[pontiac_boy]

Hey guys,

I need some advice. Over the past year or so i have been working on getting my Lemans back on the road. My plans for the car are to have a street/strip car. The motor was recently completed and the transmission is in the process. One of the things that concerns me is the fact that the new motor is most likely not going to produce enough vacuum to properly operate the power brakes. I have been told that a common thing to do is to just switch to manual brakes but i have been unable to find any detailed information on it. Last time i drove the car the break pedal was almost to the floor so at minimum i will be needing to replace the master anyway. The car still has all of the original brake components including the booster, so now would probably be a good time to change things anyway, however i am trying to find out what all would be required to make the swap. Any help would be greatly appreciated. Again its a 72 Lemans with power disc front and drum rears.

[GT182]

You can keep your power brakes but you need to add another way to create vacuum if your engine won't make enough. Old Goat 67 did with his 67 GTO at one time... PM him and ask what he used back then. Charles knows his stuff. LOL Just kidding. He really does know.

He now uses hydroboost.... but with that you'll need shoulder belts so you won't go thru the windshield in a panic stop. That's no joke as I've driven his 67 and it does stop like you won't believe. Yes he does have shoulder belts for that reason.

[Chris65LeMans]

I’ve been very happy with my hydro boost. I have it paired with 4 wheel disks. I don’t have shoulder belts, but it definitely stops good. Once or twice, some idiot has turned in front of me, I was preparing for impact, and .... I stopped in time b

[pontiac_boy]

I wont be running power steering, so hydro boost isnt an option. The car wont be seeing a ton of street miles. I am try to gear it more toward a track car that i can drive a mile to work in back every now and then when i feel like it. Or take it to a car show/meet on occasions.

[GT182]

You don't need to run power steering. But you can still use a power steering pump to run the hydroboost. Just run the lines too it alone. I bought the power steering pump for my 66 and was going to do that at one time but never have.... someday maybe and stay manual steering only.

[chipster]

In 1972 you could buy the LeMans with manual disk brakes, so the parts are available to switch to manual. You need the manual disc master cylinder because the bore is smaller for more leverage. You need to move the pushrod from the bottom hole in the pedal lever to the top hole. You'll probably need to bend up some new brake lines from the combination valve to the master cylinder. I'm not sure if the pedal pushrod is the same part or not.

[First Bird]

Manual brakes here. No need for cost/complexity of Hydroboost. Properly sized master cylinder - that means smaller than PS - with some good discs up front will stop very well.
Talk to this guy. He's an expert in brakes and very helpful - Tobin at Kore3.

[GT182]

Check on www.PirateJack.net for the MC you need. The prices are right too.

Check in the Master Cylinder Kit section and then got to www.Scarebird.com for the kit for the brake caliper brackets. You do not need to change out the drum brake spindles. He'll tell you what you need to finish... calipers/pads, hoses, and rotors. The kit should be this one, the same as my GTO. GTO B kit..... https://scarebird.com/index.php?rout...&product_id=67 The kit is for 14" wheels but everything works for 15" wheels. I used the same kit for my 15" Cragars.

[indymanjoe]

OP what did you end up doing? looking to go to manual myself and am getting all kinds of conflicting info.

[Scarebird]

We used the drum/drum master on a 68 Firebird and when we switched to 69 style disc it worked perfect.

[AG]

Originally Posted by Scarebird

We used the drum/drum master on a 68 Firebird and when we switched to 69 style disc it worked perfect.

The 1968 drum/drum Firebird master worked well with the D52 style GM calipers? What is the bore on the master, 7/8"?

[Scarebird]

1".

Yes, D52 with the 2-15/16" Ø pistons. Note as we did to the customer that you have to carefully watch the fluid level as the reservoir is smaller.

[TCSGTO]

Do you have to remove the residual pressure valve from the front of the drum master cylinder when converting to front discs? If so, how hard is that to do?

[george kujanski]

I didn't, and the brakes feel ok. Next time I open the system, I think I will do that, just because.

I think you need to pull out the flare seat carefully, and the check valve is behind it.

George

[Scarebird]

Most high mounted masters do not have RPV's - easy way to check is use a paper clip straightened out and poke - hit something squishy - that's the RPV.