Help!!!-engine trouble

Hello all, I will start by thanking you far taking time to read and reply to this. I have a 1968 Mustang with a 302 and a Demon 625cfm Road demon jr. and a relatively mild comp cams cam (I think it's specs are
something like 168 degrees and .460 inches of lift) Right now it is set at about 16 degrees advance (the cam manufacture reccomends 14-20) and I have tried all the way from 10 degrees retarded to 30 degrees advance. It has a c-4 transmission that was JUST re-built, and I dont know how the engine ran before the rebuild because they were rebuilt at the same time. Now, the problem is that the engine runs GREAT in park or neutral, but as soon as the transmission is shifted into gear, the rpms drop (as the should, I think) and the engine soon dies if it's not given gas. The engine doesnt pull under acceleration, either. The car has power breaks, which are somewhat "soft"....which leads me to believe that there is a vaccum leak, yet the engine will pull 10-15 inches if the timing is set right. The vaccum needle usually jumps around +/- 1 inch too. I'm not sure if that amount is typical for the cam described above. Is there a vaccum leak? Would a leak cause the problem described? What else could it be? Does anyone have good methods for finding vaccum elaks? I really have no idea how to search for them. Thanks for all your help!! If you need more info, ask, I'll check this post regularly.
-Dan
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The easiest way to check for a vaccum leak is with an unlit propane torch. You don't need a lot of gas from the torch to make the idle jump when you find the leak. Others use starting fluid but I've burned my hand a couple times from the ether igniting so I shy away from that unless there's nothing else around. Check carefully for hoses and other odds and ends not hooked up seeing as this is a new build-up.
Happy modeming, Bill
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Many years ago, I got "bit" by an intake gasket with really tough end seals (the cork ones).... Since then, when ever I torque an intake on any Windsor engine, I repeat the torque process several times.... it's amazing how much you can "gain" on subsequent passes. Once you don't gain any more turns (or partial turns), you are done...
HTH
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Jim Warman wrote:

thanks for your help, i'll try these things and let you guys know
-dan
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look at the carby or dizzy. make sure your vac advance is ok on the dizzy and butterflies are opening fully under full throttle (engine off). The reason I say this is because I had a 400 (LTD) with a reaqlly leaky inlet manifold and carby but it never acted the way u describe. It did have std cam tho.

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