Posted By: charger RTSE
Pinging six pack - 02/21/11 12:41 AM
Basically a stock motor.
Mopar performance dissy adjustable set at 18 deg.with brown and silver springs.Timing set at 20 deg before. I set it with a vacuume guage and it idles realy good.
Rear carbs are factory 1/8 turned out on the idle screws.
6.5 power valve.
Jets in cenre carb are 63.
Car now pings when i step on it should i up the jet size to 65 what are others running or do i have to do something with the rear carbs.
Posted By: Mobarge
Re: Pinging six pack - 02/21/11 12:47 AM
That power valve seems kinda big.
Posted By: GomangoCuda
Re: Pinging six pack - 02/21/11 01:50 AM
Have you read this? Might help.
http://www.moparts.org/Tech/Archive/elec/29.htmlHave you checked the actual total timing with a light?
What axle gear ratio are you using? Torque Converter?
I normally use 65 or 66 jets in the center carb on 6pks.
Posted By: Dave Watt
Re: Pinging six pack - 02/21/11 05:23 PM
Check the total timing, seems like the Mopar Performance distributors have a lot of timing advance built into them. If you are set at 18* initial, it's probably over 40* total timing which will ping like crazy.
Posted By: SomeCarGuy
Re: Pinging six pack - 02/21/11 08:51 PM
I'm going to guess he has over 40 degrees all in. Way too much.
If it pings only with the vac advance, try adjusting it.
Posted By: six-barrel
Re: Pinging six pack - 02/21/11 10:27 PM
If it truly a stock motor thats likely too much initial timing.
Have you tried the max vacuum test to see what the engine requires. (up the advance until max vacuum is established then back it down 1". While doing this you will need to keep adjusting the idle rpm).
Whats the cam duration @50?
If it's truly stock then 10-14 initial would be more appropriate. Depending on which heads but 38 degrees may be too high and depending on which springs are in the distributor your curve may be too aggressive.
Posted By: RapidRobert
Re: Pinging six pack - 02/22/11 01:42 PM
on the timing I'd set initial w the vac gauge method (max vac then back off 1 in hg while resetting your idle speed) then shorten the slots to get 36 total (vac adv disconnected/plugged) then play w springs staying just under the pinging point at WOT up thru the gears on your hottest/driest day) THEN plug in vac adv & work w it staying just under the pinging point at PART throttle (high vacuum) above the RPM where the springs (mech adv) are fulled advanced (3/32" allen wrench & CCW delays the start of the slope (needs higher vac to start it but the amt stays the same) and may need to further limit the arm travel (the amt) into the can by soldering strips of feeler gauge on either side of the notch or source a can w less vac (it's stamped on the arm (in dist degrees) & a can w ~7-9 might be a good start. You want the can for better mileage/cleaner plugs but it will take the most work of all the dist subsystems to get it spot on as it has 2 adjustments. Get the timing right THEN on to mixture (A/F meter-best, plug reading-so so). Want no pinging/overheating & better too rich (to a point) than too lean so yeah I'd exp w bumping the jets up
Posted By: lewtot184
Re: Pinging six pack - 02/22/11 04:10 PM
something else to look at is if the combustion chambers are getting oiled. check the plugs an look for some "oil tracks". the intake may not be sealing properly.
Posted By: charger RTSE
Re: Pinging six pack - 03/03/11 09:26 AM
Well put in 67 jets in the center carb now no pinging.
Timing is set at 12 initial and 22 in the dissy total 34. I might try bumping up the initial to 14 to give me a total of 36.
Posted By: Kern Dog
Re: Pinging six pack - 03/03/11 10:15 AM
Ken at Hensley performance said that a good guideline is to use a power valve that is half the number of your idle vacuum. If you idle with 13 inches of vacuum, the 6.5 PV may be within the proper range. My 493 with the '509 cam has about 7-8" of vacuum and I have a 3.5 PV. Some believe that running rich is better than lean, but dumping too much fuel into the motor can and will result in scored rings, scuffed piston skirts and cylinder wall damage. The unburned fuel washes away the oil film on the cylinder walls. I dont profess to be a pro engine builder, but I have had some experience on this one. I am currently dealing with this very thing. I had an oil consumption problem and smoke on full throttle, and upon teardown, I found the situation I described. Tuning is everything. It may be beneficial to make friends with a guy at a smog shop. These guys can get you closer to ideal than we can.
You don't need to increase jet size, you need to get your timing where it belongs. About 14- is enough for a stock engine. You can dump all the fuel in it you want but you don't have a "lean" condition. You have too much timing. I had a 10 to 1 360 I built 8 years ago or so and I tried that. Didn't work, ran way better and quicker with 32-34 total timing. Actually picked up a half second when I dropped below 36 degrees. I couldn't believe it. It pinged as well but was far from being lean.
