4th gen master cylinder bore?
#1
Senior Member
Thread Starter
Join Date: Oct 1999
Posts: 6,621
Likes: 0
Received 2 Likes
on
2 Posts
Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
4th gen master cylinder bore?
Anybody know the bore? I'm looking at replacing the 190k mile MC with something a little less messy and maybe even designed to give a firmer pedal... I like the 4th gen cap instead of snap Tupperware cover and if it's got a larger bore I'd a very happy camper.
#2
Member
Join Date: Nov 2003
Location: Ft. Leavenworth, KS
Posts: 462
Likes: 0
Received 1 Like
on
1 Post
Car: 83 TA, 89 TTA, others
Engine: ZZ4 TPI, LC2 turbo v6
Transmission: several, mostly broken
I just disassembled a used '94 MC that I'd bought to answer the same question. It's a 1.00" diameter bore straight through (not a stepped bore like the thirdgen MC).
The replacement parts catalogs indicate that the '98-02 MC is different from the '93-'97. How it's different, I don't know, since I haven't examined one of those yet.
The replacement parts catalogs indicate that the '98-02 MC is different from the '93-'97. How it's different, I don't know, since I haven't examined one of those yet.
#3
Senior Member
Thread Starter
Join Date: Oct 1999
Posts: 6,621
Likes: 0
Received 2 Likes
on
2 Posts
Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
Dave, what do you mean stepped bore. Don't tell me the primary and secondary are different bore's.... is that just the disc/drum mc or all? Do you have those dimensions?
I confirmed tonight the bore is 1" for 93-97 from a buddy's old mc. Now I need a newer LS1 mc. I'm glad they've got 1" bore. Now to find the cheapest new/rebuilt.
I confirmed tonight the bore is 1" for 93-97 from a buddy's old mc. Now I need a newer LS1 mc. I'm glad they've got 1" bore. Now to find the cheapest new/rebuilt.
#4
Member
Join Date: Nov 2003
Location: Ft. Leavenworth, KS
Posts: 462
Likes: 0
Received 1 Like
on
1 Post
Car: 83 TA, 89 TTA, others
Engine: ZZ4 TPI, LC2 turbo v6
Transmission: several, mostly broken
All thirdgen MCs that I'm aware of were stepped bore.
In the late 70's, for fuel economy reasons, GM began using "low drag" calipers where the caliper piston seal was redesigned to help pull the caliper piston back away from the rotor when not under pressure. Obviously, this increased the piston travel necessary to apply the brakes. So, to compensate for this increased piston movement (i.e. fluid volume), they introduced something called a "quick take up" MC -- I've also heard it referred to as a "fast fill" type. The intent of which is to supply a large volume of fluid in a very short amount of pedal travel, then function like a normal MC beyond that.
Basically, you have a very large diameter piston at the back of the MC bore, that does the initial take up, then a bypass valve opens and vents the fluid pressure to the main MC bore, so that the MC functions as normal. Actually, you can see the quick take up valve at the bottom of the fluid reservoir -- it's that funny little plastic thing down there in the rear hole.
As far as thirdgen master cylinders go, I believe the bore diameters were as follows (first number is the main bore, second number being the quick take up bore):
PBR ALUMINUM CALIPER REAR DISC and ALL REAR DRUM
24 & 31.75MM CYL BORE (i.e. .944" main bore)
MC P/N: GM 18030555, or Delco 18M313
IRON CALIPER REAR DISKS
25.4 & 36MM CYL BORE (i.e. 1" main bore)
MC P/N: GM 18030556, or Delco 18M314
In the late 70's, for fuel economy reasons, GM began using "low drag" calipers where the caliper piston seal was redesigned to help pull the caliper piston back away from the rotor when not under pressure. Obviously, this increased the piston travel necessary to apply the brakes. So, to compensate for this increased piston movement (i.e. fluid volume), they introduced something called a "quick take up" MC -- I've also heard it referred to as a "fast fill" type. The intent of which is to supply a large volume of fluid in a very short amount of pedal travel, then function like a normal MC beyond that.
