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Recently, I changed the timing chain on my L46 engine - it was a bit loose when I removed the old one, so I replaced it with a double link c I bought a new timing cover that is for a 69 L46 or 70 Camaro LT1 as the old tab was broken off and the chain. At the same time, I sent my balancer out to a well-respected repair depo in California to be rebuilt. You can see the new chain with the timing dots lined up before I closed it up and put on the new balancer. I also bought and installed a new timing chain cover whose fit was advertised as for a L46 or 70 Camaro LT-1. Here is the issue: When I used a piston stop to ascertain TDC, the balancer groove did not line up - in fact it was several inches off. So I assume either:
1. My TDC find was improperly done -- I will do this again to check.
2. The balancer outer ring was not put on correct.
Thanks for the replies. I did turn the assembly to the #6 so it would be easier to line up the dots (when the old timing chain was on) - so yes, it was set for #6 , my bad. However, even knowing that, shouldn't the balancer notch, when lined at true TDC be in line with the cover pointer? Assuming I did the check for TDC correct using the piston stop, I assume the only 2 things might be the timing cover ( which looks similar to my old one) or the balancer?
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Would still be top dead center, just on exhaust, not compression. The line should line up, depends on if you have the correct cover for your diameter balancer. If it is on there solid and the chain is on correctly and the dots lined up correctly. Remark your balancer with a paint pen and a scribe or buy a timing tape and stick in on there.....it'll be easier to get to 36º that way too
How did you use the piston stop tool. I've seen piston stop tools with different lengths.
Proper, is to rotate the engine until it contacts the piston stop, mark the balancer. Then counter rotate the engine until it contacts the piston stop again, then mark the balancer. Exactly In between the marks is true top dead center.
Thanks for the replies. I did turn the assembly to the #6 so it would be easier to line up the dots (when the old timing chain was on) - so yes, it was set for #6 , my bad. However, even knowing that, shouldn't the balancer notch, when lined at true TDC be in line with the cover pointer? Assuming I did the check for TDC correct using the piston stop, I assume the only 2 things might be the timing cover ( which looks similar to my old one) or the balancer?
Was your piston stop screwed into cyl #1 ?
When the piston stop is screwed into cyl #1 (driver side aka Left head, fully forward), and the #1 piston is at its TDC, the timing groove-mark on damper should align with zero on timing cover's timing tab. I cannot recall the exact specifics, but about 1969-1970 the dampers' location of timing groove was changed; the zero mark on tab changed concordantly. Many a clever fellow has been befuddled by a mismatch between damper & tab; many.
To confirm your piston stop method: with the stop in cylinder #1, gently crank the engine by hand until the piston touches the stop. Mark the balancer to a reference point. Rotate the engine by hand in the opposite direction until the piston touches the stop and make a second mark at the reference point. Rotate the engine so that the reference point is as close to the mid-point of the two marks as possible. This is TDC.
Post a few photos of the balancer face and the timing cover face.
Was your piston stop screwed into cyl #1 ?
When the piston stop is screwed into cyl #1 (driver side aka Left head, fully forward), and the #1 piston is at its TDC, the timing groove-mark on damper should align with zero on timing cover's timing tab. I cannot recall the exact specifics, but about 1969-1970 the dampers' location of timing groove was changed; the zero mark on tab changed concordantly. Many a clever fellow has been befuddled by a mismatch between damper & tab; many.
This is not correct. The other folks have told how to use a piston stop correctly.
A few pics of my timing pointer and balancer from the driver's side. I'll have another go at using a piston stop and getting TDC. At this point it is either the wrong timing chain cover or the balancer
was not correctly refurbished, is that fair to say? Interestingly enough, the balancer guy sent me the wrong (someone else's) balancer and I had to send the one I got back to the actual recipient.
Here is the link to where I got the timing chain cover: 1969-1970 All Makes All Models Parts | 3946870 | 1969-70 Camaro, Chevelle, Impala, Nova, Truck; Timing Chain Cover; Small Block; for 8" Balancer | Classic Industries
It lists 69-70 Corvette as a correct fitting.
A few pics of my timing pointer and balancer from the driver's side. I'll have another go at using a piston stop and getting TDC. At this point it is either the wrong timing chain cover or the balancer
was not correctly refurbished, is that fair to say? Interestingly enough, the balancer guy sent me the wrong (someone else's) balancer and I had to send the one I got back to the actual recipient.
