Guys,

I was going to try to find out where my TDC is so I can determine how much my timing mark is off by.

I bought a screw in TDC locator from Jegs. Anyone have any advice on using this critter.

And I understand not to turn the engine over with the starter etc. :)

I plan on installing the TDC locator. Turning the engine over till it makes contact. Marking the balancer with respect to the 0* mark on the tab. Then reverse rotating it back around 360* till again it makes contact with the TDC locator. Marking the balancer again. The 1/2 way mark between the two marks on the balancer SHOULD be the manufactured line on the balancer.

If its not then I will move the balancer man line to 0* and see where the middle point corresponds to the timing Tab mark. I suspect its going to be at about 6-8* off.

Just for those that are wondering why I am going through all this. Its because my car, compared to corky's like a crap load of timing. ~42* total. While Corky runs about 30* total.

42* total advance is nearly impossible, as your getting VERY close to mechanical cross firing. The posts on the distributer are only located 45* apart.

This tells me that my balancer is marked wrong. The keyway in the crank is off a little, the timing tab idicator is wrong, or all the above are off a little to result in a lot.

I will get to the bottom of it. If it comes out on zero and everything is right, then I am truely stumped. But moreso in the logic department.

Anyone ever use one of these screwin piston stops? Any pointers?

I did not think the spark plug hole was on enough of an angle to allow the stop to interfere with the piston. But them again I never really looked at it real close along those lines.

The piston TDC locator is made up of two pieces, an outter (the size of a spark plug) and an inner that is allowed to be moved inward and outward to extend deeper into the cylinder.

Here is a picture:



Let me know what you think. :cheers:

 

I have that exact one too and also have no clue how to use it. :D

 

How I descibed above is how to find true TDC. Without degreeing the cam again. We degreed the cam, but did not put the balancer on to see how the manufactured line on the balancer lined up with the zero mark on the timing tab. So that is how you do it as I explained above.

I just thought someone might have some experience using on of these TDC locators, as I did not think the SP hole was angled enough downward toward the piston so the if my assumptions before are correct the ID screw would just pass over the piston with no interference to the piston and hence no locating a definative point to measure from. But apparely there is enough angle to get interference

 

Hey Jesse I have clicked on the dyno sheet link before. Now I want to click on the bouncey boobies and I cant. What are you doing to me here? :skep:

 

Hey Jesse I've never seen that kind of tool. I use to use one on my motorcycles. It was kinda similar you screwed it in #1 and it had like a slide that once the slide stopped coming up you'd turn a set screw and lock it(TDC).
We never turned the engine backwards because of the chain slack which I believe is always more on the back side.

Just my $.02

 

Not sure what your Q is. Your description on how to use it is accurate.

Install in SP #1. Rotate by hand until it stops. Mark. Reverse rotation until it stops. Mark. 1/2 way in between is TDC. (Zero timing mark.)


The more you screw the center piece in, the more distance between the 2 marks. Still accurate (depending on your chain slack).

 

BTW I made one out of a bolt. Just found a bolt w/ the right dia, and cut the threads into it. I removed the first 1.5" of the threads to help the in and out.


Once you make the first mark, don't move/readjust the SP stop tool till you make the second mark.

 

here is what I would do.

remove all sparkplugs (makes it east to turn by hand.)
place a dowel in the #1 spark plug hole
turn over the engine by hand until the dowel reaches its highest point
install the tdc tool with the slug backed all the way out
screw in the slug until it stops
turn the engine away from TDC and screw in the slug a couple of threads
finish the procedure you described above.

 

Thanks guys. Yes I should have added that I do not plan to adjust the stop after the first mark.

The tool I figured would be easy enough to make. But I figured while I was ordering stuff (5 point harness) for another 10 bucks I might as well same myself the time, and just buy one. :)

I will report back what I find. Wanna take guesses how far off it is. LOL.

It really doesn't matter what I find. As I have on the dyno seen the best timing/[performance is exactly where I have it set. I guess its just for piece of mind. Also I don't like telling people I have 40*+ timing on the car either. They look at me like I have 3 heads. As I would them also.

Thanks all for the added support. At least now I know it in theory should work and explain the "Mystery of the super advanced timing" :D :cheers: :thumbs:

 

What "chain slack"? The key chain??? The stop stops the piston. Da piston connected to da con rod; Da con rod connected to da crank; Da crank connected to da damper. Da damper has da marks. HEY! This could be a song. We don't need no stinkin' chains! Not in THIS opperation.

RACE ON!!!

 

Sounds like you got it figured out, but I always used one of the big crank sockets that slip over the snout and lock on the key way. THen you can use a long 1/2" drive breaker bar or rachet to rotate the motor, being very careful not to hit the piston on the bolt too hard. Splitting the difference in the degree wheel will give you TDC, like you said.