Basically, you have a very large diameter piston at the back of the MC bore, that does the initial take up, then a bypass valve opens and vents the fluid pressure to the main MC bore, so that the MC functions as normal. Actually, you can see the quick take up valve at the bottom of the fluid reservoir -- it's that funny little plastic thing down there in the rear hole.
As far as thirdgen master cylinders go, I believe the bore diameters were as follows (first number is the main bore, second number being the quick take up bore):
PBR ALUMINUM CALIPER REAR DISC and ALL REAR DRUM
24 & 31.75MM CYL BORE (i.e. .944" main bore)
MC P/N: GM 18030555, or Delco 18M313
IRON CALIPER REAR DISKS
25.4 & 36MM CYL BORE (i.e. 1" main bore)
MC P/N: GM 18030556, or Delco 18M314
Last edited by Dave_Jones; 05-16-2009 at 03:34 PM. Reason: posted incorrect data
#6
Senior Member
Join Date: Dec 2003
Location: Minneapolis, MN
Posts: 690
Likes: 0
Received 2 Likes
on
2 Posts
Car: 1989 Camaro RS
Engine: ZZ4 350
Transmission: T-5
Axle/Gears: BW 9-bolt w/3.73
Originally posted by JPrevost
Now to find the cheapest new/rebuilt.
Now to find the cheapest new/rebuilt.
#7
Senior Member
Thread Starter
Join Date: Oct 1999
Posts: 6,621
Likes: 0
Received 2 Likes
on
2 Posts
Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
Dave, so it's not really a differential bore it's just a quick fill. I thought you ment the primary was a different size than the secondary (front/rear). I guess the quick fill mc on our cars would explain why the rear drums didn't have the residual pressure valve!
Thanks.
Yeah, new is likely unless the price difference is 3x. I don't mind working on my car, what I don't like doing is overspending so I walk that fine line. I've never, and I do mean never, had a rebuilt part fail on me. I can't see how people screw up rebuilding a mc. Then again most of the rebuilt parts I buy are from circle track guys or I do it myself... The other reason I was considering the rebuilt was for the material. A few posts have covered this but the new mc's for OUR cars have been iron and the rebuilds OEM aluminum... what about the 4th gens. Are their "new" mc's iron as well?
Thanks.
Yeah, new is likely unless the price difference is 3x. I don't mind working on my car, what I don't like doing is overspending so I walk that fine line. I've never, and I do mean never, had a rebuilt part fail on me. I can't see how people screw up rebuilding a mc. Then again most of the rebuilt parts I buy are from circle track guys or I do it myself... The other reason I was considering the rebuilt was for the material. A few posts have covered this but the new mc's for OUR cars have been iron and the rebuilds OEM aluminum... what about the 4th gens. Are their "new" mc's iron as well?
Trending Topics
#8
Member
Join Date: Nov 2003
Location: Ft. Leavenworth, KS
Posts: 462
Likes: 0
Received 1 Like
on
1 Post
Car: 83 TA, 89 TTA, others
Engine: ZZ4 TPI, LC2 turbo v6
Transmission: several, mostly broken
FWIW, I recently purchased a used '98-02 MC, for comparison.
It's also a 1" bore. The MC body is practically identical to the '93-'97 style, and even carries the same casting number.
Internally there's some minor differences, none of which are terribly significant IMHO. (Specifically, the secondary piston can move a bit further in the '98+ MC before it hits its stop, the primary piston is somewhat redesigned, and there's a bit of difference in the piston springs but I doubt anyone would be able to tell once it's all assembled and installed.
The biggest difference is the reservoir. The '98-02 reservoir is quite a bit larger, has a couple of extra baffles, and also has provisions for a low fluid warning switch. Also, the '98-02 MC is tapped for an M10 fitting on the primary side, and an M12 on the secondary side, while the '93-97 was tapped for M10 on both.
HTH,
It's also a 1" bore. The MC body is practically identical to the '93-'97 style, and even carries the same casting number.
Internally there's some minor differences, none of which are terribly significant IMHO. (Specifically, the secondary piston can move a bit further in the '98+ MC before it hits its stop, the primary piston is somewhat redesigned, and there's a bit of difference in the piston springs but I doubt anyone would be able to tell once it's all assembled and installed.
