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Pinging and power...
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Author:  BigBlockBanjo [ Tue Dec 18, 2007 6:57 pm ]
Post subject:  Pinging and power...
Well, I started driving my car longer distances recently....and I am getting some ping. :? I always thought that pinging was a result of "advanced ignition" either by pre-ignition or early spark. So I retarded the timing, and it got worse. Power dropped considerably. So I advanced the timing in small increments: the power increased each time, and "ping zone" got higher in the RPM range. I kept raising it until power started falling off again. I can not get rid of the pinging at any timing setting. I richened the mixture with smaller primary rods, and now it only pings at WOT. I shaved .100 off the block, none off the head. The pistons are .100 in the hole. I thought the compression was 9.25, but I guess it could be higher? I think part of the problem is the large advance on the cam....I advanced it one tooth (on the cam gear), to increase the cylinder pressure. Maybe It's too high now, to run 87 octane?
If it starts pinging, I have to pull the choke a little to stop it, and my gas mileage stinks right now. What do I need to do? Run High-Octane, or spend the time setting the cam back to normal. This makes me tired... :roll:
Thanks for any help.
Author:  LUCKY13 [ Tue Dec 18, 2007 7:36 pm ]
Post subject: 
Set the cam back, one full tooth is way to much advance. Then after setting the cam you may be in need of jetting the carb because of the higher compression.


If it was me, I would run the 91/93 gas ( what ever you have locally). You can really gain more timing & power by running the premium, it will also benifit you with better fuel milage if you tune the timing to work with the premium fuel ( all the advance it can stand on the base timing). Ofcourse you may need to recurve you distributor to where it does not adfvance as far so you can gain timing on the base to help with this. I find that anywhere between 15 & 20 on the base timing works good, then limit the advance to where it stops at 32 to 35. Run no vacume advance when set this way. I am up to 24 mpg doing this way with the premium fuel. With the higher compression you should be able to run close tho this, but trial and error will tell what you can get by with.


Also you might need to go colder on the spark plug heat range now that you have higher compression.

Its all a big balancing act that takes testing & tuning to find what your engine needs. But if you take the time to go through it all it should give you better power plus great fuel milage.

But first you need to put your cam back where it was.


Jess
Author:  sandy in BC [ Wed Dec 19, 2007 5:55 am ]
Post subject: 
By changing your cam timing you increased your Dynamic compression ratio....

shaving .100 off the block should leave you with less than .100 piston/deck height.

I agree with Lucky....go back one tooth.....then get some offset bushings and go about 4 degress to start....
Author:  Aggressive Ted [ Wed Dec 19, 2007 8:15 am ]
Post subject: 
BigBlock,

I know my cam is smaller than yours however, I have advanced my cam 4 degrees which gives it the torque but not enough to cause it to ping. I can over time it however, which doesn't make it ping but instead surge or misfire.
This had me going down the same route as you, richening the mix, which really didn't solve the problem.

I have the initial set at 16 degrees, mechanical at 16 degrees and vacuum advance at 20 degrees for 52 degrees total at 2500 rpm cruise.

If I advance the initial to 20 degrees it will misfire by slowly raising the rpms in a no load situation or if I am at cruise it will surge but not ping. Pressing down on the accelerator slightly to reduce the vacuum advance will make it go away.

I think your very close, and walking a fine line on the tuning. I agree with the guys and their comments. One tooth advance (15 degrees) is too much and doesn't allow you much wiggle room for fine tuning.

Let us know your results after you make the changes. :)
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