[indetrucks]

I understand the 68 timing mark tab is further out to accommodate the larger 68 balancer, but thought my smaller 67 balancer would still show the timing marks in the same general area.

Now when I check the timing, my 67 balancer timing marks are WAY off. Do I need a bigger 68 balancer or did I do something wrong when I removed/reinstalled my 67 balancer after installing the 68 timing cover?

GTO runs great, just wanted to check the timing and can't now because it's so far off the 68 timing tab.

Thanks!

[Kenth]

There is NO way to correct this issue without the correct 1967 (1966 is the same) timing cover.
You could however use a dialback timing light to set initial timing since the 0 on both covers is on the same spot.

[johnta1]

Here is one way:

Timing Mark Calculator

[Chief of the 60's]

Originally Posted by Kenth

There is NO way to correct this issue without the correct 1967 (1966 is the same) timing cover.
You could however use a dialback timing light to set initial timing since the 0 on both covers is on the same spot.

Wrong.

Rotate engine to obtain TDC and remark balancer.

[Johnny99]

I believe the marks are in the same spot on both balancers. The issue is probably that the balancer is so far away from the timing tab that you are viewing the tab/marks at an incorrect angle, so they appear to be off.

I had this problem with a 72 engine using a small 65 balancer. Change your POV and the timing will either appear advanced, retarded or correct.

If you don't want to change the balancer or want to set the timing while waiting for the new balancer to come in you can use a straight edge from the marks on the tab through the center line on the balancer and make marks on the timing cover closer to the balancer to get a better reading.

[242177P]

Originally Posted by Chief of the 60's

Wrong.

Rotate engine to obtain TDC and remark balancer.

You do realize there's a huge mismatch here, right?

I was able to "change" the timing on this mockup by 4-6 degrees simply by shifting around slightly.

[Chief of the 60's]

Originally Posted by 242177P

You do realize there's a huge mismatch here, right?

I was able to "change" the timing on this mockup by 4-6 degrees simply by shifting around slightly.

The mark on the timing cover is stationary and cannot be moved as it is casted into the timing cover.

The balancer however is a round piece of metal that really does not care where the mark goes. As long as TDC is marked on the balancer and matches the pointer on the timing cover, it will work as it should.

Sorry if you cannot improvise and only rely on matching parts or things the come in a box via mail order.

[indetrucks]

Thank you for the response guys!

I am super bummed, I came across the 68 cover and swore when reading about using it on my 67 that all things pointed to it being compatible in every way, except the timing mark being located a bit higher to accommodate for the larger diameter balancer.

So from what I just read, I can either:
A: use a 68 balancer
B: Set the timing at TDC and "re-mark" the smaller 67 balancer at 0.

A side observation, currently when I check the timing, the original timing marks on the 67 balancer are no where near the timing tab on the 68 T-cover. It's so far off that it makes me think I re-installed the balancer incorrectly.

Could I have installed that balancer on incorrectly? It should only go on one way (line the slot on the balancer up with the woodruff key on the crank?

Again, thank you all for your time.

[Chief of the 60's]

Marks are a guide not an etched in stone reference. A good tuner will always double check TDC with timing marks. What would people do if there were no marks on a new balancer?

[indetrucks]

Makes sense Chief, I will set the timing at TDC, then re-mark the balancer accordingly.

[Chief of the 60's]

Originally Posted by indetrucks

Makes sense Chief, I will set the timing at TDC, then re-mark the balancer accordingly.

15 minutes of your time is cheap. Buying more parts and taking apart your car is not. In the long run, if it bothers you that much, make changing it your winter project. Enjoy the car NOW

[indetrucks]

Originally Posted by Chief of the 60's

15 minutes of your time is cheap. Buying more parts and taking apart your car is not. In the long run, if it bothers you that much, make changing it your winter project. Enjoy the car NOW

Agree!!! Part of the reason I'm bummer, I just got done with installing that cover, new EVERYTHING up front and dreading having to remove it again. I will remark the balancer and enjoy the summer!

Thank you guys!

[Chief of the 60's]

I was just thinking about this the other day. If you have never done this before, here is a tip you must adhere to. Never back the crank up. If you have past true TDC you need to rotate again. Even if you only past it by a couple of degrees. Reason being is the slack in the timing chain. The chain must be taut to achieve proper timing mark location. Any backing up at all of the crank allows slack in the timing chain and throws TDC off.

Sometimes I'm not the best at explaining things as for the most part, doing something is just second nature to me.

[Johnny99]

Originally Posted by Chief of the 60's

I was just thinking about this the other day. If you have never done this before, here is a tip you must adhere to. Never back the crank up. If you have past true TDC you need to rotate again. Even if you only past it by a couple of degrees. Reason being is the slack in the timing chain. The chain must be taut to achieve proper timing mark location. Any backing up at all of the crank allows slack in the timing chain and throws TDC off.

Sometimes I'm not the best at explaining things as for the most part, doing something is just second nature to me.

