Master Cylinder Will Not Fit

[1969_Mach1 333]

I tried installing a new master cylinder I bought from my local NAPA auto parts store for my 1969 Mach 1 and it won't fit between the power brake booster and the shock tower.  Did some research and its a Raybestos master cylinder.  The last master cylinder I puchased from NAPA was shaped slightly different and fit easily.  The description for the one I just purchased states its a newer lighter weight casting.  The car has factory power front disk/rear drum brakes.  What brand OEM type master cylinders will easily fit?

 

Thanks

[Brian Conway 264]

This the one I got from NAPA.  Brian

[3pedal 95]

I tried installing a new master cylinder I bought from my local NAPA auto parts store for my 1969 Mach 1 and it won't fit between the power brake booster and the shock tower.  Did some research and its a Raybestos master cylinder.  The last master cylinder I puchased from NAPA was shaped slightly different and fit easily.  The description for the one I just purchased states its a newer lighter weight casting.  The car has factory power front disk/rear drum brakes.  What brand OEM type master cylinders will easily fit?

 

Thanks

 

I used a Raybestos MC36251....1"...be sure it has a residual pressure valve in the front port... thats for the rear drums...

[jholmes217 65]

Our cars came with two different kinds of brake boosters. One is a Bendix, and the other is Midland. Are you sure you received the correct one? I replaced my master cylinder and booster earlier this summer. I had to loosen the booster in order to get the master cylinder off because it was just too tight in there. I also had to leave the new booster loose in order to put the new master cylinder in. I couldn't put them in as a unit. Fair warning though, those nuts that hold the booster in are hard to reach. I recommend taking the seat out so you can lay flat and get under there. Also, when you have the master cylinder off, make sure that it didn't leak brake fluid into the booster. If it did, the booster will need replaced or rebuilt also.

[1969_Mach1 333]

Brian Conway, thanks, I have that same part number for the master cylinder, M1929.  Same as I bought last time a few years ago.  This one is shaped slightly different than the last time I purchased that part number from Napa.  The ports for the brake lines on this one have a long casting boss protruding out the side of the master cylinder which is causing the problem.  I  might have to loosen the booster like jjholmes217 did so it will move a little to get the master cylinder on.

 

jholmes217, I've fought those brake booster nuts many times.  It's a pain, but I've got it down.  Without the master cylinder installed I can get the booster out in about 10 minutes.  So far, no back injuries.  FYI, if you remove the hood hinge spring on the drivers side (with the hood propped up) you can remove and install a Bendix booster without removing that shock tower brace that goes from the firewall to the shock tower.

[RPM 1,190]

FYI, if you remove the hood hinge spring on the drivers side (with the hood propped up) you can remove and install a Bendix booster without removing that shock tower brace that goes from the firewall to the shock tower.

Good to know info, thanks!

[Brian Conway 264]

So why not go back to NAPA and get the right part ?

[ray1970 88]

Things can get very tight..

[1969_Mach1 333]

So why not go back to NAPA and get the right part ?

It's the correct part.  Apparently it's had a design change since the last time I purchased the same part number or Napa got this one from a different vendor.  The previous master cylinder with the same part number was shaped differently and fit without any issues.  I might try one more time at NAPA.  Maybe the same part comes from several different vendors and I was unlucky this time.

 

My last one from NAPA looked just like this Scott Drake one from Summit Racing.  There are no protruding casting boss' where the lines attach to it.   But the Scott Drake master cylinder is expensive. https://www.summitracing.com/parts/sdk-c7zz21404wdb 

[Brian Conway 264]

A friend just got a 69 428 CJ Torino and the forward brake line fitting is on the front and faces downward rather than toward the fender apron.  Maybe you just got one meant for another application ?

[RPM 1,190]

How much is the m/c off? Can it be clearanced just a tad to fit?

[1969_Mach1 333]

It's close. I might be able to file or gring off the corners a little that are causing the problem. Basically, chamfer the problem corners. I don't want to spend $100 for the Scott Drake master cylinder. If NAPA doesn't have a different shaped master cylinder I will start chamfering the problem corners. I am at the point when you don't care if it gets ruined trying to make it work. I'm sure many of us have been there.

 

I should have saved the one I removed and just rebuilt it. It slipped on and off easily.

 

Not my thumbnails.

[ray1970 88]

I had to remove the export brace and jack the car from just behind the tower and it flexed just enuf to get it in.

