non low drag calipers

bbc-olds

Frequent Racer
Jun 7, 2008
542
2
18
Malin OR
Working on a 83 Cutlass that I am converting to manual brakes. Have the master cyl setup off a manual brake s10. Using a 7/8 bore master from a 79 Gbody. Pedal travel is too much and I am assuming the front calipers have too much travel for the Master(assuming they are of the low drag design). Would like to get non low drag calipers but all I have found is all parts places list the same caliper from 78-87 redardless of application. Kits too. Does anybody have a specific part number for them? Or all non low drag for all aftermarket rebuilders? Some have put ck valves in the front and may do that but would rather not.
 

Supe

MalibuRacing Junkie
May 21, 2003
15,116
0
36
Charlotte, NC
Most of the aftermarket are non-low drag. You may want to give Speedway Motors a call and confirm. They sell a ton of metric calipers for the IMCA/roundy round guys.
 

malibudave1978

Amateur Racer
Jun 8, 2004
226
0
0
Houston, TX
If you have the stock from the factory calipers on your Cutty, they are most likely LOW drag. Just make sure you are running the stock prop valve for disc/drum brakes and make sure your rear shoes are adjusted out against the drum (this will cause a excessive pedal travel and no pressure). If you are not running a stock prop valve, you will need to run a 2lb residual valve in the front lines and a 10lb residual valve for rear drums and a 2lb residual valve for rear disc brakes. An adjustable prop valve is optional to adjust your rear brakes for any type of setup. Of course, make sure your system is free of air and your master cylinder is functioning correctly (stock type master cylinders have been known to be defective when new/rebuilt).

It is my opinion, but I cannot prove, that almost all rebuilt calipers are NON low drag.

"Metric" calipers were used from 1978 through about 2003. From 1978 to 1981, they were NON low drag. From 1982 to about 1997, they are most likely LOW drag. From 1998 to 2003, they are NON low drag. "Metric" calipers were used on 1978 - 1988 g-body cars, 1982 - 2003 S10 trucks and SUVs, and from 1982 - 1992 3rd gen Camaros and Firebirds.

There are actually two different "metric" caliper casting designs. The early design are from 1978 - 1997. The later design is from 1998 - 2003. The part numbers are the same for regardless of casting design. You can technically get one of the designs for the drivers side of the car and the other design for the passenger side of the car, regardless of brand.

I have found that the auto part stores selection is not the best quality.

The AFCO calipers with part numbers 7241-9004 and 7241-9003 are NON low drag regardless of how they are advertised. These are rebuilt units, but are good quality. You may get an older design or a newer design or both when you order a pair.

Calipers that are the same quality as the AFCO calipers above are Centric brand NON low drag calipers. Part numbers 14162065 and 14162066. You may get an older design or a newer design or both when you order a pair.

AFCO has brand new calipers for $49.99. These are the only brand new, stock size piston, cast iron calipers that I know about. Part numbers are 6635003 and 6635004. I have yet to see a pair of these calipers so I cannot comment on them.

There are after market aluminum "metric" calipers from Wilwood and AFCO that bolt in place of stock calipers. These run about twice as much as the stock cast iron versions.
 

bbc-olds

Frequent Racer
Thread starter
Jun 7, 2008
542
2
18
Malin OR
Thanks for the replies. I read most of your posts on this subject(David) and I think I might have another reason for the excess pedal travel. When you mentioned the rear brakes I realized that the rear brakes are now drum brakes from a 92 ford Explorer(9in rear). Further research revealed that it now has 7/8 rear cylinders instead of the 3/4 that came on the car. Would that not have a effect on pedal travel in addition to the calipers? Car has 65000 original miles and I assume it has the original calipers. Can they be rebuild into non low drag pieces?
 

malibudave1978

Amateur Racer
Jun 8, 2004
226
0
0
Houston, TX
bbc-olds said:
Further research revealed that it now has 7/8 rear cylinders instead of the 3/4 that came on the car. Would that not have a effect on pedal travel in addition to the calipers? Car has 65000 original miles and I assume it has the original calipers. Can they be rebuild into non low drag pieces?

Though the 7/8" wheel cylinders are substantially larger than the 3/4" wheel cylinder, the amount of fluid needed to operate either one is very little compared to a caliper.

It is highly unlikely that its the larger wheel cylinder is causing your issues.

Do you have the stock prop valve installed on the frame?

If you do not, you will need a 2lb residual valve for the front brakes and a 10lb residual valve for the rear brakes. An adjustable prop valve is also recommended to dial in your brake bias.

If you brake calipers are stock, they are LOW drag and will not work with a 7/8" bore master cylinder causing NO pedal at all.

Are your rear drum shoes adjusted out against the drums? This will cause no pressure or little pressure when brake pedal is pressed with your foot.

