How much effiency does 400 use

[Footjoy]

I have a friend with a street rod. The car is about 2800 pounds, he has a 350 about 225 hp with a turbo 400. We have tuned it new wires, plugs, stock cam and Carter four barrel but this car only gets 10 mpg. Can the TH400 eat up gas milage?

Just curious.

fj

[GetMore]

Not really, they take a touch more than a TH350, but I don't think it'd be enough to notice. You did not mention what the gear ratio is in the rear or where he is driving it.
An overdrive transmission will get you better mileage, but driving style can possibly make a bigger improvement. If you drive it very easy, coast to stops, and generally try to keep off the throttle as much as possible you might see a huge difference. It's not as much fun to drive that way, but it does save fuel.

[MonzaRacer]

first thing is on a 350 mild motor as you have, set it up with about 14 to 18 degrees initial timing, use light springs on centrifugal advance and make sure it works. Reset tidle as timing speeds the engine up, then use manifold vacuum, yes use it as you will be making power timing with out it and vacuum advance is your mileage.
I currently have my 78 c10 with a blueprint 355 th400, lt4 hot roller, tall version holley street dominator and when it was in my 71 monte carlo(4000lbs) 355 gear it could make 18.
but I agree, more tech info would help.

generally I run my timing with idle as slow as it can idle, vacuum unhooked at top of timing tab (thats on ds side of engine) check it its usually around 16 or 18 degrees. also check for slipped ballancer as that can kill mileage, if it rattles at take off try next step up on accel pump arm or bigger shooter. May even need 89 octane. If it rattles at cruise add on step stronger spring to ONE side of advance at a time.
Lee Abel
AFTERMARKET PERFORMANCE

[Steve Chryssos]

There's parasitic loss and then there's slippage. What does your friend's car have for a torque converter?