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Hello,

I have a 52 M37 with a stock engine, except for a 12 volt electronic ignition. I think I have the engine timed right and my spark plugs look normal, but after running hard (50 to 55mph) for 15 min or more I get a real loud backfire about 30 secs after I shut the truck off.

If I let it idle for a minute or two after fast driving, it sometimes does not do but then again it sometimes does. Thats the only ignition problem I have with the truck. Other than that, it starts and drives normal.

Has anyone else had this issue?

Thanks!
Tom

You mention a backfire some 30 seconds after the ignition is turned off. This does not seem to be an ignition problem, but fuel vapors igniting in either the intake manifold or the exhaust system. How does your temp guage look after a hard run? If your engine is running too hot, that could be the cause of your problem.

I don't THINK I am running to hot. I have never rebuilt the radiator, but have flushed it and have decent coolant in it.

Since I installed a heater, I plumbed those lines from the block. I have my temp gauge hooked to the plug in the steel line running from the radiator and that gauge doesn't show the truck running too hot. I wonder if that is not a good place for the sending unit and I am getting a false readings.

My heater never throws off too much warmth, so I didn't think I was running too hot.

i thought I would repost this request to see if there were any fresh ideas....

Thanks!

Your temp gauge sender is definitely in the wrong place. It should be in the port on the left side of the head near the back of the block. This area is where the coolant will be the hottest & the only place you will get an accurate reading.

And it is tucked up just behind the oil canister, so it may be hard to spot.
Gary

Hello crazy_lab, And I have a 19 and 52 M37, with 12 volt "points" ignition. I also have a bang when I turn the engine off...Have to hold my ears if I shut off in the garage. Have not yet set my timming, but as Charles suggested, it will be at 4* BTDC. Am all ears as to why else this might occur, besides water temp too high; by the way, what should the water temp be?

peter e mark wrote:Hello crazy_lab, And I have a 19 and 52 M37, with 12 volt "points" ignition. I also have a bang when I turn the engine off...Have to hold my ears if I shut off in the garage. Have not yet set my timming, but as Charles suggested, it will be at 4* BTDC. Am all ears as to why else this might occur, besides water temp too high; by the way, what should the water temp be?

Depends on what temp your thermostat is. A 180* should run at around 185-190*.