May not work on more solid cars......

[3pedal 95]

Things can get very tight..

 

Those brake lines look dangerous...rust is not your friend

[Max Power 74]

This is common with rebuilt stuff from anywhere, much less NAPA. My last master had different size fitting for the brake lines and I had to use adapters. I will not do that again, I will spend the money for the right part.

 

The part that seems to vary the most is PS pumps. No telling where the low pressure feed nipple will be pointing. Straight back? Up? Or like me, right at the oil pressure sending unit, changing my belt size requirements and giving me a 1/4" amount of adjustment. This is why guys with really old cars tend to have their properly fitted components rebuilt rather than trading them in for another rebuilt that may not match 100%.

[ray1970 88]

My lines are very rusty..Have new ones in stock but have been whating till the next time i pull the motor to put them on.

Problem is the motor just keeps running.

Not much room down there to work on rusty lines.

[JeffTepper 4]

I've had this issue twice and found that there are a couple of possible causes:

 

First, over time, part consolidation by manufacturers result in a "similar" part becoming the only choice at the parts counter even if it is not an exact fit physically:

 

Second, the Midland and Bendix boosters I have seen are different depths so what might fit a Midland will likely interfere with the shock tower on a Bendix;

 

Several years ago, I learned that due to parts consolidation as described above, there was no other choice available for this application in the standard distribution channels.  I ended up taking the old non rebuild-able Master Cylinder with part number clearly visible to Power Brake Exchange and they found the correct length rebuild-able core with the same part number in their discard pile.  An hour later I had a rebuilt ,master that actually fit the Bendix booster without issue (this was a '68 big block convertible);

 

A month ago, I purchased a brand new Raybestos Master Cylinder for a '69 Mach1 (part # 36251 ) to replace a leaking master.  This time the old leaking master could not be removed from the Bendix booster due to interference with the shock tower.  I ended up crawling up under the dash to loosen up the booster enough to slide it over to allow the old master to come off the mounting studs.  The new master  was then installed on the Bendix booster and everything was buttoned back up.  I suppose that when the Bendix booster fails, I could try and source a Midland booster for the added room it allows.

 

In any event, another PITA solution in the name of "efficiency".

[RPM 1,190]

Thanks Jeff, and welcome to the forum. Most first posts are asking for help.

[1969_Mach1 333]

Yes, thanks for the info Jeff.  Are you saying the Midland booster is shorter than the Bendix booster?  I know getting the MC over the studs is usually the issue.  But does the spacer between the booster and MC on Midland boosters cause any clearance problems?  Midland boosters are easy to find.  West Coast Classic Cougars sells Midland boosters that are locally rebuilt.  Probably rebuilt by Brake Booster Exchange in Oregon since West Coast Classic Cougars is in Oregon.  I don't know what happens to the core charge if you don't have a Midland booster for a core. 

[Brian Conway 264]

     Jeff brings up a good point.  The retailers in the name of efficiency seem to be going the generic route as in one size fits all   When i got the, M1929, MC from NAPA I think it was a $5.00 core charge.  I just kept my original and compared the two before leaving the store.  I got my replacement Bendix 6954 booster replacement on line, no core charge, and still have the original FORD Midland service replacement.  They live together in the garage.  They don't eat much and don't fight.  

     Mach 1;  I did not notice any size difference, front to back, between the two boosters.  Maybe 1/4 " clear after install at the shock tower and MC for both models.  Did not loosen the booster but did install the MC with an approach that was at an angle.  Tight but went together just fine.  I suggest you try to get a correct MC.  You never know how many times you may have to re-visit this area.  Brian

[1969_Mach1 333]

I got the MC to fit okay.  Since I finally got a new front seal for my original brake booster I decided to remove the Scott Drake Bendix "copy" brake booster and reinstall the original and see what happens.  Well ..... even though the Scott Drake looks almost identical to the original in shape and dimensions, something is a little different.  I can easily install and remove the master cylinder with the original booster back on the car.  I thought of trimming the two studs on the Scott Drake booster but then I wouldn't be able to return it.  I purchased the Scott Drake booster because I didn't think I would be able to purchase a new front seal for the original booster.

 

I already mentioned the master cylinder issue to Summit Racing, they sent me a prepaid return label to return the Scott Drake booster.

 

Thanks for everyone's help.