I would suspect your problem is in the distributor. The Delco distributors had centrifugal advance built into the distributor. Two weights counter balanced with small springs would advance the spark in addition to the vacuum advance. I am thinking one or both springs are weakened or broken which would advance the spark prematurely at mid-range speeds and the rattling would disappear as the engine reached higher RPMs. Has the distributor shaft been lubricated? a sloppy distributor shaft could also play havoc with timing issues. There are other possible problems that would require knowing the year of the vehicle, if the engine and the flywheel are original, has the electrical system been converted to 12 volt, and the model number of the distributor would all be helpful. 

Bob, I appreciate your help. I really do. I suspected the distributor because all symptoms could be bettered or worsened by tweaking the distributor.  The internal advance seems the likely culprit. But how to remedy it is the question. The shaft and all seems like new. Its a Delco Remy model 1112333, ser: 0B06. Thats the way it's stamped on the plate inside.  But the numbers seem reversed. Maybe a factory mistake?

BTW it is 6v. A lot of the parts of the engine are 1940. The block assembly is 1950, 216.

Also Im wondering why Im listed as a new member? I've been a continuous member since 2005.

Posted by: @roger-goetze-2

↑

Also Im wondering why Im listed as a new member? I've been a continuous member since 2005.

Roger, it's not "new" to the club but to the forum. It's the way we keep spammers at bay. All "new" forum users must have 5 approved posts before their full site privileges are unlocked. Spammers won't hang around long enough to create five normal posts just to get to post a hit-&-run spam post. Unapproved posts are never seen by anyone but the Moderators. You need one more then you're good to go.

Thats good to know. Thanks for the info.

I pulled the distributor out and took the floor plate out. The springs seem strong. They snap the counter weights into place easily. I took pics if that would help. But there seems to be nothing out of place. The curvature of the edges I can't assess. They seem ok.

Maybe a kit? But the whole distributor is like new. No slop anywhere.

I believe 0b06 is 1940 or another year ending in zero, February 6th.

Sounds like your distributor is in good shape. 

Dave

How could I test the  springs for proper tension? With a certain weight? Stretching it?

You mentioned that your timing was set at TDC with a light.  How far do you have it advanced with the octane selector?  Maybe it needs a few more degrees.  Just a thought.  Mike

Roger,

Sorry for the long delay in responding to your questions.

The problem with diagnosing issues with vintage cars is that over the years different mechanics have worked on the car, different parts, and unorthodox repairs have been made. In the here and now any problem requires a dive into the history of your car. The issue you may be experiencing may be as easy to cure as switching to a higher octane fuel, adding a lead substitute to your fuel, or rolling up your sleeves and diving into the engine.

216 engines were designed to run on leaded gasoline. Today's fuels do not have lead. lead was used to dampen pre-ignition and the rattling sounds under higher RPM and heavier loads. Engine cam shafts were changed in the early 50's from forged steel to cast iron which required different distributor drive gears to prevent wear. Power-glide equipped cars used slightly different distributors and vacuum advance assemblies than manual shift cars.  Timing marks on flywheels differed in the 50's. 

Understanding the history of your car is where diagnostics must begin. Start with these questions

• what year is your car and how long have you been driving it?
• has this problem cropped up recently or has it persisted as long as you have been driving the car?
• What might have changed when the rattling first started? 
• does the car have the original engine and if not when was it changed?
• was the donor engine ever rebuilt or had major work done to it?
• what are the "CON NUMBERS" and serial number of the current engine?
• Is the distributor original to the engine?
• What is the breaker plate number in the distributor (1112333 is not listed in my parts books how about 1112353 or 1112383)
• does the vacuum advance have a number stamped into the bracket?
• Is the flywheel original to the engine? remove the flywheel pan and find the casting or GM part number to check.
• is pre-ignition the source of the rattling sound you hear from the engine?
• when in second gear does the sound fade away if you stay in second then speed up to say 40 MPH? Same in 1st and 3rd?
• what kind of fuel are you burning? have you tried going to 93 octane or added lead substitute to your fuel?

You should go on line and find "235 chevy guy" drill down in his topics on distributors, flywheels, & cam shafts. After reading his technical papers I'm sure you will understand why they may be pertinent to your problem.

I should have a few 216 distributors in my stash of old parts. If all else fails get in touch with me and I'll send you one. 

Remm

Like I said, Ive driven this car with this motor for18 years. Never did it have this timing knock until I completely rebuilt the motor. The block is 1950. So all new parts are supposedly 1950. So I don't know where to go with that. 

Also to the suggestion that advancing the spark will solve preignition, I don't see how. It would make early firing worse. The distributor is in pristine shape and worked perfectly until the overhaul.  That leads me to believe it's not the distributor  itself.

Roger,

Master parts catalog 1929-1950 lists 6 different part numbers for the mechanical advance springs in distributor distributors made between 1936 and 1950.. There are also 2 different part numbers for the weights themselves. You can find this information in section2.388 and section 2.389.

If you can find a Delco Remy Training Manual section "C" printed in back 1958 (#5133) under the chapter on IGNITION SYSTEMS- DISTRIBUTORS you will find a thorough explanation of the workings of the mechanical advance weights, springs, and their effect on the timing of your engine.

When you dive into this chapter you will find that the wrong or weak mechanical advance springs will permit premature spark advance at lower RPMs than what the distributor is designed to provide. The symptoms would be premature ignition at moderate RPMs which would then disappear as the engine reached higher operating speeds. The prematurely advanced firing rate would be more appropriate at higher RPMs and one could expect the pinging to fade away as the RPMs increased. Does that sound familiar or am I missing something? 

You might try calling Advanced Distributor in Shakopee, MN. I don't know if they are still around but I recall reading some interesting Technical papers that they had published.

Good Luck