I posted awhile back about my brake issues.Thought it was a vacuum issue due to a large cam.Finally got the vacuum pump on and things didn't change.I have 2 man bled,vacuum bled,gravity bled and pressure bled,no improvement .Pedal feel is good just don't seem to make enough pressure.
Booster seems to be holding.Brakes worked fine before I changed engine,new flex lines front and rear.Didnt change calipers because they looked good but they are unknown.Changed master cylinder all rotors and drums were turned.New pads and shoes.Rear wheel cylinders appeared to be new.Rear brakes adjusted properly.Ive been chasing this problem for nearly 2 years now.Dont seem like they are making enough pressure to " clamp".Brakes won't pump up.I haven't just started throwing parts at it yet because I thought it was an engine vacuum problem.Maybe I just need to replace and upgrade everything,should've done that to begin with but there was no issue before.
OK - I might have something for you to check. When I put mine back together, I went with all-new factory-style everything (OEM replacement), to include new brake lines, calipers, master cylinder, distribution block, etc. - literally "everything" except the booster, since I ran into issues trying to get an OEM-style new one or mine rebuilt. I got it all back together, bled, and I could not get my pedal to firm up - couldn't figure it out... chased my tail for about a year after I got the car running - after several pumps, it would hold, but not good enough for driving.
After I received the booster and installed it, the problems still persisted - so 'that' wasn't it.
I did some more research, bugged the guys here, and thought about trying a bunch of different things... and then the light bulb went on for me when I was under the car - I'd installed the calipers on the wrong sides (passenger on driver, drive on passenger). Crap! Once I swapped them back to their correct sides and bled the system again, it was all golden... finally. The way I determined it was noticing that the bleeder valve was lower than the brake line inlet. Duh... felt like an idiot afterward.
I don't know if that might be your issue, but it wouldn't hurt to check just in case. (although, you did say the brakes worked fine before the engine swap and you didn't change the calipers)
Have you checked your power brake distribution block? I understand that if the proportioning valve gets 'tripped,' it won't work right until it's 'reset,' which I ain't gonna lie - I'm not entirely sure what that means.
Do you have your brake booster vacuum line system hooked up to the base of the carb, or straight to the intake manifold inlet toward the rear of the engine? I put an elbow on mine and went straight off the intake manifold. My 351C-2V has a pretty healthy cam in it (CompCams Magnum 270HR - 270/270, .566" lift, 110 degree lobes - 215/215 @ .050") - haven't experienced any vacuum issues.
Sorry if I've thrown out things that you've already checked - these are the things I've run into with mine.
Hope it helps.
It's on manifold vacuum. Calipers are on correctly.I haven't gotten into proportioning valve or distribution block issues yet.I talked to gps brakes and got some advice on some things to check.My cam is 590/620 247/257@ .050 110lsa I'm making about 8-10" of vacuum at idle.Pump is supposed to put out 20".
I've adjusted mc pushrod at least 5 times too.I bet I'm getting close to 5 gallons of brake fluid used over the last couple years.
or your local parts store may have one you can borrow.
'73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, soon to have Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, 750 CFM double pumper, Holley Street Dominator intake. Still a work in progress.
'73 F code convertible. Bright red. Needs total restore.
The cam isn't in a 351c so it's not really a monster.Its in a 521.I really want to think it's the booster but it holds vacuum.