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View Full Version : Timing Issue "Sort Of" 84 S&S 351W Carb


jimmyj
06-29-2008, 09:58 PM
:confused:My engine was running excellent but didn't look to good, so I recently painted my engine. I took most of the stuff off the top and front of the engine to paint it. I did not remove the distributer or the harmonic balancer. When I placed the spark plug wires back on the boat, it would not fire. I finally got someone else to take a look at it and we discovered that the spark plug wires were one position off (#1 on distributer needed to back up to #8 and so forth). After changing all the wires one position, the boat cranked and ran really good. Sounds like the story's over huh!

I loaded the boat back on the trailer and took it home to flush out the salt water. While it was running, I decided to take out my timing light and just fine tune my timing. I hooked everything up and to my suprise the boat is running and the timing marks are way ahead. If I try and turn the distributer to get on the marks the engine dies. If I move the distibuter to where it sounds the best, the engine runs excellent. Some people say that, by ear, is the real way to set timing on an engine, but I am a visual guy and like to see the timing marks.

Anybody have any ideas?

Storm861triple
06-30-2008, 01:15 AM
Assuming that you hooked your timing light to the correct plug wire, your harmonic balancer's outer ring has slipped on the inner hub, causing the timing mark to be off, on the balancer itself.
Since the 351w is externally balanced, this COULD cause a slight imbalance issue. Bottom line, you probably need a new balancer.

As for timing, by ear IS best. Although there is a factory "spec", this is a conservative spec, designed to be safe under any and all conditions. For YOUR elevation, temp, octane, etc, "feed it what it wants". Take the boat out, w/the engine cover off, and have someone run it up to WOT throttle and hold it there. While runing WOT, carefully move the distributor to achieve MAX RPM's. There will be a bit of a "plateau" where the movement of the distributor doesn't little to nothing. Make your final setting on the "retarded" side of that plateau, and you're done. Your boat won't run any better than that, no matter what "the book says".

jimmyj
06-30-2008, 10:25 AM
Is there any way to tell if this balancer has slipped? I don't know of anything I could have done to cause it to slip. The boat was running great and lined up with the timing marks before this, and I only ran the boat with the flush kit never going over 1000 rpm. I know I have my timing light on #1, I checked it again after reading a recent post.

JimN
06-30-2008, 10:41 AM
"Some people say that, by ear, is the real way to set timing on an engine, but I am a visual guy and like to see the timing marks."

The people who say this are either too cheap to buy a timing light or want to impress others with their BS.

Get the #1 cylinder to TDC, make sure the rotor is pointed at the #1 plug wire and set it to 10BTDC. MAke sure you remembered that cylinders 1-2-3-4 are on one side and 5-6-7-8 are on the other side. Wiring it like a GM motor won't work. Mark the plug wires and distributor cap for #1. Also, make sure you know what direction the rotor turns.

"your harmonic balancer's outer ring has slipped on the inner hub, causing the timing mark to be off, on the balancer itself."

If it ran well before, there's no reason to think it slipped from painting.

Storm861triple
06-30-2008, 01:36 PM
"Some people say that, by ear, is the real way to set timing on an engine, but I am a visual guy and like to see the timing marks."

The people who say this are either too cheap to buy a timing light or want to impress others with their BS.
Really? Are you saying that the motor can run NO BETTER than it can with factory settings? I hope not, because that's just not true. I have a timing light in my Snap-On box, BTW, so I'm not cheap. At least not when it comes to tools.


"your harmonic balancer's outer ring has slipped on the inner hub, causing the timing mark to be off, on the balancer itself."

If it ran well before, there's no reason to think it slipped from painting.
I never said that it slipped from painting. I'm saying that it's possible that it has slipped over time (it is 24 years old). If he is doing the proceedure correctly, and using the proper "#1 cylinder", then the next thing to check is the balancer.

The boat was running great and lined up with the timing marks before this.
Certainly, nothing you did during your "aesthetic tune up" could have caused the balancer to slip. I didn't realize (or read througly) that you had checked the timing before the work. If the timing checked out O.K. before the work, it should check out O.K. after as well. I know you said you are sure that you were on the real #1 cylinder, but...

JimN
06-30-2008, 03:58 PM
"Are you saying that the motor can run NO BETTER than it can with factory settings? I hope not, because that's just not true"

Assuming for a minute that the company that made the motor did some testing before bringing the motor to market, How much better will it run because of someone who "sets it by ear"? Also remembering that they were trying to hit whatever emissions numbers from that time, while it may be possible to get a little better response due to more advance, it's not possible to hear the absolute onset of detonation while the boat is hauling azz down the lake. If it's stock, it'll only do so much but to address both this and the balancer slipping, he said it ran excellent before he stripped it down to paint it. I never said it happened from painting, I was saying that it wouldn't have happened just from that. If it did slip previously and someone timed it by ear, it's possible that this can cause the timing mark to be off but if it slips, won't it keep slipping?

Storm861triple
06-30-2008, 06:23 PM
Assuming for a minute that the company that made the motor did some testing before bringing the motor to market, How much better will it run because of someone who "sets it by ear"?
Depending on the criteria, possibly a lot. Few on this forum care much about emissions for one thing, so that changes the criteria. Also, Keep in mind that neither MC, PCM nor Idmar "made the motor". Ford did and there is no magic in the placement of that car motor, into a boat. In fact...
it's not possible to hear the absolute onset of detonation while the boat is hauling azz down the lake.
Detonation won't happen (at least not before the onset of power LOSS with advance)on a properly running 351w in a boat for two reasons;
1. Low compression
2. Cold operating temps.

