Merc Timing Problem

"77 Merc 351 Windsor right-han

"77 Merc 351 Windsor right-hand, 233hp, 2bbl, points ign, single screw inboard.

I set the idle timing at around 10 degrees. There a problem with the timing advance. It quickly advances 7 degrees to 17degrees total, but as I rev it further, it stays at 17 degrees total. I'd be grateful for ideas on how to fix this.

I opened up the distributor and did the following:

- turned the rotor ccw and it snapped back
- pulled the plate, and was able to push the weights out with the springs expanding and then pulling back.
- lubricated it a little

Then started the motor, hit it with the timing light. It was 10 degrees at idle as it should be, but would still only advance 7 degrees, even at 4000rpms.

I saw that there was one lighter spring and one heavier spring connected to the opposite weights. Then there were tabs on the weights that popped up through grooves in a plastic bar that crosses the distributor housing and through the shaft. It seems that the grooves limit how far the weights are permitted to swing out.

So is the very small timing advance I'm seeing related to the size of the springs/weights or range of their movement? Or should I be looking at something else?

Thanks, Dave"

"I'd guess wrong weights o

"I'd guess wrong weights or springs got put in when it failed the last time. getting some of those parts now is a challenge to say the least.

If there's a good engine shop in your area, they may have or can get you set up with somebody with a distributor machine. The other choice you have is to get some springs that fit and go thru the trial and error drill.

You may also reinspect the weights and pins. sometimes they will wear and you may find a burr that keeps the weights from going all the way out.

If the engine revs out to WOT and doesn't overheat, you may want to check the timing with a different light, especially if its the advance type...they've been known to be out of calibration."

Napa and CAP sell spring and w

Napa and CAP sell spring and weight kits for gm distributors. Summit racing and many other online parts stores sell them also.

They only cost around $15- $25 for the kits.

At least get a set of springs and it will come with instructions as to what color springs will give you for a given rpm vs advance.

"Tonight I pulled the bigger o

"Tonight I pulled the bigger of the two springs out, leaving one of the weights free. Started it up and hit it with the timing light and it advanced to 30 total degrees very quickly by 1,500rpms, and that advance remained as a straight line at 30 total all the way up to 4,200rpms.

The curve chart in the manual shows the spec advance as a straight line from 10degrees at idle to 30 total as it hits 2,000rpms. And then the line flattens out a little and gradually goes up to 34 degree total advance by 4000rpm.

So with only one spring right now, the advance is a little to quick up. I guess I need to get some different gauge springs and experiment to slow the rate of advance up to 2000 rpms.

But even with the heavier of the two springs out, the total advance I saw was 30 degrees at 4,200rpms. The spec is to achieve 34+ total degrees. Should I widen the grooves a touch, which limit the advance, so I can get it up to 34 degrees? The bar with the grooves that limits the movement is plastic, so I can push out each groove a little with a drill bit.

"

According to that graph it say

According to that graph it says 22 to 26 degrees.

so with ten initial plus the above that would = 32 to 36 degrees thus you are shooting for the middle of 34.

OK

Has someone reworked that distributor before??

What is the history?? Do you know?

RARLEY do people play with that stuff but it can happen........

Tell us more.........

Also please refere to post 3 i

Also please refere to post 3 if you feel the need to modify the springs and wieghts......

"K-think the windsor means non

"K-think the windsor means non-GM distributor

Dave - you may find a dremel tool helpful for slot adjusting. I'd be happy hitting the low end of the curve...remember, what is now sold as gasoline isn't the same as when that curve was defined...better safe than sorry.

Each distributor has its own quirks. Generally, total advance achieved is limited by the slot(s) length and the rate is controlled by the springs. Matched springs yield a linear rate; differing springs provide two different slopes - lighter usually being steeper."

"Yes, it's a Ford, and the

"Yes, it's a Ford, and the distributor I just picked up at ebasicpower.com.

So Makomark, I'll leave the total advance as is for now and try a few different springs to hopefully match the advance curve. The heavier spring that was installed in it had almost no give and was limiting total advance to 17degrees (10 at idle plus another 7 at highest rpm). So I pulled it and now it shoots up 20 degrees quickly to 30 total.

Thanks."

I understand Ford

It is

I understand Ford

It is the springs I was refering to as most are about the same style. would make for cheap and easy way to see if it wouold help.

Something here actually sounds like a mechanical issue of some kind............If it is the springs then they are partally frozen or have lost the ability to strech.