brake and stumble question
05-12-2011, 08:28 AM
#1
Thread Starter
Join Date: Nov 2010
Location: Il
Posts: 4
brake and stumble question
New to the Mustang world and have a few questions.
Bought my first Ford a few months back, I'm was born Chevy guy so this is a new world for me. I've got a long way to go, but I've learned a lot in the past few months.
I have a '66 conv. C code that I bought out of NC. Very solid car. I'm struggling with 2 problems that I'm hoping you guys can help with.
Brakes:
The brakes on this car are terrible, no kidding my 1955 Chevy, also with manual drum brakes, stops 10 times better than the Mustang. The pedal is incredibly hard to press, almost requires 2 feet to stop it. When I got the car home and got it on the lift, I pulled all the drums. As the previous owner indicated, brand new drums, hardware, wheel cylinders and shoes. Even the MC looks new. The shoes looked a little glazed, so I hit them with some 80git on the DA. The insides of the drums looked like they've recently been turned so I didnt see any issue there. Buttoned everything up and it still stops like a Mack Truck. The only thing I can come up with, is that when the PO had the brakes, entirely, replaced maybe they used the wrong MC?? One with a different bore possibly. Is that possible? Is there an easy way to identify the correct MC to make sure I have the right one installed? The MC installed on the car is still a single reservoir (fruit jar). I'm about to the point where I'm going to swap disc brakes on the front with a dual MC. What am I missing? Anything else that you guys can think of that could be an issue? Also, all the lines look good.
Stumble:
Stock engine, again 289 with a 2100 carb. The car barley ran when I got it, to correct the issues I've upgraded to a Pertronix (have them in my Chevy's absolutely love Pertronix) rebuilt the carb, new cap rotor, plug wires, set the plugs to .040. Set the rockers (stock hyd cam) had some really loud rocker noise. Car actually runs now, pretty well I'd even say.... Except.... There's a stumble off idle that I cant tune out. I've been able to reduce it a bit by changing the location of the accelerator rod linkage. I now have it set on the accelerator pump on the outside hole, closest to left side fender well and at the highest hole on the cross shaft on the side of the carb. When I rebuilt the carb I verified that the shooters and all the jets were factory sizes. New accelerator pump, new power valve. Where do you guys have your linkage set? My thought is maybe the power valve is bad since it's not transitioning from idle circuit to main circuit without a stumble. What do you guys think?
Thanks in advance for any help and suggestions.
Bought my first Ford a few months back, I'm was born Chevy guy so this is a new world for me. I've got a long way to go, but I've learned a lot in the past few months.
I have a '66 conv. C code that I bought out of NC. Very solid car. I'm struggling with 2 problems that I'm hoping you guys can help with.
Brakes:
The brakes on this car are terrible, no kidding my 1955 Chevy, also with manual drum brakes, stops 10 times better than the Mustang. The pedal is incredibly hard to press, almost requires 2 feet to stop it. When I got the car home and got it on the lift, I pulled all the drums. As the previous owner indicated, brand new drums, hardware, wheel cylinders and shoes. Even the MC looks new. The shoes looked a little glazed, so I hit them with some 80git on the DA. The insides of the drums looked like they've recently been turned so I didnt see any issue there. Buttoned everything up and it still stops like a Mack Truck. The only thing I can come up with, is that when the PO had the brakes, entirely, replaced maybe they used the wrong MC?? One with a different bore possibly. Is that possible? Is there an easy way to identify the correct MC to make sure I have the right one installed? The MC installed on the car is still a single reservoir (fruit jar). I'm about to the point where I'm going to swap disc brakes on the front with a dual MC. What am I missing? Anything else that you guys can think of that could be an issue? Also, all the lines look good.
Stumble:
Stock engine, again 289 with a 2100 carb. The car barley ran when I got it, to correct the issues I've upgraded to a Pertronix (have them in my Chevy's absolutely love Pertronix) rebuilt the carb, new cap rotor, plug wires, set the plugs to .040. Set the rockers (stock hyd cam) had some really loud rocker noise. Car actually runs now, pretty well I'd even say.... Except.... There's a stumble off idle that I cant tune out. I've been able to reduce it a bit by changing the location of the accelerator rod linkage. I now have it set on the accelerator pump on the outside hole, closest to left side fender well and at the highest hole on the cross shaft on the side of the carb. When I rebuilt the carb I verified that the shooters and all the jets were factory sizes. New accelerator pump, new power valve. Where do you guys have your linkage set? My thought is maybe the power valve is bad since it's not transitioning from idle circuit to main circuit without a stumble. What do you guys think?