In a car, it's entirely likely that that same engine would run into detonation before it reaches max power/torque...but most cars operate at 210* - 230*F. The boats don't run that hot; certainly mine doesn't; ~165 is the highest I ever see. So, compared to a car, in a boat, the heads are cooler, intake is cooler, carb is cooler, and "underhood temps" are cooler. All that combined w/the crappy low compression of the 351w adds up to a motor that will start to lose power w/advance before the onset of detonation. Again, I'm talking about the OP's engine here, not the newer Chevs, which feature higher compression ratios and fast(er) burn combustion chamber technology.

he said it ran excellent before he stripped it down to paint it....If it did slip previously and someone timed it by ear, it's possible that this can cause the timing mark to be off but if it slips, won't it keep slipping?
Good point if someone timed it by ear before; it could "run fine". The thing about this situation that is confusing me now is that the OP said in post #3 that the "The boat was running great and lined up with the timing marks before this"....but now it doesn't?? Doesn't make any sense at the moment.

Lining up timing marks and the engine dying, and then setting "by ear" and the marks are way off, is symptomatic of a balancer that has slipped, in my experience. Will it keep slipping? Yes (if it has already slipped). I've had balancers that have cut/machined groves clear through the timing chain cover as the outer hub slid "back" on the elastomer.

denverd1
06-30-2008, 06:42 PM
Well, this should be relatively easy to diagnose. What condition is the dampener rubber in?? cracked or wrinkled anywhere?

Is it also possible that the engine was timed to a different cylinder? You mentioned the cap and rotor were off by one cylinder. the cap and rotor were off so you moved them and happened to find the "correct timing" but it doesn't match up with dampener (crank position) because the firing order was started on a different cylinder? Basically, it is wrong in two places that cancel each other out. Cylinder 8 could show you the correct timing if my half-baked hypothesis is right.

flipper
06-30-2008, 06:47 PM
Depending on the criteria, possibly a lot. Few on this forum care much about emissions for one thing, so that changes the criteria. Also, Keep in mind that neither MC, PCM nor Idmar "made the motor". Ford did and there is no magic in the placement of that car motor, into a boat. In fact...

Detonation won't happen (at least not before the onset of power LOSS with advance)on a properly running 351w in a boat for two reasons;
1. Low compression
2. Cold operating temps.

In a car, it's entirely likely that that same engine would run into detonation before it reaches max power/torque...but most cars operate at 210* - 230*F. The boats don't run that hot; certainly mine doesn't; ~165 is the highest I ever see. So, compared to a car, in a boat, the heads are cooler, intake is cooler, carb is cooler, and "underhood temps" are cooler. All that combined w/the crappy low compression of the 351w adds up to a motor that will start to lose power w/advance before the onset of detonation. Again, I'm talking about the OP's engine here, not the newer Chevs, which feature higher compression ratios and fast(er) burn combustion chamber technology.


Good point if someone timed it by ear before; it could "run fine". The thing about this situation that is confusing me now is that the OP said in post #3 that the "The boat was running great and lined up with the timing marks before this"....but now it doesn't?? Doesn't make any sense at the moment.

Lining up timing marks and the engine dying, and then setting "by ear" and the marks are way off, is symptomatic of a balancer that has slipped, in my experience. Will it keep slipping? Yes (if it has already slipped). I've had balancers that have cut/machined groves clear through the timing chain cover as the outer hub slid "back" on the elastomer.

I beg to differ....I have had 4 out of 8 pistons with big holes in them to say otherwise. Not saying it wasn't my own fault, but the holes were there, and I didn't hear anything till the fatal bang.

Storm861triple
06-30-2008, 07:03 PM
With 4 holes, I think you had other root causes or issues. That is incredibly severe damage for no audible detonation.

Jesus_Freak
07-01-2008, 02:57 PM
...Detonation won't happen (at least not before the onset of power LOSS with advance)on a properly running 351w in a boat for two reasons;
1. Low compression
2. Cold operating temps.

Interesting....are you saying this is true across the full range of expected variations in cylinder/valve carbon content, fuel quality, spark plug style/heat rating, air temp, and engine WOT run time?

Muttley
07-01-2008, 03:25 PM
Having just done the same thing, I'm going to have to go with you having the timing light on the left front plug, rather than the right. (Chevy's are on the left). Here's the wiring & firing:

http://www.carmemories.com/cgi-bin/viewzoom.cgi?image=2055

Then, set it to 10BTDC.

...everyone else is soooo complicated!:(

Edited for dyslexia. :rolleyes:

Storm861triple
07-01-2008, 03:27 PM
Interesting....are you saying this is true across the full range of expected variations in cylinder/valve carbon content, fuel quality, spark plug style/heat rating, air temp, and engine WOT run time?Well for me and my boat (92, 240 hp engine) it is. I'm sure there are less than ideal conditions that would contribute to detonation for sure. I run 85 octane in mine though, and I set my timing as described in my first post. I never did hear detonation, even when the engine started losing power from over advance. And of course, I set my final timing at the "retarded" end of the power plateau. This adjustment was made about 6 years/500 hours ago.

-Tom

flipper
07-01-2008, 03:32 PM
Having just done the same thing, I'm going to have to go with you having the timing light on the right front plug, rather than the left. (Chevy's are on the right). Here's the wiring & firing:

http://www.carmemories.com/cgi-bin/viewzoom.cgi?image=2055

Then, set it to 10BTDC.

...everyone else is soooo complicated!:(

Other way around

Muttley
07-01-2008, 04:49 PM
Other way around


Uhhh... that's what I meant. :cool: