dstuckmann
Member
Hi, I just joined and I hope its OK to pose a question on a C-Body, a 1970 Chrysler 300 convertible with 440 TNT (Magnum) and added 6-Pack. The question at this point is regarding timing. The car always pinged somewhat but its getting quite bad, even a low loads and RPM. I disconnected the vacuum advance which was connected to the carb port. This helped a little but is still bad.
Here is a breakdown of the car's setup. Most of this was done by the previous owner.
440 TNT 375HP
Rebuilt and bored .030 over
6-Pack - I have not tweaked the carbs for about 9 years now but just checked fuel levels and they are still good.
No choke plate or idle solenoid
Holley 5.5 Power valve
Holley 122-66 main jets
Edelbrock 5090 75cc E-Street aluminum heads
Comp Cam 21-306-4 Per Comp Cam - Great replacement for 440 6 pack and largest cam with stock converter.
Grind 270H
Intake and exhaust duration 270
Intake and exhaust duration at .050 lift 224
Intake and exhaust lift .470
Lobe separation 110
Exhaust Close ATDC: 21
Intake Open BTDC: 29
Exhaust Open BBDC: 69
Intake Close ABDC: 61
TTI Headers
MSD Streetfire CDI with Blaster 2 coil
Chrysler electronic distributor
Timing marks are accurate
Auto trans with stock converter
3.23 gears
Cold compression is 150 plus or minus a couple.
The car runs pretty nice with the exception of the pinging. It will turn off without run on and will hot start with just a touch of the key. Gets about 13 mpg on the highway. I do think its running a bit rich as I feel that I should have to blip the throttle more to keep it running at a cold start. The car will idle (slowly) on its own after a minute or two.
If I time it by “ear” and highest vacuum, its at 42 before at 900 rpm with 17 psi of vacuum. I could not get it to idle below 900 even with the idle speed screw completely backed out. I did not mess with any carb settings. My understanding is this may be normal depending on the camshaft.
Currently the timing is set at 12 before with an idle of 850 with the vacuum advance is disconnected and its pulling about 15.5 inches of vacuum. I’m using a ‘70s vintage Craftsman timing light with the spring coil that attaches directly to the plug. Not sure if the MDS is messing with this old timing light or not.
At 1500 rpm the timing already shows 32 before.
At 2000 rpm the timing increases to 38 before. I did not check it past 2000 rpm.
I’m thinking that the mechanical is coming in way too fast but I'm looking for your expertise. Should I try different springs or just bite the bullet and get the FireCore distributor.
Thank you all in “advance” for help a C-body guy out!
Here is a breakdown of the car's setup. Most of this was done by the previous owner.
440 TNT 375HP
Rebuilt and bored .030 over
6-Pack - I have not tweaked the carbs for about 9 years now but just checked fuel levels and they are still good.
No choke plate or idle solenoid
Holley 5.5 Power valve
Holley 122-66 main jets
Edelbrock 5090 75cc E-Street aluminum heads
Comp Cam 21-306-4 Per Comp Cam - Great replacement for 440 6 pack and largest cam with stock converter.
Grind 270H
Intake and exhaust duration 270
Intake and exhaust duration at .050 lift 224
Intake and exhaust lift .470
Lobe separation 110
Exhaust Close ATDC: 21
Intake Open BTDC: 29
Exhaust Open BBDC: 69
Intake Close ABDC: 61
TTI Headers
MSD Streetfire CDI with Blaster 2 coil
Chrysler electronic distributor
Timing marks are accurate
Auto trans with stock converter
3.23 gears
Cold compression is 150 plus or minus a couple.
The car runs pretty nice with the exception of the pinging. It will turn off without run on and will hot start with just a touch of the key. Gets about 13 mpg on the highway. I do think its running a bit rich as I feel that I should have to blip the throttle more to keep it running at a cold start. The car will idle (slowly) on its own after a minute or two.
If I time it by “ear” and highest vacuum, its at 42 before at 900 rpm with 17 psi of vacuum. I could not get it to idle below 900 even with the idle speed screw completely backed out. I did not mess with any carb settings. My understanding is this may be normal depending on the camshaft.
Currently the timing is set at 12 before with an idle of 850 with the vacuum advance is disconnected and its pulling about 15.5 inches of vacuum. I’m using a ‘70s vintage Craftsman timing light with the spring coil that attaches directly to the plug. Not sure if the MDS is messing with this old timing light or not.
At 1500 rpm the timing already shows 32 before.
At 2000 rpm the timing increases to 38 before. I did not check it past 2000 rpm.
I’m thinking that the mechanical is coming in way too fast but I'm looking for your expertise. Should I try different springs or just bite the bullet and get the FireCore distributor.
Thank you all in “advance” for help a C-body guy out!