440 engine ping question

[clazar]

I have a 70 RR 440+6. I have Mopar electronic ingition w/vacuum advance. The timing is set @ 5 btdc. I do run a mixture of 110 octane with 93 unleaded. The spark plugs are gapped at 35. Is there a different combo i should try to relieve the pinging???

Chuck

 

[Cranky]

Is the engine stock or modified and have you checked to see what your compression tests numbers are? Lots of things that can cause ping including high engine temps. We need to know more info about the car's combo to give you good info on what to do....

 

[clazar]

Completely stock. Just electronic ignition only. Compression is good. Engine temp usually runs 180-185.

Thanks
Chuck

 

[furyus]

Weren't some of the Mopar electronic distributors giving too much advance, making it necessary to weld up the advance slots?

 

[Lionized]

Completely stock. Just electronic ignition only. Compression is good. Engine temp usually runs 180-185.

Thanks
Chuck

Have you tried running some more advance? Try around 10 - 12°.

 

[Cranky]

Ok...what is the PSI on a compression test? What's total timing and when does it start pinging? Does it ping as soon as you stab the throttle or does it start after the rpm starts to rise? In most cases, I ran my initial timing well over 5 degrees but total usually wasn't all that high. Also, if your advance is too quick, that could also be part of the problem along with being too lean. How many miles are on this engine? Has it been pinging since it was rebuilt (assuming it has been) or has it just started pinging recently? There's several things you can try but it's hard to diagnose something with minimal information....

 

[clazar]

Ok...what is the PSI on a compression test? What's total timing and when does it start pinging? Does it ping as soon as you stab the throttle or does it start after the rpm starts to rise? In most cases, I ran my initial timing well over 5 degrees but total usually wasn't all that high. Also, if your advance is too quick, that could also be part of the problem along with being too lean. How many miles are on this engine? Has it been pinging since it was rebuilt (assuming it has been) or has it just started pinging recently? There's several things you can try but it's hard to diagnose something with minimal information....

I don't remember what the psi was. But it was good. Engine Like the car has 26500 on it. No rebuild. Pinging comes in when i give it gas at about the 3000 rpm range appx. It has been pinging for quite some time. I don't run it hard, just jump on it a little to clean it out. But if i run a high volume of race gas, it will stop the pinging.

 

[dla4567]

With out compression and timing info, you're not going to get much help.

 

[lewtot184]

if the engine is a stock 10.5:1 flat top piston with iron heads it'll never run on pump gas; even if the pope thru a gallon of holy water on it. high compression and no quench. it's also probably getting some oil thru the valve seals if they've not been changed in years.

 

[Ranger16]

Does it run on (diesel) when shut off?

 

[68GTX4SPEED]

I had the same problem with my 1970 440-sixpack, 2355, zero decked, 906 with 88cc, FelPro 0.039, cam 282-484 purple, at least 99 octane, now I have replaced the 906 with Edelbrocks RPM and engine will run again next summer.

 

[dla4567]

My 440 is about stock. Cylinder pressure (cranking) is 185psi, 906 heads. When I switched from 110 to 93 octane fuel, I had to back off timing from 38 degrees to 34, and have it come in much later (from 2200 to 3400), I also had to reject and tune the carbs (62 main jet to 65). On hot days (over 90), I can still get a ping if I jump on it. There's just no substitute for good fuel. Hope this helps.

 

[clazar]

Does it run on (diesel) when shut off?

No problems on shut down.

 

[69L48Z27]

OP - what is your total timing and when is it all in? You have some answers already posted in the thread. You'll probably find your timing in the high 30's with total timing and it's all in by that 3000 RPM mark. If you base is too low then you need to 'recurve' and limit the added timing in the distributor.

 

[AR67GTX]

Although the 6-pack cam has a bit more duration than the 440-4bbl cam it's still a fairly mild hydraulic cam for the engine displacement that maintains relatively high cylinder pressure at low and medium speeds - thus prone to pinging. A hotter cam that bleeds off cylinder compression at lower engine speeds is often more forgiving of lower octane fuel. My 67 GTX has a completely stock 68 440 in it and with 36 degrees total timing I get pinging under acceleration. I reworked my distributor for 16 degrees initial advance and 20 degrees crank mechanical advance but that hasn't really done much. I haven't tried backing it down to 34 degrees. I usually throw a little Octane 130 booster in it (real tetraethyl lead - mail order only - not cheap - not street legal) and that takes care of it. Custom building your distributor curve may get you where you need to be but if not there is always this.

http://www.hi-flow.com/hp016os.html

 

[lewtot184]

the only cure is kb184 quench dome pistons with the open chamber heads.

 

[Dreamcatcher]

Something wrong with your advance. Back in the day the best premium fuel was only 101 to 103 and they ran fine. I run the same set up as you and we only have 91octain out here. Never had a ping problem. The more advance the more prone to ping. I run stock advance with a pro comp dist. Of coarse our elevation is higher and that lets you get away with more compression and advance. Also a lean condition can also cause a ping issue.

 

[Cornpatch MO]

If the vacume advance is hooked up and working properly, when you hit the go pedal and the vacume drops, the timeing retards to prevent pinging and helps fuel economy. Could it be your timeing is not retarding?.....................MO

 

[mentor70]

i would definitely get the distributor re-curved, they ALWAYS have too much vacuum advance.

you can fix somewhat fix it yourself by following the vacuum advance tuning instruction in the old Mopar engine bible.

 

[69L48Z27]

Wouldn't WOT be mechanical advance? Not vacuum?