The biggest difference is the reservoir. The '98-02 reservoir is quite a bit larger, has a couple of extra baffles, and also has provisions for a low fluid warning switch. Also, the '98-02 MC is tapped for an M10 fitting on the primary side, and an M12 on the secondary side, while the '93-97 was tapped for M10 on both.
HTH,
Last edited by Dave_Jones; 10-16-2005 at 02:59 AM.
#10
Member
iTrader: (3)
Join Date: Jul 1999
Location: Latham NY USA
Posts: 300
Likes: 0
Received 0 Likes
on
0 Posts
Car: 91 Formula
Engine: 350
Transmission: T-56
Axle/Gears: 10 Bolt 3.23
Are the external dimensions of the LS1 master any differant than the stock master cylinder? Any room that can be saved around the master cylinder for me the better. My blower intake sits right in line with the master.
#11
Member
Join Date: Nov 2003
Location: Ft. Leavenworth, KS
Posts: 462
Likes: 0
Received 1 Like
on
1 Post
Car: 83 TA, 89 TTA, others
Engine: ZZ4 TPI, LC2 turbo v6
Transmission: several, mostly broken
LT1/LS1 MC is a little more compact than the thirdgen style.
I'll try to snap a pic or two for comparison.
I'll try to snap a pic or two for comparison.
#12
Member
iTrader: (3)
Join Date: Jul 1999
Location: Latham NY USA
Posts: 300
Likes: 0
Received 0 Likes
on
0 Posts
Car: 91 Formula
Engine: 350
Transmission: T-56
Axle/Gears: 10 Bolt 3.23
Sweet, gonna look in to that then, hell even if it's only half an inch it will be well worth swapping in. Pictures appreciated
#13
Senior Member
Thread Starter
Join Date: Oct 1999
Posts: 6,621
Likes: 0
Received 2 Likes
on
2 Posts
Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
The 4th gen mc should bolt in so long as the pedal assemblies relativity to the ground is the same as that of our 3rd gens. If it isn't, then the angle might be or or the pushrod length could be different because of the power assist. I think it would provide a nice alternative.
#14
Member
Join Date: Nov 2003
Location: Ft. Leavenworth, KS
Posts: 462
Likes: 0
Received 1 Like
on
1 Post
Car: 83 TA, 89 TTA, others
Engine: ZZ4 TPI, LC2 turbo v6
Transmission: several, mostly broken
Originally posted by Mark A 91Formula
...hell even if it's only half an inch it will be well worth swapping in.
...hell even if it's only half an inch it will be well worth swapping in.
#20
Senior Member
Thread Starter
Join Date: Oct 1999
Posts: 6,621
Likes: 0
Received 2 Likes
on
2 Posts
Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
Originally posted by Dave_Jones
, the '98-02 MC is tapped for an M10 fitting on the primary side, and an M12 on the secondary side, while the '93-97 was tapped for M10 on both.
HTH,
, the '98-02 MC is tapped for an M10 fitting on the primary side, and an M12 on the secondary side, while the '93-97 was tapped for M10 on both.
HTH,
#21
Originally posted by Dave_Jones
PBR Rear Disc or Rear Drum cars: 25.4 & 36.0mm (i.e. 1" main bore)
(MC P/N: GM 18030556, or Delco 18M313)
Delco Morraine (Iron) Rear Disc: 24.0 & 31.75mm (i.e. .944" main bore)
(MC P/N: GM 18030555, or Delco 18M314)
PBR Rear Disc or Rear Drum cars: 25.4 & 36.0mm (i.e. 1" main bore)
(MC P/N: GM 18030556, or Delco 18M313)
Delco Morraine (Iron) Rear Disc: 24.0 & 31.75mm (i.e. .944" main bore)
(MC P/N: GM 18030555, or Delco 18M314)
the bigger bore units was used in 88,
the smaller bore masters were used from 89-92
is bigger better?
would it make sense to put an 88 big bore master in my 89.
My 1LE brakes suck in my 89, and it must be the master.. so I'm tempted to use the bigger bore master from 88....
what are your thoughts??
