Timing 101, timing lights

[Yancy]

Warning, Newbie questions ahead:

I'm interested in going to DUI mostly for the reliabilty, although improved performance would be nice too. Anyway, I was reading through the DandCextreme install for the DUI and I follow it all the way to "just set the timing and your off".

The scout is new to me and i'm sure needs the timing adjusted anyway, but that is something i haven't done before and feel a little intimidated. Sure i could take it to a shop, but I would like to do it myself to get the experience.

Any suggestions on which timing light to buy? do i need a digital or advance light? I have seen some digitals with built in tach for ~$100.

Will the service manual i ordered cover this at all?

I think understand the theory of adjusting the timing: goal is to get the spark timed to ignite the fuel just before the piston reaches TDC.
But I'm fuzzy on what the timing light itself does... The timing gun shines the light when the piston is at TDC? And when the light shines, I'm looking for what/how do i know when to adjust?

(I've ordered a service manual. It's 'in the mail'. I tried a search and ready many posts on timing but most were concerned with the finer points of advance,retard,etc. And googled timing. learning...)

Thanks in advance,
Yancy
77 SSII 345 t19

[ERIC KNUTSEN]

I’m no expert but

The timing light shots a high power flash of light at the same time your spark plug lead shot the volt to your plug.
1 cleans the harmonic balancer that is bolted between your block and lower fan pulley to remove any dirt/oil also clean the timing mark on the timing cover.

2 get some white paint or even better liquid paper and mark the grove on the harmonic balancer also the groves on the timing marks. This will make the for easier viewing

3 with the motor not running connect the timing gun using the number 8 cylinder and loosen the distributor clam down bolt.

4 start the motor point the timing gun at the timing marks to see where the timing is it in correct turn the distributor till you has the line on the harmonic balancer lined up with the correct timing mark

5 turn off motor tighten the clam bolt and test drive.

I have my timing set at 15 deg advanced most people would find around 8 deg adv better some have to run 0 deg adv. This has to do with a number of things including hight above sea level compression ratio and the quality of the fuel. On the test drive you should make sure you cant hear a nocking or pinning from the motor under load i.e. pedal flat at low RPM”s if this happens follow steps 1 to5 with a less advance.

On a side not keep all leads and hands clear from the fan blade during the timing as you are working real close to it.

Eric

[WilliamEHardy]

Also, just to add a point - time the engine at correct idle speed to prevent the mechanical advance from giving you an incorrect setting, as well as disconnecting & plugging the vacuum advance line to the dizzy (for the same reason).

[ERIC KNUTSEN]

Originally Posted by WilliamEHardy

Also, just to add a point - time the engine at correct idle speed to prevent the mechanical advance from giving you an incorrect setting, as well as disconnecting & plugging the vacuum advance line to the dizzy (for the same reason).

good point
forgot that.

eric

[WilliamEHardy]

You probably do it automatically, without giving it a second thought - it's amazing the things like that we just "do"..............

[Jim Grammer]

Originally Posted by Yancy

Any suggestions on which timing light to buy? do i need a digital or advance light? I have seen some digitals with built in tach for ~$100.

That would be handy for an electronic ignition where the dwell function of a separate meter would be wasted. OTOH pretty much any timing light will do what you want. Over the years I have 'graduated' to a Craftsman dial-back light that cost me about $60 on sale. It's a solid unit, I use the dial back feature, and I especially like the removable pigtail.

I think understand the theory of adjusting the timing: goal is to get the spark timed to ignite the fuel just before the piston reaches TDC.
But I'm fuzzy on what the timing light itself does... The timing gun shines the light when the piston is at TDC? And when the light shines, I'm looking for what/how do i know when to adjust?

The timing light is a stroboscope that is synchronized with the spark on the cylinder to be timed(#8 on an IH SV-8). The strobe effect 'freezes' the TDC indicating marl(a machined groove) on the crankshaft balancer. The timing reference marks on an SV are cast into a scale boss that protrudes from the timing cover, and are raised numerals/hash marks. You are comparing the strobe'd 'stationary' position of the balancer timing mark with the scale on the timing cover. The compared position tells you where spark is occurring relative to TDC. You partially loosen the distributor hold down bolt and rotate the distributor to alter the timing as needed.

Fair warning - if you are working on a Scout II with the hood installed, there is a pretty small 'sweet spot' to view the timing marks. You will find that some creative positioning of both the timing light and your eyeballs is needed

[Yancy]

Originally Posted by Jim Grammer

The timing light is a stroboscope that is synchronized with the spark on the cylinder to be timed(#8 on an IH SV-8). The strobe effect 'freezes' the TDC indicating marl(a machined groove) on the crankshaft balancer. The timing reference marks on an SV are cast into a scale boss that protrudes from the timing cover, and are raised numerals/hash marks. You are comparing the strobe'd 'stationary' position of the balancer timing mark with the scale on the timing cover. The compared position tells you where spark is occurring relative to TDC. You partially loosen the distributor hold down bolt and rotate the distributor to alter the timing as needed.

Thanks Jim, that was exactly the info i was looking for.

Also i found this file useful...
http://www.harborfreight.com/manuals/3000-3999/3343.pdf
manual for a timing light.


-Yancy