Diameter of Torsion Damper- 1999, 5.0L

[johno270583]

Hi All

Anyone know what the diameter of my Torsion Damper/ Harmonic Balancer would be?

The marks on it to set timing are fairly well rusted away, so would like to put timing tape on it to make sure I am setting timing exactly.

I have seen various posts on other websites of 7- 8", but most of these were for 4.3L.

Help would be appreciated, I have checked my 2 manuals and cant find any specs.


THanks

Andrew

[pascavone]

I have a 2001, 5.0 MCM, two barrel with Thunderbolt V. My question comes about timing. I copied this out of the tech manual and I don’t know what step (3) means (base timing mode). Can someone post a pick or give me some detailed instruction as to how to do it. I did do a search on timing and base timing mode, but all I found was to put it into the base timing not how to do it.

Thanks in advance,
Shep

Timing
Thunderbolt V Models
1. Connect timing light to number 1 spark plug wire.
2. Connect a shop tachometer to the engine.
IMPORTANT: Before starting the engine, connect a jumper wire from the ignition timing
lead to a good ground. This has to be done before the ignition key is turned ON
to lock the Ignition Module into Base Timing Mode.
3. Before starting the engine, connect jumper wire from timing lead to a good ground.
NOTE: The PUR/WHT timing lead is located towards the front of the engine near the fuel
line or near the distributor, as equipped for your model.
4. Start engine and run at 1300 rpm until it reaches normal operating temperature.
5. Disconnect throttle cable from the carburetor.
6. With engine at idle rpm, adjust the carburetor idle rpm screw to the specified engine idle
rpm.
7. With the engine still at idle rpm, check the ignition timing. If incorrect, rotate the
distributor until timing is correct. Torque clamping screw to 18 lb-ft (25 Nm).
8. Adjust the idle mixture screw. Inward is LEAN, outward is RICH.
9. Recheck ignition timing.
10. Stop engine. Remove timing light, jumper wire and shop tachometer.
IMPORTANT: Timing jumper wire has to be removed or the Ignition Module will stay
locked in the Base Timing Mode and it will not be able to advance the ignition timing
correctly when the engine rpm is increased.
11. Adjust and reinstall throttle cable. Open and close remote control throttle lever to make
sure that the carburetor’s throttle lever returns against the rpm adjusting screw every
time.
12. Restart the engine, increase rpm to 1300 then return to idle position slowly and shut the
engine off. Ensure that the carburetor throttle lever came back against the idle rpm
screw.
13. Shut engine off.




3. Before starting the engine, connect jumper wire from timing lead to a good ground.
NOTE: The PUR/WHT timing lead is located towards the front of the engine near the fuel
line or near the distributor, as equipped for your model.
1. Find the Purple/white wire near the carb.
2. Pull the plug out of the purple wire
3. Make a jumper wire that will plug into the purple/white wire with an alligator clip on the other end so you can hook it to a good ground.
4. Connect your jumper wire from that purple/ white wire to ground.

Move to step 4 in your instruction

[johno270583]

Sorry, I dont know what relevance the above has to my question. I can set the timing ok, however I am worried I am not setting it at 10* on the Harmonic balancer, as it is heavily rusted and the marks are nearly gone.

I want to know the diameter of the Harmonic balancer so I can either 1. Measure myself where 10* is and mark on the balancer, or 2. buy timing tape to attach to balancer to find 10*.

I have just found a new one online advertised for a GM 5.0L, which is 6 3/4", would this be correct? Going off my current faint timing marks, I would think this would be close, as each mark would be 2*, and they are (sorry, about to go metric on you all) about 3mm spaced (6 3/4"= 171mm/ 2 = 85.5mm Radius. C=2 pi R= 536.94mm / 360= 1.49mm per 1* x 2= 3mm per 2*)

Thanks in advance.

Andrew

[ss3964spd]

Wish I had an answer for you Andrew. In a heavy duty application like a boat engine my first guess would be that the balancer is 8" but I really don't know.

Regardless, you will still need to know if the single existing mark on the balancer references 0* (or TDC) or, as you were saying in your other thread, 10* BTDC. Otherwise you won't be able to correctly position the tape.

[johno270583]

Ok, I will have to try to measure it in the tiny space that I have to work in my bilge.

I had always thought that the single existing marks was to indicate the correct setting for timing. ie. 10* BTDC.

However in doing plenty more reading, I have read that there are other timing marks on the damper, rather than on the housing. On my damper, which is pretty rusty, I had not noticed these until the other day, as they are basically gone (at least I think they are timing marks!!)

As a test I put boat into base timing, loosened distributor clamp, and played around with the timing to listen how it affected motor, and definitely ran alot better as the timing was advanced slightly. So I have marked where I think 10* is, but would like to get an exact measurement for this so it is not just a guess. I have timing set at my new mark, and the motor runs a hell of a lot better, though havent done a water run yet.

So yes, I am an idiot, and I think I have been trying to run the boat timed at 0* timing, which will hopefully explain a few things, though still havent water tested to confirm, but will be trying to get in and measure damper to ensure I have correct timing, and double checking that the timing mark I have it set to is 10*.

Still, I dont think this will be the answer to my other post, unless it being potentially timed at 0 for so long has caused some problems internally.

[ss3964spd]

No chance of getting in there and cleaning the rust off the damnper?

Since the distributor is adjustible there has to be some markings somewhere, either on the pointer/tab that is bolted to the engine or around the damper itself.

For instance, on the one car I have that still uses a distributor, the damper has just 1 mark, which indicates TDC for cylinder 1. There is a flat metal tab position over the damper and it is welded onto the timing chain cover. The tab has a "0" mark, as well as 10 other marks on either side of the 0. So, if the mark on the balancer is lined up with the 0 mark on the tab, it's at 0 degrees BTDC - no advance or retard.

Dan

[johno270583]

I have tried to sand off the rust, but couldnt see any markings on the damper close to the 0 mark.

I didnt get a chance to measure the damper today, but the motor ran very well on the water, so I must be close to the mark.

I will measure next time and advise.

[johno270583]

I measured the Torsion damper on the weekend, diameter is 8", so was right on with my marking of 10* BTDC.

I hope this is helpful for someone else at some stage.

[ss3964spd]