Great tip. I never knew that. Just like tuning a guitar

[indetrucks]

Originally Posted by Chief of the 60's

I was just thinking about this the other day. If you have never done this before, here is a tip you must adhere to. Never back the crank up. If you have past true TDC you need to rotate again. Even if you only past it by a couple of degrees. Reason being is the slack in the timing chain. The chain must be taut to achieve proper timing mark location. Any backing up at all of the crank allows slack in the timing chain and throws TDC off.

Sometimes I'm not the best at explaining things as for the most part, doing something is just second nature to me.

Great tip indeed and understood! I was going to get to this over the weekend, so perfect timing!

[242177P]

Timing chain slack does what???

The hub is securely bolted to the crank. Unless there's been some catastrophic failure, valvetrain does not affect TDC.

[Sirrotica]

Chief, I don't want to get into a pissing match here, please consider this.

The cam and timing gears could be out of the block and it won't affect finding TDC on the crank because it relies on the pistons and rods and a solid stop to mark the crankshaft balancer or a dial indicator on top of the piston. Turning the crank forward and then backing up, making the marks. Then split the difference between the two marks giving you TDC. Because the engine is assembled you can't find TDC using a dial indicator, so a stop inserted through the spark plug hole would be the most efficient way to verify TDC on an assembled engine.



Now if you're timing the cam, (degreeing it) the timing chain does need to be tight in the clockwise turning direction, however the OP is trying to find TDC on the crank balancer, not degreeing a camshaft.

Another way of remedying this mismatch is to use this tab sold on Ebay:
https://www.ebay.com/itm/Pontiac-Tim...4AAOSwzrxUvrwA



But you would have to extend the tab further (weld or fab a way to move it further towards center) to use it with a small diameter balancer.

Another possibility is the late model (77-79) Pontiac 265,301, and 400 engines used a timing cover with a bolt on timing tab from the factory. I do remember that those engines used an abbreviated balancer, seems to me it was smaller diameter than the standard balancer. Finding a timing tab from one of these engines may be the answer to your dilemma.

Picture of late model timing tab:



Depending upon the OPs fab skills it would be possible to keep the small balancer and make, or adapt one of the bolt on timing tabs I've referenced here.

[Chief of the 60's]

Originally Posted by 242177P

Timing chain slack does what???

The hub is securely bolted to the crank. Unless there's been some catastrophic failure, valvetrain does not affect TDC.

Why don't you get a car first before crap comes out of your keyboard.

[Chief of the 60's]

Originally Posted by Sirrotica

Chief, I don't want to get into a pissing match here, please consider this.

The cam and timing gears could be out of the block and it won't affect finding TDC on the crank because it relies on the pistons and rods and a solid stop to mark the crankshaft balancer or a dial indicator on top of the piston. Turning the crank forward and then backing up, making the marks. Then split the difference between the two marks giving you TDC. Because the engine is assembled you can't find TDC using a dial indicator, so a stop inserted through the spark plug hole would be the most efficient way to verify TDC on an assembled engine.



Now if you're timing the cam, (degreeing it) the timing chain does need to be tight in the clockwise turning direction, however the OP is trying to find TDC on the crank balancer, not degreeing a camshaft.

Another way of remedying this mismatch is to use this tab sold on Ebay:
https://www.ebay.com/itm/Pontiac-Tim...4AAOSwzrxUvrwA



But you would have to extend the tab further (weld or fab a way to move it further towards center) to use it with a small diameter balancer.

Another possibility is the late model (77-79) Pontiac 265,301, and 400 engines used a timing cover with a bolt on timing tab from the factory. I do remember that those engines used an abbreviated balancer, seems to me it was smaller diameter than the standard balancer. Finding a timing tab from one of these engines may be the answer to your dilemma.

Picture of late model timing tab:



Depending upon the OPs fab skills it would be possible to keep the small balancer and make, or adapt one of the bolt on timing tabs I've referenced here.

I am sure you realize that there can be up to 4 degrees in crank rotation back and forth before the cam moves. More as the chain wears. There is also several degrees of crank rotation back and forth between crank, rod and piston. Hitting true TDC is obtained when all parts are tight. Any backing off at all will not give you true TDC and can be off 2 degrees or more when you mark the balancer. I was taught this by 2 big name racers. One had the best damn garage in town.

[Sirrotica]

The stop method is going to do away with the 3-4 degrees of dwell at TDC, and dividing the degrees in half is going to give you true TDC. I realize that with a dial indicator on the piston you can miss true TDC by a degree or two, but a positive stop method there is no dwell time around TDC.

FWIW, I'll stay with the stop method and dividing the degrees by 2 for my finding true TDC, you can do it any way you'd like.

This video is made by a performance shop, this is how I do it. They do discuss the 3-4 degrees dwell time around TDC and how this method eliminates that area of potential error. It requires turning the crank both ways to get the average to divide it by 2, it eliminates the dwell at TDC: https://www.bing.com/videos/search?q...0A54&FORM=VIRE

I'm done with the conversation, and not going to discuss it further. Many times there are more than one way to arrive at the same result, I'm fine with that.