Thanks in advance for any help and suggestions.
05-12-2011, 11:46 AM
#4
2nd Gear Member
Join Date: Aug 2009
Location: Nebraska
Posts: 475
For the brakes. It is a different master cylinder for manual and power drum brakes. And for power drum there was a mid production change in march of 66. Its been many years since i have messed with 66 brakes but if memory serves me right there is a difference in pistion size with the power drum pistion being smaller, but dont hold me to that.
Do you have any problems with the drums releasing after you let off the pedal? Does it have a pull when braking?
A car this old and if it still has the original lines then its possible to have corrosion building up in the lines blocking pressure to a cylinder or out of the master cylinder. Its hard to trouble shoot this until the blockage is really bad. But if you try and bleed the brakes(for troubleshooting purposes open the bleeder before pressing the pedal) and one wheel has less fluid coming out then you might have a line blockage. Its rough but it will show a severe blockage of a brake line. Or you could disconnect all the lines and blow air through them to try and find a blockage.
If you decide all the lines are good or that you have the wrong MC then here is a link to a dual MC kit. If you arent planning on showing in concours class then i would recommend this conversion just for safety.
http://www.cjponyparts.com/dual-bowl...5-1966/p/DBC1/
66 manual drum MC
http://www.cjponyparts.com/master-cy...-1966/p/BMC02/
66 power drum MC pre 03/66
http://www.cjponyparts.com/master-cy...-1966/p/BMC05/
66 power drum post 03/66
http://www.cjponyparts.com/master-cy...-1966/p/BMC06/
For the stumble. Have you sprayed everything down for vacuum leaks? Whats your timing set at and does it advance properly with RPM increase? What is the vacuum looking like with a gauge, any bouncing on the needle or low? Does it backfire when it stumbles? My first thought is a small vacuum leak or blockage in the power circuit.
Do you have any problems with the drums releasing after you let off the pedal? Does it have a pull when braking?
A car this old and if it still has the original lines then its possible to have corrosion building up in the lines blocking pressure to a cylinder or out of the master cylinder. Its hard to trouble shoot this until the blockage is really bad. But if you try and bleed the brakes(for troubleshooting purposes open the bleeder before pressing the pedal) and one wheel has less fluid coming out then you might have a line blockage. Its rough but it will show a severe blockage of a brake line. Or you could disconnect all the lines and blow air through them to try and find a blockage.
If you decide all the lines are good or that you have the wrong MC then here is a link to a dual MC kit. If you arent planning on showing in concours class then i would recommend this conversion just for safety.
http://www.cjponyparts.com/dual-bowl...5-1966/p/DBC1/
66 manual drum MC
http://www.cjponyparts.com/master-cy...-1966/p/BMC02/
66 power drum MC pre 03/66
http://www.cjponyparts.com/master-cy...-1966/p/BMC05/
66 power drum post 03/66
http://www.cjponyparts.com/master-cy...-1966/p/BMC06/
For the stumble. Have you sprayed everything down for vacuum leaks? Whats your timing set at and does it advance properly with RPM increase? What is the vacuum looking like with a gauge, any bouncing on the needle or low? Does it backfire when it stumbles? My first thought is a small vacuum leak or blockage in the power circuit.
Last edited by rtintwo; 05-12-2011 at 12:00 PM.
05-12-2011, 12:27 PM
#5
2nd Gear Member
Join Date: May 2011
Location: texas
Posts: 254
Drum breaks basicly suck, There's nothing wrong with them they just are that way. If it helps, they will get a little better as they are used. You want the car to stop like a modern car, put some modern breaks on it.
The stumble is in the carb, Change the carb for a quick fix, or rebuild it.
The stumble is in the carb, Change the carb for a quick fix, or rebuild it.
