Guest tdawg Posted August 22, 2005 Share Posted August 22, 2005 First post so be gentle guys. I have a 1973 240Z with a 3.0 Rebello motor. I have the Toyota 4X4 in front and the 280ZX and Maxima disc setup on the rear. Things went well and the brakes were strong until I switched the carbs and intake manifold. I had twin 50mm SU's and converted to triple sidedraft OER (essentially Mikuni) carbs with the six runner intake. During the last half of the brake pad life the pedal became somewhat soft and grabby. Thought it was the MC so converted from original 7/8 to 15/16 out of a 79-81. Seemed to make things a little worse instead of better. My thesis is that the manifold vacuum is different now that I am ported up to one runner instead of the intake for the rear 3 cylinders as was the case with the old SU setup. Any experience with this or suggested remedy? Quote Link to comment Share on other sites More sharing options...
Trevor Posted August 22, 2005 Share Posted August 22, 2005 You might look at plumbing a "T" in the Vacuum tubing to draw from both ends of the intake. Check for leaks. Quote Link to comment Share on other sites More sharing options...
Thumper Posted August 22, 2005 Share Posted August 22, 2005 Hook up a vacuum gauge and see if what kind of vacuum you are getting. Also check to make sure the brake booster is holding vacuum. Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted August 22, 2005 Share Posted August 22, 2005 On my forced induction set up I am looking at using a VW Electric Vacuum pump for the brakes and heater system. VW make one for its diesel cars for the brake booster. This is not exactly what the brake one is but will bive you the idea. http://cgi.ebay.com/ebaymotors/Central-Locking-Vacuum-pump-VW-Quantum-santana-locks_W0QQcmdZViewItemQQcategoryZ42612QQitemZ7989862351QQrdZ1QQsspagenameZWD1V Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 22, 2005 Share Posted August 22, 2005 You would expect less vacuum therefore less assist, meaning a harder pedal. Weird that you would describe them as grabby, unless maybe you're getting a bit of assist and then you lose the vacuum, which makes the pedal harder... Vacuum canister or a vacuum pump off of a diesel might be just the thing for you as SHO-Z suggested. Quote Link to comment Share on other sites More sharing options...
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