Cause of low RPM "lope"

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Cause of low RPM "lope"

Postby jethro » Tue Nov 01, 2016 3:13 pm

Just out of curiosity--- what causes the low RPM lope ?
I am thinking that it must be some kind of mechanical feedback from the block rocking ---
and the guts of the fuel control getting a "bump" from the rock some how. When I bring it off the
stop- just barely-- like 100 rpm --- it quits.......

Tim
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Re: Cause of low RPM "lope"

Postby spencerdiesel » Sat Nov 05, 2016 7:31 pm

My friends VE had the fuel screw bottomed HARD by the previous owner, and the FSS plunger was partially boogered/missing. The truck would surge at low rpm, he gutted the FSS and it quit surging. Don't know if yours is a similar problem or not. I read in your other thread you don't have a tach, but you got any idea what the idle speed is? Roll down the road in OD (slightly downhill) and slow the the truck to idle while in gear. Take not of the road speed and put the info in the gear ratio calculator thingy. That'll tell you close to what the idle is.

Or you could just set in by ear :)
1992 W250, 5 speed, 4.10, Ext. cab Ext. bed, 12.5k winch, 75 gal. fuel tank

H1C/18

Fuel: THD 6x10 VCO sticks, THD 12 psi piston pump, THD fuel pin, 366 spring, fuel screw 2 turns in, timing to the head/ >1/4”
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Re: Cause of low RPM "lope"

Postby jethro » Mon Nov 14, 2016 6:57 pm

it doesn't lope any till I get the rpm way down into the basement ---- I would guess 500 rpm maybe.
I would guess it is set maybe about 700 (just guessing by ear...)
Know any alternate ways to measure it ?
I have a little electronic box which measures audio frequecncies for tuning musical instruments.
I wonder if I could use that at the tailpipe to find the frequency of the combustions--- If I could figure out the ratio of
bangs to rotations that might do it very accurately------
Would it just be 2 revolutions for every combustion hit ????? (4 cycle engine ??? is that right ??? )

Tim
will try tomorrow and see if it can pick up a frequency out of it ----

there Is also something called a "vibra-tach" which is just a flexible beam with a sliding adjustable weight.
don't know how low it goes. seen it used on model aircraft engines to get RPM (some go up to 40,000 +)
jethro
fuel screw!!!!
 
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