Get a piston stop and check that tdc is tdc on your balancer. 46 degrees is not out of the question at 3500 rpm and no load. The ecm will advance timing in this situation (equivalent to a vacuum advance). 12-16 degrees of vacuum advance above the mechanical advance for an old style distributor is well within reason. Try retarding the timing 2 or 3 degrees at a time until the ping goes away before you hole your pistons.

 

If your KB pistons are flat-tops you are running approx 11:1 compression with 113 heads......a bit dicey with pump gas

 

This could be the main issue but one question I have is this a new problem that developed over time or has this problem always been present since the rebuild?

 

I had the same experience.

 

Pretty much been around since rebuild...fwiw, I have been driving around with the est wire disconnected and base timing set to 12 deg. Thats as much as I can advance it w/o pinging. Rather punchy off the line but kinda flat on top. I will be checking tdc soon...

 

check your cats, my friends 1990 was pinging like hell and did kinda like what your saying chunk of his main cat broke loose and caused a restriction which in turn caused havoc on the timing. His car would surge and seem like misfiring which I think was the ecm retarding, ran hotter then normal, got considerably quieter, didnt like rpms over 3,000. couldn't pull 6th, was fine around town and much like yours did great as long as you didn't exceed 1/2 throttle, anything more and it would fall on it's face.

another odd thing it did was car engine made a horrible sucking noise almost like a few vacumn cleaners running.

he never got the glowing exhaust or codes btw. His car even passed smog like this and gave no general ideas of the cat being at fault.

maybe not your problem

 

My gut feeling is you have too much compression, with aggressive part throttle timing, too little knock retard, and too high of a water temperature to work with pump gas without making some changes. I am making an assumption that since this condition has existed since the rebuild the compression ratio is at or above 11 to 1. I caculated 11 to 1 figuring pistons in the hole .02, .051 head gasket, 58cc head volume. If this information is not correct the compression will be different.

To make a pump gas car operate with 11 to 1 compression and short cam timing like you have will require some modifications.

-Put a 160 degree T-stat in the car and program the fans for on at 175 off at 165 or add a manual switch to turn them on at will. The engine must be cool to work with 11 to 1 compression. (Don't worry about this being too cool, it will work fine and the engine life will not be reduced. Detonation on the other hand will reduce engine life.)

-Have a custom chip made that reduces your part throttle timing (above 1/3 throttle where you experience the detonation). Have somoone scan the car to see what load values experience detonation and then change those timing tables to eliminate the detonation.

-Also have the part throttle and full throttle knock retard amount changed to allow for more retard in the event that it is still detonating once in a while when the car gets hot or some poor gas is run through it. You mentioned that a fixed 12 degrees has no detonation but has poor performance, well that would be a safe ignition timing set point. In other words have the knock retard table set-up to pull enough timing to get down to 12 degrees of advance so if detonation is experienced it can be eliminated.

I believe with the correct tuning you will be able to eliminate this problem, good luck!

 

I have often thought that compression could be high as well...good to know if thats the case it can still be sorted out with some tuning. I am going to still check to make sure tdc is correct, if that checks out o.k., I will move on to a scan (will likely do that anyway). BTW, the car performs surpisingly well locked in at 12 deg (12.9 1/4). I am very excited to see how this pulls when everything is fixed.

 

I would think you should be happy with that time

 

I am happy with it... but I know it has never run right and is capable of better.

 

I was able to get a datalog recorded yesterday. The only thing that jumped at at my untrained eye is there were no knock counts recorded or knock retard, just said 0.0
Considering it was knocking and pinging the whole time, this would likely have something to do with it, right? The only codes were for low tps voltage(it was about .53-.54 ) and est (since I previously had it unplugged).