The Ford Barn

Bob NH · 09-05-2022, 09:05 AM

How should I correct "back firing" through the exhaust pipes when coasting down hill ? Vehicle runs quite well and air/gas mixture seems OK ?

supereal · 09-05-2022, 01:21 PM

Check for a vacuum leak in connections to the carb and the intake manifold, and the intake manifold gasket. It can be a cracked rubber hose or other bad connection that allows air into the fuel flow. Backfiring can cause problems, and should be identified and fixed.

cadillac512 · 09-05-2022, 03:14 PM

I'd first make sure there are no exhaust leaks-even small ones, especially at the manifolds. After that I'd check for vacuum leaks and proper idle speed, as well as making sure the ignition system is in top shape, including timing.

Terry

Bob NH · 09-05-2022, 05:08 PM

Good starting point guys, thanks, Bob

drolston · 09-05-2022, 09:24 PM

If the mixture is too rich you can get some backfiring. Some of my buddies in high school thought it was funny to pull out the choke when backing off the throttle to make it backfire.

A bones · 09-06-2022, 05:48 AM

Sponsored Links (Register now to hide all advertisements)

Do you run MMO? As in Marvel Mystery Oil.
I know that many believe it to be Hokum.

I would like to point out that back when, every filling station sold their own particular brand of valve top oil, as a gasoline additive.

Cars needed it then, flatheads haven't changed. The market has however.
The only one that I'm aware of is MMO. Add to gas Add to oil
Mostly though add to gas.

Bob NH · 09-06-2022, 10:06 AM

Chuckling here. Back in time, we liked a spark plug and model "T" coil along with a toggle switch under the dash to get that great blue flame out the pipes ! Some guys were getting caught so I made mine removable . I do add MMO often when gassing up just think it helps.

supereal · 09-06-2022, 02:54 PM

The mystery of Marvel oil is why anyone buys it. If you are having valve problems, it is likely due to sticking caused by carbon buildup on the stem. "Top oilers were sold years ago, before the advent of todays oils. Putting anything besides fuel in the tank now just causes problems.

JayChicago · 09-06-2022, 09:23 PM

I lived with an intermittent miss for first couple of years with my car. I didn't believe any snake oil was going to repair my old engine. Finally added MMO to the gas tank. The miss was gone on the first drive! Now I am a born-again believer.

Don't know if the MMO acts as a lubricant or a solvent for carbon on the valve stem. It cured my problem so fast that I thought there wasn't enough time for a solvent to cut the carbon build up, must just lubricate the stem. Whatever, it worked.

Apparently MMO has the right chemical makeup to help the sticky valve problem common on long-stored Ford flatheads.

09-05-2022, 09:05 AM	#1
Bob NH Senior Member Join Date: May 2010 Location: Meredith, N.H. Posts: 766	Back firing How should I correct "back firing" through the exhaust pipes when coasting down hill ? Vehicle runs quite well and air/gas mixture seems OK ?

09-05-2022, 01:21 PM	#2
supereal Senior Member Join Date: Jul 2014 Location: Iowa Posts: 1,634	Re: Back firing Check for a vacuum leak in connections to the carb and the intake manifold, and the intake manifold gasket. It can be a cracked rubber hose or other bad connection that allows air into the fuel flow. Backfiring can cause problems, and should be identified and fixed.

09-05-2022, 03:14 PM	#3
cadillac512 Senior Member Join Date: Apr 2019 Location: Kansas Posts: 922	Re: Back firing I'd first make sure there are no exhaust leaks-even small ones, especially at the manifolds. After that I'd check for vacuum leaks and proper idle speed, as well as making sure the ignition system is in top shape, including timing. Terry __________________ "It don't take but country smarts to solve the problem" (Smokey Yunick) '41 Merc Town Sedan / 260" 8CM engine '66 Fairlane four door / "warmed up" 302

09-05-2022, 05:08 PM	#4
Bob NH Senior Member Join Date: May 2010 Location: Meredith, N.H. Posts: 766	Re: Back firing Good starting point guys, thanks, Bob

09-05-2022, 09:24 PM	#5
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Re: Back firing If the mixture is too rich you can get some backfiring. Some of my buddies in high school thought it was funny to pull out the choke when backing off the throttle to make it backfire.

09-06-2022, 05:48 AM	#6
A bones Senior Member Join Date: May 2010 Location: CLAYTON DE Posts: 1,283	Re: Back firing Sponsored Links (Register now to hide all advertisements) Do you run MMO? As in Marvel Mystery Oil. I know that many believe it to be Hokum. I would like to point out that back when, every filling station sold their own particular brand of valve top oil, as a gasoline additive. Cars needed it then, flatheads haven't changed. The market has however. The only one that I'm aware of is MMO. Add to gas Add to oil Mostly though add to gas. __________________ Enjoy yer day. Tom Hate can't fix what it started.

09-06-2022, 10:06 AM	#7
Bob NH Senior Member Join Date: May 2010 Location: Meredith, N.H. Posts: 766	Re: Back firing Chuckling here. Back in time, we liked a spark plug and model "T" coil along with a toggle switch under the dash to get that great blue flame out the pipes ! Some guys were getting caught so I made mine removable . I do add MMO often when gassing up just think it helps.

09-06-2022, 02:54 PM	#8
supereal Senior Member Join Date: Jul 2014 Location: Iowa Posts: 1,634	Re: Back firing The mystery of Marvel oil is why anyone buys it. If you are having valve problems, it is likely due to sticking caused by carbon buildup on the stem. "Top oilers were sold years ago, before the advent of todays oils. Putting anything besides fuel in the tank now just causes problems.

09-06-2022, 09:23 PM	#9
JayChicago Senior Member Join Date: Jan 2019 Location: Chicago Posts: 732	Re: Back firing I lived with an intermittent miss for first couple of years with my car. I didn't believe any snake oil was going to repair my old engine. Finally added MMO to the gas tank. The miss was gone on the first drive! Now I am a born-again believer. Don't know if the MMO acts as a lubricant or a solvent for carbon on the valve stem. It cured my problem so fast that I thought there wasn't enough time for a solvent to cut the carbon build up, must just lubricate the stem. Whatever, it worked. Apparently MMO has the right chemical makeup to help the sticky valve problem common on long-stored Ford flatheads.