[53Chev]

I have had my timing locked in last season at 36 degrees accross the board and it is still pinging badly on heavy acceleration. I have been told an advance curve kit may fix this. Before you all go suggesting other avenues such as octance levels, timing adjustments, carb adjustments, etc etc etc etc etc. All obvious avenues of diagnosis have been attempted. This garage is a performance garage that builds racecars and services muscle cars exclusively and they come highly recommended. There shop is so clean you could eat off the floor. I have put over 500 bucks into them trying to diagnose the reason for the pinging to no avail. We are getting ready for round two. I dont think the pinging was there before the timing was locked in last fall. I do not plan on tackling this myself, but would like to at least have an idea of a direction to go with when I take the car in next week.

Any constructive suggestions or ideas?

Any constructive advice would be appreciated.

 

[Junkyard Dawg]

An advance curve kit dictates when the centrifugal advance comes on thru the use of weights and lighter/medium/heavier springs.

 

[53Chev]

In laymans terms please?

 

[Whiskey]

That was in laymans terms. These are the weights and springs you will find under your rotor in your distributor. The kits will include three sets of springs and different weights to replace the stock ones. Then you try each set of weights untill you get the advance curve you want. Oh Yeah you can mix the springs also so that you may end up with one light and one medium spring or whatever works best. Bill

 

[53Chev]

I still think you missed my point. I'm not a fellow Rocket Scientist nor do I have the same IQ level as Einstein. WHAT does an advanced curve kit do? You explained it to me in technical terms as if I had taken it apart and put it back together again. You make it sound like parts for a Time Machine.

What does it do to make my car run better?

Or does it have some other magical properties? Can it clean my dishes while I sleep? Does it allow me to see into the future? Will it braid my nose hair into corn rows? Or is it just something that they stock in auto parts stores that we can spend our money on and once installed, do not see any noticable difference in performance on our already expensive money pits we call "chevelles"?

 

[mike pratola]

The springs and wieghts are mounted on the distributer shaft. They act as a govener. One end of the wieght is mounted on a pin and allowed to pivot outwards. The spring is mounted at the free end so as to keep the weight pulled in. As the distributer shaft spins, the centrifugal force causes the free end to swing out. As the shaft spins faster, the force of the weight overcomes the force of the spring and the weight swings out even more. This mechanism is tied to the pionts cam so the cam can run ahead of the shaft as the weights swing out. This advances the timing. By changing the spring tension or the size of the weight you can taylor how much advance you get and when you will get it. The kit gives you and assortment of wieghts and springs you can mix and match untill you find the right combo that works for you. For what it's worth, I never had much luck with locking in the advance on a street engine. Back in the day we used the advance curve for high horse 327 (350? 375?) as a starting point, but that was 30 years ago, and with the improvements in camshaft design and manufacturing I'm sure thats 'old school' now. Hope this helps.

 

[53Chev]

Thank You!

 

[charbilly2001]

I would reexamine that 36* total. Most of us don't generally go above 30*@ 3000 RPM on todays gas.

Perhaps you might consider turning the wick down a bit.

Generally speaking pinging will come from two things. Either you have too much timing at whatever RPM you are experiencing OR you are feeding oil into your engine. Oil had no antiknock properties and as such will cause pinging and/or detonation. Since you don't mention oil I'll assume that your engine isn't burning oil.

In your case timing looks like the culprit. You can fiddle with advance weights and try to hit the magic spot or you can search out a shop that has a good distributor machine and have them recurve your distributor to a gentler place so your engine won't ping anymore.

Finally, you might be troubled by carbon deposits. They will also cause pinging, especially if you have any sharp edges on your pistons ( You did remember to sand off all sharp edges on your pistons didn't you?) they will collect carbon and under the right circumstances they will act like glow plugs and cause preignition. The solution here would be to de-carbon your engine. Some would do that by holding the engine at a high speed ( 3500 RPM would do it) and slowly pour water into the carburetor. The water hits the carbon and then flashes to steam blowing the carbon off the piston. Its very effective.

You can do the same thing with automatic transmission fluid however in that case you pour the fluid into the carburetor fast enough to drown the engine and then let it sit for a few minutes. The tranny fluid will saturate the carbon and when you refire the engine the carbon will go out the tail pipe. Its entirely possible that you'll foul your plugs so remove them after you stall the engine with tranny fluid and clean them off with some CRC Brakleen degreaser.

The downside of using tranny fluid is the gigantic white/blue cloud of smoke you'll make. Might startle the neighbors.

 

[53Chev]

My engine has less then 1000 miles on it since it was manufactured last summer. I doubt carbon deposits are the problem.

 

[Johnny O]

Will it braid my nose hair into corn rows?

Disturbing!! But at the same time, fascinating

 

[136679ss]

Thank You!

How about this. A curve kit is a series of weights springs and bushings which dictates how and when degrees of advance are applied based on your RPM/Vacuum/Idle circuit. It gets a little more complicated but you wanted it in simplistic terms. JN