sin3504
Member
Posts: 13
Loc: Adams Tn
Reg: 02-21-06
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09-10-12 11:49 AM - Post#2268381
I converted my 53 chevy to a v8/700r4 and I put in a s10 blazer rear end in it with all new brake shoes and wheel cylinders. The problem I have is this. I had changed it to dual master prior to changing the rear end and the brakes worked great, now with the s10 rear end the brake pedal is very hard to push and it does not stop very well. the car has drum/drum breaks.Could it be the wheel cylinders are the wrong size? Thanks for any help.
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VANDENPLAS
Frequent Contributor
Posts: 1458
Age: 33
Loc: ontario canada
Reg: 07-29-09
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09-10-12 12:28 PM - Post#2268394
In response to sin3504
Did you replace the s10 brakes?
You could have a seized wheel cylinder
With the drums removed if someone presses on the peddle do the shoes move?
Do you have a fire wall mount or under floor master? Booster?
When you bleed the brakes if someone is holding the pedal down and you crack a rear bleeder does the fluid " shoot out " or just dribble out?
What year and from what car is the master out of?
What size is the brake line going to the rear?
A little more info and what if anything have you done to correct the issue is needed
Cheers
Every mother on Earth gave birth to a child.Except my mother,she gave birth to a legend .
ALWAYS TRUST PEOPLE WHO LIKE BIG BUTTS,THEY CANNOT LIE. |
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sin3504
Member
Posts: 13
Loc: Adams Tn
Reg: 02-21-06
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09-10-12 01:34 PM - Post#2268422
In response to VANDENPLAS
I replaced the wheel cylinders, shoes, and drums all new. Fluid shoots out from the cylinders when bleeding. With the car on jack stands all 4 wheel lock when the pedal is pressed. I just finished the car build yesterday and when I test drove it the pedal was like pushing on a rock. The car would stop but it took some pushing presure. I converted to a 70 model mustang dual master cylinder under the floor mount before the conversion and the brakes worked fine. The front brakes are stock 53 I belive they are 1 1/8 inch bore and the rear now are 3/4 bore. I havent done any trouble shooting or replaced anything to correct the problem yet, just seeing if anyone else had this problem when they converted to a s10 rear end. Thanks for your reply.
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NWMO 52 Chevy
Contributor
Posts: 574
Loc: Northwest Missouri
Reg: 11-10-10
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09-10-12 07:59 PM - Post#2268552
In response to sin3504
sin3504,
If I'm not mistaken, the stock wheel cylinders on the rear of a 53' would have been 1" (I know they are on my 52'). While I don't think it is your only problem, the 3/4" bore in the rear is too small.
Your dual MC is designed to provide the same pressure out of each port. The area of the wheel cylinder in the front is almost exactly 1.0 sq inch, whereas the 3/4" bore in the rear has only 0.44 sq inch of area. With equal pressure via the MC, you will be getting over twice as much force on your front brakes as the rear.
As stated above, the 52' used a 1" bore in the rear which provides 0.79 sq inch of area. Ideally, GM used a smaller wheel cylinder in the rear to help compensate for the weight shifting forward when applying the brakes. More weight on the front wheels needs more braking on the front wheels. I beleive the main thing you want to establish is a set up where your ratios are nearly stock (front to rear) AND have enough braking in the rear that your rear tires lock up BEFORE the front.
The shop manual available online at Keith Hardy's site covers this pretty well I believe.
I've no experience with them, but there are pressure control valves available as well to establish appropriate distribution. I believe these are more often seen when a person chooses to run disc up front vs drum in the rear.
With all that said, if your current system was bled and providing pressure as it should, I would expect a pretty severe front braking condition. This would not explain why the added pressure is needed. I wonder if your front brakes never operated as well, but you didn't notice it because the rears were doing the work. With the smaller rears and the fronts possibly not responding properly, that would explain the added pressure (nearly twice as much) is necessary.
Lastly, and I'll wrap up this lengthy response, you may have air in the system somewhere. I know when working with a frame mount MC, they recommend bench bleeding. Based on reading, the lower MC position creates some different challenges and often includes valves to maintain a minimum pressure on the wheel cylinders to keep them from bleeding back, though I'm sure those were not used in the 50's. Any leak (particularly at the wheel cylinders) will suck air into the lines as gravity pulls the fluid back to the MC.
Chris
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Ross_S
Senior Member
Posts: 407
Age: 72
Loc: Pahrump, NV
Reg: 07-05-02
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09-10-12 10:13 PM - Post#2268566
In response to NWMO 52 Chevy
 Air in the lines would cause a soft ,not hard , pedal. If the brake pedal is hard to push I would look into the M/C being possibly frozen and/or pedal linkage for binding, linkage angles or obstructions.
