Ok guys, I need a little help to firgure out my carb whistle. I figured it was a vacuum leak as I am having a hard time with holding the idle, but I can't find it. I get a whistle when I rev the motor up and while I'm driving. It goes away when the motor comes back down to idle. Here's what I have and what I've done. Q-jet, spacer plate, SP-1 intake, the only lines on the carb are for the PVC and dist. advance. One line on intake maniford for trans vacuum modulator. Checked lines, replaced PVC, replaced carb to intake gaskets(one on both sides of spacer, I used the '76 style for the extra thickness). Could it be the gaskets in the carb itself, intake manifold gasket, throttle plate bushings? I sprayed carb cleaner on suspect areas while it was running and I don't notice any idle change. I was before I changed the base gaskets, but not now and still have the whistle. Any Ideas? Thanks.
How about the brake booster? Have you measured manifold vacuum with a gauge? What kind of SP1 is it, new?, what pattern, Q-jet or Square bore? Do you know the history of the carb? When did it start doing this?
Car has manual brakes, It's a dual pattern SP-1, not sure how old it is. I don't have a vacuum gauge, but when I disconnect the PVC it kills the motor. The whistle started earlier this year but had no effect to the idle. I had the trans out for a rebuild and replaced the rear main seal in the motor. Now the whistle is louder and changeing idle. Also, the carb was set up by the previous owner. All that I have changed on it was the idle.
All SP1's have the dual bolt pattern. I mean is it a Q-jet plenum or Square bore plenum? Can you run it without the spacer?
I would put a vacuum gauge on it. Then spray around the gaskets. You will see the gauge increase when you hit the leak. On the newer SP-1's there is a threaded hole at the back below the carb. Is it capped? I know this is obvious but I thought I'd mention it. Double check the modulator connection at the back of the intake.
Thanks Larry. I am beginning to think it has to be the modulator line. I sparyed the fitting in the intake but not the rubber hose to the line. When I go back over to the garage I'll pull the line off and cap the fitting to see if it goes away. Man, its always something when I want to get this thing loaded up to go racing. Thanks again. See you in Columbus.
