Hi All,

Following another thread where the OP was asking about replacing the rocker arms on #1 Cylinder, it was suggested he find TDC. I inquired as to exactly how that's done on an LT1/LT4, given I haven't found any timing marks on mine. Being "Old School," this is my first foray into motors with no timing marks. So... I did a little investigation and offer the following for your perusal:

Some of the posters said, "there's an arrow on the harmonic balancer." They gave no reference to where this arrow is located or what it's supposed to point to. Upon investigation, I found a knowledgeable poster who shared that the mythical arrow on the balancer is actually not on the balancer... it's on the hub! According to him it's only used one time, at the factory, to time the engine and hidden from view once the engine is placed into the car. According to this poster, with the hub visible, #1 Cylinder is at TDC with the timing mark pointing straight up.

I happen to have a brand new LT1 crank hub. Upon checking, I did indeed find a blue line marked upon a raised "arrow" of sorts. Here's a picture of it:



Investigating TDC further, I found a poster who said he used a "Squeeker" to find TDC. Never having heard of a TDC Squeeker, I did a Google search which led me to the following YouTube video... which is positively brilliant!


With the engine off, at TDC the cylinder goes from compression to suction (what would be the power stroke), which stops the "squeeker." Brilliant!

Further searches on YouTube revealed two other reasonably simple methods for finding TDC. One uses a Compression/Vacuum gauge combination and the other uses a "Piston-stop" method. I wouldn't use the piston-stop because I'd be afraid it would mar the piston but I present both videos for you here:

Compression/Vacuum Gauge Method

Piston-stop Method

I hope some of you find this informative. As for this Old Wrench, I miss my timing light!

 

See post #2 in this thread: http://forums.corvetteforum.com/c4-t...r-lt1-4-a.html

 

Unless I'm missing your intent, that seems to answer the question of finding TDC when the timing cover is off and the timing chain/gears are exposed. I was interested in finding TDC with nothing removed except, perhaps, one or more spark plugs.

 

On my '96 there is a triangle mark on the balancer that lines up with the raised mark on the hub. This is probably the "arrow" that is referenced by another poster.

Here is a photo with the triangle visible -

 

Using the piston stop method on an LT1 with an aftermarket cam you have to remove the piston stop after you hit it the first time and then reverse the rotation to hit the stop from the other direction or a valve will hit the piston stop and could do damage to something.

 

Thanks, SilverCE! Is there a mark on the block or timing cover that can be seen with the engine mounted in your car?

 

Nope.

 

Not that I have seen.

 

Why do you need to find TDC ?

Forget all that you ever knew about timing a small block.

The hub has no keyway cut into it; while it is supposed to be installed with some regard to TDC, in reality, it can be anywhere, and since the damper bolts to it, there is nothing on the damper that in any way relates to TDC.

The only way around this is to purchase an after market hub with a keyway machined into it.

 

Before digital engines and electronic tune-ups, TDC was the starting point for any good tune-up. From there we had to consider vacuum advance, centrifugal advance and total advance. (Just centrifugal and total advance for most hot rodders.)

However, even without the necessity of TDC for digital tune-ups, TDC is still helpful for such things as valve adjustments. With a proper timing mark for TDC, you can adjust half your valves and, 360° later, again on the TDC mark, you can adjust the rest of your valves.

For me, a professional wrench through the '70's, it's just hard to imagine engines without timing marks!