Here is the link to where I got the timing chain cover: 1969-1970 All Makes All Models Parts | 3946870 | 1969-70 Camaro, Chevelle, Impala, Nova, Truck; Timing Chain Cover; Small Block; for 8" Balancer | Classic Industries
It lists 69-70 Corvette as a correct fitting.
When you did the TDC check you turned the engine in one direction and then the other and the center point of those two movements did not line up with zero on the tab?
There are however 3 different timing mark positions used by Chevy over the years. The 68 and earlier timing marks did line up with the crank keyway, and also the bolt hole in the balancer. But that was moved in 1969, roughly 10* counterclockwise. Both timing tabs and balancers changed. But not the keyway.
For 68 and earlier the keyway nd the TDC mark lines up below the #1 timing cover bolt above the balancer. For 69 the timing mark almost hits the 2nd bolt.
1969 and 1986 balancers and their TDC mark. The keyway did not move. The keyway is at 12 o'clock on both of these.
Your timing chain. Since the two dots touch that is the #6 firing position TDC. #1 is also at TDC, just not in the firing stroke. The green line is the keyway and it lines up below the 1st timing chain bolt as it should. The Approximate position of a '69+ TDC mark is shown in Red, aiming at the 2nd bolt.
Your timing tab appears to be correct for a '69+ TDC. It aims at the 2nd bolt.
However I see no TDC timing mark on your balancer at that location.
The correct way to use a piston stop is to bump the piston gently into the stop, somewhere around 30* Before TDC. Then turn the engine in reverse until it is around 30* after TDC, and it should bump the stop again. Mark the balancer in both locations where the TDC mark hits the balancer. Use masking tape and a sharpie. Measure the distance, cut it in half, and exactly halfway (in the middle) is your true TDC.
Factory tabs are frequently, but not always, off a couple degrees, 1-2* either direction. So if your are off, believe your measurements. Racers always correct the tabs by grinding to a point. For a correct car, you may just want to make a note in your notebook. EX: " True TDC is 2* BTDC, not TDC as marked." etc.
Last edited by leigh1322; Jul 1, 2025 at 12:35 AM.
Jim, What's not correct, sir?
What's the solution?
Leigh1322 has it described correctly.
The piston stop is infinitely adjustable...you can use it with any position of the piston EXCEPT TDC. Screw it in so it stops the piston somewhere BEFORE TDC...and then rotate the engine the opposite direction until it hits it again. It doesn't matter how far down the cylinder it is....just split the difference between the two positions for true TDC. You won't be able to get the piston to TDC if you have the piston stop in far enough.
I don't think a "rebuilt" damper can be trusted. Used but good original or a generic replacement, preferably SFI Certified. They do not need to cost that much.
The solution is to use to use the piston stop as described to find the stop points in both directions then draw a zero line exactly half way between those 2 stop points with a silver sharpie. Use that silver line to set your timing. What you do with that "rebuilt" damper after that is up to you.
Zero and 36 degrees is pretty handy. Every 90 degrees helps too but thats just overkill for some applications.
The piston stop is infinitely adjustable...you can use it with any position of the piston EXCEPT TDC. Screw it in so it stops the piston somewhere BEFORE TDC...and then rotate the engine the opposite direction until it hits it again. It doesn't matter how far down the cylinder it is....just split the difference between the two positions for true TDC. You won't be able to get the piston to TDC if you have the piston stop in far enough.
JIM
JIM:
I believe I understand what you found deficient in my reply; is that my reply was not as "complete" as you would prefer.
First, I realize I'm a very new newbie HERE. But, please do consider I've been at this work for quite some time; far longer than this site's existed.
And, with that time & experience, I do have (and have had) a good handle on use of a piston stop with chevy V8 and many others.
I fully realize the piston stop is used within a "range" and that's it's rather useless without that range.
My concern with the OP's piston stop usage was that perhaps Maybe he had installed it in #6 while he was trying to find TDC for #1. I inquired of that very matter.
In that same instance, I made an assumption that, if OP were using a piston stop, he also understood requirements for using it over a limited "range".
And (that otherwise) OP "KNEW how it worked".
JIM, I didn't try to write out full, complete and proper "work instructions" for the piston stop task; but I can.
What I'm finding HERE is that some long time members express how they do Not appreciate all those important details; while others demand them.
And, how a fellow who's just checked in catches hades from both directions.
Your timing tab appears to be identical to my '70, so it should be correct for your engine.
My balancer failed several years ago, with some investigation, I discovered that the ZZ4 engine balancer was the same, so installed that one.
Using the piston stop method, my tab and balancer mark are off about 1 degree.
For the engine guys