#22
Senior Member
iTrader: (3)
Join Date: Jan 2004
Location: K.C. Mo.
Posts: 684
Likes: 0
Received 0 Likes
on
0 Posts
Car: '89 GTA 9,000 MILES
Engine: 350
Transmission: 700R4
Axle/Gears: 3.27 9 bolt
Originally posted by Dave_Jones
FWIW, I recently purchased a used '98-02 MC, for comparison.
It's also a 1" bore. The MC body is practically identical to the '93-'97 style, and even carries the same casting number.
Internally there's some minor differences, none of which are terribly significant IMHO. (Specifically, the secondary piston can move a bit further in the '98+ MC before it hits its stop, the primary piston is somewhat redesigned, and there's a bit of difference in the piston springs but I doubt anyone would be able to tell once it's all assembled and installed.
The biggest difference is the reservoir. The '98-02 reservoir is quite a bit larger, has a couple of extra baffles, and also has provisions for a low fluid warning switch. Also, the '98-02 MC is tapped for an M10 fitting on the primary side, and an M12 on the secondary side, while the '93-97 was tapped for M10 on both.
HTH,
FWIW, I recently purchased a used '98-02 MC, for comparison.
It's also a 1" bore. The MC body is practically identical to the '93-'97 style, and even carries the same casting number.
Internally there's some minor differences, none of which are terribly significant IMHO. (Specifically, the secondary piston can move a bit further in the '98+ MC before it hits its stop, the primary piston is somewhat redesigned, and there's a bit of difference in the piston springs but I doubt anyone would be able to tell once it's all assembled and installed.
The biggest difference is the reservoir. The '98-02 reservoir is quite a bit larger, has a couple of extra baffles, and also has provisions for a low fluid warning switch. Also, the '98-02 MC is tapped for an M10 fitting on the primary side, and an M12 on the secondary side, while the '93-97 was tapped for M10 on both.
HTH,
#23
Senior Member
Join Date: Dec 2003
Location: Minneapolis, MN
Posts: 690
Likes: 0
Received 2 Likes
on
2 Posts
Car: 1989 Camaro RS
Engine: ZZ4 350
Transmission: T-5
Axle/Gears: BW 9-bolt w/3.73
Originally posted by Jetmeck
I plan to remove the troublesome combo/proportioning valve and put an adjustable valve in line rear along with a line lock in front when I do ED's c4 upgrade.
I plan to remove the troublesome combo/proportioning valve and put an adjustable valve in line rear along with a line lock in front when I do ED's c4 upgrade.
#24
Supreme Member
iTrader: (1)
Join Date: Jun 2001
Location: Tacoma, Wa
Posts: 3,109
Likes: 0
Received 25 Likes
on
17 Posts
Car: '91 TA vert
Engine: turboLSx
Transmission: T56
Axle/Gears: 3.23
Originally posted by MurcoRS
an adjustable prop-valve running straight off the rear chamber will limit the total amount of pressure available to your system overall. I've seen a few do it here and report success but check back with them after 10-15K miles of use.
an adjustable prop-valve running straight off the rear chamber will limit the total amount of pressure available to your system overall. I've seen a few do it here and report success but check back with them after 10-15K miles of use.
#25
Re: 4th gen master cylinder bore?
The delco part numbers listed above by Dave_Jones are WRONG. They are reversed. Here are the correct ones:
With RPO REAR DRUM BRAKES POWER BRAKES 24 & 31.75MM CYL BORE
(MC P/N: GM 18030555, or Delco 18M313)
With RPO REAR DISC BRAKES POWER BRAKES 25.4 & 36MM CYL BORE
(MC P/N: GM 18030556, or Delco 18M314)
The GM numbers were reversed..thisis straight from the Delco on-line parts site (and the box beside me)
Dave_Jones, can you update that post?
With RPO REAR DRUM BRAKES POWER BRAKES 24 & 31.75MM CYL BORE
(MC P/N: GM 18030555, or Delco 18M313)
With RPO REAR DISC BRAKES POWER BRAKES 25.4 & 36MM CYL BORE
(MC P/N: GM 18030556, or Delco 18M314)
The GM numbers were reversed..thisis straight from the Delco on-line parts site (and the box beside me)
Dave_Jones, can you update that post?
