1967 289 HI-PO Wants A lot of Timing - Vintage Mustang Forums
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post #1 of 30 (permalink) Unread 09-29-2018, 01:36 PM Thread Starter
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1967 289 HI-PO Wants A lot of Timing

Hopefully someone can help...

  • Complete rebuild on the motor about 3 years ago but not run until now.
  • 289 HP (Shelby version) pretty much stock everything except a mild roller cam and hydraulic lifters.
  • Verified TDC = 0* on the balancer.
  • Dwell is 33*.
  • RPM measured with a DMM though there's about a 200 rpm difference between the DMM and the tach (lower on the DMM) - the tach was just rebuilt and calibrated so not exactly sure which to trust but trusting the DMM for now.
  • Using the vacuum method to set initial and the initial setting on a timing light to measure, the motor seems to like 35* initial at idle (750 rpm) - wow, and 60* all in a little over 2500 rpm. I get just under 15psi of somewhat steady vacuum then backing off the timing just a scosh. Really doesn't want to idle anywhere near smooth with anything less.
  • Have not actually driven the car to check for detonation at the current setting - want to make sure it's safe to do so first.
  • Tuned idle mixture using the vacuum method - seems to like 3/4 turn in from initial 1-1/2 turns out.
  • Had a bad coil but that's been replaced.
  • Valves were set by someone else earlier this year so I can't personally verify.
  • The distributor was not rebuilt, just freshened up, but don't remember having this timing issue before restoration started.

Have I missed anything?

I've run out of ideas, all help welcome.

Thanks!
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post #2 of 30 (permalink) Unread 09-29-2018, 02:03 PM
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are you checking initial timing with the vacuum advance disconnected and plugged?

'67 Coupe, 347 w/ Holley Terminator EFI
AOD w/ B&M short Megashifter
EPAS w/ Bruno Box
Shelby Drop, 17" Replica's
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post #3 of 30 (permalink) Unread 09-29-2018, 02:12 PM
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Needs to be checked with vacuum disconnected. Dwell should be around 29-30. Max timing should be less than 40. 36 would be ideal. Id bet when you drive it under load you will get significant pinging.

Regards,
Patrick
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post #4 of 30 (permalink) Unread 09-29-2018, 02:14 PM
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Are you sure your balancer is marked correctly?

Regards,
Patrick
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post #5 of 30 (permalink) Unread 09-29-2018, 02:19 PM Thread Starter
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Quote:
Originally Posted by bacchus203 View Post
are you checking initial timing with the vacuum advance disconnected and plugged?
Yes - sort of. This is mechanical advance. Power brake booster hose is disconnected and plugged. Taking vacuum off booster check valve port.
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post #6 of 30 (permalink) Unread 09-29-2018, 02:21 PM Thread Starter
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Quote:
Originally Posted by patrickstapler View Post
Needs to be checked with vacuum disconnected. Dwell should be around 29-30. Max timing should be less than 40. 36 would be ideal. Id bet when you drive it under load you will get significant pinging.
Mechanical advance. Dwell spec. is 30-33, it's right at 33.
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post #7 of 30 (permalink) Unread 09-29-2018, 02:25 PM Thread Starter
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Quote:
Originally Posted by patrickstapler View Post
Are you sure your balancer is marked correctly?
As nears as I can tell it is. It's the original balancer and marks are stamped in. I manually set rotating assembly to TDC on #1 and verified 0deg. mark at cast-in pointer.
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post #8 of 30 (permalink) Unread 09-29-2018, 02:36 PM
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Quote:
Originally Posted by nmb67fb View Post
As nears as I can tell it is. It's the original balancer and marks are stamped in. I manually set rotating assembly to TDC on #1 and verified 0deg. mark at cast-in pointer.
the balancer has a rubber lining that dampens it a little. The rubber gets old and can allow the balancer marking to rotate and be off, so when it is pointed at 0 degrees, it it not actually 0 degrees.

It sounds like you did actually bring the #1 piston up to TDC and checked the balancer markings.

Does your distributor have a vacuum advance canister on it? If so, it needs to be disconnected when checking initial timing.

'67 Coupe, 347 w/ Holley Terminator EFI
AOD w/ B&M short Megashifter
EPAS w/ Bruno Box
Shelby Drop, 17" Replica's
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post #9 of 30 (permalink) Unread 09-29-2018, 03:44 PM Thread Starter
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Quote:
Originally Posted by bacchus203 View Post
the balancer has a rubber lining that dampens it a little. The rubber gets old and can allow the balancer marking to rotate and be off, so when it is pointed at 0 degrees, it it not actually 0 degrees.

It sounds like you did actually bring the #1 piston up to TDC and checked the balancer markings.

Does your distributor have a vacuum advance canister on it? If so, it needs to be disconnected when checking initial timing.
No canister, mechanical advance.
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post #10 of 30 (permalink) Unread 09-29-2018, 05:53 PM
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Cam intalled out of proper alignment with the crank shaft? Would that cause this or if it is retarded, would advancing the timing more sort of compensate for it?


65 2+2, 331, C4 presently apart for complete a restore
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Last edited by macstang; 09-29-2018 at 06:04 PM.
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post #11 of 30 (permalink) Unread 09-29-2018, 07:07 PM Thread Starter
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That's one of the potential causes running through my mind... not a fun fix if it is.
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post #12 of 30 (permalink) Unread 10-01-2018, 05:38 PM Thread Starter
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Any other thoughts? Distributor position maybe?

Thanks.
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post #13 of 30 (permalink) Unread 10-01-2018, 07:35 PM
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First step is to verify true TDC is where you think it is. Use a piston stop in the #1 spark plug hole and find true TDC. Only then can you verify the 0 timing mark on your damper actually lines up with the pointer. Make sure you don't crank the engine using the starter with the piston stop in place or you could put a hole in your piston.

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post #14 of 30 (permalink) Unread 08-10-2019, 03:48 PM Thread Starter
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Still have this issue...

Any thoughts on what the symptoms would be if the distributor were stabbed a tooth or 2 one way or the other?

Checked the dwell today and it was running at 34deg, adjusted points (dual point dist.) so that it's back to 33deg (gapped from 0.020 to 0.022 but the spec. is 0.020). Readjusted timing with a vacuum gauge and it wanted another 2deg of timing so initial is set at 32deg, yikes! It scares the crap out of me that all in timing is, well, outside the limits of my current toolset.

When out for a run and to be honest it felt like it was running better than it did the last time with no discernible ping, etc.

So, would really like some feedback from those who would know (in been-there-done-that) as to what symptoms I might see if the distributor was actually off a tooth or 2.

Thanks!
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post #15 of 30 (permalink) Unread 08-10-2019, 04:31 PM Thread Starter
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Upon further review... I guess being a tooth off isn't possible.
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