Huh?? can you all help? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Momboy007 · 10-15-2008, 10:52 PM

Hello All,
I just got a quick question for all of you.
Please recall I picked up a 69 GMC 3/4 ton Custom Camper with a 396 with just over 30K miles on it, it is completely stock and never has had any work, anyhow, it runs on the roughish side, so just out of curiosity, I put my entire hand on the air cleaners snout and did not let any air in and it still ran almost identical. Does this mean I am sucking air from somewhere else? How to find the leak, if so?
Thanks all in advance,
Rick

MDC · 10-15-2008, 10:58 PM

Yea it sounds like an air leak. First two places to look are the carb base gasket and the manifold gaskets. Make sure any unused vac ports are capped and check the rubber hoses to any that are used. If the hoses are cracked, they are sucking air.

**El Jay** · 10-15-2008, 11:26 PM

Get a can of carburetor cleaner and start spraying anywhere you might have a vacuum leak; carburetor base, vacuum hoses, etc.

If the engine speed picks up, or the motor smooths out when spraying any particular location, you've most likely found a vacuum leak.

Hope that helps you a tad.

**Classic Bowties** · 10-16-2008, 12:17 AM

Quote:

Originally Posted by Momboy007

I put my entire hand on the air cleaners snout and did not let any air in and it still ran almost identical.

Be sure and check the air cleaner base (backside & underneath) for any extra added holes/slots, seems to be a commonly found modification.

cdowns · 10-16-2008, 05:26 AM

have you done the normal tune up stuff on it like cleaning points setting dwell ,cleaning plugs setting gap checking timing and setting timing checking advance changing air and fuel filters // checking for dryrotted vaccume ines

**special-K** · 10-16-2008, 08:27 AM

All that means is your filter assembly is letting air in other than the inlet.It doesn`t make a vaccuum putting your hand over there.And,how long did you block the air into the housing.You still get air from the crankcase,too.If it`s still all original.

**LockDoc** · 10-16-2008, 09:45 AM

-
If you haven't put a new air filter in it yet that is the first thing I would do....

LockDoc

Momboy007 · 10-16-2008, 08:05 PM

Hello All,
Thank You all so much for the info, This Weekend I am going to be attempting a tune up and I will keep you all posted on what I find.
Another question, is Dwell angle the same as gapping the points?

Thanks again all that contributed to the post
Rick

msgross · 10-16-2008, 08:18 PM

lots of guys ditch the points and go with a hidden digital ignition under the cap or install HEI.

don't know about your inlet issue though, sorry

cdowns · 10-16-2008, 08:23 PM

yes the dwell angle is same as setting point gap ,its done with a meter and is a bit more accurate than the feeler gauge method but if all you've got is the feeler gauge that will get you in the ballpark too

68C15 · 10-16-2008, 09:05 PM

does it have a heat riser coming from the bottom of the snorkel down to a baffle on the exhaust manifold?

a more accurate test would be to place your hand over the front air horn of the carburetor.

Momboy007 · 10-16-2008, 09:12 PM

Yes, it does have the riser, it is completely original, it even has a working smog pump
Thanks,
Rick

MightyFine69 · 10-16-2008, 10:38 PM

hey.............

Momboy007 · 10-17-2008, 05:34 PM

Hello All,
After getting everyone's help with this post I have decided to do a full tune up on the girl this Weekend, Where can I find the spec's like spark plug gaps, piont gap or dwell, stuff like that?
Thanks all again for all your help
Rick

68gmsee · 10-17-2008, 06:11 PM

Pretty awesome finding an original 30k mileage truck... My 68 GMC had a little over 28k but I bought mine about 15 years ago.

Putting your hand over the air breather intake and no change in the engine is not an indication of an air leak. On the old ones they suck air in all around them -at least mine does.

Re: tuneup specs. When you get the parts ask the counter person to look up the specs like spark plug and point gap. They usually have them available in their computer. Timing is usually in the service manuals which I highly recommend you invest in.

One other thing, on these old trucks the gas tanks get pretty grungy and gummy, especially if they sit for a long time without being driven a lot. So be sure and install and or replace a good inline filter before the fuel pump to keep the crud out.

Mine smoked and acted like it had bad rings but it turned out to be old gummed up gas in the tank.

**special-K** · 10-17-2008, 06:07 PM

sounds good.Let us know how it turns out.

10-15-2008, 10:52 PM	#1
Momboy007 Registered User Join Date: Mar 2008 Location: Southern California Posts: 82	Huh?? can you all help? Hello All, I just got a quick question for all of you. Please recall I picked up a 69 GMC 3/4 ton Custom Camper with a 396 with just over 30K miles on it, it is completely stock and never has had any work, anyhow, it runs on the roughish side, so just out of curiosity, I put my entire hand on the air cleaners snout and did not let any air in and it still ran almost identical. Does this mean I am sucking air from somewhere else? How to find the leak, if so? Thanks all in advance, Rick

10-15-2008, 10:58 PM	#2
MDC Registered User Join Date: Oct 2005 Location: N Texas Posts: 727	Re: Huh?? can you all help? Yea it sounds like an air leak. First two places to look are the carb base gasket and the manifold gaskets. Make sure any unused vac ports are capped and check the rubber hoses to any that are used. If the hoses are cracked, they are sucking air. __________________ 67 C10 Shortbed 327 05 F150 4x4 NO APPOLOGIES 's 02 Xpress X19 02 Yamaha VMax 150 www.xpressboats.com Nothing says 'poor craftmanship' like wrinkles in your duct tape