#26
Member
Join Date: Nov 2003
Location: Ft. Leavenworth, KS
Posts: 462
Likes: 0
Received 1 Like
on
1 Post
Car: 83 TA, 89 TTA, others
Engine: ZZ4 TPI, LC2 turbo v6
Transmission: several, mostly broken
Re: 4th gen master cylinder bore?
Yikes, you're right, I did switch the numbers. And it was more than just transposing the GM part numbers, I also reversed the applications.
Hope that didn't mess anyone up too much!
How's this look?
PBR ALUMINUM CALIPER REAR DISC and ALL REAR DRUM
24 & 31.75MM CYL BORE
MC P/N: GM 18030555, or Delco 18M313
IRON CALIPER REAR DISKS
25.4 & 36MM CYL BORE
MC P/N: GM 18030556, or Delco 18M314
Hope that didn't mess anyone up too much!
How's this look?
PBR ALUMINUM CALIPER REAR DISC and ALL REAR DRUM
24 & 31.75MM CYL BORE
MC P/N: GM 18030555, or Delco 18M313
IRON CALIPER REAR DISKS
25.4 & 36MM CYL BORE
MC P/N: GM 18030556, or Delco 18M314
#27
Member
Join Date: Jun 2002
Location: Hockessin, Delaware
Posts: 491
Likes: 0
Received 0 Likes
on
0 Posts
Car: Red 91 RS Camaro
Engine: LO3 with Comp Cam
Transmission: 700R4
Axle/Gears: 4th gen rear
Re: 4th gen master cylinder bore?
So which MC would give the best performance? The 98+ has the same fitting sizes as the stock 3rd gen MC lines correct? Is its better to have an adjustable Proportioning valve or just the stock valve from a 4wheel disc setup?
#29
Supreme Member
Join Date: Aug 2001
Location: Costal Alabama
Posts: 2,136
Likes: 0
Received 1 Like
on
1 Post
Car: 1989 Iroc-Z
Engine: 350, ZZ4 equivalent
Transmission: Pro-Built Road Race 700R4
Axle/Gears: 3.23 Dana 44
Re: 4th gen master cylinder bore?
84-88 F-body MS
Step Bore
Front brake bore: ~1.42" 36mm
Rear brake bore: 1" 25.4mm
18030556 GM
18M314 (Ac-delco)
Check out my site for a pull list of MS: http://www.lukeskaff.com/car/brakes/...Clyinder_Specs
Also you can use this setup with rear drums.
#30
Re: 4th gen master cylinder bore?
The 98-2002 LS1 MS has the same fittings as the 84-92 F-body. I suggest the 84-88 rear disc brake master cylinder over the LS1 MS due to a larger bore size
84-88 F-body MS
Step Bore
Front brake bore: ~1.42" 36mm
Rear brake bore: 1" 25.4mm
18030556 GM
18M314 (Ac-delco)
Check out my site for a pull list of MS: http://www.lukeskaff.com/car/brakes/...Clyinder_Specs
Also you can use this setup with rear drums.
84-88 F-body MS
Step Bore
Front brake bore: ~1.42" 36mm
Rear brake bore: 1" 25.4mm
18030556 GM
18M314 (Ac-delco)
Check out my site for a pull list of MS: http://www.lukeskaff.com/car/brakes/...Clyinder_Specs
Also you can use this setup with rear drums.
That along with Earls brake hoses and good pads/shoes should help the complete system.
#31
Supreme Member
iTrader: (18)
Join Date: Dec 2007
Location: Minnesota
Posts: 1,924
Likes: 0
Received 12 Likes
on
9 Posts
Car: 84 camaro, 88 trans am, 98 camaro
Engine: Modded , stock, LSX modded
Transmission: 700r4, 700r4, t-56
Axle/Gears: 327, 308, 373
Re: 4th gen master cylinder bore?
anyone running a LT1 master to stock 3rdgen prob valve lines?
Thread
Thread Starter
Forum
Replies
Last Post