Popping Noise

[rallyace]

Here is one for the brain trust... I have a 51 Plymouth Cambridge with a recently rebuilt 218, single carb, an overdrive transmission and a custom made driveshaft with Spicer universal joints.  When under load I get a popping noise that seems to come from the left side of the engine and its frequency seems to be linear to engine speed. This happens both with the OD engaged and disengaged. Oil pressure is 40 at idle and 45 when at speed. Compression is good (90 to 95 psi in all cylinders). I cannot sense any leakage from the exhaust gaskets or manifold.  It happens in all three gears. The noise disappears when not under load. I have used a stethoscope to see if there is any internal knocks in the engine and have not heard anything unusual at idle, when revving to about 3000 rpm and when the engine is coasting back down to idle. Is there anything in the clutch or transmission that may be causing a popping noise? I am at a loss as to what could be the problem.  Any help will be greatly appreciated.

 

Mike

[DJ194950]

Put the rear end up on jack stands under the rear axle to get tires clear of ground. May want the front up a bit on stands also for safety sake or just some strong wheel chokes in front of the front tires,

 

Best to have someone help by putting in gear and accelerating thru the gears while you listen with scope as needed to get to he area of the noise and try to get the noise exact location.

 

DJ

[knuckleharley]

1 hour ago, rallyace said:

Here is one for the brain trust... I have a 51 Plymouth Cambridge with a recently rebuilt 218, single carb, an overdrive transmission and a custom made driveshaft with Spicer universal joints.  When under load I get a popping noise that seems to come from the left side of the engine and its frequency seems to be linear to engine speed. This happens both with the OD engaged and disengaged. Oil pressure is 40 at idle and 45 when at speed. Compression is good (90 to 95 psi in all cylinders). I cannot sense any leakage from the exhaust gaskets or manifold.  It happens in all three gears. The noise disappears when not under load. I have used a stethoscope to see if there is any internal knocks in the engine and have not heard anything unusual at idle, when revving to about 3000 rpm and when the engine is coasting back down to idle. Is there anything in the clutch or transmission that may be causing a popping noise? I am at a loss as to what could be the problem.  Any help will be greatly appreciated.

 

Mike

U-Joint?

[Tooljunkie]

Pull line off vacuum advance and road test. 

[greg g]

In the resources area there is an old article regarding a noise coming from the bell housing.  It's from the original pages of the old forum format.  See if you can find that.  If not maybe the webmaster will chime in as I think it might have been one of his posts.

[plymouthcranbrook]

Can you post a vid or recording of the noise?  Really hard to get an idea Without hearing it.

[rallyace]

Update:

Well I spent some time under the car today and found that the shift linkage bracket on the shaft that changes the gears on the transmission was loose and the nut that holds the bracket on the shaft was inaccessible. I had cut an access point in the transmission tunnel when I installed the OD transmission last year so it was not that difficult but it was time consuming. I am not sure this is the problem but it could have been keeping the gear change linkages from fully engaging the shift dogs. Next up, get the interior parts I removed back in, get the car on the ground and road test. First, time for the Syracuse game.