All Six Help! Pinging & Detonation

[John Ha]

This may sound silly but have you checked your distributor hold down clamp? Sometimes the bolt works loose and lets the distributor move or even pop up a bit

 

[sixtseventwo4d]

With that range of play I would also check the distributor for gear wear and it's end play; for peace of mind and certainty as well.

 

[Radiator Springs]

Thanks for the posts, but yes, hold down clamp is rock solid.
The dizzy is a brand new (1 week ago) rebuild from Cardone and is in great condition.

 

[chad]

is it a LOM DIzzy?

 

[66Fastback]

You should not have any detonation with these low compression engines. Bill mentioned checking the TDC of the harmonic balancer. I had issues years ago where the ring was slipping and it was impossible to set timing with the timing light. Pull the #1 plug and check to see if you are on compression stroke and check position of the harmonic balancer and the timing mark. If it is not correct, order a new ore rebuilt balancer. In the meantime you may have to time by ear until a new balancer arrives.

 

[Radiator Springs]

Hi all.
Okay, good news. I found the issue...vacuum leak, (see photos).
I used some yellow tape to cover over the connectors on the line from the intake to the distributor.
Also covered the the staked silver cap that is on the outside of the carb on top of the power valve.
Took the car on a run and ....no pinging. Took the tape off the carb power valve cap...no pinging.
So, the leak is at the connector, either at the distributor or the intake.
Shout out to the folks (sixseventwo4d, wsa111, Big six Farmer) who were saying lean, ie vacuum leak.

 

[chad]

sorry there wuz no pic on the 5/14.
"a pic is worth a..."
25 post later...
8^0

 

[Big six Farmer]

Your very welcome, and that is what makes this forum so great. Guys jumping in to help out, putting collective minds together... What tipped me off was you said the Sparkplugs were white, a bad sign... From back in my Street racing days, no wide band testers where around yet. It was just old school plug reading. Then jet the Carb. up or down, it got you close. But reading Spark plugs is still a good way to make sure you are not running so lean that you risk melting/ busting pistons... No doubt we are all happy for you.

 

[gb500]

I dont understand how a vac leak thru the loadomatic pipe would.
A) give big enough vac leak to make it lean. The drillings to the venturi are about 12 thou dia.
B) leak vac to dist diaphram means distributer wont advance (or reduced advance) and hence less timing

 

[sixtseventwo4d]

I believe on these particular distributors a loss of vacuum either throws off the scv or just plainly allows the dist to over advance at the wrong time.
If I'm incorrect here I'm intent to learn from you. I just learned that yellow tape IS good for something

 

[chad]

above (@ blue horizontal line) tech archive

Load-O-Matic Distributor & Spark Control Valve

How The Stock Load-O-Matic Distributor Works Here is a little clarification on how the "Load-O-Matic" distributor works, along with the infamous "Spark Control Valve" (or SCV). Not only is it important to know how they work, especially if your...

fordsix.com

is bout best explanation.
Bill hasa lill sketch showing the internal passages that helps explain too.

 

[66Fastback]

I dont understand how a vac leak thru the loadomatic pipe would.
A) give big enough vac leak to make it lean. The drillings to the venturi are about 12 thou dia.
B) leak vac to dist diaphram means distributer wont advance (or reduced advance) and hence less timingI

I believe the high temps are caused by the lean mixture of the vacuum leak as well as the "retarded" timing. Retarded timing generates more heat coupled with the lean mixture causes higher temps. I recently trashed my wife's truck engine. She had bought an '82 Chevy truck that I borrowed. Post Mortem I found that the vacuum lines were disconnected and not plugged and the electronic spark control had been disconnected. Lethal combination of no ignition advance and lean mixture.