Lets talk timing... again

[Plymouthfan]

I've got my timing pretty much where I need it with 10 initial and 38 total and with the vacuum advance hooked up it reaches 49 total (52 was recommended). I still get a ping under heavy load after the car gets hot. If I let it cool down a bit the ping goes away. What's going on? Still too much advance? It's an 8 year old Mopar Performance dizzy with the light spring.

I still need to run it without the vacuum advance hooked up and see what happens. I'm heading to Atco in 8 days and I'd like to get it sorted out.

 

[Big John]

I'd leave the mechanical advance alone for the time being and try backing off the vacuum advance a bit at a time and see what happens. I believe the MP vacuum advance is adjustable with an allen wrench through the hose nipple.

Just out of curiousity, are you running a 160 degree thermostat? Sometimes that will let the engine run just enough cooler to help.

 

[Plymouthfan]

I'll have to check the thermostat... don't recall.

According to an article about timing with vacuum advance in Mopar Enthusiast a few months ago, you want your total at 52º with the advance plugged in. Mine was totaling at 60º and I had lots of problems. I had to have my initial at 0 to not ping. I backed off the vacuum to 49º total then was able to get my base timing where it needed to be.

Still I got that damn ping when hot. :brickwall:

 

[mac]

this totally my opinion, but this is what is working for me. initial at 20 (no problem cranking), total mechanical at 36 and total with vac adv is 50 at 2500 rpm. if there is anything other than a stock cam then intial should be closer to 16-18. that will obviously change total. i am currently running a newer MP dizzy so that adjustment is a little easier. i have been told countless times that a timing curve is put in place first and then the carb is adjusted to match. maybe it could be a float bowl adjument or a main jet change. (easy if it is a holley) look at the plugs for help (i like using #7 and #8) to see where the mixture is. i am running a six barrel but the steps are the same. i was chasing alot of gremlins thinking it was my old restored carbs or even my cam choice. once i got the timing curve in place with a good dizzy, everything else fell in place and i actually got to enjoy my car for the whole summer. all the bucking and jerking and pinging are gone. :cheers:

 

[Plymouthfan]

Wow Mac, 20 initial! I'd have to definitely recurve to get those numbers. Never heard of an initial that high on a street car, but if it's working for your car, it's working. I have a Holley this time around, so I have a bit more room to play.

I took it out today for a short while. First I blocked off the vacuum, got on it a while and had no pinging. Then I reconnected the vacuum and still no pinging. I know the car was at full op temp, but no pinging today. Last time it pinged after driving for a couple hours, but it was way too hot to cruise around all day today to wait for it.

 

[mac]

well it isn't always for the street. :drive: