Power brake booster
 

Can anyone help me figure out what brake booster I have on my 68.. Only #'s I can find are 39137. We installed the wilwood master cylinder with the 1-1/8" bore but now the brakes aren't firm.. We bench bled the system and bled the lines.. Thinking it's the booster now gonna replace it http://i1183.photobucket.com/albums/...B99FA88BC6.jpg

How were you brakes b4 the new master? Was the booster always in the system or is it new with the master?
What brake setup are you running Disc/drum... Disc/disc?
I have also recently done a disc disc conversion and it liked a 1" master better, it gave me a more favorable pedal feel over the 1.125 with a booster.
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Re: Power brake booster
 

Sorry for not putting more details I'm running disc/disc..the booster was on the truck with the old master cylinder and they worked great..I swapped the master cylinder because the old 1 was ugly and I hated the way the reservoir looked.. I talked to summit racing and the recommended this http://m.summitracing.com/parts/tff-2228nb
But couldn't guarantee it would work

Re: Power brake booster
 

Also I guess I'm stuck with this 1-1/8" cause I've already installed it and has fluid in it... Next time I'll buy the complete assembly booster and all lol

Re: Power brake booster
 

By this statement I would say that you booster is not your problem if everything worked well before. A booster will not just fail all of a sudden with a master change. My question now would be was the master you took off a 1-1/8"?

Re: Power brake booster
 

it looks like a truck booster say 90 through 94ish. If you dare to take the paint off the tag [right in the middle top part] you might get more help to narrow it down but I'm with the above poster that the booster just doesn't go bad because of a master change. Check your line the rubber ones and make sure they are not ballooning with the new master it may have tons[not actually] but you know more pressure than before

Re: Power brake booster
 

The rubber lines are the most neglected part of the brake system (my experience from my days in the repair biz). Once they're cracked and ugly, it's easy to condemn them. A set of 40+ year old hoses should be immediately suspect. I hope you've replaced them already, putting a bunch of new stuff on an aging system might not be a prudent course of action. If the hoses are all intact, the master cylinder piston diameter is probably the source of your ills.

Re: Power brake booster
 

The lines were replaced last year.. I pulled the sticker and the paint flaked off
http://i1183.photobucket.com/albums/...AD164623D7.jpg

Re: Power brake booster
 

That eliminates that possibility. Bench-bleed the new master, it's a good opportunity to flush the system. It's cheaper and easier than using someone else's car to stop with!

Re: Power brake booster
 

Take the MC apart from the booster. Have some one with you and push in on the MC rod and see if the brakes work. If so look at the booster pin to see if it's long enough to get full pressure to the MC.
This may help you out also.:chevy:

http://67-72chevytrucks.com/vboard/s...d.php?t=498293

Re: Power brake booster
 

Boosters don't make pedal feel firm or soft unless it's not working then it's EXTREMELY hard. What bore master did you replace? If it was 1 1/8" I would say you still have air in lines, if it was a 1" then the smaller bore would have a different feel then the new one.