Holley 1920 Very slight stumble...

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snufy

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Hi All,

I've got a 71 valiant, 225 with a autoline rebuilt 1920.

It seems to have a very slight stumble when slowing down then accelerating sudden or turning left or right. (float height issue?) It will sometimes stumble ever slightly and then catch and go.

The car actually runs and drives, 99%.

Is there a way of getting rid of this? or am I just too OCD?

I've checked the vacuum (18, perfect) and adjusted the idle 750-800 and tried with both the timing at "0" and at 8-10 degrees BTDC, the car runs stronger at 8-10 BTDC overall, but the stumble is still the same regardless.

I can visually confirm a very strong squirt from the accelerator pump as well.

Both idle screws and the mixture screw are very responsive. It runs very strong besides this occasional stumble. Idles perfect always.

Fuel Filter looks relatively new as it has been driven and not stored.

All vac lines are relatively new and no cracks or issues as far as I can see?

I'm lost now...
 
Your float may be a little heavy.....I would put in a new float and try raising the float level a little...Should be 3/16 when turned upside down from the edge of the casting to the top of the float....Just weigh your float when you take it out to see which one you have....They have two different floats....7.5 grams and 12 grams....Both are available as I have bought both....
 
Also, timing is better at 8-10 versus 0 degrees....But it wouldn't hurt to put even more timing in it....I run about 15 degrees at idle and all in at 35 or 36 and runs great.....
 
starting in 1968 all / most chrysler engines had a lean i idle circuit. the carter carbs can be fixed by drill ing the idle tube. and are easy to drill. most are .032-.035". takes a spacial drill bit and steady hands. and you only drill .001"-.002" at a time. but the holley carb is near impossible to drill. the tube is inside the metering block. i did one once but it took all afternoon to fix the metering block.
 
Update, still need some help, found a junkyard 1920 with the same size float, problem is 95% gone... turning left and going straight I almost never get any stumble now. However I still get a stumble turning right and accelerating, if I'm turning right down hill it will stall.

Float a bit low? I just replaced it with the bowl cover off, I didn't take the whole carb off and measure upside down..

on a second note, this is much nicer to work on then motorcycle carbs, I didn't get one drop of gas on me changing the float, it was fantastic. I was prepared for the worst.
 
Does it have the little baffle in the fuel bowl? I think those were in there to help prevent fuel slosh during turning.
 
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