Master cylinder ID help needed

[83Stepper]

So a little back info on what I've got. 83 Stepside that was originally a 4.1 I6 3 on the tree. PO swapped the 4.1 for a mild build 350 sbc and moved the column shifter to the floor. Appears that the PO, or one of them, had intentions of hot rodding it and did some funky stuff. Won't get into all the details but yeah it's been a process just to make it a daily again.

TL/DR; doing the brakes and appears that the master cylinder is toast. Pedal is fine to about 3/4 then gets really hard to depress and can't bleed the rear brakes. So I'm leaning towards the master is done for. Believe it's a JB1 system with manual brakes and 11" rear shoes, no RPO on the glovebox door. Casting number on the master is 18006812. Rough measurement of the bore without tearing into it appears to be approx 1 3/16", 30mm-ish.

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Trying to at least find a rebuild kit, but no luck so far online. Swear these things are non-existent or I've got a Unicorn. Canadian built truck if that helps any. Not seeing any signs that this was a power unit that had the old vacuum booster removed. Any help would be greatly appreciated.

 

[Keith Seymore]

For 1983 the base manual system is JB1 and the master cylinder is part number 18006064 broadcast code CU.

Built in Oshawa makes no difference.

K

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[83Stepper]

For 1983 the base manual system is JB1 and the master cylinder is part number 18006064 broadcast code CU.

Built in Oshawa makes no difference.

K

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Greatly appreciated! Did some digging and found some info but nothing like this. Appreciate you and the info!

 

[Made in Flint]

Apologies for being late to this thread, but do you know if the 83 master cylinder is the same as the 84? The numbers on the bottom of my 84 MC match the OP's, except that I have an 83 CFD 2 instead of OP's 82 CFD 5.

 

[Keith Seymore]

Tell me more about your truck and I'll tell you which master it should have.

Model, series and GVW rating, please, and manual vs power brakes.

K

 

[Made in Flint]

1984 C10 4.1L 250c.i. Manual brakes, 4900 GVWR

 

[Keith Seymore]

Well done -

For 1984 the base manual system is JB1 and the master cylinder is part number 18008064 broadcast code CV.

I want to go back and correct my post #2: upon further review it looks like the '83 part number is the same 18008064. There was sort of a smudge there on the chart, but in the context of the other part numbers an 18008xxx number would fit.

They did change the broadcast code for some reason (from CU to CV) but the specs are essentially the same.

Based on this I would say the '83 and the '84 master cylinders are interchangeable.

K

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[Made in Flint]

Excellent, thank you for the quick reply!!!

 

[83Stepper]

@Made in Flint My truck has the exact same specs, 250 I6, manual brakes and should be 100% interchangeable. GM played the carryover game a lot with these trucks where the exact same part was used from model year into the next. Assuming this would be the case with the masters and possibly the change of the broadcast code to distinguish year model variations? But glad to hear you got it sorted out and as always thanks to @Keith Seymore to the great plethora of info!