FE Power Forums
FE Power Forums => Non-FE Discussion Forum => Topic started by: bsprowl on April 30, 2022, 05:32:18 PM
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I'm working on a 331 small block jeep with a Holley carb for my nephew. When the throttle closes quickly the the engine stalls. I was thinking that it needed a dashpot.
Today we went to a local car show and and none of the cars with Holleys had dashpots.
Engine starts and runs fine. It just stalls when the throttle closes rapidly. Any ideas?
Bob
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I don't have any experience with the dashpots but it was my understanding the problem they solve was just on automatic vehicles. When I hear Jeep, I think manual. Is the car an automatic? If so, does the stalling just happen when in drive, or does it do it in park as well?
Pat
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4 speed with granny low and transfer case. It stalls/dies almost every time you let off the throttle unless you do it very slowly.
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If the tune is spot on, a dashpot may help to slow the throttle's closing.
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Some questions
How low is it idling warm?
Where are the mixture screws (turns from bottom) and do they respond normally?
Where is initial timing set now?
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Maybe try cracking open the secondaries a little and closing the primaries a tad to keep the proper idle rpm and see if that helps. you'll have to pull the carb as the set screw adj. is from the bottom most likely.
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Start with the basics
Proper idle rpm
Like my 427 Stang says check timing and idle mixture screw placement.
Sounds like a vacuum leak but make sure the basics are checked. Sometimes
We think the worse before the little things.
Also make sure that it isn’t dribbling fuel.
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OK. The engine builder selected and installed the carb (which has the airhorn removed so we don't know exactly what it is.) It appears to be a 600 or 700 CFM recently manufactured 4160 with vacuum secondaries. The metering plate numbers are hidden.
I'll start with the basics when I work on it during my next visit. I checked the float level which was good - both bowls were letting a very small amount of gas dribble out with the plug was removed. The mixer screws moved an 1/8th of a turn out reduced the stalling a bit. An 1/8 of a turn in made the engine miss so I put it back immediately.
Thanks.
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I was going to suggest richen up the idle up a hair.
Most times when a throttle snaps shut the engine goes very rich followed by very lean. often the recovery with an idle that is too lean causes this sort of issue.
This is actually the purpose of the dashpot. When engine is set at the lean limit for idle with a load, this helps relax the closing point so the idle well has a chance to recover before throttle is fully closed.
Especially important when autos and A/c etc as a tuner sets the idle at "perfect" no load... lets sat 12.5:1, but when put in gear idle drifts to 14:1, a/c kicks on and engine wants to stall.
I have never actually had a newly bought dashpot work well, seems like they are all too stiff and it always hangs the idle open too much.
Original dashpots seem to work great.
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I haven't seen or used a dashpot on any carb, especially a Holley, in like a gazillion years. I'd do same as above - a little more secondary and make sure the primary only just sees the transition. Back the idle feed screws out another 1/4 turn. Maybe bump the idle another 100 RPM. Run as much initial timing as possible and limit total.