 

That is a great tool for turning the crank, with the damper off. Since he is checking the accuracy for his TIMING marks, it may be difficult to use that tool with the damper in place.

RACE ON!!!

 

What you wrote is the right way to use the tool, although I too have made my own. I do have one problem with what you wrote though-

"42* total advance is nearly impossible, as your getting VERY close to mechanical cross firing. The posts on the distributer are only located 45* apart."

When you are 42 degrees advanced, it doesnt mean that the rotor fires 42 degrees before the terminal for that wire, it means the rotor fires 42 degrees before the cylinder reaches TDC. The rotor will line up with the corresponding cylinder being fired no matter what the timing. There is some variance though, and Nascar teams as well as others do index the rotor to the terminals in the cap. When you adjust the timing you are turning the distributor body, which in turn moves not only the cap/terminals, but the points (old style) or pickup (electronic) in unison with the cap. Hence- no change in rotor to cap timing just by turnng the distributor body. So 42 degrees advanced isnt any closer to "mechanical crossfire" than any other time setting. Did I explain that alright? it seems kind lengthy now that I read it back.


[Modified by SBNova, 10:33 PM 8/15/2003]

 

Hey Ski-Man:

I've used one of these for years. It works GREAT on a stock L98, but won't work with my AFR heads and JE 11:1 dish pistons. I can screw it all the way in, and it still won't touch the piston! Don't bend the h*ll out of it like I tried, it still won't touch the piston...

When I degreed my new ZZ409 cam this past fall, I ended up sticking a welding rod all the way into the chamber so it would stop the piston near the edge, next to the cylinder wall. Very tricky, but with some practice, it was very reproducable.

Of course, the best way is to pull a head. But with the heads on, whatever piston stop method you use, you will still need to afix a degree wheel to the crank to determine TDC between the two measurements.

Good luck! -Bill

 

You're on the money on how to use it...install, rotate, mark, reverse rotate, mark, measure, divide by 2, ZERO mark. A degree wheel is real handy when doing this and also I like to install a Mr Gasket timing tape to the balancer that has a full 360* graduation. Once you find zero put the tape on with zero corresponding to your verified zero mark. Then you can check timing, advance and total timing with your timing light.

With all the "pounders" you've built, kinda hard to believe you've never used one before...

Sounds like fun! Good luck! :seeya

 

If this piston stop thingy will work in the plug hole, wouldn't it be easier to screw a dial gauge in there to find TDC.

This is how I used to do it on my Yamaha 2 strokes, and it was very accurate.

BTW, I still think your timing light is goosed. :D

 

Thanks guys,

And Yeah your right with the timing and cross firing, but not entirely I believe. Follow me here. I'm still in a safe range and still closer to the correct post for this reason. When we set our base timing we unplug the ESC (electronic spark control) when we do that we only get 6* advance, the cap is turned to align the rotor to cap to fire 6* before the piston reaches 6* before TDC. Now unlike older cars, we plug back in the ESC and we are at 20*+ at idle, the main spark table adds the difference between desired spark at idle and the base, in this case its around 14*, assuming 20* is the desired idle speed and LV8.

Now at WOT the ESC adds even more timing. For a total of in my case 32*. But because I have my base set at 12*...I'm really at:

base in chip 6* + 6* more at base (lying to computer) + 26* + 6* (Power Enrichment) = 42* Total Advancement is exactly what I'm running if everything lines up with the zero mark! But I know its going to be off.

This is a good example of, give the motor what it wants and not what you think it needs. In other words many people would have never taken the timing up that high to find the sweet spot. My car 2* more or 2* less looses about 40HP and 50 ft-lbs of torque on a dyno in either direction!

Ok back to the point at hand, cross firing. Now while I agree that my base timing is only advanced 12* forward or BTDC, when the ESC kicks in and fires the spark an additional 30* advanced the potential for cross firing is there.

Clear as mud right.......This is really a moot point since I think the base timing is off. If its off by 10* ten my base is really only at 2* advanced and my total adance using the above proven to be correct way to determine total spark is only 32* total. And a more realistic value, but regardless of what I dind even if the true total timing is 42* total its staying there.

This entire exercise is to just for my own personal piece of mind and to answer a question that has been buggin me since I found the total timing it needed. Heading out to the dealership to do the necessary work on it....

Need to:

Need to pull the valave covers, for us 89+ guys you know the treat that is with the AC unit.

Set the RRs for the first time since the building of the engine.

Perform the Piston stop exercise to bet my true timing

and maybe take down out the D44 for inspection....that might have to wait till tomorrow dependind on how I feel after the before mentioned.

:cheers: :cheers: :cheers:

Talk to you all later. :cheers: