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Stalling during stopping after engine is warm
I have a 427FE S/O, medium riser. I have 2 4bbl holley 4160's (450cfm each) that were recently rebuilt. I've been struggling with tuning these things.
Whats happening is after running it for a bit and getting the engine all warm, it will stall out during a hard (or even medium) stop. I have to pump the gas again to get it started and a bit of black smoke comes out. These Holleys have a primary bowl (rear) and secondary bowl (front) on each carb. I've adjusted the primary bowls on each carb to make sure its not starving during a stop. I've never touched the secondary bowls on either and wondering if i need to set the bowl level on those also? Any help appreciated, i'm a novice and looking for help. TIA |
Do your primary (rear) bowls have vent whistles? If not fuel will go up vents and flood venturies under braking.
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Yes they do.
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Im almost ready to get new carbs. Any suggestions on type to help rid myself of the many issues I've had with these old (1967) Holley's?
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This is not an uncommon problem.
Get the float levels set properly. High float levels in the back will probably aggravate the problem but you also don't want them too low and starve the engine for fuel when needed. The fuel is forced through the system during braking. I had the same problem with a custom Holley 780 double pumper The builder did some magic and most of the problem went away. Vent whistles will help and are recommended but not an absolute solution. I've tried most "solutions" and didn't find one on my own. A new carb isn't a guaranteed solution. If a sales guys insists that the new carb will fix the problem, get it in writing with a return tag. Jim |
Installed a crossover vent tube on quick fuel carb. Works well for hard stops in autox events.
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I'm now not sure if i have vent whistle. Could someone post a pic? I see a 'vent' on both carbs at the primary bowl. It closes when i throttle the gas. Is that it?
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re our PM, which I can't get to work now.... here's what I was trying to send you:
Hi Craig: Here's a pic of a Holley Carb where you can see the two tubes.... straight pipes, open at the end, pointing straight up: http://di3-3.shoppingshadow.com/pi/i...40x400-0-0.JPG Here's a picture of installing the rubber hose with vent hole: http://i.imgur.com/0TwEs5a.jpg And here's a version of the finished modification: http://www.rockcrawler.com/techrepor...-Vent-Tube.jpg Remarkably I found all these pictures doing a Google Image Search for "holley vent tubes" As I mentioned before, I havn't tried any of this, but if I can get my brakes to work better, and the stalling actually happens.... then I think I will try this. John |
If you want a matched set of BJ BK carbs contact Carls Ford Parts. I found a mint Low Riser intake at Carlisle and rather than chance old and worn carburetors, I went Brand new. Very little tuning to get them dialed in.
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Mils,
You'll probably need help. https://www.holley.com/support/carburetor/ Exploded views and then MORE. Find 4150/4160 as most likely what you have or at least close. Then you should search out tuning books on Holley carbs. HP Books does a pretty good job, there are others. Vent whistles are inside the float bowls attached to the metering blocks. If you haven't disassembled the carb you won't see them. Otherwise they are hollow plastic (white) about 1/2 inch wide, 1/8 inch thick and 1-1/2 inches long. They press into the metering blocks, usually a friction fit. Jim The solution provided by Argess may solve the problem. I didn't have much luck with the connecting tube fixing my braking issues. Strange enough the engine didn't die or even stutter when hard braking in reverse. BTW a new carb may help but may also force you to learn how to tune the idle, main and secondary circuits. Don't forget power valves and air bleeds. Got any local OLD guys that know how to tune a carb? Most of the younger guys falter if they can't hook it up to a confuser, er. computer. Jim - certified old guy. |
Thanks Jim! Unfortunately, i'm also an old guy, relatively speaking of course. Strangely enough, each carb only has 1 whistle pipe at the front of each carb. The rear of each carb has the whistle hole but no pipe.
Should i fab one and give it a try? |
Mils,
Buy whistles and put them in, Summit, Jegs or your local hot rod shop will have them. It's the back barrels (secondaries) that are causing the trouble. Reset the float levels to the bottom of the window - normal. Give it a try. Lowering the rear float level an 1/8 of an inch would be worth a try but this may cause a starvation condition under full acceleration. Fixing this is a little bit of experimentation at a time. Jim |
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If your rear bowls are in fact for your primaries then you have your carburetors on backwards. To do this you would need some creative throttle linkage. However, if in fact your primaries are your back two barrels, you might want to turn your carbs around to face the correct direction before beginning any modifications and test them in the positions they were intended to be run. Ed |
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It is the Primary sides flooding the engine on sudden stops in this scenario. So all things need to be addressed, bowl vent whistles installed on primary and secondary, extended vent tubes or alternative options for bowl vents, correct or "just under" float levels, idle mixture and speed adjusted correctly, etc. |
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in retrospect i think all the others are backwards, :rolleyes: but , the tuning won't help the float itself is a contributing factor, the lemans bowls, side pivot, offers relief of this condition but won't fit the 2x 4 setup. the hose pictured above connecting the two vent tubes is a help. the vent whistles offered in the holley kits don't fit the factory style metering blocks. |
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Well bust my britches! That's what happens when a non FE guy starts spouting off about FE stuff. Apologies there, I did not intend to send you off into the weeds with bad info but that's what it was — bad info!! :o Ed |
It's funny how the manifold is designed that way, maybe trying to centralise the carbs over the engine. Still would take the same amount of room, and the carb would function better if facing as Holley intended.
Only engine I've seen that has the carbs facing backwards. |
yeah i think it is due to the position of the runners, some runners would be starved if primaries were inverted, i guess there's a lot to be desired with the 1958 design of the FE
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Only one real answer is EFI. I struggled with carb flooding for years and tried lower float levels, circulating bowl fuel back to the tank, side mounted center pivot dual fours, dual center pivot 500 cfm 2 barrels and an 1100 cfm Dominator built by a Holley trained tuner. The dual two barrels worked best but EFI solved all my problems with braking and cornering fuel slosh. I also had whistles, vent tube connectors and jet extenders the only thing that worked with the side pivot floats was running the fuel level 4 flats down from the sight plug. That will go lean at high engine loads so I don't recommend it for anything but short autox's or normal street driving.
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