V8 Conversion MPG Average (1 Viewer)

[JONNYFJ]

Hey Guys I am just curious to see what kinda gas millage you all are getting out of your V8 Conversions If you could state the Displacement and if its EFI,TBI, or Carb. I personally only get between 6 to 8 MPG out of mine (I have a lead foot), but with raising fuel prices that will have to change. Looking Forward to seeing what you all got.

 

[dgangle]

Q-Jetted 350, H42, 3.70's w/ 33's. I get between bad and worse. My 16 gal poly tank lasts about 100-125 miles which equates to 7-9 MPG. If I need economy, comfort, be able to hear the radio/phone or to be incognito, I drive the 4Runner.

The words VJ40 and economy cannot be used in the same sentence. It's the law.

 

[JONNYFJ]

Q-Jetted 350, H42, 3.70's w/ 33's. I get between bad and worse. My 16 gal poly tank lasts about 100-125 miles which equates to 7-9 MPG. If I need economy, comfort, be able to hear the radio/phone or to be incognito, I drive the 4Runner.

The words VJ40 and economy cannot be used in the same sentence. It's the law.

I like that last bit O so True

 

[camcruiser13]

10 maybe

 

[iaintscared1969]

Go Vortec! EFI systems can also achieve some gains. Old school is cool but everyone likes the HP and the gas mileage. Cake and eat it too.

 

[dgangle]

Agreed. However a lot of us aren't that smart to figure out all those wires and stuff. I have 6 wires to my small block: 12V to the coil, battery & ignition to starter solenoid , oil/water sending units and a good ground. Any moron mechanic in the world including me can troubleshoot that! I personally would hate to try and work on someone else's EFI graft.

 

[JONNYFJ]

I have been eye ballin the Gen III LS1s for a good time know, but holy **** they are pricey. And I am no ASE mechanic. To me all those wires means one thing $$$$ for someone else to deal with it. When I get back from Iraq I might just have to look deeper cause 410hp and 14 to 16 MPG sure does sound good

 

[2damslow]

I have a mild cam in a rebuilt 350 with the holley 2d projection. The trans is the stock 4speed stick adapted with the Mark's adapter and I get about 11 around town. The exhaust is still a bit rich, so I think I may get more if I ever got the O2 sensor kit for the pro-jection.

 

[dgangle]

Remember lean (or leaner) = hotter. And cooling is a whole different battle to deal with.

 

[jagota]

I have been eye ballin the Gen III LS1s for a good time know, but holy **** they are pricey. And I am no ASE mechanic. To me all those wires means one thing $$$$ for someone else to deal with it. When I get back from Iraq I might just have to look deeper cause 410hp and 14 to 16 MPG sure does sound good

You won't get that.

 

[JONNYFJ]

Lethal Performance did a LS1 swap on a CJ that sits on 44's the dudes gettin 14 to 16 MPG highway. My 40 will never see anything bigger that a 37 with the right tuning I should be able to get around that. Hell anythings better than what I get now

 

[dgangle]

I call Bullshitz. Tell your source to clarify/prove it. Do those figures/stats include a Mexican overdrive (coasting downhill with the engine off)??????

 

[JONNYFJ]

True True Thats coming from the owner of the shop thats trying to sell me the damn thing

 

[dgangle]

no s***z. If you wanna buy mine in gets whatever milage you want in order for you to buy it. Consider the source!

 

[iaintscared1969]

OK if a 60 series Vortec gets 15-16 with a vortec how can a smaller some what lighter vehicle not get somewhere's close?? Just trying to stir the pot! ;p This is a good discussion.

LS1 is pricey but you can go 5.3 for less and still have plenty of go. Recam it for the low end and you are set.

Granted your tire size and gearing will make a difference. That's why you need to know your driving style and your want's.



Yes the wiring can be a bit frustrating but I only hook up 6 wires on my installs.

 

[dgangle]

...but I only hook up 6 wires on my installs.

Please elaborate. I am all ears.

 

[JONNYFJ]

I just talked to moose over at lethal he said No BS on the MPG with a chip and some other little goodies he said it can be done. The CJ was not his first he has also done 2 TJs and a Blazer. Thing is all of them had automatics w/overdrive... Something I don't got

 

[iaintscared1969]

First off I have my harness made by FIS. I custom order the length and options. Makes for a super easy job and well worth the time. If you use a stock harness you have to supply the ECU with the same basic connections as you do a 350. But you also have to tear the harness down. A good source for instructions is from Downey off road cost a whole 5.00 and gets you everything you need to know. I did a couple of the stock harness but I never liked how they lay out in the vehicle. Plus the time to clean it up and re loom it and delete pig tails was never a lot of fun.

 

[iaintscared1969]

Sounds like you need a 5 speed!! Auto's are nice but I prefer to change a clutch than rebuild an Auto.

 

[Brian in Oregon]

About 8 to 9 mpg with the Holley 650 Truck Avenger.

About 10-11 mpg around town with a QuadraJet. I can't say for certain yet what the highway mileage is. I do know that there is a big mpg difference between 55-60 mph and 65 mph. 65 mph is not economical with 4.10 gears, even with 33" tires. I'm doing 2550 rpm at 55 mph. Wish I had overdrive or a 5-speed.