yay, another disc swap question! 1972 LWB with '73 parts

[Mr Martensite]

Greetings,

Its been a year or two of mowing yards and saving money but the boy who is 15 is ready for the upgrades to his '72 long bed.
The day he bought it![image]1471[/image]

Here is where I'm at:
-original drums 4 corners
-found donor '73 and pulled i-beams and arms,
-pulled '73 MC with booster and linkage to attached to pedal,
-pulled brake line orifice fittings going into '73 MC
-'73 tie rod was bent due to how the forklift lifted the front end (salvage yard guy, not me) --> looks like and measurements show '72 tie rod will fit '73 spindles no problem

Installed new '73 king pins (same size as '72), rotor (bearings) and calipers/pads, new '73 MC with Booster
[image]1470[/image]

MY QUESTION: I intend to use the original '72 Brake Pressure Differential Valve and plumb into new '73 MC...will I need to use the fixed orifice fittings from the OLD '73 MC on the NEW '73 MC? If the larger pot of the MC is for front disc, the OLD '73 MC actually had the smaller orifice on the big pot. Does this make sense? I placed the NEW '73 MC fitting next to the old one for reference see image. I intend to run an aftermarket proportioning valve for the rear drums.
[image]1465[/image]
[image]1463[/image]
Seeing the different orifice sizes has me curious as well as the thread sizes of the fittings are opposite of the OLD '73 and NEW '73 MC (in opposite spots)

new '73 MC is Raybestos MC36399 part number. [image]1466[/image]

Lastly the brake pedal attached to the NEW '73 MC is now 2" lower (closer) to fire wall...I assume this is due to less travel required for booster and I intend to fab new bracket for switch...Does this sound normal?
[image]1468[/image]

If you are still with me, I appreciate your input on this as I'm working to make this safe as possible for my child and brakes tend to be important for stopping!

[basketcase0302]

MY QUESTION: I intend to use the original '72 Brake Pressure Differential Valve and plumb into new '73 MC...will I need to use the fixed orifice fittings from the OLD '73 MC on the NEW '73 MC? If the larger pot of the MC is for front disc, the OLD '73 MC actually had the smaller orifice on the big pot. Does this make sense? I placed the NEW '73 MC fitting next to the old one for reference see image. I intend to run an aftermarket proportioning valve for the rear drums.

Nice to see a young man getting into a bump! More respect for him working for his upgrades-versus the silver spoon way...
Your post is kinda' confusing to me as to which "splitter" you'll use, (the original differential valve or the aftermarkter proportioning valve) as you won't use both if done properly.

I would not swap the orifices from one port to the other, (unless the "pots" are reversed). Yes the largerone is for the front so that might necessitate moving the orifices. If the fittings on the lines don't match simply get a double flare tool and a fitting kit from Summitt, (and practice/practice/practice a lot before acutally making the double flare on the lines on the truck if you've never flared brakelines before as they split real...easy making it dangerous).

Look closely at the 73' MC pushrod as many of them were adjustable, (yeah a pain in the butt to get to it as if memory serves me right you can't adjust it out without pulling the assembly back off the firewall. Or...when I put the 79' brakes inmy 73' I took the 79' pedal assembly, (shoot me a PM with an email and i'll send a few pics showing the difference in the bump versus dent pedal assembly's-never post an email here as it attracks spammers and bots). My dent pedal assembly raised my pedal back off the floor, (I had the same problem).

[DuckRyder]

NPDs catalog at one point said that the reservoirs might be reversed in size and don't worry about it, I've seen replacement MC that were like factory, were reversed and were equal.

Your pictures are small but it think your orifices are just adapters (I have seen this as well).

I think PB and manual pedals are different (your truck was non-power brake and you are converting it?)

I used the factory distribution block with an adjustable proportioning valve in the rear line.

You may find my project thread of interest ...

[Mr Martensite]

Apparently I forgot to click the "notify me" box when posting this and just now saw the replies! Doh!

@basketcase0302: Thanks for the kind words...my goal is to teach 'em life skills and working on your own and paying your own way as you indicate is not too common these days!!!

on my '57 F100 I just used brass tees as distribution blocks and an aftermarket proportioning valve with the booster and MC and had zero issues. The '72 has the brake pressure differential valve and is used as the distribution block. I've read other instances of using it right along with an aftermarket proportioning valve with no issues as DuckRyder indicates above as well.

The main question I had was the orifice sizes on the new '73 MC appear different from the salvage yard '73 MC and is that an issue? DuckRyder explains what I am seeing as well as they are same, but different.

I will see about getting the '73 brake pedal but I've read they are different from the '72's (yes mine is 4 drum to front disc from '73, rear drum)

@DuckRyder, did you convert to a different pedal?

Thanks for both of y'alls replies!

[DuckRyder]

@DuckRyder, did you convert to a different pedal?

Mine is a factory power brake truck. I think you would need a pedal from a power brake (bump side) truck, but i'm not familiar with the 73 booster. I believe this is why all the aftermarket conversions say they will only work with manual brake trucks.

https://www.summitracing.com/parts/sum- ... odel/f-100

You might find useful information here:

http://www.fordification.com/tech/clutc ... ackets.htm

[basketcase0302]

I proved discrepancies in the brake tech article years ago, (by using the brake pedal frommy 79' where the article states it wil not work) and he refused to change it.

And I hesitated to confirm those were actual "orifices" as i too have had to change the flare fitting on the 3/16" brake line at the MC before, (as there are no less then two different sizes of fittings that screw into the MC).