VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 216 "Popping Noise"

I have a fully restored 1941 Spec. Del. Coupe, w/rebuilt stock 216 w/ 12,000 miles. The car runs GREAT & starts instantly even after 30 days of not being run. And I mean, "instantly."

In addition it does not over heat, gets great milage and purrs at ALL speeds w/or with out a load and idles * smoothly. No misses or hesitations. Car has new plugs, points, plug wires, etc.

* BUT!!! I have a soft "popping" noise coming out of the exhaust pipe when the car idles. Maybe every 8-10 seconds, cold or warm. Do I need to adjust the carburetor or my hearing aid ??

I purchased the car in Salt Lake City {4,200 ft.} & I live in Redondo Beach Ca {10 ft.}.

Thanks
Michael41

I recommend two things to do:

1. Adjust the valves.

2. Set air mixture screw on the carb.*

*Use a vacuum gage and set for most vacuum.

Sounds like you have a good engine despite the soft popping from the exhaust. I would verify the ignition timing is correct since that is something easy to do and can cause popping noise from the exhaust or the carburetor, depending on whether it retarded or advanced.

You can also try increasing the gap on the spark plugs a little and see if the popping noise diminishes or goes away.

Plugs, Points, Cond. Valves & Timing just done with the tune up, 200 miles ago. Only thing we did not do was "adjust" carb...

"Popping" was there before & after tune up.???

Not sure it matters but the Eng. was rebuilt 12,000 miles ago, it has an over bore, balanced crank, rods and pistons. stronger rods, slightly "bigger" cam, resurfaced head & block, polished valves {Intake & exhaust} bigger valve springs. etc. The goal was a stock 216, but bullet proof the builder told me. And yes she does purr and run like a dream.

Just the slight "popping" noise. But I will go over every thing one more time.

So, would the altitude change make a difference in the Carb. adjustment ??

Thanks for your help,
Michael41

Mike 41
As Ray suggested adjust the carb idle mixture, as you mentioned that amount of altitude difference will make a difference. I would expect you will find it a little rich and the excess fuel is burning in the exhaust causing the "pop". When you done the tune was the spark plugs a sooty black, is the indication they should be a mid grey although unleaded fuel may make them a darker grey.
Tony

Since the "popping" was there before and after the tune up, it could be that the slightly bigger cam is part of the problem.

:eek: :eek: :eek:

I tend to agree with Ray and Tony, set up the carb with a vacuum gauge, eliminate any possibility of different settings from the higher altitude rebuild.

The Popping is probably extra unburnt fuel building up and igniting in the exhaust.

Okay...I have to ask...how/where do you attach the vacuum guage.
Best wishes,
Chuck

Disconnect the hose to the windshield wiper. Connect the vacuum gage there.

Make all adjustments for maximum vacuum reading. You can even set the timing with a vacuum gage. This is the best way to set the air/fuel screw on the carb.

Watch the gage for smooth readings. Invest in one of the blue Motors Manual that is at every swap meet. There is a world of good information in those books. Buy the oldest one you can find.

Long ago I could set the timing with a vaccuum gauge but have since forgotton how. Do me a favor and jar my memory banks so I can do it again if necessary.

Thanks.

With the gage connected as above, at idle, loosen the clamp on the distributor and move the distributor for maximum vacuum reading. Tighten the distributor. Check the timing with a timing light for more accuracy.

Before you follow the instructions above, make sure the points are set according to the specifications. A dwell meter is the ideal tool for this chore.

Correct me if I'm wrong but isn't it better to set timing with a vaccuum gauge? It's my understanding using a vaccuum gauge will allow for the wear in an engine where a timing light won't.

The 1949/54 manual has a section on how to set the timing with a vacumn gage when working in a shop that has no timing light. Hard to believe isn't it.

One thing I would suggest is before you hook up anything be darned sure you don't have a tiny vacuum leak, like at the vacuum advance, or the wiper switch valve, intake manifold, carb insulation block, worn throttle shaft (vacuum leak) etc. if you can't find a leak like a loose connection at the vacuum port for the advance hook up the vacuum gauge as Ray suggested.

The vacuum advance port should not have vacuum at idle. You need to find a connection point below the throttle butterfly and the wiper takeoff point is the ideal place.
Tony

once upon a time sour notes were flowing from the tail pipe of my 31. no amount of mixture adjusting seemed to quell these notes. I discarded the Champion spark plugs intalled by the previous owner and replaced them with a set of real spark plugs, ACs gapped at .040. such a sweet serenade now upon my ears.

bravo maestros of VCCA Chat!!

My suggestion was not to hook up a vacuum gauge at the Vacuum advance port, but to check for leaks at that connection, I do know that a small leak there will mess up the engine's idleing

Da-Pop is gone, She purrs like a kitten.

Thanks Ya-all, Good advice.
Michael41

Mike41:
That's great, but what cured the pop? Timing? Spark plug gap? Vacuum leak? Something else?

Coach

Hey Michael,

Coach (and me too) calling 'foul.' HA!

I'm sure we're all pleased the 'pop' is gone..... but, NO FAIR telling us the pop is gone without telling us 'the fix.'

The pop is gone, the pop is gone....

Bill.

Well guys, everyone offered good advice and I do appreciate it all. :)

Ok, some back ground: Car has great valve clearance to spec, so no adjustments were required, there were no vacuum leaks any where and the {new} plugs were gapped to spec. Oh and the points were perfect.

Sooooo what cleared up the "pop" {instantly} ? Well it was a combo of a quick adjustment in the timing & a carb adjustment. Now she's perfecto! I can balance a nickel on the valve cover.

As stated, the car was restored and driven for 3 years at an altitude of aprox. 5,000+ feet. Car resides at 23 feet. Hence, the air/fuel mix. & timing.

Thanks to you all & the ever correct chevgene. As always you were all helpful & very funny.

Michael41

Note that I made NO comments during this thread (surprise)........I would have had you remove the pistons or something like that

You are right chevgene.....but you did answer this question for me several weeks ago and finally, 2 days ago I found your notes, Followed them and "Viola!!"

But I was close to removing the pistons..

Michael41

PS: What are pistons?