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Username Post: getting 11 mpg        (Topic#315351)
Dixie wrecked 
Forum Newbie
Posts: 1

Reg: 08-31-14
08-31-14 07:44 AM - Post#2480822    

Hello all! I posted this on third gen forums, not much help offered.

Anyway. I've got a 85 trans am, recently built motor, getting a whopping 11mpg!

The motor is a 355, stock bottom end, stock cam from an early 80s truck, cast l98 heads with stock 1.94 valves, completely re worked and milled, stock rockers, a holley dominator dual plane intake, a Holley 4160, with a delco point type dizzy. Headers, true dual straight pipes with stacks. 9.1:1 CR

Trans is a 700r4, stock converter, non lockup,
Rear end is a 3:42 posi, with 31" mud tires.

It runs fine, and the 305 I had before this with the exact same setup got 13mpg average.

Even with no lockup, I'm running 1600-1700 rpm at 60-65..

I had 75 jets and a 6.5 PV in my primaries,
Obviously running rich, so down jetted to 73, running rich but a little better. Down to 70, still blowin that black, at full throttle it cuts out like its not got enough fuel, at the same time as it blows black smoke..
Yet with 75 jets it doesn't cut out all.

Heck, I put 66 jets in, and I was blowing even more smoke! You'd swear it was a diesel!

I'm not sure if my carb is just worthles, or if it might possibly be my ignition.
Delco point type dizzy, point gap .019 with new cap, points, condenser, rotor, wires and plugs, base timing at 14°btdc, full advance is 33

Tried hei at first, a one wore vac advance Accel, and blew 8 coils and modules within a couple months.

Being 20 with a DD that takes 3 tanks of gas a week, it makes doing anything quite difficult, so any help is appreciated


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