Pinging on hard accell

[mjb765]

71 340 Challenger, unknown cam is pinging on hard accell. Runs great other than that, but when I get on it the pinging starts. Timing looks way advanced at idle--in the 20-25degreee range. Should I try retarding it a bit? I'm using only  premium fuel--should I try some octane boost first since the motor runs good?

[422STROKER]

Is it a stock distributor?  Did you disconnect the vacuum advance when checking it?

Tom

[mjb765]

Is it a stock distributor?  Did you disconnect the vacuum advance when checking it?

Tom

It was converted to Mopar electronic ignition and yes I disconnected the vac advance.

[Strawdawg]

set total mechanical advance to 34 degs and see how that does

[MEK-Dangerfield]

Given your initial timing results, I'm surprised you didn't have more pinging.

I would try to get down to 16* BTDC or so.

[ksierens]

General rule of thumb for me is to advance it until it ping, back it off just until it stops.

[422STROKER]

Unless you limited the total mechanical advance considerably you will need to lower the initial advance.  did someone set up the distributor for you?  Is this a new problem, if so since when what changes.

Tom

[mjb765]

Unless you limited the total mechanical advance considerably you will need to lower the initial advance.  did someone set up the distributor for you?  Is this a new problem, if so since when what changes.

Tom

Haven't really touched anything and never noticed this happening before yesterday. Distributor is stock out of the conversion kit. If I retard it the motor does not seem to runs as well at idle or on accell. The motor runs fine except for the pinging--other than that good throttle response and good idle. Just wondering if it might be fuel.....still thinking about tossing in a bottle of octane boost--is it worth a try?

[Strawdawg]

waste of money...most octane boosters will raise the octane from 93 to something like 93.3...that is what the can means when it says it will raise the octane two or three points.  If you want to try more octane, then either get some better gas, or add a gallon of xylene or toluene to about ten gal of gas.

Sort the timing out, that is the best course.

[Chryco Psycho]

Add av gas instead of octane boost !!
where is the total timing at ?
 If it is a conversion dist you can adjust the mechanical advance , if it runs well with 20* + at idle just shorten the total advance  so it in the 36* range

[burdar]

Before you start adjusting things, spray some carb cleaner around the base of the carb and around the intake gaskets.  A vacume leak can cause pinging.  If the RPM changes when you spray around those areas, you have a leak.

 

[422STROKER]

Haven't really touched anything and never noticed this happening before yesterday. Distributor is stock out of the conversion kit. If I retard it the motor does not seem to runs as well at idle or on accell. The motor runs fine except for the pinging--other than that good throttle response and good idle. Just wondering if it might be fuel.....still thinking about tossing in a bottle of octane boost--is it worth a try?

Well, the total mechanical timing may be too high.  You can adjust the vac advance can as well to fine tune a part throttle ping.  CCW will make the advance come in at a higher vacuum number.

If it's an MP dizzy, there will be 2 torx screws inside the dist.  these need to be adjusted to limit the total to the recommended 34-36 range.  This will allow you to maintain the high intial your motor wants.  I run the same dist and this is how I have mine set up.(20+32+high40's on the vac adv).

Tom

You may have gotten some bad fuel.  Do you have ethanol normally in the gas?

[mjb765]

Well, the total mechanical timing may be too high.  You can adjust the vac advance can as well to fine tune a part throttle ping.  CCW will make the advance come in at a higher vacuum number.

If it's an MP dizzy, there will be 2 torx screws inside the dist.  these need to be adjusted to limit the total to the recommended 34-36 range.  This will allow you to maintain the high intial your motor wants.  I run the same dist and this is how I have mine set up.(20+32+high40's on the vac adv).

Tom

You may have gotten some bad fuel.  Do you have ethanol normally in the gas?

Being that I didn't remember noticing this ping before the other day, I am hoping for bad fuel being the answer. It is only at close to full and full throttle accell, so I am going to be nice to it for the rest of this tank and then go try fresh fuel before I start messing with the distriutor.

[422STROKER]

Sounds good, just keep an eye on it.

Tom