Conversation Between 4wydnr and 1978f250cummins

Hey Sean, I don't mind. I never drove my truck without the cummins in it. I had weak vacuum brakes so I did a hydroboost swap using a gm hydroboost unit. When I removed the original booster it was full of brake fluid, so that was my trucks issue.
As for yours I'm not certain, I've read brake hoses can collapse internally causing trouble. I have about $100 in my hydroboost setup and it's the second best modification I've done on it.

Hello, my name is Sean and I hope you don't mind me asking a few questions about your cummins swap.

I swapped in my 1989 6bt in my 78 f250
Converted my c6 to a np435(from a 1978)
every single part for the manual conversion from a 1978 f250
Used very thick o.d marine grade 3/8 I.d for my vacuum line and a new check valve on the booster(my pump has two lines that t into one line that I assume goes to the booster, it was cut when I bought the engine)
I kept my stock c6 brake booster, with the new manual pedal assembly.
refilled the mounting hole on the brake booster rod that comes through the firewall, mounted my manual pedal to the automatic stock brake booster. Stepped on the brakes and blew a line.
Replaced the line topped off the fluid but haven't bleed the line yet.
I have a very stiff pedal that doesn't not stop the truck now.
My brakes worked mint when it had the v8 but the truck sat a while til I did the swap.


How did you fix your brake issues for your cummins?