C1 340hp high speed timing

[Chris H.]

I can now get my car to idle around 650 -700 somewhat nicely with a spec'd timing of 10 degrees. Still need to tune in the carb.

However when I run up the RPM to +2500 the timing advances somewhere around 30 degrees and does not come back down to 13-17 degrees per spec. There is no vacuum system to control advance on this '62.

What is wrong? How do I know what weights I have and if they are working properly? Never done this before and need more info than what I read in the manuals. Most of what is in the archives is vacuum systems.

Thanks

[Jack H.]

Re: C1 340hp high speed timing

A common malady is for grease beneath the centrifical weights to dry out making them 'sticky'. Fix is EASY....remove weights & springs, clean with carb cleaner, clean the mounting surface, apply fresh grease by hand and reinstall the weights/springs.

[Chris H.]

Re: C1 340hp high speed timing

Weights were very easy to move but I took them off and cleaned them up, put a light coating of oil on them and put them back on. Also made sure that the mounting plate was easily moved relative to the shaft.

Still running high advance at 2500 rpm. After putting on the inside rotor cap I could feel underneath and the weights were easy to move. I did notice that there are 2 different springs. One was easier to sttetch than the other.

What next? This distributor was rebuilt many years ago and now has few miles on it.

Chris

[John H.]

Re: C1 340hp high speed timing

Chris -

The 985 non-vacuum advance distributor centrifugal advance spec calls for advance to start at 700 rpm, 9*-13* at 1600 rpm, and max of 22*-26* at 4600 rpm (all in addition to the initial timing). If it isn't returning to the initial timing spec you set after revving it up, one or both of the weight springs may not have adequate tension, and the weights aren't being fully retracted at idle rpm.

[Chris H.]

Re: C1 340hp high speed timing

OK, I am misunderstanding something. My specs say I should have 13-17 at 2500 RPM. It is returning to 10 degrees at 650 rpm.

Are you saying that at 1600 I should be reading 10 + 9-13 (total 19-23) and 10 + 22-26 (total 32-36) at 4600? If so everything is probably OK. I do need to pick up one of those degree stickers for the balancer to be more accurate.

Thanks, Chris

[John H.]

Re: C1 340hp high speed timing

Chris -

Yes, you should be OK with that - the specs I quoted for the 985 are shown in the chart at the back of the ST-12. Buy yourself a dial-back timing light for Christmas and you won't need a "timing tape" for the balancer

[Chris H.]

high speed timing - Sun tach tester in Detroit?

John, funny that the numbers you got from the ST-12 do not match the numbers in my ST-12. Perhaps yours is from a different year? AWWW, now I get it, you doubled the rpm since the distributor RPM quoted is half the engine rpm!!

The number I mentioned earlier was on a Sun spec card for my car and it has "Ignition Advance" at 2500 at 13*-17*. If I assume a straight line for the centrifugal advance curve(from 1600 to 4600) I get 15* advance from the distributor at 2500 RPM. Add that to the engine spec of 10* at 700 rpm you set a total advance of 25* at 2500 rpm. This is a bit higher than the 13-17 spec on the Sun card. I think my car is running more advance than 25* at 2500 and much more than the 17* spec on the card. I guess I am confused what the spec at 2500 on the Sun card means.

Anyone know who has a tach machine in the Detroit area? I think I want to take the tach somewhere and get it checked out.

Thanks, Chris