brake booster rod length????
Thread Starter
Drifting
Joined: Oct 2003
Posts: 1,352
Likes: 18
From: Dallas Texas
brake booster rod length????
Does anyone know what the brake booster rod length should be on a 74 - measured from the front of the booster or how to set the required length accurately?
Thanks
Thanks
Burning Brakes
Joined: Feb 2002
Posts: 752
Likes: 31
From: Melbourne Australia
OK, others may have different approaches, however this is the way I do it....
You want zero preload on the master cylinder piston but minimum free travel.
Start by lengthening the rod a bit, then place the master cylnder on the booster by hand and see if the rod bottoms in the master cylinder hole before the master cylinder flange contacts the booster. Do not push on the master cylinder because you do not want to depress the piston at all.
Step 1)If it does, keep shortening the rod a little and testing until the master cylinder flange touches the booster just before the rod bottoms in the master cylinder piston. Now you're done.
Step 2)If it doesn't, lengthen the rod some more unitil the rod bottoms in the master cylinder piston before the cylinder flange contacts the booster. Then go to step 1).
Hope this helps..
Joe
You want zero preload on the master cylinder piston but minimum free travel.
Start by lengthening the rod a bit, then place the master cylnder on the booster by hand and see if the rod bottoms in the master cylinder hole before the master cylinder flange contacts the booster. Do not push on the master cylinder because you do not want to depress the piston at all.
Step 1)If it does, keep shortening the rod a little and testing until the master cylinder flange touches the booster just before the rod bottoms in the master cylinder piston. Now you're done.
Step 2)If it doesn't, lengthen the rod some more unitil the rod bottoms in the master cylinder piston before the cylinder flange contacts the booster. Then go to step 1).
Hope this helps..
Joe
Melting Slicks
Joined: May 2001
Posts: 2,812
Likes: 4
From: Gig Harbor Wa
May be a dumb question, but how do you shorten or lengthen the rod? My rod is not threaded and it looks like a piece of barstock with a rounded end and grooves in it.
Edit: Just realized the original post was for a 74, my booster is from an 82 with the shorter rod.
Edit: Just realized the original post was for a 74, my booster is from an 82 with the shorter rod.
Burning Brakes
Joined: Feb 2002
Posts: 752
Likes: 31
From: Melbourne Australia
Many of the rods are adjustable. I can't tell you which years.....The adjustable ones have a hex below the rounded end whch can be used to turn the rounded end out of the rod.
If it is not adjustable, you'll need to ensure there is no preload on the rod and almost no free travel.
If all the parts are from the same year i.e. 82 master cylinder, 82 rod and 82 booster then should be OK. If you are mix'n'matching, then you'll need to test everything carefully to ensure no preload and virtually no free travel on the rod. You can shorthen the rod if it is not adjustable, but might have to find a longer or adjustable rod if it is too short.
Hope this helps,
Joe
If it is not adjustable, you'll need to ensure there is no preload on the rod and almost no free travel.
If all the parts are from the same year i.e. 82 master cylinder, 82 rod and 82 booster then should be OK. If you are mix'n'matching, then you'll need to test everything carefully to ensure no preload and virtually no free travel on the rod. You can shorthen the rod if it is not adjustable, but might have to find a longer or adjustable rod if it is too short.
Hope this helps,
Joe
Melting Slicks
Joined: May 2001
Posts: 2,812
Likes: 4
From: Gig Harbor Wa
I am using a 2001 master cylinder an 82 booster and the pushrod was advertised as 78-82. Supposedly the 2001 and 82 masters have the same depth hole. I don't see any adjustability to the rod I have so if it doesn't work I guess I'll have to have one machined to the right length.
Thanks
Thanks
Burning Brakes
Joined: Feb 2002
Posts: 752
Likes: 31
From: Melbourne Australia
You can use my test above to see if the rod is too long.
If you think it is too too short, you might be able to put a little modelling clay or plasticene in the hole in the master cylinder, assemble the master onto the booster and then disaasmble and see what thickness the clay is to give you an esimate of how short the rod is.
Otherwise if you have vernier calipers or depth gauges you can probably measure everything you need to...
Best regards,
Joe
If you think it is too too short, you might be able to put a little modelling clay or plasticene in the hole in the master cylinder, assemble the master onto the booster and then disaasmble and see what thickness the clay is to give you an esimate of how short the rod is.
Otherwise if you have vernier calipers or depth gauges you can probably measure everything you need to...
Best regards,
Joe
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