High Pitch Whistle - help please

[Rob H.]

Re: High Pitch Whistle - help please

Kevin - the points you bring-up make perfect sense. Thank you for the detailed trouble-shooting instructions. I will tackle it this weekend and let you know the outcome.

Much thanks,
Rob

[Rob H.]

Re: High Pitch Whistle - help please

Rob,
...Greg Woodruff said it sounded like the base of the carb and the body of the carb had a warped surface and needed to be planed.
Mr. Woodruff was right - planed both surfaces and no whistle

My problem unfortunately persists. I was able to get the hood open and inspect where the noise was coming from - it was indeed emanating from the carb/air cleaner area.

Is anyone familiar with the procedure Peter mentions above?

The carb base plate was a bit warped and not sitting flush on the top of the carb. I planed it as suggested, and doubled-up the gaskets as mentioned by Kevin to no avail.

I would love to have more of a breakdown of the procedure Peter mentions - maybe I missed something...

Also checking vacuum leaks as I go. Thanks in advance for any help or advice you can offer-up!
Rob

[Jack H.]

Re: High Pitch Whistle - help please

Could you have a pin hole or poorly connected vac hose? Remember part of the Shark vac system to operate the wiper door and headlights runs through the firewall and into the cockpit to connect to the WSW door relay (back of tachometer), the HL and wiper door over-ride switches (below the steering column) and to the headlight switch itself before exiting back out through the firewall...

[Rob H.]

Re: High Pitch Whistle - help please

Jack - Its a definite possibility...but would that explain the fact that the noise is coming from the area of the carburetor?

Rob

[Jeffrey S.]

Re: High Pitch Whistle - help please

Rob:
Has this carb been rebuilt? It is possible that the whistle is coming from worn shafts that need to be rebushed. A large amount of air is being sucked in and if any goes through the bushings it could produce the whistle. If you can spray some carb cleaner at the shaft ends when you hear the whistle it may indicate this. Just a thought.
Jeff

[Jack H.]

Re: High Pitch Whistle - help please

Guess I missed you saying the noise could be localized to the under-hood area. That's why I 'picked on' the cockpit vac lines as a potential source... If you're SURE the source is underhood, at/near the carb, then I'd begin fault isolation efforts there.

You've got really two areas to inspect: (1) the carb + intake, and (2) vac lines running off the intake + surrounding hoses routing vac to various headlight & wiper door components.

The olde rule of thumb approach of checking the integrity of a carb is to get the engine running at idle and CAREFULLY spritz a little carb cleaner here/there to see if you hit a 'hot spot'. That will typically exhibit itself with a brief increase in engine idle RPM as the carb cleaner is sucked into the carb/intake and richens the fuel mixture.

Typical culprits include: worn carb throttle/choke shafts that need to be re-bushed, warped carb component pieces that need to milled to re-true them and carb gasket + torque down hiccups. Also, while relatively rare, you CAN encounter an intake manifold with a hairline crack that opens/closes sporadically based on heat and the stress of motion.

On the vac system, the pickup point is a fitting in the intake behind the carb with rubber hoses connecting to down stream components that include the in-line plastic vac filter, the in-line metal check valve, Etc. You can have areas of the rubber tubing that've abbraded by rubbing against adjacent engine components, have pin hole(s) in them or are cracked/checked at their ends where they install on the inlet/outlet nipples of various vac components.

[Rob H.]

Re: High Pitch Whistle - help please

Jeff - I had my carb re-built about 18 months ago...

Jack - I will trouble shoot the areas you so graciously detailed this weekend and let you know the results.

Thank you both - your feedback it is very much appreciated!!!

Rob

[Douglas L.]

Re: High Pitch Whistle - help please

Rob,

Had the same thing on a 67BB with a Holley. When the engine was cold - no whistle. When the engine warmed to a certain temp - obnoxious whistle. The problem was the base plate on the carb. It was warped. The hotter engine increased the warping causing the whistle. This was on a rebuilt carb! My solution was to replace the base plate. Stacking gaskets isn't a good idea because it really doesn't solve the problem. And overtightening the carb bolts can be costly. I recommend you try a new or rebuilt base plate.

[Jeffrey S.]

Re: High Pitch Whistle - help please

Rob:
Even though you had the carb rebuilt, it doesn't necessarily mean that the shafts were checked or rebushed. It depends on what kind if rebuild was done and by whom. I would still check this area for leaks.
Jeff

[Jack H.]

Re: High Pitch Whistle - help please

YES! Some simply disassemble, install a rebuild kit and re-assemble. It's the real PRO's who grade their own report card by pacing the finished carb on either a flow bench or 'mule' engine...

[Rob H.]

Re: High Pitch Whistle - help please

I finally found the culprit!!! The vacuum seal to the distributor was shot. I replaced it and all is good and she is driving better than ever! Not, of course, before having my carb throttle rebuilt and re-bushed (but it needed that anyhow at some point).

Thanks to all who helped me solve my dilemma! It is SO nice to be driving her down the road and all I hear is the purr of the engine.

Best,
Rob

[Michael M.]

Re: High Pitch Whistle - help please

Rob, what do you mean by "vacuum seal to the distributor"? Was it the vacuum advance cannister?

[Douglas L.]

Re: High Pitch Whistle - help please

Rob,

Same question as Michael. The vacuum advance is the only vacuum part of the distributor. I suppose one could make a noise if it was failing. But as far as your car running better, a functioning vacuum advance definitely makes a difference.

[Rob H.]

Re: High Pitch Whistle - help please

Sorry I was not more clear...it was the vacuum advance.

Here is the long story - I pulled the carb to see if it was not sealing correctly due to the surface warps. It was not warped. However, in taking it off, I realized that the throttle arm was loose and needed to be re-built and the butterflies needed to be straightened (might as well do proper house cleaning as long as you have already moved the furniture, right?). I refitted the carb back on with two new seals as well as a stainless steel heat shield - to ensure a tight fit. Next symptom...the car was still not idling properly and still making that awful noise. From the posts I knew it must me a vacuum problem. Which led me to the vacuum advance. There was a leak in the diaphragm. I replaced the vacuum break control and adjusted the idle. Now she just purrs. Not to mention it does not sputter when I turn her off (a symptom I had previously thought was due to non-leaded gas).

This was a very frustrating problem, but almost makes me appreciate her all the more now that she is running so well.

Thanks again for all the help!

Rob

[Douglas L.]

Re: High Pitch Whistle - help please

Rob,

It's a good feeling when an aggravating problem that didn't seem to have an answer is fixed! Congrats.