The bore being larger in the master is fine but the stroke may be shorter than that of a 92. I had the same trouble when i put 91 model disc on my 83. I had to run the 91 master.
My understanding is that combo valves "real" purpose is safety. It is there to make sure you retain one braking system if the other goes away (front/rear). First thing I would do is eliminate that from the system (temporarily) and see if you experience a change.
Your combo valve could be an issue I've had issues with mine while bleeding. For instance I only had front brakes. Cause while bleeding the rear lines if you push the pedal to quickly the proportioning valve will snap completely over and limit fluid to end you are bleeding. Fail safe if you lose a brake line wheel cylinder ect, that way you can still stop the vehicle. As far as your long pedal travel you have to much flex line on your truck although you can't see the lines swell but trust me they are. The shop here locally won't even make you braided lines that are longer than factory unless it just for a wheeler. Technically they are not DOT because they swell. If you add hard line everywhere possible, that will greatly improve your pedal travel.
Ok, here’s my assessment. I believe one of two things. I think the problem may be in the combination valve. My 2000 Chevy has hydroboost and it has a Dana 44 out of a 79 f250 with the dual piston calipers, rear is the factory 14 bolt with dual piston calipers. I completely removed all the abs and ran new 1/4 inch hardline to all the brake hoses frame side, 3/16 on the axle side. It stops perfect with a perfect pedal. I originally had a proportioning valve to help with rear lockup but it wouldn’t pass enough fluid even fully open. I think the combo valve you have may be undersized or faulty. Bypass it and see what you get. Otherwise your master cyclinder size is two small. One more thing, if those are the cheaper stainless lines have someone watch them while you hit the pedal. We had some that would swell up but not leak on a buddy’s truck
Creepycrawler I have my suspicions about the combo valve too. I will probably windup bypassing it to see if that helps. The rear lines are cheap summit band hoss, the fronts are russel, I can’t see any hose bulging.
thekingofcows also not sure on ford hydro boost but my Chevy hydroboost goes down a lot farther if the trucks not running, if the ford was the same and you had a bad hydro boost could that cause the problem?
I don't know how send a break lines diagram for your truck you run the lines like 83 Chevy one line to the back with you line lock off the proportioning valve and one line to the right side and one for the left side off the proportioning valve the two line on the master cylinder go to the proportioning valve .Ford and GM has the best brakes systems
jeremy3798 not on this model Ford,the bottom outlet on the combo valve is plugged from the factory, also the extra 3ft of restriction would not make the pedal softer. It is inconsequential; if anything it would make the pedal firmer. Thanks for taking time to comment though.
The bore being larger in the master is fine but the stroke may be shorter than that of a 92. I had the same trouble when i put 91 model disc on my 83. I had to run the 91 master.
My understanding is that combo valves "real" purpose is safety. It is there to make sure you retain one braking system if the other goes away (front/rear). First thing I would do is eliminate that from the system (temporarily) and see if you experience a change.
Your combo valve could be an issue I've had issues with mine while bleeding. For instance I only had front brakes. Cause while bleeding the rear lines if you push the pedal to quickly the proportioning valve will snap completely over and limit fluid to end you are bleeding. Fail safe if you lose a brake line wheel cylinder ect, that way you can still stop the vehicle.
As far as your long pedal travel you have to much flex line on your truck although you can't see the lines swell but trust me they are. The shop here locally won't even make you braided lines that are longer than factory unless it just for a wheeler. Technically they are not DOT because they swell. If you add hard line everywhere possible, that will greatly improve your pedal travel.
Ok, here’s my assessment. I believe one of two things. I think the problem may be in the combination valve. My 2000 Chevy has hydroboost and it has a Dana 44 out of a 79 f250 with the dual piston calipers, rear is the factory 14 bolt with dual piston calipers. I completely removed all the abs and ran new 1/4 inch hardline to all the brake hoses frame side, 3/16 on the axle side. It stops perfect with a perfect pedal. I originally had a proportioning valve to help with rear lockup but it wouldn’t pass enough fluid even fully open. I think the combo valve you have may be undersized or faulty. Bypass it and see what you get. Otherwise your master cyclinder size is two small. One more thing, if those are the cheaper stainless lines have someone watch them while you hit the pedal. We had some that would swell up but not leak on a buddy’s truck
Creepycrawler I have my suspicions about the combo valve too. I will probably windup bypassing it to see if that helps. The rear lines are cheap summit band hoss, the fronts are russel, I can’t see any hose bulging.
thekingofcows also not sure on ford hydro boost but my Chevy hydroboost goes down a lot farther if the trucks not running, if the ford was the same and you had a bad hydro boost could that cause the problem?
Try swapping front and rear at master if it's mor proportioned to the rear just a thought I don't know shit though lol
Look at how a ppv is hooked up 5 lines
I don't know how send a break lines diagram for your truck you run the lines like 83 Chevy one line to the back with you line lock off the proportioning valve and one line to the right side and one for the left side off the proportioning valve the two line on the master cylinder go to the proportioning valve .Ford and GM has the best brakes systems
jeremy3798 not on this model Ford,the bottom outlet on the combo valve is plugged from the factory, also the extra 3ft of restriction would not make the pedal softer. It is inconsequential; if anything it would make the pedal firmer. Thanks for taking time to comment though.
The t in the front it needs to be 2 lines
jeremy3798 wouldn’t a single line make pedal firmer if anything?
thekingofcows no you need the 2 lines for valune
You figure it out yet