65 Power Brake Master Cylinder

[Robert C.]

The NCRS manual says all 65's with PB have 3/16" lines. Many parts catalogs list 3/16" lines for Early 65 cars, and 1/4" lines for late 65 cars and 66 cars. I have a Jan 65 car #108226. Is it true all 65 model year cars should have 3/16" lines on the Power Brake master cylinder? If there was a change to 1/4" lines in the 65 model year, anyone know the break point? Thanks in advance!

[William C.]

Re: 65 Power Brake Master Cylinder

If it changed, it was well after January.

[Michael H.]

Re: 65 Power Brake Master Cylinder

Robert,

Bill is correct. The change to the 66 style master cyl probably didn't occur until late in the 65 production run. At the time of change, the same 3/16" brake lines were used through the end of 65 production but adapter fittings were used at the master cyl to connect the smal lines to the cyl.

If I remember correctly, there's no mention of this change in the AIM.

[Mike M.]

Re: 65 Power Brake Master Cylinder

vin9302, a 375 hp roadster with 20K miles on it, that i bought in 1970, has the 3/16" lines.. mike

[Michael H.]

Re: 65 Power Brake Master Cylinder

Let me clarify my confusing previous post. The small 3/16" brake lines on a 65 with power brakes were used all year to the end of 65 production. The only thing that changed during the 65 model year for that application was the master cylinder. Late 65's received 66 master cylinders.

The 66 model year used 1/4" brake lines.

[Wayne M.]

I always wondered; (12555 had small lines)

... and here I thought that the size of the LINES changed, as I had to buy a new Delco PB master cylinder in 1975 and had to use the reducers included with the new (tapped for large fitting) M.C.

[Michael H.]

Re: I always wondered; (12555 had small lines)

Wayne,

You probably missed getting the original 1st design master cyl by a few years as the part was discontinued and replaced in service with the "kit" that included the 65 2nd design/66 cyl and two fittings.

The 2nd design part with adapter fittings could be installed on 1st design/early 65's with no additional mod's and that's why there was never any mention of the change in the AIM. (that I'm aware of)

Older parts books list the "005" cyl as 65 1st design and the "321" cyl as 65 2nd design/66.

I don't know when the 2nd design cyl entered 65 production but I suspect it was probably at least May/June 65.

[Jeff S.]

Re: 65 Power Brake Master Cylinder

Do you have a reference source for this information?

[Michael H.]

Re: 65 Power Brake Master Cylinder

Older parts book clearly call out 1st and 2nd design for the 65 model year. Parts books printed after early/mid 70's would only show the 2nd design for all 65 and 66. A 69 printing of the parts book mentions that the fitting thread size for the first design, "005", is 3/8" and the thread size for the 2nd design "321" is 7/16".

[Michael H.]

Re: 65 Power Brake Master Cylinder *NM*

[Jeff S.]

Re: 65 Power Brake Master Cylinder

Thanks. I thought perhaps you might have found an engineering or assembly instruction change for using inverted flare adaptors in such a case. I guess it could have happened; just seems unlike the General to do so.

[Michael H.]

Re: 65 Power Brake Master Cylinder

Actually, it was likely the easiest way to get the new 321 on line. With fittings installed, there would have been absolutely no change in the assembly procedure at the plant and if only a part number was changed, there would have been no need to note the change on the AIM drawing, other than for possible inventory control. (I'm a little surprised it wasn't noted) Wish I knew exactly when this change occured. Somewhere, I have pic's of brand new 65's with the 2nd design cyl and adapter fittings.

[Page C.]

Re: 65 Power Brake Master Cylinder

This subject comes up every now and then like the 1967 big block hoods on small blocks cars. The Oct 1964 parts book only list the 005 PB master cylinder and my Oct 1968 parts book is has the same listing as Michael's showing both types. So somewhere between the two parts book the 2nd design appears. I remember buying the 2nd design and the Delco # 174-382 and you got the 1966 type with adapters. I have seen some pretty late cars (vins in the 23000 range) with NO adapters. Michael also mention the lack of any reference in the assembly manuals and I have not been able to find anything either. One thing to also remember is back in the late 1965-1970 era people where not getting these resleeved they replaced them just like they replaced the calipers.
Just some food for thought.
Page Campbell

[Todd H.]

Re: 65 Power Brake Master Cylinder

Is there any possibility that a 1966 car in the 5600 VIN range could have had the first style master cylinder installed at the factory? The car has 1/4" brake lines, but had adapters installed to match up the 3/16" outlet ports. The early style master was removed from the car in about 1982 and replaced with a 2nd stlye Delco replacement.