05-12-2011, 12:40 PM
#6
6th Gear Member
Join Date: May 2009
Location: PA
Posts: 5,232
Brakes:
The brakes on this car are terrible, no kidding my 1955 Chevy, also with manual drum brakes, stops 10 times better than the Mustang. The pedal is incredibly hard to press, almost requires 2 feet to stop it. When I got the car home and got it on the lift, I pulled all the drums. As the previous owner indicated, brand new drums, hardware, wheel cylinders and shoes. Even the MC looks new. The shoes looked a little glazed, so I hit them with some 80git on the DA. The insides of the drums looked like they've recently been turned so I didnt see any issue there. Buttoned everything up and it still stops like a Mack Truck. The only thing I can come up with, is that when the PO had the brakes, entirely, replaced maybe they used the wrong MC?? One with a different bore possibly. Is that possible? Is there an easy way to identify the correct MC to make sure I have the right one installed? The MC installed on the car is still a single reservoir (fruit jar). I'm about to the point where I'm going to swap disc brakes on the front with a dual MC. What am I missing? Anything else that you guys can think of that could be an issue? Also, all the lines look good.
Something is screwed up, because I also have a 1955 Bowtie, and the brakes are pretty equal to the drum brake Mustang. First diagnose the brakes. Once they are operating properly, consider adding power boost. The only booster worth considering is the MPB repro of the OEM unit. Get the one with the dual master. If you plan performance driving, change to front discs. Get a kit that duplicates the OEM K/H brakes. They install on your existing spindles, makes the whole conversion a one-evening job. Excellent brake.
Stumble:
Stock engine, again 289 with a 2100 carb. The car barley ran when I got it, to correct the issues I've upgraded to a Pertronix (have them in my Chevy's absolutely love Pertronix) rebuilt the carb, new cap rotor, plug wires, set the plugs to .040. Set the rockers (stock hyd cam) had some really loud rocker noise. Car actually runs now, pretty well I'd even say.... Except.... There's a stumble off idle that I cant tune out. I've been able to reduce it a bit by changing the location of the accelerator rod linkage. I now have it set on the accelerator pump on the outside hole, closest to left side fender well and at the highest hole on the cross shaft on the side of the carb. When I rebuilt the carb I verified that the shooters and all the jets were factory sizes. New accelerator pump, new power valve. Where do you guys have your linkage set? My thought is maybe the power valve is bad since it's not transitioning from idle circuit to main circuit without a stumble. What do you guys think?
I'm thinking outside this box. Any engine requires proper tuning of all components for proper operation. I'd be willing to bet that Johnson was President the last time the advance curves were set on your distributor. You've checked everything else, and I've seen small changes in advance curve turn a dog into a tiger.
The brakes on this car are terrible, no kidding my 1955 Chevy, also with manual drum brakes, stops 10 times better than the Mustang. The pedal is incredibly hard to press, almost requires 2 feet to stop it. When I got the car home and got it on the lift, I pulled all the drums. As the previous owner indicated, brand new drums, hardware, wheel cylinders and shoes. Even the MC looks new. The shoes looked a little glazed, so I hit them with some 80git on the DA. The insides of the drums looked like they've recently been turned so I didnt see any issue there. Buttoned everything up and it still stops like a Mack Truck. The only thing I can come up with, is that when the PO had the brakes, entirely, replaced maybe they used the wrong MC?? One with a different bore possibly. Is that possible? Is there an easy way to identify the correct MC to make sure I have the right one installed? The MC installed on the car is still a single reservoir (fruit jar). I'm about to the point where I'm going to swap disc brakes on the front with a dual MC. What am I missing? Anything else that you guys can think of that could be an issue? Also, all the lines look good.
Something is screwed up, because I also have a 1955 Bowtie, and the brakes are pretty equal to the drum brake Mustang. First diagnose the brakes. Once they are operating properly, consider adding power boost. The only booster worth considering is the MPB repro of the OEM unit. Get the one with the dual master. If you plan performance driving, change to front discs. Get a kit that duplicates the OEM K/H brakes. They install on your existing spindles, makes the whole conversion a one-evening job. Excellent brake.
