VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 35 Standard Backfires

After sitting all winter I started up my 35 Standard. It now backfires thru the Carb. has a miss in it and pops in the exhaust. I checked the Timing, Spark Plug Gaps, Points and Valve clearances. Started it up, nothing changed. Any ideas? Don't know what could have happened over the Winter with it sitting.

Valves are sticking.

With a fast idle slowly pour some Marvel Mystery oil down the carb throat add more slowly until it dies. let it sit over night, and that should free up the valves and rings.

Sounds exactly like I thought. I did pour some MM oil in put kept it running. Will try your suggestion, thanks.

Route your tailpipe to some gopher holes and do double duty work!

jon, its only feb 9, winter is not officially over till MARCH 21 according to the calendar .

mike

I did it and man did it ever smoke up my Garage! And it's not Winter here today, about 60deg!!

I started up the 35 and there seems to be a big difference. Although there is still some backfire so I am going to give it the same treatment. I'll be out of town for a few day so I'll start it up when I get back. Maybe I just need to take it out and drive it 15 or 20 miles at a good speed?

Jon,
Adding a couple of glugs of ATF or MMO to each tank full will help lube the intake valves.

Points can get a lot of crud on them. I have had two of my vehicles act up. Both were points. Check your points!!!

Just returned from Phoenix. I flooded my 35 with MM oil before I left. Started it up and it does not backfire like it did but still has a miss and does not idel smooth. I checked the points. Don't know what else to do. Could I have a bent push rod?

You could have dirt in the low speed jet. Place #3 plug wire on #4 cylinder and #4 wire on #3 spark plug. Remove air cleaner, start engine and hit the gas pedal several times and engine will back-fire through carburetor. This will blow the dirt out of the low speed jet...........if that is the problem.
If that does not work remove valve cover and squirt MMO on the valve suides. If a push rod is bent it will make it shorter and that will increase the rocker arm to valve stem clearence causing a cicking noise.

DAMN COOL INFO AND BLOWING STUFF UP OR OUT...........

MIKE

I switched the wires but it didn't seem to make any difference. Didn't have time to remove the Valve Cover. May tomorrow. I did ground out each spark plug without much difference except for the third cylinder and when I did that one it almost stalled the Engine. Don't know what that means if anything.

How about a compression test? Easy to do, and might tell you if your valves are sticky.

Jon.

As long as it is not making any strange noises I would take it out and drive it at 50 MPH for several miles to free any valves if it is a valve sticking and then do a compression test if rough idle is still a problem. That would at least isolate the bad cylinder.

Exactly what I was going to do. Thanks for your help. I'll let you know next week.

Does it have fresh gas?

It does. It ran out and I just put 5 gals. in.

Run at 50 mph a few miles and re-check. Could be a valve is closing or opening slowly. Put Marvel mystery oil in gas and crankcase. It will smoke but will lube the valves. That is what I do to keep mine free after a Winter storage. Removing the cover will let you hear (clicking) and possibly see a hanging valve as slow idle.

Thanks, I'll try it tomorrow.

I drowned the Engine with MM oil. Put ATF in Gas Tank and MM Oil in Crankcase. I could not drive it yesterday as it was cold and rainy. Drove it today. Could not get it up to 50 MPH. Barley made it to 30. No power, backfired thru Carb. Barley made it back home. I cannot see any pushrods bent if they are. Don't know what else to do but can't drive it until I get some power.

Could be points, dirty or mis-adjusted, condenser, or broken valve spring.
Spitting back through the carburetor indicates an intke valve not closing. Cause for that would be a valve sticking or broken valve spring. Also check if the spark plug wires are properly installed and going to the correct cylinders. A mouse may have rearranged them over the winter.
If it were mine I would remove the valve cover and inspect the valve springs, start the engine and observe the rocker arm travel and watch for a push rod wobbling around as it spins. A bent push rod should not cause the back fire but indicates a valve did stick.
Also you could have fouled one or more of the spark plugs dumpimg all that oily stuff through the engine.

I would do a compression test as suggested above. Also check the exhaust system for blockage (mouse nest)?

I'll do a compression test. No Mice in my garage.