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butter
07-10-2007, 02:35 PM
I recently checked my timing (’92 ps205 w/ 351W HO), and discovered that it was set to 20 degrees BTDC (specifications call for 10 degrees BTDC). This was a surprise, as the engine starts, idles, and runs great. Upon further investigation, I learned that the timing does not advance more than a degree or two at higher RPM. I’m sure the previous owner/mechanic set the initial timing to compensate for the lack of timing advance. If possible I would like to correct this.

Based on what I have read in some earlier threads, I expected that the weights and springs in the distributor were likely rusted, broken, seized, etc… However, when I opened the distributor up, I found the springs to be intact, and everything seems to move freely (despite some light rust scale on the weights). I disassembled and lubed everything up for good measure anyway, but I still don’t get any timing advance with increased RPM. I am stumped as to what else could be preventing the timing from advancing. Any ideas?

Thanks!

WilliM1940
07-10-2007, 08:04 PM
The only idea I can come with is the distributor was removed and set back a couple of teeth off or more.

kurtr
07-11-2007, 10:44 AM
In my youth we would change the springs on the distributor weights to get the advance to happen at an earlier engine rpm. Kits were available from the hot rod shop to do this. It would be hard to tell if you have the stock springs in the distributor or not. If some one change the springs to weaker ones the advance could be all "in" at and idle. I would also watch the cam on the dist shaft to ensure that it is moving when the weights are be moved.

tommcat
07-11-2007, 11:44 AM
do you have vacuum advance? if so was it unplugged when you checked the timing?

pilot02
07-11-2007, 11:57 AM
Never seen a vacuum advance set up on a boat. Typically mechanical only.

butter
07-11-2007, 04:46 PM
The only idea I can come with is the distributor was removed and set back a couple of teeth off or more.

Thanks for the idea. (I actually made that mistake with a 351W truck motor I rebuilt several years ago). However, I believe the position of the distributor teeth only affects the initial timing setting, and has no effect on the overall timing advance mechanism.

butter
07-11-2007, 04:48 PM
In my youth we would change the springs on the distributor weights to get the advance to happen at an earlier engine rpm. Kits were available from the hot rod shop to do this. It would be hard to tell if you have the stock springs in the distributor or not. If some one change the springs to weaker ones the advance could be all "in" at and idle.

Yeah, I have been wondering if they are the correct springs, or if they are too stiff, weak or whatever. I guess I could check the timing statically (if I can remember how), and if the static timing is significantly less than what I have measured at idle, then perhaps the timing is advancing “all in” at idle as you suggest. Thanks for the info.

I would also watch the cam on the dist shaft to ensure that it is moving when the weights are be moved.

Yes, the cam appears to move properly. (Actually there is no cam, since it is an electronic ignition distributor, but the shaft does seem to move as it should when the weights are moved.)

butter
07-11-2007, 04:50 PM
do you have vacuum advance? if so was it unplugged when you checked the timing?

pilot is correct. This is a mechanical/centrifugal (no vacuum) advance distributor, as found on most marine applications. Thanks for the input though.

tommcat
07-11-2007, 05:46 PM
pilot is correct. This is a mechanical/centrifugal (no vacuum) advance distributor, as found on most marine applications. Thanks for the input though.
wasnt sure, mine doesnt even have a distributor so i had no comparison and all the 351s i've worked on were in trucks and cars.

if you want to see if the springs are too heavy or weight too light you can pull off one spring and recheck the mechanical advance. if it then increases significantly you can be pretty sure there is a problem with the mechanical part of it.

one thing to note, over the years i have found the outer ring on a few balancers move which will throw your timing numbers all off.