Got a Whistle but no Turbo. NEED CARB HELP
 

I have a 77 silverado with a stock 350 other than an RV cam and headers. I swapped out the Quadrajet in favor of a 2 bbl holley. Everything works fine except theres a really high pitched annoying whistle sound under load. I have a vacuum gage installed on my truck and it comes in at exactly 8" vacuum. I can't find any vacuum leaks and the truck seems to be running fine. Didn't have this problem before the carb swap so it has to be something I did but I am stumped. Anybody have any idea what could be the cause? Any help would be greatly appreciated as this phantom vacuum leak is driving me nuts.

Re: Got a Whistle but no Turbo. NEED CARB HELP
 

It runs fine with 8" of vacuum? Did you mean 18"?

Re: Got a Whistle but no Turbo. NEED CARB HELP
 

No I meant 8". It only comes in under the load of acceleration. It idles right around 18" vacuum though

Re: Got a Whistle but no Turbo. NEED CARB HELP
 

whistle = vacuum leak, befor the engine get's to warm, spray some carb cleaner around the intake and carb. the carb cleaner will find it.

from what carb to what carb ?

Re: Got a Whistle but no Turbo. NEED CARB HELP
 

Swapped from a Qjet to a 500 Holley 2 bbl. I'll have to try that carb cleaner trick. I suppose if there's a tiny vacuum leak I'll hear the idle drop when carb cleaner is sprayed on it?

Re: Got a Whistle but no Turbo. NEED CARB HELP
 

Naw, you should hear the idle RAISE.

The carb needs that vacuum to deliver fuel (at idle). Less vacuum equals less fuel, which equals low or poor idle. When you spray that carb cleaner in the area of the vacuum, it will be sucked in and burned as a fuel, which will increase RPMs.

Another method I've seen people use is to get a rubber hose on a propane bottle and manipulate that around the carb and vacuum lines. Same principle, when you get the propane into the area of the vacuum, the propane will get sucked in and burned, causing the RPMs to increase. This tells you the area of the vacuum leak.

Re: Got a Whistle but no Turbo. NEED CARB HELP
 

Alright thanks for clearin that up. Never thought to try anything like that, hopefully get to it later this week

Re: Got a Whistle but no Turbo. NEED CARB HELP
 

lol @ thread title


Or some people will use WD-40 to find leaks. Its a bit thicker.