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 50hotrod
"2nd Year" Silver Supporting Member
Posts: 365
Age: 56
Loc: Wisconsin
Reg: 07-25-11
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09-10-12 11:14 PM - Post#2268567
In response to Ross_S
Brakes worked fine before the rear end swap.
Now the pedal is hard to push.
This indicates the master cylinder bore size is no longer matched to the wheel cylinder size unless you accidentally crimped a brake line somewhere down the line. I'd check for that first.
Well, you know what's wrong with the world today
People done gone and put their Bible's away
They're living by the law of the jungle not the law of the land
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sin3504
Member
Posts: 13
Loc: Adams Tn
Reg: 02-21-06
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09-11-12 05:47 AM - Post#2268603
In response to 50hotrod
Thanks everyone for the response, I checked all the lines last night to ensure they were not crimped or bent (all Good) no leaking cylinders.
Bled all 4 wheel cylinder again and no air in the lines. All the front and rear brakes/lines/mc
/hoses were new and working fine before I changed the rear end. I drove it again last night and it will stop but, the pedal is still very hard to push, nothing bent or miss aligned. Does anyone know where to get a 1" bore wheel cylinder for the s10 rear end? I have found a 7/8 cylinder this might work better than the 3/4. Again thanks for your help.
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 bobg1951chevy
"6th Year" Silver Supporting Member
Posts: 4867
Loc: Ellijay, GA
Reg: 02-18-08
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09-11-12 06:58 PM - Post#2268802
In response to sin3504
Maybe BOB HAYDEN will see your post, he has a s10 in his 54. 
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bobg1951chevy
"6th Year" Silver Supporting Member
Posts: 4867
Loc: Ellijay, GA
Reg: 02-18-08
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09-11-12 07:08 PM - Post#2268804
In response to NWMO 52 Chevy
sin3504,
If I'm not mistaken, the stock wheel cylinders on the rear of a 53' would have been 1" (I know they are on my 52'). While I don't think it is your only problem, the 3/4" bore in the rear is too small.
Your dual MC is designed to provide the same pressure out of each port. The area of the wheel cylinder in the front is almost exactly 1.0 sq inch, whereas the 3/4" bore in the rear has only 0.44 sq inch of area. With equal pressure via the MC, you will be getting over twice as much force on your front brakes as the rear.
As stated above, the 52' used a 1" bore in the rear which provides 0.79 sq inch of area. Ideally, GM used a smaller wheel cylinder in the rear to help compensate for the weight shifting forward when applying the brakes. More weight on the front wheels needs more braking on the front wheels. I beleive the main thing you want to establish is a set up where your ratios are nearly stock (front to rear) AND have enough braking in the rear that your rear tires lock up BEFORE the front.
The shop manual available online at Keith Hardy's site covers this pretty well I believe.
I've no experience with them, but there are pressure control valves available as well to establish appropriate distribution. I believe these are more often seen when a person chooses to run disc up front vs drum in the rear.
With all that said, if your current system was bled and providing pressure as it should, I would expect a pretty severe front braking condition. This would not explain why the added pressure is needed. I wonder if your front brakes never operated as well, but you didn't notice it because the rears were doing the work. With the smaller rears and the fronts possibly not responding properly, that would explain the added pressure (nearly twice as much) is necessary.
Lastly, and I'll wrap up this lengthy response, you may have air in the system somewhere. I know when working with a frame mount MC, they recommend bench bleeding. Based on reading, the lower MC position creates some different challenges and often includes valves to maintain a minimum pressure on the wheel cylinders to keep them from bleeding back, though I'm sure those were not used in the 50's. Any leak (particularly at the wheel cylinders) will suck air into the lines as gravity pulls the fluid back to the MC.
Chris
STOCK M/C IS 7/8", frt cylinders are 1 1/8", rear is 1".
Info is seen lower left column.
http://chevy.oldcarmanualproject.com/chevyresto/53...
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sin3504
Member
Posts: 13
Loc: Adams Tn
Reg: 02-21-06
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09-14-12 08:48 AM - Post#2269571
In response to bobg1951chevy
Man,,, you learn something enery day. The problem with the brakes were the wheel cylinders. I had bought everything new for the rear end change and the wheel cylinders I got were for a 2 wheel drive truck. I replaced them with the 7/8" four wheel drive cylinders and low and behold BRAKES...Thanks, everyone for your help,, now it's off to the Holley Power tour next weekend Somerset KY.
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