Do you have enough pedal travel to operate the master cylinder? Master cylinder piston should be about 7/8" to 1.0" in travel. If you have a 6 to 1 pedal ratio, your pedal will travel about 6 inches. If it is less than this, then you are not getting the volume needed to the calipers to operate them effectively.

Do you have the stock 30 year old rubber lines? Rubber lines deteriorate over time and will balloon causing excessive pedal travel. Replace them with new rubber lines (cheapest) or replacement stainless steel flexible brake lines.

To maximize your manual brakes, run 100% organic pads and shoes with an FF rating. Organics have better friction properties at lower temperatures. They require very little heat to operate effectively compared to Semi Metallics and Ceramics which require more heat to operate. If you are using Semi Metallics or Ceramics, this will require more pressure to stop the car (compared to Organics) to stop the car until the brakes get to a certain temperature. Though organics do not like big temperatures for sustained period of time, organics are good for a daily driver or drag car because the pads will not see extreme heat for extended periods of time during their use.

Lastly, your master cylinder may be bad. Even new and rebuilt master cylinders are not known for their reliability.

Does you car stop? I ask this question to say that a manual brake equipped cars will have a long pedal stroke. Smaller master cylinders need longer pedal strokes to move the volume of brake fluid to operate the calipers effectively.
 

bbc-olds

Frequent Racer
Thread starter
Jun 7, 2008
542
2
18
Malin OR
Has factory Prop valve. Rear brakes adjusted out. No air in system. Original brake lines(are getting replaced). No brakes on 1st pump/better on 2nd/ firm pedal on 3rd. Good call on the organic pads. Will switch to them after getting this figured out. Good that you mentioned the pedal travel. Don't think I am getting the right amount of travel based on your post. Think maybe a longer pushrod is in order. Will measure it when I get home.

Isn't the difference in calipers in the seal around the piston? All parts houses list the same kit for 78-87. Will a kit with square seal work with my calipers and make them non low drag. Calipers are not expensive but with my luck I would get low drag calipers. Don't mind low pedal but it needs to stop on first push.

Found a lot of different problems with this car as opposed the my other car. Being a lot faster I went to Exployer rear disc and Aluminum Wilwood calipers right off. Master is a strange unit with a trz adapter plate. pedal goes down about 3/4 travel but stops good. No residual valve in either end.

Thanks for taking the time to respond to this. Have read your posts on this on a couple of different websites and has been eye opening. Didn't think converting to manual brakes would be such a task. Would have left the power brakes on but cam said otherwise.
 

malibudave1978

Amateur Racer
Jun 8, 2004
226
0
0
Houston, TX
bbc-olds said:
No brakes on 1st pump/better on 2nd/ firm pedal on 3rd. Good call on the organic pads.
Isn't the difference in calipers in the seal around the piston?

This sounds like a LOW drag caliper issue.
bbc-olds said:
Isn't the difference in calipers in the seal around the piston? All parts houses list the same kit for 78-87. Will a kit with square seal work with my calipers and make them non low drag?

It should, but there has been documentation about the piston housing bore being machined with a bevel to accentuate the LOW drag feature. I do not think this is the case. I think the piston seal is the only thing that makes a caliper LOW drag. A square (normal) seal should correct the LOW drag feature to NON low drag (normal) only if the machining of the caliper piston's bore is square also.
bbc-olds said:
Didn't think converting to manual brakes would be such a task. Would have left the power brakes on but cam said otherwise.

You would think it would be as simple as changing out the master cylinder, but with the firewall angle (not normal compared to other vehicles), LOW drag/NON low caliper inconsistencies with stock and stock replacement calipers, stock master cylinder replacement quality, and sometimes changing to non stock brake components (i.e. rear disc brakes) put additional variables that compound on one another and complicate the conversion. Some people don't have issues when converting to manual brakes on a g-body, but other people have more issues converting to manual brakes on g-bodies.

The variables are:
*LOW drag calipers
*Quality and type (LOW or NON LOW drag) calipers replacements. Are they LOW drag or NON low drag? Most likely replacements are NON low drag (normal) calipers.
*Quality of replacement master cylinder. New and rebuilt stock replacement master cylinders seem to have issues more than normal. Angle of firewall limits master cylinder selections.

Other variables:
*Removing prop valve requires adding 2lb residual valve in the front lines and a 10lb residual valve for the rear drum brakes and a 2lb residual valve for rear disc brakes.
*Size of piston in a rear brake caliper if converting to rear disc brakes.
*Size of piston in front brake caliper if using a different caliper than stock.
*Rubber brake line age.
*Using Semi Metallic and Ceramic brake pads that require additional heat to work effectively.
 

bbc-olds

Frequent Racer
Thread starter
Jun 7, 2008
542
2
18
Malin OR
Pushrod moved to top hole. information acquired by the replies has been really helpful in addition to reading Dave.s posts on the subject. Special thanks to Dave for taking the time to help with this. Will be rebuilding the calipers and see where it goes.
 

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