Vacuum Relays
Thread Starter
Melting Slicks
Joined: Apr 2007
Posts: 3,189
Likes: 111
From: Tolland CT
Vacuum Relays
It appears I need all three vacuum relays. After 41 years, filters all missing, I am not surprised.
Two options are available, reproductions or OEM. The price for OEM is about double.
Question.... Are the OEMs NOS or just supplied through A/C Delco?... If they're not NOS, I'd think there's a chance they're not much better than the others, only a higher price tag.
Anybody had recent experience with either?
There was a thread on this recently but I haven't been able to find it.
Two options are available, reproductions or OEM. The price for OEM is about double.
Question.... Are the OEMs NOS or just supplied through A/C Delco?... If they're not NOS, I'd think there's a chance they're not much better than the others, only a higher price tag.
Anybody had recent experience with either?
There was a thread on this recently but I haven't been able to find it.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
You could also try removing the piston and wiping on a thin coat of rtv and reinstalling.
(I can share with you how to get the piston out from the bottom and back in with very little effort.)
(I can share with you how to get the piston out from the bottom and back in with very little effort.)
Thread Starter
Melting Slicks
Joined: Apr 2007
Posts: 3,189
Likes: 111
From: Tolland CT
I may tinker with the worst one if your process seems promising.
Please do share!
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Actually you don't have to modify the split pin, just make sure it doesn't remove too much OD on the shaft.
The shaft is .100 , maybe you can leave more diameter with the dremel.
You can grab the piston on its inner metal sleeve with needle nose pliers.
I've found if I hand pick 4-36 nuts I can find ones that will grab the .100 shaft,I put a dab of 2 part epoxy on to make sure the nut stays.
The o-rings I talked about were for the pistons I'm working on but a couple guys here have put o-rings inside the old piston to make it seal better,I'll see if I can find the thread for you.
The shaft is .100 , maybe you can leave more diameter with the dremel.
You can grab the piston on its inner metal sleeve with needle nose pliers.
I've found if I hand pick 4-36 nuts I can find ones that will grab the .100 shaft,I put a dab of 2 part epoxy on to make sure the nut stays.
The o-rings I talked about were for the pistons I'm working on but a couple guys here have put o-rings inside the old piston to make it seal better,I'll see if I can find the thread for you.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Here is a method, it was disassembled to see how to repair. Still working.
http://forums.corvetteforum.com/c3-g...of-vacuum.html
To do it from the bottom would be good.
http://forums.corvetteforum.com/c3-g...of-vacuum.html
To do it from the bottom would be good.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
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Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
One other thing. If the piston rubber is hard you will have to use the rtv method and I would recommend putting the piston back in the way it came out. I've found the bore can have up to .002 taper.
Thread Starter
Melting Slicks
Joined: Apr 2007
Posts: 3,189
Likes: 111
From: Tolland CT
I took one apart, not hard at all. It appears the rubber cup doesn't seal well to the cylinder. I may try the O ring approach. Where do I find O rings? NAPA? Is there a standard size I'd request? Never had to buy one before.
Le Mans Master
Joined: Aug 2006
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
The "O" rings are 5/16X3/16X1/16 I got them at Lowes.
Or PM me your address and I'll send you some.
Or PM me your address and I'll send you some.
Thread Starter
Melting Slicks
Joined: Apr 2007
Posts: 3,189
Likes: 111
From: Tolland CT
The closest size O ring I could find at Lowes was a #47, 11/32 x 7/32 x 1/16.
When I tried to use this O ring I found it flared the rubber a bit too much and kept popping out. I trimmed a few to get the diameter down slightly. It worked fairly well, much better than before, but doesn't hold vacuum for more than 15 seconds or so..
What would I expect from a new relay? Should it hold vacuum for a long period? I wonder if we expect some leakage, hence the filter on the end..
I may try the RTV approach next but am starting to lean to buying new ones.
When I tried to use this O ring I found it flared the rubber a bit too much and kept popping out. I trimmed a few to get the diameter down slightly. It worked fairly well, much better than before, but doesn't hold vacuum for more than 15 seconds or so..
What would I expect from a new relay? Should it hold vacuum for a long period? I wonder if we expect some leakage, hence the filter on the end..
I may try the RTV approach next but am starting to lean to buying new ones.