Replacement Chevrolet master cylinder

[Grant Bowker]

Visually, the ebay master cylinder is consistent with the commonly found 1" size. I believe there was also a 1-1/8" cylinder made.
The NAPA kits 3 and 33 kits look similar in style, so without measurement I wouldn't assume the seller is wrong. The Raybestos kit for the 1" bore is MK3, consistent with the NAPA information in the ebay listing. The Raybestos kit for the 1-1/4" cylinder is MK33 so possibly the NAPA 33 might also be 1-1/4" but this is not confirmed.
I believe the casting number on the 1-1/4" cylinder (ebay listing gives 5450256) ends 61. On checking the 1-1/4" cylinder I have at home awaiting sleeving has 5450261 cast into it.
Personally, I would not be comfortable taking 1/8" all round off the wall of the cylinder without a lot of careful measuring and thinking. Even more so if removing a bit extra to allow for the sleeve.

[Guy Verstrepen]

mss is a look at this site www.chevsofthe40s.com/

[Harry Moon]

Don't use the new master cylinder #5454576E as it has insufficient volume and requires excessive travel and while i'm hesitant to say defective the hole in the side for the sensor lines up with the seals which then tears the seals.....

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[Guy Verstrepen]

https://www.generaaltjes.nl/Content/...6642-15715.jpg

turning - milling - boring work.
his name is fred Send metalwork.
info@fred-verschragen.nl
the man lives in the Netherlands

[Grant Bowker]

To try to bring together another thread on CMP Chev master cylinders http://www.mapleleafup.net/forums/sh...aster+cylinder

This is rapidly becoming one of the "the more you study, the more you realize you don't know" things.

I recently pulled out a couple of master cylinders (all 1-1/4") thinking I would send them for sleeving to be "ready when needed". It turned out I had 4 master cylinders sitting. 1 side mount and 3 base mount. The side mount shows part number 5300918 (crosses to Wagner FD-4194). All base mount seem similar in sizing but were not measured with any precision tooling. One has number 0260 cast in the side and it looks as if there were other digits that were supposed to be there. Possibly the whole number 5450260 as in the C15A parts book? The other two have 5450261 cast in. The end caps for the base mount cylinders were all hexagonal to take a wrench but the one for the side mount was round and ribbed. Although they are all 1-1/4 bore, the end caps from the base mount exchange with each other but there's no way the one from the side mount can be threaded into a base mount cylinder (too large). I've no idea why Delco would have done that. The Chevrolet Master Parts Catalog 1929-1948 makes reference to several 1-1/4" master cylinders with different part numbers for the assemblies (not matching any of the numbers above) but all seem to use casting number 5450259 as a starting point. it is not clear if this is a side mount or base mount part.

[Grant Bowker]

Today I installed kits into two of the master cylinders I had previously sent out for sleeving.

I had one kit from Jimmy Carter http://www.oldchevytrucks.com/cart/i...319?sdes=me319 and one Raybestos kit MK33 (from ebay for about 1/3 less than the Jimmy Carter kit that also had a sticker on the bag saying "33").
On starting the second cylinder, I noticed that the new piston didn't want to enter the bore easily. It turns out that the sleeve had been installed slightly off-axis to the cylinder bore so there was a tiny lip on one side of the bore. Nothing that would affect function, just enough to either force you to put the piston in from the pedal end of the cylinder (and risk turning the lip over) or require a tiny amount to be ground from half the circumference of the cylinder wall to permit putting the guts in from the outlet end. It only took a couple of minutes with a stone in the Dremel, more time to realize what had happened and set up than to do the grinding. With the lip out of the way each kit went into the cylinder easily, seems to be a proper fit.

To avoid the chance of damaging your new piston, I suggest that if you have had cylinders sleeved that you try fitting your old piston assembly (if in good enough shape that you are sure it won't score the sleeved cylinder) into the bore to check for unwanted lips at the ends of the sleeve. In my case the lip was at the outlet end of the cylinder.

[Hanno Spoelstra]

This is a 1.25” bore master cylinder with side mount. One would have to make a bracket like Barry did - scroll up.

“1936- 1946 Brake Master Cylinder Early Chevrolet and GMC Larger Trucks”
SKU ME164
https://oldchevytrucks.com/me164.html

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