Pinging at half throttle and on !

[moparwacko]

Depends on how your builder built it:

New school? Newer cam profile, aluminum heads, lower static compression , etc., and yes you have yourself a "pump gas" motor.

Old school? Old DC or MP purple shaft, iron heads, 10.5+ compression, you have
yesterday's pump gas motor. If it was an old school build, feed it that way.
Back when dinosaurs roamed the earth

My old school mix is 2 to 1
91 octane ethanol free 10 gal
100 octane LL AV fuel/Sunoco blue-purple, your choice 5 gal
Works for me- and smells great!

Does anyone else remember buying Cam 2 at the pump?

 

[moes]

I would check your total timing out first and then check it with your vacumm advance plugged in. If this is happening at part throttle your vacumm advance is coming into play, it could be adding to much advance for your motor to handle

 

[Kern Dog]

Big blocks are freaking finicky

No, they are no different than a 318/360, a V6, a slant six or any other engine that isn't tuned properly.
First up, just about any old engine was built needing more than the cheap low octane fuel. The "regular" leaded gas on the 60s and early 70s was approximately 94 octane and the R/T models needed even more than that due to their higher compression 440s and 426 Hemi mills. Todays 87 octane gas is piss water for an old carbureted engine with 9.0 compression or more.
Secondly, most stock distributors have a long advance curve. People set the base idle timing to a stock setting of 5-8 degrees before TDC and low speed performance sucks. It does not knock at WOT though.... They set it to 10-12 degrees and while the idle improves and the part throttle feel is good, it knocks and pings at wide open throttle. The fix? You need to modify the distributor so that the amount of advance it delivers is LESS. I'm talking about a shorter advance curve, less total mechanical advance.
WHY ? Well, if the distributor has 28 degrees of advance built in as many do, a setting of 12 degrees at idle ends up with 40 degrees by the time you are at 2500 rpms or so. Just about any engine will knock at 40 degrees unless you are running some 110 octane or higher fuel.
The trick is to shorten the advance curve. Most engines feel more responsive with more base timing than the factory spec. This is partly because many of us build engines a bit hotter than stock. A bigger cam needs MORE base timing. I run 17 degrees at idle, 34 degrees total in my car. My distributor HAD a 28 degree advance that had to be adjusted to a 17 degree curve limit. Again....17 degrees at idle, another 17 degrees is added to arrive at a total of 34 degrees at around 2400 rpms. I'm at 10 to 1 compression and have aluminum heads.

 

[YY1]

My '69 440 with "some kind of cam" in it runs fine on a mix of 93 and no-eth 90.

The good thing about big blocks is that the dist is up front and easy to play around with.

I always keep my hold downs just tight enough to hold, but loose enough to turn with moderate hand force.

I have the best luck doing borderline WOT from a standing start in gear, then making an adjustment.

Back off till it quits pinging. then if you want, advance until it starts again, then back off just a bit.

This works 100% of the time where as calculating advance degrees may not.

** unless you have a bad return springs or a leaky diaphragm.

Pinging and dieseling are sure signs of too much advance. Adjusting it should help both.

 

[Bb70charger500]

Thanks guys I will play with it more today I'm wondering if the distributor isn't junk then I don't know it it's new or rebuilt or 1968 ?

 

[Ranger16]

Gotta agree with the 'water' or 'seafoam' method. Water is cheap&plentiful(!).

AND it won't foul your plugs.