2,550-2600 RPM max after changing plug wires

[bradp]

It is plausible as the prop control lever is about 12-15 inches from where you guys were working on the distributor caps.

Keep checking but do some in a safe manner.


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[Skates97]

Ok, put new plugs in (the old ones were very sad) and it runs much nicer/smoother. I put in the Tempest REM37BY plugs. The mag checks on run-up are cleaner with the right mag dropping about 50 rpm but the left still drops more, about 100 rpm. I did use the digital tach and at low rpm it is dead on, but at higher rpms it seems to read about 80-100rpm lower than the mechanical tach. So when I'm seeing 2,550 the digital is reading about 2,450-2,470 rpm. Either way I am not getting 2,700 rpm. And,  I'm starting to question my memory about getting 2,700 before. I know when we first started my CFI made a point of having me look for 2,700 on the tach when we went full power to take off, so I'm fairly certain we were getting it, but the mind and memory is a funny thing... 

Anyway, after coming back I pulled the sides and cowl off and took a look (now that you guys told me what I'm looking for). With the prop cable forward it does not go all the way to the stop. I think it is about a 1/4 inch shy. So, Monday when the A&P is there I'll put in a call to see what he will charge to adjust the prop cable.

Edited January 22, 2017 by Skates97

[Guest]

8 hours ago, Skates97 said:

Ok, put new plugs in (the old ones were very sad) and it runs much nicer/smoother. I put in the Tempest REM37BY plugs. The mag checks on run-up are cleaner with the right mag dropping about 50 rpm but the left still drops more, about 100 rpm. I did use the digital tach and at low rpm it is dead on, but at higher rpms it seems to read about 80-100rpm lower than the mechanical tach. So when I'm seeing 2,550 the digital is reading about 2,450-2,470 rpm. Either way I am not getting 2,700 rpm. And,  I'm starting to question my memory about getting 2,700 before. I know when we first started my CFI made a point of having me look for 2,700 on the tach when we went full power to take off, so I'm fairly certain we were getting it, but the mind and memory is a funny thing... 

Anyway, after coming back I pulled the sides and cowl off and took a look (now that you guys told me what I'm looking for). With the prop cable forward it does not go all the way to the stop. I think it is about a 1/4 inch shy. So, Monday when the A&P is there I'll put in a call to see what he will charge to adjust the prop cable.

In some cases the outer cable slips in its clamps, causing a loss of travel and lower RPM.  With the cowls open wiggle the outer cable to see if it's secure.

Clarence

 

[N6758N]

2 hours ago, M20Doc said:

In some cases the outer cable slips in its clamps, causing a loss of travel and lower RPM.  With the cowls open wiggle the outer cable to see if it's secure.

Clarence

 

+1, make sure he makes sure the cable housing is secure before adjusting the cable to hit the max RPM stop. Glad you found the solution!

[Skates97]

On 1/22/2017 at 3:58 AM, M20Doc said:

In some cases the outer cable slips in its clamps, causing a loss of travel and lower RPM.  With the cowls open wiggle the outer cable to see if it's secure.

Clarence

 

The outer cable wasn't loose, but you can see in the picture where it had wiggled its way up.

Here the cable is back down where it belongs, the set screw hits the stop now, and I'm getting the full 2,700rpm! Thanks for pointing me the right direction.

 

[carusoam]

Nice photos Richard!

Fabulous speed from noticing the issue, to identifying the problem, to getting the solution in place...

what is the missing half moon bite taken out of the support that the prop control cable is screwed into?

Go MS!

Best regards,

-a-

Edited January 30, 2017 by carusoam

[Skates97]

50 minutes ago, carusoam said:

Nice photos Richard!

Fabulous speed from noticing the issue, to identifying the problem, to getting the solution in place...

what is the missing half moon bite taken out of the support that the prop control cable is screwed into?

Go MS!

Best regards,

-a-

I don't know... It's an L shaped bracket and just has that little section that looks like it was filed out of it. I guess somewhere in the past 50 years someone did that to route a cable or something by there without it rubbing on the support. Maybe they had something at one point running between the cable and the support? Your guess is as good as mine. I'm finding out, as I'm sure many of you have, that with an old plane there are all kinds of "odd" things.

[Guest]

8 hours ago, Skates97 said:

The outer cable wasn't loose, but you can see in the picture where it had wiggled its way up.

Here the cable is back down where it belongs, the set screw hits the stop now, and I'm getting the full 2,700rpm! Thanks for pointing me the right direction.

 

I would replace those clamps with AN742 series steel clamps.  The ones you have are MS21919 series aluminum/rubber clamps. Likely the rubber dried out and lost its grip on the cable.  The second one is the same clamp with the rubber removed.  Normally the second smaller clamp is shimmed to the same height as the first larger one.

Clarence

[Skates97]

5 hours ago, M20Doc said:

I would replace those clamps with AN742 series steel clamps.  The ones you have are MS21919 series aluminum/rubber clamps. Likely the rubber dried out and lost its grip on the cable.  The second one is the same clamp with the rubber removed.  Normally the second smaller clamp is shimmed to the same height as the first larger one.

Clarence

Anyone know the actual clamp size? I could just stop by Aircraft Spruce on my way to the airport next time I go. If not I'm guessing it's stamped on the clamp, just trying to save myself going to the hangar and then back to Aircraft Spruce.

[Guest]

5 hours ago, Skates97 said:

Anyone know the actual clamp size? I could just stop by Aircraft Spruce on my way to the airport next time I go. If not I'm guessing it's stamped on the clamp, just trying to save myself going to the hangar and then back to Aircraft Spruce.

If I had to guess, I'd say AN742-5 and AN 742-6.

Clarence

[Skates97]

Thanks, it may be the cheapest trip I ever make to Aircraft Spruce...