While waiting for my engine rebuild I'm replacing front and rear brakes. The lines were frozen to the wheel cylinders so the lines broke off. I have new wheel cylinders, but the lines have smaller fittings into the rear block on the axle. The cylinder ends are fine. Is it ok to add an adapter to the block end for both lines
You can ad an adapter but it can be harder to chase down any leaks, more fittings mean more connections means could have more leaks. You will need to make sure the adapters take flared lines. You can't just use some NPT fitting like for the cooling or fuel system, the brakes are much higher pressure over 600 psi so you have to use special adapters to stop leaks.
You may want to make sure you have the correct wheel cylinders or the correct brake line for your application before dealing with any adapters. Personally I would not use adapters in the brake system.
On a disc brake car there is one brass coupler on the passenger side that connects the hard line to the firewall line, it is designed to take double flairs.
As is the distribution block on the rear axle. The wheel cylinders except the flair from the hardline connection, so if you installed an adapter there it would need to take the flair from the hardline, and have a female inside the other side to go into the male cone in the cylinder.
If you simply install a regular step down adapter there it will blow brake fluid all over the first time to pump the system when the bleeders are closed.
Something isn't right is your car front disc and rear drum or drum and drum?
I believe the 2" is for front drums I need to look at my book, I could be wrong and 2.25 is front but the wheel cylinders should have the same threads. Where did you get the wheel cylinders?
Thinking out loud, you might have the wheel cylinders for the 250 not the 351
They made different cylinders for the i6 verse v8
There are several different size rear wheel cylinders (piston/seal/bore sizing). I learned that while sourcing them for my '72. It is important that from side to side they are the same, and they should be the appropriate size for your application (disk/drum, drum/drum, and possibly engine options). I don't have the breakdown on what the sizes were by application.
1931 Ford Model A Station Wagon
1969 Mach 1 - 351C, TKO-600, 4WDB, R&P, A/C, Shaker, Fold Down, etc.
1972 Mach 1 - 351C, FMX, PDB, PS, A/C, Fold Down, Console
1996 Mustang Cobra Convertible - 10psi Procharger