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Here's the recipe:
Magnum heads with tight quench .030. Bowls opened up. Stock valve job.
Wiesco dished pistons
Mopar Performance M1 Dual plane intake
Roller cam Compcams #20-000-9 506 lift 216 intake 224 exhaust duration.
Mopar orange box. 340 HP manifolds with a TTI 2 1/2 inch exhaust system.
Distributor that I recurved for timing all in at 2000 RPM.
This is a big one: Thermoquad 850 carb. Best carb I've tried and I've tried them all.
700R4 Chevy trany with converter lockup. But any overdrive trans would work.
3.23 8 3/4 rear end
Aluminum radiator with electric fans. Fans don't operate at anything over 40 MPH so you gain at least 1 MPG with that mod.



one question: are you running an adapter for the t-quad on the M1 dual plane, or is it capable of bolting up a spread bore?

some thoughts on the combo, it sounds like a real fun street combo, you could probably get a fair amount more power (~20-25HP & TQ) without sacraficing fuel economy (maybe even help a bit) going to headers.

you're leaving power on the table with the stock valve job in the magnum heads. it's undersized from the factory, and there's gains to be had to opening it and the pushrod pinch up (probably ~40-50HP)....would be interesting to see the power/economy difference with some lightly massaged EQ 318 (hughes "iron ram") heads or RHS heads

from what I've heard the M1 leaves something to be desired as far as performance, that it's essentially no better flow wise than a stock piece. would be interesting to try an LD340 modified to fit the t-quad....that might net you another 15-20HP....

I've thought that comp cam (XR265HR) would make a nice street cam for a small block....it must idle pretty much near stock with 408 cubes under it.

best I've managed so far with my 318 is 18mpg...combo is stock short block, home massaged magnum heads, reground cam by bullet cams, 259/259 adv, 208/208@.050, .316" lobe lift, .506" @ valve, headers, 3" single exhaust, RPM air gap, eddie 1406.

tranny is an A500, rear gears are 3.55, tires are 27" tall...car is a 5th ave, 3950lbs w/o me. I think my carb is what's holding my mileage back now...I haven't done an all highway/freeway trip, I'm guessing it'd hit 20.



Hey Patrick, I do have an adapter on my M1. It's a square bore manifold. I know I left at least 50HP on the table but I wanted a stock idle with some hit to it. I debated having a three angle valve job but just ended up having the bowls hogged out and doing a nice bowl blend. This experiment was to try to make the engine as efficient as possible with high performance as a secondary goal. I know I'll want more power in the future. I have a new crosswinds manifold I might try out. If you are not running a thermoquad I can almost guaranty you'll get 2 to 3 MPG better gas mileage with one. They are just outstanding at atomizing the fuel at small throttle openings.