Got a Whistle but no Turbo. NEED CARB HELP - The 1947 - Present Chevrolet & GMC Truck Message Board Network

CobraJetKid · 10-23-2013, 03:07 AM

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.

jlk · 10-23-2013, 04:18 AM

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

CobraJetKid · 10-23-2013, 06:39 AM

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

jitteryguy · 10-23-2013, 07:36 AM

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 ?

CobraJetKid · 10-23-2013, 11:40 AM

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?

wilkin250r · 10-23-2013, 12:52 PM

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.

CobraJetKid · 10-23-2013, 02:19 PM

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

Skunksmash · 10-23-2013, 10:14 PM

lol @ thread title

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

10-23-2013, 03:07 AM	#1
CobraJetKid Registered User Join Date: May 2011 Location: Hampton, VA Posts: 70	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. __________________ 1977 K10 Silverado "The Heavy Chevy" - 350/350/203...Version 2.0 in progress: http://67-72chevytrucks.com/vboard/s...d.php?t=576865 1972 C10 Cheyenne "The Brown Bomber" - 307/SM465/12 bolt posi...Plans for 2.5/4" drop 1992 F-150 "The Dooley" - 351C/M715 axles/six 44" Swampers...BOSS 351 stroker pending

10-23-2013, 04:18 AM	#2
jlk Registered User Join Date: Sep 2013 Location: Richland, WA Posts: 28	Re: Got a Whistle but no Turbo. NEED CARB HELP It runs fine with 8" of vacuum? Did you mean 18"?

10-23-2013, 06:39 AM	#3
CobraJetKid Registered User Join Date: May 2011 Location: Hampton, VA Posts: 70	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 __________________ 1977 K10 Silverado "The Heavy Chevy" - 350/350/203...Version 2.0 in progress: http://67-72chevytrucks.com/vboard/s...d.php?t=576865 1972 C10 Cheyenne "The Brown Bomber" - 307/SM465/12 bolt posi...Plans for 2.5/4" drop 1992 F-150 "The Dooley" - 351C/M715 axles/six 44" Swampers...BOSS 351 stroker pending

10-23-2013, 07:36 AM	#4
jitteryguy GoatLube Experss Join Date: Oct 2009 Location: clarksville, Tn. Posts: 1,337	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 ? __________________ *Goat Lube Express*, locations in Qalat,Afghanistan & Clarksville, Tn. '87 R30 dually 454/TH400 '85 1/2 ton CCSB '92 S10 350/350 '84 MonteCarlo 383/PG/9"ford '78 Malibu wagon 350/350 '78 Cutlass (project family car) '96 S10 Jimmy (Moma's)

10-23-2013, 11:40 AM	#5
CobraJetKid Registered User Join Date: May 2011 Location: Hampton, VA Posts: 70	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? __________________ 1977 K10 Silverado "The Heavy Chevy" - 350/350/203...Version 2.0 in progress: http://67-72chevytrucks.com/vboard/s...d.php?t=576865 1972 C10 Cheyenne "The Brown Bomber" - 307/SM465/12 bolt posi...Plans for 2.5/4" drop 1992 F-150 "The Dooley" - 351C/M715 axles/six 44" Swampers...BOSS 351 stroker pending

10-23-2013, 12:52 PM	#6
wilkin250r Registered User Join Date: Sep 2010 Location: Lake Tahoe, Nevada Posts: 755	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. __________________ I know a little about cars, but if you have a question about electricity or sport quads, I'm your man!!!

10-23-2013, 02:19 PM	#7
CobraJetKid Registered User Join Date: May 2011 Location: Hampton, VA Posts: 70	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 __________________ 1977 K10 Silverado "The Heavy Chevy" - 350/350/203...Version 2.0 in progress: http://67-72chevytrucks.com/vboard/s...d.php?t=576865 1972 C10 Cheyenne "The Brown Bomber" - 307/SM465/12 bolt posi...Plans for 2.5/4" drop 1992 F-150 "The Dooley" - 351C/M715 axles/six 44" Swampers...BOSS 351 stroker pending

10-23-2013, 10:14 PM	#8
Skunksmash Registered User Join Date: Sep 2012 Location: TX Posts: 1,014	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.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.