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| Looking for a replacement for 88 brake Master cylinder (Page 2/3) |
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cvxjet
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AUG 06, 06:13 PM
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I have two suggestions for you; 1) I sent an 88 caliper to Centric and they rebuilt it for me (They didn't have anything actually in stock at the time) Call their tech line and see if they will rebuild your own MC.
2) If you can not get a 88, I am running 88 calipers all around but still have the original 85 MC that came on my car- I did have to play with the proportioning valve, though.
If you see an 88 in the JY, grab some spare parts -especially the brake calipers- and apparently the MC, also. NEVER allow 88 calipers to go to the crusher![This message has been edited by cvxjet (edited 08-06-2022).]
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Rickady88GT
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AUG 07, 12:25 PM
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| quote | Originally posted by cvxjet:
I have two suggestions for you; 1) I sent an 88 caliper to Centric and they rebuilt it for me (They didn't have anything actually in stock at the time) Call their tech line and see if they will rebuild your own MC.
2) If you can not get a 88, I am running 88 calipers all around but still have the original 85 MC that came on my car- I did have to play with the proportioning valve, though.
If you see an 88 in the JY, grab some spare parts -especially the brake calipers- and apparently the MC, also. NEVER allow 88 calipers to go to the crusher!
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I agree
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sanderson231
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AUG 07, 04:32 PM
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Anybody know the difference between the 88 and pre-88 master cylinders? ------------------
formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged
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fieroguru
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AUG 07, 08:33 PM
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84-87 has a 1" front bore and 1 7/16" rear (quick take up) bore.
88 has a 15/16" front bore and a 1 7/16" rear (quick take up) bore.
The 88 master results in higher line pressure and more clamp pressure at the calipers for the same pedal force. Swapping an 84-87 into an 88 would not be recommended and would result in higher pedal effort for the same stopping performance.
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sanderson231
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AUG 07, 11:11 PM
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| quote | Originally posted by fieroguru:
84-87 has a 1" front bore and 1 7/16" rear (quick take up) bore.
88 has a 15/16" front bore and a 1 7/16" rear (quick take up) bore. |
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I measured two master cylinders. The first was out of my parts inventory and I am pretty sure it came out of an '84. The back bore was 1.410" vs 1-7/16" which would be 1.4375". The front bore was 0.94". The second master cylinder came out of an '88. It was installed by a repair shop so I am not sure that it is actually an '88. It measured the same. This was with a digital caliper. I'll recheck with a micrometer tomorrow.
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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged
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fieroguru
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AUG 08, 09:40 PM
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This is the 88 Fiero master:
Here is another one that "looks" like it has a chance of fitting and "should" be hydraulically the same. It also has a horizontal reservoir, so you don't have to worry about swapping tanks (BTW there are 2 other parts #s with angled reservoirs readily available too). I haven't verified (and probably won't), but just a little parts catalog searching shows this as a "potential" solution. E-bay shows 60 listings (some with multiple available). Use the info at your own risk...
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sanderson231
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AUG 08, 11:16 PM
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The reservoir looks the same as the 1500 Blazer MC I have on an 88 with the Lebaron brake upgrade. Maybe the one show is from the lighter duty Blazer.
The difference in pedal effort to achieve the same MC outlet pressure between 15/16" bore and 1" bore is not large. 57 lbs with a 1" bore produces the same outlet pressure as 50 lbs with a 15/16" bore. ------------------
formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged
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theogre
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AUG 09, 12:26 AM
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Sad but don't trust many "catalog" data... Examples:
Some list bore size in mm other inch even from same maker.
Some list bore size (mm) but say 1...
Pictures are often wrong. They often take 1 pic or set of 1 part and use on everything close to same format.
For working bore 88 is 24mm. most or all older are 1" or 25.4mm.
1.4mm dif makes a big charge for Pressure and Volume. Directly related to "Big MC" vs OE MC in my Cave, Brake Upgrade
IOW use old MC on 88 does same to "Big MC" on stock calipers on old Fiero... You loose line pressure and thus brake performance for same foot effort.
⚠️ 84 may have another MC depending on what RPO made w/. Does Have 2 combi valves. See my Cave, Combination Valve PN list @ bottom.
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sanderson231
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AUG 09, 05:28 PM
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| quote | Originally posted by theogre:
For working bore 88 is 24mm. most or all older are 1" or 25.4mm.
1.4mm dif makes a big charge for Pressure and Volume. |
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The reality is that the pedal force for the same outlet pressure is proportional to the square of the bores. 25^2/23.8^2 = 1.14 or 14% more effort. I not sure I could feel the difference with the butt gauge.
I just mic'd 3 master cylinders. One came off an 88. One came out of a box that I think was an 84. The third I don't know. They were all pretty close to the same. The smaller bore was about .9346" or 23.74mm. The large bore was about 1.4174" or 36.00mm. You never know what you have until you check.
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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged
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Vintage-Nut
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MAR 14, 07:00 PM
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I ordered the Centric Brake Master Cylinders 130.62030 from Summit @ $140
Today is Mar. 14, 2023 and I hope they won't cancel it.......
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