I'm looking at getting some brake line nuts from FMSI since I'm ordering brake line, and I'm trying to figure out what each of the three GM nuts go to (catalog page), i.e. front calipers, master cylinder, etc.:

#3041 - 3/16" - 11mm dia - 1.5 thread pitch
#3042 - 3/16" - 12mm dia - 1.0 thread pitch
#3043 - 3/16" - 13mm dia - 1.2 thread pitch

 

Ewww...that's a tough one. Unfortunately I don't have any spare master/prop lines around to measure them for you. I really need to make this one of the topics I know fairly well as it's asked a lot.

I think the 3041 goes to the master, none of them will be caliper fittings as those are either banjo fittings or bubble flares, #3028.

Sorry man.

Ed

 

Yes, you should. Thanks though. I'll try and figure it out.

 

Find any answers for the fitting?...I am trying to sort it out now too.

 

A little update here, as I've figured everything out.

LS1 master cylinder:
Front fitting (1/4" line, rear brakes): M12x1.0 (FMSI #3413).
Rear fitting (3/16" line, front brakes): Has a 1.5 thread pitch, but it's too big to be a 10mm and too small to be a 12mm. From looking at a FMSI parts page, it looks identical to a M11x1.5 tube nut (FMSI #3040, orange).

Other fittings:
M10x1.0 (FMSI #3028): Front/rear 3/16" hardline to caliper flex hoses (LS1 & 3rd gen).

Suppliers:
Most of the parts shops should be able to order the tube nuts, but in case you don't have any around, a good source of FMSI parts in the U.S. is Performance Tool & Supply (out of PA, 877-362-3221, eBay Store: autopartsmart). The prices are great, and I've dealt with the owner (I think?), Kevin, several times and have had no problems.

 

Thank you sir, I appreciate the good info!