Tach and Generator Seal Direction

How to keep the Cessna 170 flying and airworthy.

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interstellardust
Posts: 70
Joined: Sat Aug 28, 2010 11:36 pm

Tach and Generator Seal Direction

Post by interstellardust »

I have read through a number of other threads including Generator Leak but want to confirm which direction the seals should face since at the the tach seal seems to have been installed backwards when my engine was overhauled.

I have removed the tach bracket and generator and found the standard gasket had not been used. The gasket had been cut along the bottom of the tach braket and a seperate round gasket used under the 1101898 35 amp generator. I have not opened up the generator as I'm waiting for my A&P to arrive but the tach seal appears to be installed with the open side facing back toward the tach, not forward toward the engine. The flat closed side of the seal is flush with the front (engine side ) of the bracket.

Can you conform this is backwards?

1955 170B
SN:26917
1101898 Delco Remy Generator
Bill Garnett
1955 Cessna 170B N2974D
bill@interstellardust.com
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GAHorn
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Re: Tach and Generator Seal Direction

Post by GAHorn »

Yep..backwards. Remember you’re trying to keep the oil INSIDE the ENGINE.

(And as has been mentioned in several articles…NEVER cut that PN 652072 generator/tach-drive gasket …unless you want an oil leak.) There’s a reason Continental made that as one large gasket which serves two accessories (gen and tach). Install it fully-intact.

(The round gen gasket PN 649984 is for a different alternator installation on E165, E185, E225 and IO-360, and TSIO-360 engines.)

THIS one is PN 652072 for our C145/O300 engines (Do not alter or cut it):
PN 652072
PN 652072
9A4540E0-916F-43BC-91F3-CD7EAC92A0DF.jpeg (33.49 KiB) Viewed 1540 times
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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interstellardust
Posts: 70
Joined: Sat Aug 28, 2010 11:36 pm

Re: Tach and Generator Seal Direction

Post by interstellardust »

Well I got the old tach seal out. I made a special tool by grinding one side off an odd piece of hardware and set it on a 2x4 with a 1 1/8 in hole drilled in it. I made the tool catch the edge of the seal and after a few rotations it’s out. The odd part (other than someone cutting and installing the wrong generator gasket) is that the seal I removed is much thicker than the 632714 replacement. I wish I could post a picture but they are way to big. Comments?
Bill Garnett
1955 Cessna 170B N2974D
bill@interstellardust.com
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dstates
Posts: 473
Joined: Sun Jun 30, 2019 5:50 pm

Re: Tach and Generator Seal Direction

Post by dstates »

I also replaced my tach drive seal this last spring (along with generator seals and the shared gasket). The seal in my tach drive was also backwards. Below is a picture of the old and new seals installed.

Old Seal
snap_old.jpg
New Seal
snap_new.jpg
N1235D - 1951 170A - SN: 20118
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