How to time a mechanical pump.

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How to time a mechanical pump.

Postby mhuppertz » Mon Aug 19, 2013 2:37 pm

This is what has worked for me, and it is they way I have timed my gasser street racers too.

I get the pump just loose enough to move it, then I advance it until the truck starts missing (something other than dead smooth).

This all has to be done when the engine is hot.

At this point the truck will pop when revved in neutral.

Then I road test. Any popping or misfiring at all and I stop and retard the pump.

Once I get it all smoothed out I know I have the timing perfect, and the truck runs like a beast.

I have not tried this with a timing spacer and I assume once the pump is timed at idle with the spacer it will need to be retarded a bit to get the top end smoothed out.

I have found that at higher altitudes pump (and spark) timing needs more initial and the same total as sea level, in other words less of a spread.

I would be willing to bet that my truck would be sluggish at low RPM with the timing spacer at my altitude.
'93 W250, HTT Stage IV/16cm, POD's, cut AFC pin, Pump advanced, Pyro, Boost, Fuel Pressure Gauges all non functional, burned wiring, 3/8” fuel line, BHAF on custom intake, 3,200 Spring, ARP Studs, New Head at 392K, Detroit Locker, NV4500, other stuff…
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Re: How to time a mechanical pump.

Postby RCCUMMINS89 » Mon Aug 19, 2013 7:36 pm

I couldn't agree more with your methods.

That's exactly how I have always timed everything I've owned.

Now that I have an adjustable timing spacer...............

I time my idle to where it idles the cleanest and sounds the most crisp through the exhaust. I then back my timing spacer out all the way. I then start to turn it in a little at a time until the mid to high rpm shake goes away completely. Timing is then dialed in.
89 RC on shortened 92 diesel frame - NV4500 w/dual disc/4.10s on 37s. - Self built pump, "hot screw", lots of timing, True high volume low pressure lift pump, 62fmw/68/.7gated, 77lpm SAC Inj., Studs/O-rings,- 423/1220 Mustang - 11/16/2013 full line dealer, if you don't see it please ask.
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