MFI injection troubles .

[Grady Clay]

Kurt,

Nice looking ’69.

OK, now I have a little better picture. There is a thermostat in place on the pump but it is set to have no effect? In other words it thinks the engine is at temperature all the time? This can be done just by adding shims – you might disassemble the thermostat and look. When everything is cold, you should remove the little access plate on top of the MFI pump just forward of the thermostat. Start the engine and carefully push down on the mechanism with a small tool. See the diagrams in the linked posts. If the thermostat is truly set to not function, there should be no change in mixture.

Is the cold start system functioning? This is the solenoid on top of the fuel filter console, the thermo time switch, and circuitry. You should also check that it opens promptly, shuts off promptly, and does not leak while the engine is running. Even the slightest leak can dramatically affect the mixture. I see the plumbing on top of the air filters; make sure nothing can ever fall into the engine.

I am concerned that it runs OK when cold. That is usually a sign that it is way too rich when warm and without a thermostat to lean it out. The exhaust analyzer will tell. Some can get away with too lean when cold – if you live in Key West, Tucson, or San Diego.

No, there is not a midrange adjustment. That is why it is so important to get the mixture correct. What is the S/N of the MFI pump? You can find the numbers in the CMA.

Compression ratio is usually something not guessed at – unless it is too low. Same is true with piston to head clearance. See if you can get those numbers from the builder.
If you have the occasion to have the heads off, measure them yourself. It could be anywhere from 8:1 to 11+:1. That will have a profound effect on how everything is set.
Until you know the details, I would back the ignition timing off to a conservative 24 @ 6000 and use very high octane fuel. You don’t want to damage those beautiful 2.8 RSR pistons.

Best,
Grady

Feel free to e-mail me at gradyclay@hotmail.com although it is best to keep most everything on the Forum for all to benefit.
G.

[pjv911]

The engine builder told me it was 10.5:1 . I can see that there is 2 copper gaskets under the cylinder bases . I suppose this offers more valve clearance as well as a slight drop in compression ratio . I allready tested the valve clearance by spinning it over 8500 rpm , no traction in 1st gear on these cold new york streets . I am so impressed with the power this little bastard makes . For example today I drove home a customers 1980 euro 930 with only 37k miles . My 69` would toast it at any speed . Forget about 0-60 that wouldnt even look like a race . I cant imagine that the power may increase once the mixture is set properly . BTW Grady the car does not run well when cold . It just runs barely . Once its warm (1-2 min) then its driveable . After the oil temp starts reading something (aprox 5-8 min) the car has full power and a smooth idle . Keep in mind that here on Long Island outside temps lately have been between 20-40 deg f .

Kurt Williams

[pjv911]

I have the cold start solenoid hooked up to a dash mounted momentary switch . I will look to make sure its not leaking as well as look for the possibility of something falling in . Thanks for the warning .

Kurt Williams

[ed martin]

Kurt,

If you're are not experiencing a lot of popping through the stacks and bucking when the engine is cold and until it reachs operating temperature then my guess is your probably aready running very rich. By the way I notice your CO values are expressed as ppm. I believe the values expressed in CMA are in terms of percentages, that is to my understanding,a percentage of CO relative to the total amount of exhaust gases. So I'm not sure how ppm would correlate to percentage of CO. If I recall 4% CO is very low for an old system wereas 2.5 is optimal(new) and around 6% is the norm.

[jluetjen]

Did I miss something? Where have the CO values been posted?

[304065]

Well, the CO values are in CMA.

Having said that, I don't know anyone who can get their car to run right with a 4.0% CO value. More like, 5-6 at idle, 7-8 at 3000 RPM.

Kurt, given your setup you may want to seriously consider an LM-1 Data Logger for realtime acquisition of air-fuel ratio data. The output can be graphed against RPM so you don't have to rely on the seat-of-the-pants dyno to know where the mixture is set.