Quote:
Originally Posted by S1965C
Realizing all engines are different, would still love to learn more about your setup. Things like carb jetting, power valve, initial/full dist. advance (including springs used), ignition source/type (i.e. MSD 6AL), trans OD ratio and rear end gearing, etc. I have a similar motor with a 750 Mighty Demon and I get 10mpg on a good day.
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Here's what I have the Roush 427SR (351w) tuned with:
- 93 Oct fuel*, TKO600 5spd, 8.8" Rear End with 3.73:1 ratio.
- Annually I check the Carb Bolt down and torque to spec, 60-80in-lbs(5-7ft-lbs). When i first got the car 3 bolts were extremely loose and vacuum had leak when cold.
- Annually check Disty Cap & Rotor, replace them every 2 (maybe 3) years. MSD HiOutput/6AL puts a lot of wear & tear on them.
- Annually I run a can of Seafoam through a tank full... living in NC I can drive it year round so no need to winterize it but still do this on all my classic sports cars. I have added 2200miles on it since April 2020 when I bought the car.
- Have a MSD Hi-output Coil, MSD 6AL box, use cooler NGK BKR6E-11 Plugs , gapped at 0.045" (between .042"-045" works best).. Note: Roush specs using Autolite AR3923, heat range 3 plugs so the NGK's I use are equivalent with their heat range of number 6.
- Have a Mallory #8578 Pro-Billet Disty, Mechanical advance .. with 2 Silver (lighter) springs.
- Idle Set at 920rpm and Timing @ 15.5 BTDC ... at 4000 rpm, Timing @ 32.5 BTDC (Roush spec is 31-34 BTDC, must be LESS than 35 BTDC).
- Have a 770 Holley QF (80770-1) ... don't know exactly the jetting, nor power valve as it came from Roush as a crate engine ... sorry here...
- Currently have BOTH A/F Carb Mixture screws set at 1-1/2 turns OUT (I don't have 4 corner A/F mixture screws... just the 2 front ones). Here I spent a lot of time tweaking with 1/8 turn increments to find the sweat spot... when I bought the car in April 2020, the car came with A/F turned 1-3/4 out (on passenger side and 1-5/8 out on the driver side) so I reset them to starting at 1-1/2turns out as the documentation suggests and ended up here anyway.
.... When I bought the car , it's Idle timing was @ 10.5 BTDC... Disty Cap & Rotor were shot, Autolite plugs gapped .052"-.056" .. and I know I had vacuum leaks with the Carb Bolts looser than spec when cold. I was getting 10-11mpg at best....
NOTE: * I use regular 93 Octane even if it has some ethanol , so I tuned the engine with this type of gas..
Hope this helps and feel free to PM me for more discussion...
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