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Old 05-30-2012, 08:00 PM
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502 ramjet EFI

I've seen this question asked, and I don't see answers anywhere. My friend is trying to make the best decision (best bang for the buck) so it must be asked. What sort of mileage would you expect out of a modern 502 "ramjet" from GMPP? I'm thinking 8-9 mpg, 4200 lb car, 3.73 gears on 255/60/15

Assuming a TH400. He'd really like something with overdrive, I know that might make a difference.

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Old 05-31-2012, 01:24 AM
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Lots of variables, frontal area of car i.e. "barn door effect", how heavy your friends foot is, general tune of the engine etc. The good is the engine has FI, the bad are the cubes, the th400 and the 3.73's. The calculator shows with the 3.73 and a 27" tire he'll be spinning around 3450 rpm's @ 70 mph. Hard to tell what the mpg would be....but a nice o/d trans would sure help or stick a set of 3.0's in the rear end.
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Old 05-31-2012, 07:56 AM
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Unless he has a brand new th400; get rid of it and get into a prepped 700r4 or 200-4r. Putting the engine and trans in the car as an assembly is much easier.
Assuming hes using everything the computer needs to be happy and its dialed in, hes probably in the 10mpg area. If he was to ditch the 400; and drive like Ethel, he'd probably get 16mpg or so.

If he's dead nuts set on that 400 (even though he can get a TH350 that would be more than adequate and eat less power); have him put 3.23s in the back and get the proper converter
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Old 05-31-2012, 08:14 AM
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Computer problems with the 502 Ramjet are well documented-when he gets those sorted out I'll guess 11-12 mpg-if he puts in an OD, 14-15-as always, your Mileage may vary-
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Old 06-01-2012, 01:46 PM
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Depends big time on how he drives. My 450 hp 355 gets about 10 MPG when im stepping on it a little. Step on it alot and i get about 7. Baby it and i get about 14-15.
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Old 06-02-2012, 09:03 PM
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anyone that installs a 502 and worries about gas mileage is a fool
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