Time to change ?

I have a 79 vintage 360 that seems to change the timing when it wants. It is set at 10 btdc, as per the book, but if you check it idling with the vacuum advance disconnected in park, it reads 15 btdc, and when you check it idling in neutral with vacuum advance disconnected, it reads 10 btdc. At the current idle speed (about 900 rpm), the vacuum advance doesn't matter anyway. When you set the idle speed, the rpm drops severally when you put it in gear. You can get everything set right, like idle speed and such, but when you drive it, the idle drops dramatically at a stop sign (like to about 450 rpm). Fluid levels in both the engine and tranny are fine. Could my torque converter be causing the problem (I did have a torque converter give me problems in the past similar to this, where it wouldn't let the engine spin up enough to move the vehicle very well from a dead stop, but the timing didn't seem to change then). Does anyone have any experience with this type problem ? I am not sure whether the problem is in the distributor, torque convertor, or if I need to replace the timing chain. The latter two are kinda expensive changes if they aren't the problem.

Your problem is kinda wierd.(Nice way to start a conversation,eh? )Anyway, my first guess would be that you had the mopar perf. distributer advance springs in there. Or some other kind of quick advance springs. What I guessed happened is that your mechanical advance is starting to come on even at low idle. The mopar quick advance springs are really more of racey piece in that respect. I am going through the same thing with my 360 Mirada.
You may have also have broken one of the advance springs in the dist. Good luck!!

Here's another odd ball possibility - I once had a 6 pack Superbird that had REALLY erratic timing. You'd set it at 10 before, go around the block and it would be at 40 after! As it turned out, the woodruff key on the crankshaft had sheared, and the balancer was moving around on the crank! Yes, the crank bolt was tight. We replaced the key and the balancer and solved the problem. The engine had been rebuilt before I bought it, and someone obviously goofed.

The vacuum advance isn't even getting a vacuum signal when this is happening, so it may be the springs, but how come it is happening when the engine is actually only speeding up about 50 rpm (from idle in neutral to idle in park) ? I am pretty sure the distributor is the original style..no fancy springs. The vehicle has been running fine until now. I have the Mopar Performance Distributor in my other truck, and it works awesome..even better than the Jacobs system.

[This message has been edited by Ramcharger 4x4 (edited February 02, 1999).]

Ya know Orange Bee, that might not be so wierd. The truck has always had a vibration in it since I bought it 2 yrs ago. I thought it was a 318 torque convertor on a 360, as it is really only noticeable if you rev the engine in neutral, or at high speed (above 65 mph). I just might have to look into that. Since I swapped carbs, I may have made the problem worse. Thanks, I'll check into it.

[This message has been edited by Ramcharger 4x4 (edited February 03, 1999).]

[This message has been edited by Ramcharger 4x4 (edited February 03, 1999).]

You still could have broken mechanical advance springs.The mechanical advance and the vacuum advance are two seperate systems. There are two springs in the mechanical advance in the distributor. One spring is heavy and one spring is light. If either spring is broken you will have an advance that is really hairy and possibly non linear through the rpm range. Remember stock springs will only give you max mechanical advance at like 3000 rpm or so.
The way to test for a broken mechanical advance spring is to take the vacuum advance hose off and plug it. Then get your timing light out and check the advance throughout the rpm range writing down the advance at every 2-300rpm. Stop increasing the steps when you find no increase in advance. Rev the motor a couple of time and repeate the timing light check. If your run throughs give you different numbers you may have to pop the dist apart and see. Maybe try this (?)

Hey Mark the 9th edition engine speed secrets book says to always check your timing mark against #1 TDC,the rubber in the balancer may be failing and allowing the balance to shift causing a vibration coupled with incorrect timing.The powers that be recomend that the timing mark be checked for true regularly. Put #1 piston at TDC and check the mark, do it several times, it costs nothing and can reveal a pesky problem.LOL

check them springs!While the dist. is out check the dist. for slop in the bushings(side toside)maybe that dist is old and worn out

Check that timing chain too.Its easy.Pull off the dist cap,line the balancer to TDC,rock the balancer back and forth and watch the dist rotor if it's moving when you move the balancer the chain is probably ok if not, you know what must be done.

Well Mark, it's been like 6 weeks, what was it?