10-15-2008, 11:26 PM	#3
El Jay Gone to greener pastures Join Date: May 2007 Location: Gateway to the Delta Posts: 7,354	Re: Huh?? can you all help? Get a can of carburetor cleaner and start spraying anywhere you might have a vacuum leak; carburetor base, vacuum hoses, etc. If the engine speed picks up, or the motor smooths out when spraying any particular location, you've most likely found a vacuum leak. Hope that helps you a tad. __________________ '69 Chevy 1/2 T LWB Stepper: Daily Beater '72 GMC 3/4 T Fleet: Another Daily Beater '72 Plymouth Gran Coupe: ? "Ah women. They make the highs higher and the lows more frequent." Friedrich Nietzsche "Never kick a fresh turd on a hot day." Harry S. Truman GUN CONTROL: Never having to say, "I missed you." Always fire two warning shots into your attacker's chest area before putting a bullet between his eyes. Paraphrased from Louis Awerbuck

10-16-2008, 05:26 AM	#5
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Huh?? can you all help? have you done the normal tune up stuff on it like cleaning points setting dwell ,cleaning plugs setting gap checking timing and setting timing checking advance changing air and fuel filters // checking for dryrotted vaccume ines __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

10-16-2008, 08:27 AM	#6
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,861	Re: Huh?? can you all help? All that means is your filter assembly is letting air in other than the inlet.It doesn`t make a vaccuum putting your hand over there.And,how long did you block the air into the housing.You still get air from the crankcase,too.If it`s still all original. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

10-16-2008, 09:45 AM	#7
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,420	Re: Huh?? can you all help? - If you haven't put a new air filter in it yet that is the first thing I would do.... LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

10-16-2008, 08:05 PM	#8
Momboy007 Registered User Join Date: Mar 2008 Location: Southern California Posts: 82	Re: Huh?? can you all help? Hello All, Thank You all so much for the info, This Weekend I am going to be attempting a tune up and I will keep you all posted on what I find. Another question, is Dwell angle the same as gapping the points? Thanks again all that contributed to the post Rick

10-16-2008, 08:18 PM	#9
msgross Registered User Join Date: Jul 2006 Location: Central PA Posts: 12,201	Re: Huh?? can you all help? lots of guys ditch the points and go with a hidden digital ignition under the cap or install HEI. don't know about your inlet issue though, sorry __________________ The Garage: 1968 K-10 SWB - "Project Money Pit" 1996 Z-71 - "huntin rig" 1969 C-10 LWB (SOLD) "Project flip that truck or else" 1993 Passport, F@rd 1-ton (SOLD)"Project Cousin Eddie" My Garage Build "The 1,000 footer"

10-16-2008, 08:23 PM	#10
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Huh?? can you all help? yes the dwell angle is same as setting point gap ,its done with a meter and is a bit more accurate than the feeler gauge method but if all you've got is the feeler gauge that will get you in the ballpark too __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

10-16-2008, 09:05 PM	#11
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	Re: Huh?? can you all help? does it have a heat riser coming from the bottom of the snorkel down to a baffle on the exhaust manifold? a more accurate test would be to place your hand over the front air horn of the carburetor.

10-16-2008, 09:12 PM	#12
Momboy007 Registered User Join Date: Mar 2008 Location: Southern California Posts: 82	Re: Huh?? can you all help? Yes, it does have the riser, it is completely original, it even has a working smog pump Thanks, Rick

10-16-2008, 10:38 PM	#13
MightyFine69 Registered User Join Date: Jun 2001 Location: Traverse City, MI Posts: 97	Re: Huh?? can you all help? hey............. Attached Images __________________ 1969 3/4 ton 4x4 33's with no lift, gotta love it! A man and his truck, it's a beautiful thing.

10-17-2008, 05:34 PM	#14
Momboy007 Registered User Join Date: Mar 2008 Location: Southern California Posts: 82	Re: Huh?? can you all help? Hello All, After getting everyone's help with this post I have decided to do a full tune up on the girl this Weekend, Where can I find the spec's like spark plug gaps, piont gap or dwell, stuff like that? Thanks all again for all your help Rick

10-17-2008, 06:11 PM	#15
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Huh?? can you all help? Pretty awesome finding an original 30k mileage truck... My 68 GMC had a little over 28k but I bought mine about 15 years ago. Putting your hand over the air breather intake and no change in the engine is not an indication of an air leak. On the old ones they suck air in all around them -at least mine does. Re: tuneup specs. When you get the parts ask the counter person to look up the specs like spark plug and point gap. They usually have them available in their computer. Timing is usually in the service manuals which I highly recommend you invest in. One other thing, on these old trucks the gas tanks get pretty grungy and gummy, especially if they sit for a long time without being driven a lot. So be sure and install and or replace a good inline filter before the fuel pump to keep the crud out. Mine smoked and acted like it had bad rings but it turned out to be old gummed up gas in the tank.

10-17-2008, 06:07 PM	#16
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,861	Re: Huh?? can you all help? sounds good.Let us know how it turns out. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~



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