What size fittings on master cylinder?

[Fred 86 GN]

Picked up my new (reman.) master cylinder and vacuum booster to do the long awaited power master-to-vacuum brake conversion. I also have a line-lock solenoid I plan to put inbetween the front brake line (to the rear reservoir) and the master cylinder. Asked for a 6" length of brake line at the store and found the 1/4" diameter to be too small and the 5/16" diameter would not thread into the master cylinder ports. Are the brake lines and fittings on our TRs metric? If so, what size are they (8mm?) and where can I buy a finished piece of 3"-6" long metric brake line?

These things are never as simple as they should be!


Thanks,

 

[Fred 86 GN]

ttt

 

[tom h]

the stock OEM fittings on my 87's master cylinder are:

front 1/4" OD tube, normally uses 7/16"-24 nut.
rear 3/16" OD, normally uses 3/8"-24 nut.

I measured tubing OD by slipping an open end wrench of the same size over the tubing -- it was a near perfect fit.

I've never encountered a metric brake line on these cars. Metric brake line often also uses a "bubble flare" instead of an "inverted flare", the two styles don't mix.

 

[Fred 86 GN]

Thanks!

I knew the fittings were not standard. They are fine threads. Fellow at NAPA told me that was designed in by the factory to limit people fiddling with the brake lines.

Time for some special fittings from NAPA.

Thank you.

 

[tom h]

Fred,

those are the standard inverted flare threads ... I've never seen coarse thread used on Inv Flare.

 

[Fred 86 GN]

Ummm...

If those are standard, then why did the brake lines I tried at the counter in the local AutoZone not fit? Why did the NAPA guy tell me over the phone that they are specials? I spoke to a local GN guy and he said on his installation he needed some special fittings...

Somebody is right...maybe the parts at AutoZone were crap?

A trip to NAPA tomorrow will hopefully straighten this out for me.

It would be nice if they were standard...if that was the case then I would have been on my merry way.

I hope that you are correct and I find out in retrospect that the AutoZone brake lines were crap. That will lead to the simplest solution for me.

Thanks,

 

[tom h]

Fred,

regarding the various discrepancies ...

Beats me !

 

[Fred 86 GN]

8mm fitting.

Went to NAPA. Tried several fittings. Found the 8mm fitting threaded in properly.

So for the front wheel brake line, it is a 3/16" line with an 8mm fitting going to the master cylinder.

At least on my 86 GN powermaster unit and a standard vacuum brake master cylinder for a V8 Buick Regal, Olds Cutlass, Chevy Monte Carlo of the same year.

Tom h -- maybe the 87's are different?

Now to find an 8mm to 1/4" bushing/coupler...or I will cut the line from the combination valve and put the 1/4" fitting on, then re-flare.