Stumble:
Stock engine, again 289 with a 2100 carb. The car barley ran when I got it, to correct the issues I've upgraded to a Pertronix (have them in my Chevy's absolutely love Pertronix) rebuilt the carb, new cap rotor, plug wires, set the plugs to .040. Set the rockers (stock hyd cam) had some really loud rocker noise. Car actually runs now, pretty well I'd even say.... Except.... There's a stumble off idle that I cant tune out. I've been able to reduce it a bit by changing the location of the accelerator rod linkage. I now have it set on the accelerator pump on the outside hole, closest to left side fender well and at the highest hole on the cross shaft on the side of the carb. When I rebuilt the carb I verified that the shooters and all the jets were factory sizes. New accelerator pump, new power valve. Where do you guys have your linkage set? My thought is maybe the power valve is bad since it's not transitioning from idle circuit to main circuit without a stumble. What do you guys think?
I'm thinking outside this box. Any engine requires proper tuning of all components for proper operation. I'd be willing to bet that Johnson was President the last time the advance curves were set on your distributor. You've checked everything else, and I've seen small changes in advance curve turn a dog into a tiger.
Last edited by 2+2GT; 05-12-2011 at 12:44 PM.
05-13-2011, 09:58 AM
#7
Thread Starter
Join Date: Nov 2010
Location: Il
Posts: 4
Rintwo: Thanks for the info and great follow up question. No problem whatsoever with the shoes releasing when I get off the brake pedal. No issue with the car pulling when you first get on the brakes, even if the car is cold.
I haven't bled the brakes, so I cant comment on the lines ability to flow fluid. The pedal is right at the top but that wouldn't indicate poor flow from corrosion on the inside of the line... I think I'll bleed them this weekend though now.
Thanks for the links, it's not a show car, just a weekend cruiser so I'm not opposed to swapping out the MC.
Sprayed down the carb, doesn't seem to have a vacuum leak. I cant recall what the exact reading was when I had the vac gauge on it, I think it was 14”. The needle was steady though and did not bounce. Advance is working, I can see the indicator climb when I rev the engine. Don't recall the initial timing, I'll check that this weekend as well. Pretty sure it was between 8-12 though. Also, I was going to throw another power valve into it just in case. The car doesn't backfire or pop so I don't think I've blown the one that I installed from the rebuild kit, but I'm not sure, stranger things have happened.
I haven't bled the brakes, so I cant comment on the lines ability to flow fluid. The pedal is right at the top but that wouldn't indicate poor flow from corrosion on the inside of the line... I think I'll bleed them this weekend though now.
Thanks for the links, it's not a show car, just a weekend cruiser so I'm not opposed to swapping out the MC.
Sprayed down the carb, doesn't seem to have a vacuum leak. I cant recall what the exact reading was when I had the vac gauge on it, I think it was 14”. The needle was steady though and did not bounce. Advance is working, I can see the indicator climb when I rev the engine. Don't recall the initial timing, I'll check that this weekend as well. Pretty sure it was between 8-12 though. Also, I was going to throw another power valve into it just in case. The car doesn't backfire or pop so I don't think I've blown the one that I installed from the rebuild kit, but I'm not sure, stranger things have happened.
05-13-2011, 10:09 AM
#8
Thread Starter
Join Date: Nov 2010
Location: Il
Posts: 4
2+2GT:
Thanks for the response. You're right on the brakes. I just cant believe the Shoebox (Older, heavier) stops better than this little conv. I'll get it is straighten out even if I have to pull the whole system apart.
When I tuned the car originally, I set the timing so I had 32 degrees in by 2500. I did have some pinging going on so I then retarded it a bit to remove the ping, prob 2 degrees or so. I'm not sure what the initial timing is. I'll check that this weekend and report back.
Thanks for the response. You're right on the brakes. I just cant believe the Shoebox (Older, heavier) stops better than this little conv. I'll get it is straighten out even if I have to pull the whole system apart.
When I tuned the car originally, I set the timing so I had 32 degrees in by 2500. I did have some pinging going on so I then retarded it a bit to remove the ping, prob 2 degrees or so. I'm not sure what the initial timing is. I'll check that this weekend and report back.
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