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Earl

1941 Buick Backfires when I let off the gas.

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I know that I should be aware of what might cause this, but I'm not getting to the bottom of it. And Many of you guys know a lot more about car engines than I ever will. I have a '41 Buick Century and have been getting it to run better and better in the past year since I bought it. It really runs well now and has great power. But now it wants to backfire when I let off the gas and it will pop some when idling. This is usually from too much fuel isn't it?

I know other things can cause this as well, but it sounds more like a fuel issue to me rather than ignition. It has the dual carb set-up. And the backfire is out the tailpipe. I really enjoy reading the posts, and sure have learned a lot about these old beasts.

I thought I'd find out what you guys thought about this trouble. Thanks now.

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There are a couple of causes of backfire. One is fuel adjustment. Too lean and it may backfire in the intake. Too rich and it may backfire in the exhaust. The other cause is ignition. The timing may not be right or there may be worn parts in the distributor which causes the timing to vary when it is not supposed to. I'm thinking your dual carb Buick is running a bit rich.

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I'm not a mechanic, but I would recommend you replace the condenser in the distributor and see what happens. Even a loose wire on the condenser can do this. I had an occasion on a Chrysler (yeah not ever car I ever had was a Buick) and it actually blew out the muffler before I could get him back home (8 miles).

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Don't I remember from the dark ages that the distributor's breaker plate in Buicks of the era rotated on ball bearings? Tell me if I'm wrong. I have a vague recollection of there being the potential for a wear problem there, which would cause a looseness of the plate and allow a variation in point gap, especially with a sudden vacuum increase occurring when you let up on the gas. While it may be attributed to those compound carbs, at least take a look at this.

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Hi

While not into Buicks I have had lots of old cars in the last many years. One cause for the type of back firing out the exhaust that you describe is a small air leak in the exhaust system. It can even be a loose slip joint or a leaking gasket at a flanged joint. Even a tiny rust hole in the system. My 1986 Alfa 33 does it all the time when on the over-run with the throttle closed. Its exhaust system is so convoluted that you can never get rid of all the little leaks. I suggest that you check all the joints first.

Bernie j.

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All of the previous posts are good and I would just add; take the spark plugs out and look at them. Real black sooty plugs indicates a rich condition. They should be a clean brown color.

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You guys are good! Thanks for all the help. I got out a sheet of paper yesterday and revved the thing up and found out that it did have an exhaust leak just under the manifold below the heat riser. I would have never guessed that an air leak there would make it backfire like that.

As an aside, the bolts holding that Y pipe are the same size as the bolts on the intake/exhaust manifold and I put my wrench on one of the bolts (just to hold it) and thought it felt loose.... Almost all of them were. Gosh that thing idles almost like it should now! I think I'd better re-torque the head this weekend as well. I've had that car for almost a year now, and it finally is starting to sound and acting like one of those straight eights should! Thanks again you guys. My old sources for help on these things are all gone now. They were old 30 years ago when I had that other '41 Buick as a kid. It's good to know that there are a lot of people out there still willing to work with these old cars and try to keep them they way there were when they left the factory. I know it isn't always possible, but it's nice to know that a lot of it still is being preserved. I'm looking forward to running down to Ames in July. I know I'll be awestruck by some of the restoration work I'll see. If it's not too hot I might drive this Century down there. It really needs to be restored, but I don't think anyone will be too critical of it. Thanks again now.

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Earl, please drive to Ames. I will be driving from south Missouri in my 1950, no matter the temp.

I believe I can speake for everyone here when I say we would like to see your Century!! As is. No restoration needed. BRING it ON!!

Ben

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I agree with Ben.

There is something special about "time warp"cars that you can never achieve with even the most meticulous restoration. Now after almost 30 years my '34 Lagonda Rapier is just starting to get a nice "patina".

Bernie J.

post-51681-143138230257_thumb.jpg

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