Help ....... 1930 Ford Model A Backfire

[Joebee]

Help ..... I am having trouble ..... My Car starts fine idles fine and runs great up to about 30-35 mph. Any higher and I get a sort of backfire and gets worse the longer that I stay at a higher speed. It seems to be coming through the carburetor ...... I tried checking the timing checking the plugs (which are clean) changed the distributor cap and wires the rest of the distributor seems fine ........

[BILL WILLIAMSON]

Try enrichening it by turning choke rod counter clockwise 1/4 to 1/2 turn, maybe more. Play with it 'til you find the best running position. Bill W.

[V4F]

look for intake leak . (ether)

[ford3]

if firing out the carb it may be an intake valve sticking or a broken or weak valve spring not allowing the valve to close before the spark plug fires, try running 4 or 5 0z. of marvel mystery oil in gas tank with 10 gallons of fuel

[BILL WILLIAMSON]

He said it idles good & runs good up to 30-35, so it's probably just too lean. The FASTER you go, the more petrol it needs! Bill W.

[Patrick L.]

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There have been many previous posts regarding this. We could use a little more info. Will the car continue to accelerate while backfiring or seem to lose power? Does it return to running correctly if you just back off on the throttle and cruise along slower ? First thing I'd recommend is loosening or removing the fuel cap to see if that helps. Have you tried checking for good fuel flow ?

[Joebee]

I have tried the gas cap. And tried the choke ..... It continues to run but once it starts to backfire it will do it periodically even as you slow down. It does not lose power just a quick little hesitation. If I shut it off and wait a little and not go over 35 mph it will not backfire.

[BILL WILLIAMSON]

Yo, Joe,
Go to WWW.MODELABASICS.COM Lots of great info there! Bill W.

[Joebee]

thanks I will try that site I am missing a great tour this weekend because of this problem and it just has me depressed ....... Thanks for all the info. ..... keep them coming

[Tom Wesenberg]

Do the easy check first. Hold the coil wire 1/4" from a head nut and make sure you have a hot blue spark. A weak spark can cause your problem. A bad condenser can cause a weak spark.

[stainless steve]

Dont let this depress you ...take it on as a challage ...many publications and help here..relax get it right and enjoy the journey..

[Joebee]

Yeah I hear but I have been working on this problem for over a month now ....... And just getting a little frustrated ...... But thanks to this site I have a few more things to try this weekend .......

[Gary WA]

Joebee, what kind of carb are you using?

[austinhunt]

You said the plugs were clean, what color were they?

[stainless steve]

Im no expert like alot of guys here on the ..A.. but its still an internal combustion engine if your hearing it in your carb ..that should narrow it to a spark , fuel or intake valve type issue. you may have a valve hanging at higher rpm.or carboned up . one thing I do all the time when I have an issue is a compression test, its easy and my show a issue right away. dont do it yourself someone needs to watch the needle as its cranked to look for a wobley needle. sometimes they are mean gremlins and it takes awhile. The fuel we have today also breaks down terribly after 30 days , so dont rule out bad fuel if its old. As read here before dont just throw parts in it ,you may make it harder to fix.( I know easier said than done sometimes ) Also keep a writen log of what you have done If your like me I cant remember much of anything it may not help this time but will next time GOOD LUCK JOEBEE were all pullin for you

[BILL WILLIAMSON]

Originally Posted by Joebee

Yeah I hear but I have been working on this problem for over a month now ....... And just getting a little frustrated ...... But thanks to this site I have a few more things to try this weekend .......

Joe, the Dog just reminded me, try this,
Gradually speed up the engine, steady & see if it does it, if so, hold the RPMs & choke the carb hard with the palm of your hand, it MAY help "SUCK" through some slight obstruction in a jet or a passage. Have you tried new plugs? Marvel Mystery Oil, ATF, or any light oil misted through carb intake at fast RPMs may help if it might be a slightly sticking valve. Model A valve springs are NOT real strong. DO keep us informed. Bill W.

[Joebee]

Do you put Marvel Mystery Oil in the gas and oil as well .....

[Joebee]

The Carb is a Zenith-2 ..... and the plugs are clean with a little ash color

[Tom Wesenberg]

Originally Posted by Joebee

Do you put Marvel Mystery Oil in the gas and oil as well .....

A lot of guys put 4 oz. per 10 gallons gas. I recently started using it also. I haven't added it to my oil, but some guys use a quart of it to replace a quart of regular oil.

[stainless steve]

I suspect youve got a valve in there named Steve ...ok but just a little slow