The Ford Barn

russcc · 05-26-2016, 05:58 PM

The original engine in the '40 is plenty tired, but starts right up, and runs pretty well. Have not been out on the road yet. with it. When sitting still, and you crack the throttle pretty good, it will pop back through the carb frequently. Is that an indication of a lean fuel condition ? Thank you Fordbrainers.

Init1 · 05-26-2016, 08:14 PM

Yes it could be lean but could also be a bit retarded.
Try checking the timing first before you go to the trouble pulling the carb.

39topless · 05-26-2016, 09:38 PM

Poor some Marvel Mystery Oil down the carb with the engine running at idle. Continue until it starts smoking good and almost stalls. That should help loosen up those sticky valves. Always add about 1/4 pint of the MMO to every gas fill up.

A bones · 05-26-2016, 10:04 PM

Intake valve not sealing. Use Marvel Mystery Oil as 39topless said. Give it time, I had one go near a month of daily use 'til better.

russcc · 05-27-2016, 06:24 AM

Thank you all for tip off. MMO it is.

Bored&Stroked · 05-27-2016, 09:12 AM

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Could be a stuck valve . . . but also check and see if the accelerator pump is squirting in the carb. Sometimes when you stab the throttle, with no pump squirting, the engine will go to a heavy lean state (temporarily), then when the rpm picks back up, it will run just fine. When I've had stuck valves, they tend to be stuck all the time and I have pop-back and other issues at any higher RPM - it doesn't usually go away.

You might also run a compression check on all cylinders - see if you have one or more that are leaking/low.

jhb · 05-27-2016, 01:20 PM

I had that happen once on a 351 Windsor and it turned out to be a bad spark plug wire, how are yours ? Let us know when you find out....................jhb

deuce_roadster · 05-27-2016, 02:01 PM

I had a cheap condenser go bad and it caused the coil to fire at the wrong time, the backfire through the carbs set the oil on the K&N air filters on my 97s on fire, burnt the paint off the hood of my avatar roadster 10 years ago. I would change the condenser and see if the problem goes away. No longer use K&N for anything.

WestCoast · 05-27-2016, 02:43 PM

usually a sticking intake valve, marvel mystery oil will usually fix that, drive a 100 miles of so

05-26-2016, 05:58 PM	#1
russcc Senior Member Join Date: May 2010 Posts: 2,871	Pop back through carb. The original engine in the '40 is plenty tired, but starts right up, and runs pretty well. Have not been out on the road yet. with it. When sitting still, and you crack the throttle pretty good, it will pop back through the carb frequently. Is that an indication of a lean fuel condition ? Thank you Fordbrainers.

05-26-2016, 08:14 PM	#2
Init1 Senior Member Join Date: May 2010 Location: Oregon City, Oregon Posts: 208	Re: Pop back through carb. Yes it could be lean but could also be a bit retarded. Try checking the timing first before you go to the trouble pulling the carb.

05-26-2016, 09:38 PM	#3
39topless Senior Member Join Date: Sep 2013 Posts: 1,027	Re: Pop back through carb. Poor some Marvel Mystery Oil down the carb with the engine running at idle. Continue until it starts smoking good and almost stalls. That should help loosen up those sticky valves. Always add about 1/4 pint of the MMO to every gas fill up.

05-26-2016, 10:04 PM	#4
A bones Senior Member Join Date: May 2010 Location: CLAYTON DE Posts: 1,286	Re: Pop back through carb. Intake valve not sealing. Use Marvel Mystery Oil as 39topless said. Give it time, I had one go near a month of daily use 'til better. __________________ Enjoy yer day. Tom Hate can't fix what it started.

05-27-2016, 06:24 AM	#5
russcc Senior Member Join Date: May 2010 Posts: 2,871	Re: Pop back through carb. Thank you all for tip off. MMO it is.

05-27-2016, 09:12 AM	#6
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,267	Re: Pop back through carb. Sponsored Links (Register now to hide all advertisements) Could be a stuck valve . . . but also check and see if the accelerator pump is squirting in the carb. Sometimes when you stab the throttle, with no pump squirting, the engine will go to a heavy lean state (temporarily), then when the rpm picks back up, it will run just fine. When I've had stuck valves, they tend to be stuck all the time and I have pop-back and other issues at any higher RPM - it doesn't usually go away. You might also run a compression check on all cylinders - see if you have one or more that are leaking/low.

05-27-2016, 01:20 PM	#7
jhb Junior Member Join Date: Feb 2015 Location: Florida Posts: 23	Re: Pop back through carb. I had that happen once on a 351 Windsor and it turned out to be a bad spark plug wire, how are yours ? Let us know when you find out....................jhb

05-27-2016, 02:01 PM	#8
deuce_roadster Senior Member Join Date: Oct 2011 Location: Shelton, WA Posts: 3,825	Re: Pop back through carb. I had a cheap condenser go bad and it caused the coil to fire at the wrong time, the backfire through the carbs set the oil on the K&N air filters on my 97s on fire, burnt the paint off the hood of my avatar roadster 10 years ago. I would change the condenser and see if the problem goes away. No longer use K&N for anything.

05-27-2016, 02:43 PM	#9
WestCoast Senior Member Join Date: Sep 2014 Location: oroville calif Posts: 893	Re: Pop back through carb. usually a sticking intake valve, marvel mystery oil will usually fix that, drive a 100 miles of so