blue6t7

Wondering what is the correct master cylinder for a non power 74. I see them for 73- early 74, 67-76, 74 late - 76., some with bleed screws and some without. What is the cut off for early - late and does the correct one have bleed screws?

Thanks,
Dan

gbvette62

All 74 manual brake Corvettes used the 1" bore, master cylinder casting 5455509. At the beginning of production, the "509" had 2 bleeders in it, but at some point during the model year, GM eliminated the bleeders. The castings remained the same, they just no longer were drilled and tapped for the bleeders. I've never seen a definitive date as to when the change over took place. The same 509 casting was used from 73-76, with the only change being the elimination of the bleeders.

The same situation took place with the power brake master cylinder. Power brake cars used casting number 5460346, which originally had bleeders, but like the 509, the bleeders were eliminated from the 346, at some point during 1974.

blue6t7

Thanks for the quick reply GB. So for a non number matching car this one would be OK? https://www.corvettecentral.com/sear...A1974&q=192059

Thanks,
Dan

MelWff

Yes, that would be fine, even seems to have the bleed screws.

hunt4cleanair

This is what you want...
http://lonestarcaliper.com/p-1157-19...-cylinder.aspx

A 73/74 team is revising the 73/74 NCRS manual and after a review of this topic, wrote the following:
You'll see on that Lone Star M/C that its cast for the bleeder screws...but no bleeder screws!

gbvette62

If the NCRS has now decided that no 74 master cylinders had bleeders, I'm going to say they're wrong. I had an early 74, built in October 73 (low 7400 range VIN), and it had a master cylinder with bleeders.

I bought it in 1979, from the original owner. It had 33,000 miles on it. The owner was a bit ****, and kept everything he ever removed from the car. The complete A.I.R. system, the 4 OEM Firestone 500 blackwall tires, the stock AM/FM mono radio (a Sony stereo cassette was in the car) and all original paperwork (owner's manual, window sticker sales contract, warranty books, receipts for anything he ever bought, etc) came with the car. He'd even saved the used spark plugs, points, condensers and air filters.

Shortly after buying the car, the master cylinder failed, and I bought a new one from Chevrolet. The new MC they gave me didn't have bleeders, and I remember questioning them about it. Being somewhat **** myself, I'd kept the old MC up to about 15 years ago, when I finally sold it to Ken at Lonestar, as a core.

Of course, this isn't the first time I've disagreed with the NCRS. I'm part of the team that did the 80-82 Judging Manual, and even after 3 or 4 revisions, I know there are still things in the 80-82 manual, that haven't been corrected.

Below is a picture of the 74's engine, taken the day I bought it, and the original master cylinder, with bleeders, can be seen in this picture.

hunt4cleanair

Well, it is as it was given the availability of limited data. Our early survey vehicles are limited with the earliest VIN 8896 (Nov 10). But we have access to 1905 and I'm checking with him. He has the vehicle and the MC.

But thanks for sharing. You know these are always challenging to make a guide as accurate as possible. I'll send you my email address but would like a copy of that photo, I take it you've scanned it and I would like the full high-res version rather than the compressed contained here.