Hey Folks
Another MFI question.
I have '72 RS replica. It came to me as a 2.9 liter with MFI (with the correct RS serial number, the last digit was re-stamped to make it so. I'm hoping that is indication of the correct internals.), a modified duel out muffler. It had lots of grunt but ran very rich and was reluctant to pull much higher than 6k rpm. After a closer look it turned out to have CIS pistons and cams. After doing much reading here I decided to go back to 2.7 liter, 9.5:1 JE pistons, GE60 cams. It runs really well now but still runs rich. Black smoke on initial hard acceleration, only 13 mpg highway(8.5 on the track). My mechanic, who is not unfamiliar with MFI, and is great with early cars, went through all the standard stuff when putting the engine back together. Everything is dialed in, ignition, throttle linkages etc. I finally had it on a dyno the other day. I'll attach the graph. Not having much experience with this stuff I'd really appreciate some feedback on the results. My mechanic was pleased enough with the numbers that he's almost apprehensive about tinkering anymore. I'm doing only enough street driving to get me back and forth to the track for DEs. Mileage isn't really my concern as much as whether or not I'm washing the cylinders and contaminating the oil. Some would say richer is better than too lean (including my mechanic).
Here's the question (questions): How rich is too rich? The dyno is reading Air:Fuel somewhere between 11:1 and 13:1. Max hp 221, Max Torque 195. How do these numbers compare to a correctly dialed in RS? Am I splitting hairs or does the graph indicate an issue consistent with the smoke and mileage? We've swapped out the cold start solenoid with a proven unit. Could it be the muffler? Again, I'm not sure what's inside that. Should I go back to a single out Dansk sport muffler possibly giving better back pressure?
I spoke briefly with Gus at Pacific (very kind guy). But after giving him the details he suggested tweaking the main adjustment screw to see what happens. Funny. I thought he'd be the last guy suggesting diving right at that. Won't that just make it too lean at the top end?
In any case I'd love to hear some opinions. I guess I'm hoping for a fix less involved and costly than actually sending the pump to Gus.
Thanks in advance for any feedback.
A.T.
P.S. I'll post some pics on the "Show Your Ride" thread as soon as I clean the schmutz off the rear bumper.