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1936 Buick Model 80 Rough Idle-Tail Pipe Spit


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I wrote in a week ago about my 1936 320 straight 8 with rough idle. Valves are adjusted to spec , good compression-in fact the head has been rebuilt, head is torqued properly, carb has been apart and checked twice for float level, all new points, condensor, wires and plugs. It draws 18-20 lb manifold pressure with the needle taking a blip every time it spits. I'm running the only plug NAPA could find which is an Autolite 386. Manual suggests .024 gap. I have a Buick Factory Service manual-printed in 1937- which suggests gapping plugs at .030 to correct rough idle-I did so and it made a BIG difference but it still spits. The same 1937 era manual stresses that series 80 & 90 cars must use the correct replacement muflers to avoid tailpipe "spit"-thats the term they use-spit. Old Buick Bugle Club Member notes show members having success with other plugs that are no longer offered by Chapmpion or AC. Car pulls great and will backfire a little when you let off the gas. The car runs really bad when you to put a timing light on it and set it up against the flywheel index marks. I suspect maybe the distributor- has been pulled out prior to me owning the car- may be off by one tooth. I can time it by ear to run good but the marks don't line up. I suspect I'll pull the distributor and reinstall it according to the manual. Anybody got anymore suggestions or can any of you 320 guys tell me what plugs you are running in your cars.

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Two thoughts for you...

1. What do you know about the health of your timing chain?

2. I had occasional arcing from the spark plug wires to the spark plug wire cover. Even after installing new wires, the 90 degree metal connector that attaches to the plug will still sometimes arc to the cover. To fix this, I used electrical shrink tubing, forced over the 90 degree connector, and allowed to shrink with the heat of the engine. Works great.

An old timer (Buick mechanic) told me these covers were problems, and were often tossed away for this very reason!

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