridor at 10 MPG. . .

Hmmmm....makes me wonder what was going on in that bathroom?

I drove truck up and down the I-5 until the ****** California roads beat me into submission. Worst road maintenance I've ever experienced in the country. But hey, illegals now get free health care. They'll need it in that place.

 

[Matt69olds]

The Holley Sniper is a good system. Sure, there have been problem units, and people who have had issues. It’s not a bolt on and go system, it takes some time to get it dialed in.

I think for the money spent on EFI, you could buy slot of fuel!! Get some of the other issues sorted out first.

 

[Frankenchevy]

I’ve been happy with my sniper/dual sync. I think @bluex has many thousands of miles on his.

 

[bluex]

Ya my Sniper has been great. I had a few issues but I worked them out an I have over 7k miles on it now.

I can get around 16-17 mpg out of it on the highway. Which is about 1 mpg more than I got from the carb. Its set to idle at 14:1, cruise at 15:1, and WOT is 12.9:1. I have a mostly stock 350, it's .060 over flat top pistions, summit cam K1105, Edelbrock performer rpm, 3/4 length headers with 2.25" exhaust. NV3500 (same OD as a 700r4), 3.73 gears with a nearly 31" tall rear tire. I could get the mpg up a little more with a 3.42 gear but I like the acceleration with the 3.73 an it's not a daily so it isnt a big deal. Working on vortec head setup for a little more power now as the 70s smog heads are choking it down now.

 

[Obwonkonobe]

Ya my Sniper has been great. I had a few issues but I worked them out an I have over 7k miles on it now.

I can get around 16-17 mpg out of it on the highway. Which is about 1 mpg more than I got from the carb. Its set to idle at 14:1, cruise at 15:1, and WOT is 12.9:1. I have a mostly stock 350, it's .060 over flat top pistions, summit cam K1105, Edelbrock performer rpm, 3/4 length headers with 2.25" exhaust. NV3500 (same OD as a 700r4), 3.73 gears with a nearly 31" tall rear tire. I could get the mpg up a little more with a 3.42 gear but I like the acceleration with the 3.73 an it's not a daily so it isnt a big deal. Working on vortec head setup for a little more power now as the 70s smog heads are choking it down now.

Exactly the setup I’ve got, I just haven’t swapped my 3.73 rear end in yet, I’m running the msd atomic, and I already have the heads, but with a lame stock cam. What kind of differences did you get from the cam?

 

[Frankenchevy]

Exactly the setup I’ve got, I just haven’t swapped my 3.73 rear end in yet, I’m running the msd atomic, and I already have the heads, but with a lame stock cam. What kind of differences did you get from the cam?

Are you controlling timing with the efi? That would allow more tuning.

I wouldn’t think the stock vortec cam would be any worse mpg than an aftermarket, higher lift cam.