[grivera]

My 64 LeMans has a 400/461 is a factory style replacement with a single timing groove in it. I measured the circumference with a ribbon type measuring tape and came up with 20.866" which makes the diameter 6.645". Butler sells timing tape for a 7 inch balancer and said that's what they use on the replacement balancers but didn't say what the circumference is for those balancers. Does anyone know if a "7 inch" balancer is actually 6.648", or is there a more accurate timing tape for my balancer?

[25stevem]

Just accurately measure around from the notch 2 1/8”’and mark a new notch with a blade out of the hack saw.
That will be 36 degrees.
Every 1/16” you go more or less then that is 1 degree.

When you do the math and take your measurement of 20.886” and divide by 360 you get .059”, I don’t know about you but that’s close enough to 1/16” for me !

[wolf]

Your timing tape marks will be off by almost 2 degrees at 35 total with that discrepancy in diameters. If you just test and tune to find what your engine likes for timing, then the absolute values aren't important.

That said, EVERY time I tried timing tape on my NHRA stocker, it flew off after a few runs. And I tried several additional things to keep them on at RPM (like epoxying the ends together).

Another option is to just use a high quality dial back timing light with the stock pointer and damper mark (assuming you've verified accuracy of those).

[Goatracer1]

When racing I tried the timing tape but much preferred the adjustable timing light. Found the tape hard to read in the sun where I could just see the timing light reading.

[Shiny]

Here's an image of an MSD part on Summit that shows the sensitivity to diameter differences and amount of error.

So yes, there are timing tapes made closer to your balancer than one made for 7" diameter but 6.645 isn't one of MSD's favorites. I just replaced mine on a 70 350 and it was 6.78 dia. Like you, I just measured to be sure.



I could have used the MSD "6.75" version but for the cost, I just chose to print my own, clear-coat it, and glue it on.

And yes, a dial-back timing light would avoid all this...

[grivera]

Thanks all - good to know the adhesive sucks. I have a Mac Tools dial back light (owned about 12 years) and it’s off a couple of degrees - I assumed all would be that way so didn’t consider another quality light. If I end up removing the balancer to mark it I may decide to just buy one that is already marked. Seems the path of least resistance is a better timing light.

[Stan Weiss]

Originally Posted by grivera

My 64 LeMans has a 400/461 is a factory style replacement with a single timing groove in it. I measured the circumference with a ribbon type measuring tape and came up with 20.866" which makes the diameter 6.645". Butler sells timing tape for a 7 inch balancer and said that's what they use on the replacement balancers but didn't say what the circumference is for those balancers. Does anyone know if a "7 inch" balancer is actually 6.648", or is there a more accurate timing tape for my balancer?

► 20.866 / pi = 6.641854

If you have not made a timing tape see how this works.

Stan

[ta man]

Originally Posted by 25stevem

Just accurately measure around from the notch 2 1/8”’and mark a new notch with a blade out of the hack saw.
That will be 36 degrees.
Every 1/16” you go more or less then that is 1 degree.

When you do the math and take your measurement of 20.886” and divide by 360 you get .059”, I don’t know about you but that’s close enough to 1/16” for me !

I have did something similar over the years. On the engine I put the timing mark on the balancer at 16 degrees and then I scribe a new mark at 4 degrees after TDC. This gives me an accurate 20 degree reference mark. So when setting the timing I use the 20 degree mark and add what I see on the timing tab.

[Apache Warrior]

I measured the circumference and then divided by 360.

Took that measurement and multiplied by 34 (where I wanted total timing).

Checked total timing with a dial-back timing light with vacuum advance disconnected and engine RPM @ 2,500 RPM and I was spot-on.

[grivera]

Originally Posted by Stan Weiss

► 20.866 / pi = 6.641854

If you have not made a timing tape see how this works.

Stan

I haven’t- thanks for creating. Is this meant to print to scale?

[Stan Weiss]

Originally Posted by grivera

I haven’t- thanks for creating. Is this meant to print to scale?

You are welcome.

That needs to be printed at 100% in landscape mode. You said the circumference was 20.866". Since this is 180 degrees or half of that so you can double check this after you print it that it is 10.433".

Stan