Hard Pedal - Team Camaro Tech
Brakes, Suspension & Steering Conversion questions, Steering & Handling

 
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post #1 of 6 (permalink) Old Nov 3rd, 01, 02:21 AM Thread Starter
 
Join Date: Jul 2001
Location: Dallas, Texas
Posts: 13
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I just upgrading the entire brake system on my 68. Front and rear disk, new (small) big block booster, master cylinder, proportioning valve, lines, braded SS hoses, everything. Complete matched system from MP Brakes.

I'm very satisfied with everything BUT... when I hit the pedal the first time to stop or slow down, the pedal feels fine, firm, and with the proper amount of feed back and travel. If I have to push the pedal the second time, within a very short time of hitting it the first time (traffic), I get a very hard pedal and very little travel. I really have to push on it to slow down. This has almost got me in trouble a couple of times.

I have checked really close for vacuum leaks. Vacuum is comming directly from the intake manifold, new (real) vacuum hose to the booster, check valve seems ok... I'm lost as to what it can be. I'm running 18 to 20 inches of mercury at idle.

Any of you guys got anything else for me to check?

Thanks for any input.

Fletch

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1968 pro-touring 350cid
1981 drag 454cid
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post #2 of 6 (permalink) Old Nov 3rd, 01, 06:20 AM
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David Pozzi
 
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Location: Central California, USA
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Check out the ID size of your vaccum hoses and fittings.
It sounds like there is poor air flow through the vaccum lines to replenish vaccum in the booster.
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer
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post #3 of 6 (permalink) Old Nov 3rd, 01, 06:19 PM
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I have seen many new and reman. boosters go bad, you do have a vacuum problem.......
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post #4 of 6 (permalink) Old Nov 4th, 01, 04:46 AM Thread Starter
 
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David/sixt9d... You guys may be on to something... poor volume. I have checked the vacuum hose and associated components. The hose is DOT approved, 11/32" (0.343) VL. The 90 degree manifold fitting is barbed and for 11/32 ID hose, so it is slightly smaller in the inside diameter. The plastic (*#$%##)90 degree fitting that fits into the booster is sized about the same as the manifold fitting. Both have a ID of ~0.200. This seems a little small doesn't it?

It would be easy enough to change the manifold fitting and hose for larger ID units but the rubber grommet in the booster will only accept a small fitting. I guess I could always take out the fitting, it's grommet and resize the booster hole for a larger grommet. This would give me much better flow rates. What ya think?? Thanks for the input.

Fletch
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post #5 of 6 (permalink) Old Nov 4th, 01, 07:40 AM
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David Pozzi
 
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That's a small hose size.
I think the stock firstgen uses a half inch id hose and check valve.
If you can upsize to that size, I think the booster will respond better.
Try a unibit on the booster hole.
Get some magnets and put around the hole and drill it out with someone holding a vaccum cleaner next to the bit.
Hopefully the magnets will catch any metal that falls inside and you can get it out from inside with your fingers.

Also anything you can do to reduce the stroke of the booster will help.
If you have the iron rear calipers like Deville or Trans Am/Camaro they can fail to self-adjust and the low pedal will create excess travel problems.
David

------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer
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post #6 of 6 (permalink) Old Nov 5th, 01, 04:44 AM Thread Starter
 
Join Date: Jul 2001
Location: Dallas, Texas
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Thanks David,

As always, you guys seem to gome through. Man, this group is A-OK in my book. A guy can get some serious help here when he needs it.

I'm gathering all the necessary stuff to enlarge the hose diameter now... will let you know how it turns out.

Thanks again,

Fletch
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