Engine surging

grumppyoldman

grumppyoldman

Well-known member
Driving along at a steady speed the I can feel a surge in the engine. it's not flooding and doesn't seem to be starving for fuel because I push on gas pedal and it speeds up. Just thinking about what it could, am wondering about the leather brake in the helmet dist. could be too loose and causing it to do this. I didn't set it tight when I got it back from Bubba's overhaul. Any Ideas? It's my 41 Coupe. Al
 
Sounds a little bit like impending vapor lock. It may not kill a running engine, but the fuel level in the float chamber drops, which cuts fuel flow through the jets a little. Hit the accelerator pump, an off she goes, - for a little bit.

Does this happen on hot days? Do you have an electrick fuel pump?
 
I have a 39 Mercury and had the same problem .I asked an 83 year old Mechanic still working .His answer set the timing back 2 degrees . I have not done mine yet, let us know if it works. John.
 
I would like to find the answer to this problem also , that is what my 39 pkp. Is doing .I have tried 3 carbs the one on it now is rebuilt . 2 rebuilt helmet distrbs.2 rebuilt fuel.pumps and still have this surging but will excelerate ,I might add all prof. Rebuilt . Which way advances the timing on a helmet up or down . Vaccum is only showing about 15 in @ idle .THank You . sunshine
 
JSeery I don’t want to step on the original post ,but to answer your ? About the vacuum I’ have checked all of the obvious places . My engine rebuilder says it cannot be the valve guides . With the low mileage on the engine . Thank you Sunshine
 
I have a pressure regulator and gauge between the fuel pump and carb. set at 2 1/2 #, and yes its been hot down here. It started doing this when I put no-ethenol gas from Buckie's a couple of weeks ago. No water in carb., fuel filter looks clean. I tightened up the leather pad on dist. and no change. Never had vapor lock problem before but have to check that now, since it's been so hot here lately. Might raise the pressure to 3 1/2# also to see if it's low on fuel. Need to get it running good since I have it up for sale. Al
 
Non-ethanol fuel should be less prone to vapor lock. Fuel is blended with winter blinds and summer blends. It could be possible that the non-ethanol fuel was still winter blind. The winter blinds vaporize at a lower temperature.
 
Ethanol fuel burns faster. Maybe a lean condition causing a surge.

Old hit misses when running out of fuel rmp up before shutting down. Assuming the fuel is atomized finer and causing quick combustion. Just a thought.
 
sunshine said:
I would like to find the answer to this problem also , that is what my 39 pkp. Is doing .I have tried 3 carbs the one on it now is rebuilt . 2 rebuilt helmet distrbs.2 rebuilt fuel.pumps and still have this surging but will excelerate ,I might add all prof. Rebuilt . Which way advances the timing on a helmet up or down . Vaccum is only showing about 15 in @ idle .THank You . sunshine
Click to expand...


Up on a 3 bolt.
https://fordbarn.com/forum/showthread.php?t=147104


Motor turns clockwise. Cam CCW.
https://www.fordbarn.com/forum/showthread.php?t=25065


Low Vacuum, could be a leak, carb idle settings, or dizzy. The word professional is interesting and sometimes subjective.. sometimes.

If rings are good (which you can check with a vacuum gauge too, if it idles with vacuum and you dump the throttle and the gauge hit's 0, rings are bad, 99 out of 100. 5lbs or more, probably not.) just need to fine tune. One thing at a time.


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Thank you Tinker for your help . The 2 dist. I have tried are Bubbas , the present Carb. Is Charlie’s , I consider them professionals. And not the problem . The Vacuum gauge I have is showing about 15 inches at lIdle in an area on the gauge. That says timing ajust . Could this be valve guides. My engine rebuilder says no . Because it has only 300 miles on it. There is a vacuum leak somewhere As stated before I have checked all obvious vacuum connections to no results . I have done a compression check cold . All Cylinders at. 100 to 110 .I am trying one thing at a time ,between test runs. Thank everyone for trying to help me BOB
 
Tubman , I am sorry . But what am I assuming I have exsplained everything I have tried I think I have bothered you Guys enough . Thanks again BOB
 
Whoa. I think you are missing the point I wanted to make. A distributor from "Bubba" and carburetor from "Charlie ny" are the best you can get, anywhere. I am just saying that you just can't automtically eliminate when looking for the problem. What if one or the other got dropped hard while being shipped? No knock on either of these guys, but you cannot control what happens to your product once it leaves your shop.

Do not worry about bothering us; most of us live for this sort of thing. Most of the time, we can provide some useful information; occasionaly, we learn something we didn't know before. It's all good.
 
down on the crab two bolt BTW

You can trust both, of course. hundreds of threads on their work. I've even had multiples rebuilt under to insure yrs of running.

The compression check (to me) says the valves are okay. I leak down test (which it shouldn't with valves closed) could be better to tell compression loss, as a compression check only tells you peak compression (leak down which could indicate rings not guides, *** it is a new engine and needs to be run on the road to seat the rings/etc)... ugh


Maybe the guides are leaking. It'd be uncommon. It'd have to be really bad to effect vacuum that much. But I guess


Thinking it's just some fine tune fun. Turn the idle screws in till it stalls then out a half turn. (does this effect vacuum?)... if the carb idles do nothing to effect the vacuum I'd start there. you have gone through a few things all at once, so.. who knows

Its a system you can put a nice new carb on a motor but if it's pulling trash from the tank, it'll not be good. Or like a clogged radiator and new water pumps.

Interesting anyway. Maybe try another vacuum gauge. Interested in the updates...Pulling for you!


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Thank You Tinker , When I change a part like a carb. Or the dist.and I get the same. results . I eliminate that as the problem. I have even tested the carb on another engine with good results. I am running a filter in the fuel pump bowl..When I changed fuel pumps. And checked the bowl for trash there was none . Since my last post I have run the engine and now have a valve rapping pretty loud . This is new , it quiets down some as the engine heats up . Thank you. BOB
 
Take a long ride and check your plugs when you get home, if they are white or light colored it's lean. If you have some richer main metering jets ( 52-55) give them a try. I'm guessing you use the 10% alc, gasoline, try some good 100% petroleum gas. Also timing can do the same thing if it is too far advanced, good luck, Chuck.
 
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