timing engine -what does it mean when engine is sucking air through exaust ports - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Scott26 · 11-17-2012, 08:23 PM

im rebuilding a 350 and i put the starter on it to turn it over. I put my finger over the #1 spark plug hole but it doesnt push any air out. But it is sucking air through the exaust ports on the head. there are no spark plugs in the engine right now.Does anyone know what the problem is ? i lined up timing marks am i 180 out?
thanks

Seventy · 11-17-2012, 08:30 PM

You put the timing gears dot to dot?

Scott26 · 11-17-2012, 08:37 PM

yes dot to dot

Seventy · 11-17-2012, 08:40 PM

You might double check, but I dont think dot to dot is correct on a lot of timing gears. For some reason its striking me as a mistake Ive almost made, and it would make it 180 out.

Scott26 · 11-17-2012, 08:54 PM

hmm so thats the only thing that would cause it?

thesickc10 · 11-17-2012, 08:57 PM

If your exhaust is sucking in your chain is on wrong. Does the same thing when the wear off and skip a tooth. Pop it off and take a look at it.

kelsfine69 · 11-17-2012, 10:31 PM

Dot to Dot is ok. You just need to find TDC and re-install the dizzy to #1.

INSIDIOUS '86 · 11-17-2012, 10:33 PM

Be safe and degree the cam with the intake centerline method.
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**LEEVON** · 11-18-2012, 12:11 AM

Valves are adjusted incorrectly.

Desert1957 · 11-18-2012, 09:46 AM

Here is a Pic of a Dual Roller setup, but you get the idea.

Also recheck the valve adjustment like suggested earlier in this thread, rotate the engine over (by hand) spinning the push-rods with your fingers for intial lash, then due your 1/2 or 3/4 turn preload.

Desert

1LowToy · 11-18-2012, 04:21 PM

I think you all thinking way too much. Turn the the crank in the proper direction and it should be exhausting through that port

Desert1957 · 11-19-2012, 01:42 PM

Quote:

Originally Posted by 1LowToy

I think you all thinking way too much. Turn the the crank in the proper direction and it should be exhausting through that port

Original post said , He put the starter on, I assumed he was using it to crank the engine. He never mentioned cranking it by hand , which is the only way it could be spinning backwards.

Desert

1LowToy · 11-19-2012, 06:50 PM

Thats the only way I know an engine will draw in air from the exhaust port. If he's using the starter then he has a boat cam that is designed to be rotating in the oposite direction. I.e. a boat with twin engines.

11-17-2012, 08:30 PM	#2
Seventy Registered User Join Date: Oct 2012 Location: Kansas Posts: 22	Re: timing engine -what does it mean when engine is sucking air through exaust ports You put the timing gears dot to dot?

11-17-2012, 08:37 PM	#3
Scott26 Registered User Join Date: Nov 2010 Location: Fresno California Posts: 65	Re: timing engine -what does it mean when engine is sucking air through exaust ports yes dot to dot __________________ 1986 GMC Sierra Classic 4X4

11-17-2012, 08:40 PM	#4
Seventy Registered User Join Date: Oct 2012 Location: Kansas Posts: 22	Re: timing engine -what does it mean when engine is sucking air through exaust ports You might double check, but I dont think dot to dot is correct on a lot of timing gears. For some reason its striking me as a mistake Ive almost made, and it would make it 180 out.

11-17-2012, 08:54 PM	#5
Scott26 Registered User Join Date: Nov 2010 Location: Fresno California Posts: 65	Re: timing engine -what does it mean when engine is sucking air through exaust ports hmm so thats the only thing that would cause it? __________________ 1986 GMC Sierra Classic 4X4

11-17-2012, 08:57 PM	#6
thesickc10 Registered User Join Date: Sep 2010 Location: New Hope, PA Posts: 279	Re: timing engine -what does it mean when engine is sucking air through exaust ports If your exhaust is sucking in your chain is on wrong. Does the same thing when the wear off and skip a tooth. Pop it off and take a look at it. __________________ 1985 c10 355 th350 (working on 4 speed conversion to super t10) 1979 camaro 358 super t10 2003 f250 superchip slp exhaust

11-17-2012, 08:23 PM	#1
Scott26 Registered User Join Date: Nov 2010 Location: Fresno California Posts: 65	timing engine -what does it mean when engine is sucking air through exaust ports im rebuilding a 350 and i put the starter on it to turn it over. I put my finger over the #1 spark plug hole but it doesnt push any air out. But it is sucking air through the exaust ports on the head. there are no spark plugs in the engine right now.Does anyone know what the problem is ? i lined up timing marks am i 180 out? thanks __________________ 1986 GMC Sierra Classic 4X4

11-17-2012, 10:31 PM	#7
kelsfine69 18 Till I Die Join Date: Mar 2005 Location: Alberta, Canada Posts: 1,522	Re: timing engine -what does it mean when engine is sucking air through exaust ports Dot to Dot is ok. You just need to find TDC and re-install the dizzy to #1. __________________ 2011 GMC Acadia 1969 GMC BBC LS7 2007 GMC Crew Duramax 1987 Camaro Iroc 350 Tuned Port Injection 42000Km 1987 Chevrolet Silverado 350 TBI 1987 Chevrolet Silverado 350 TBI(yes 2) Take me drunk, I'm too home...

11-17-2012, 10:33 PM	#8
INSIDIOUS '86 Registered User Join Date: Jul 2009 Location: washington Posts: 4,178	Re: timing engine -what does it mean when engine is sucking air through exaust ports Be safe and degree the cam with the intake centerline method. Posted via Mobile Device __________________ 377 sbc thumpr cam autogear m23 muncie 3:73 Detroit trutrac 3''spintech prostreet mufflers xpipe 1 3/4 headers build thread !http://67-72chevytrucks.com/vboard/s...d.php?t=577217 Iroc gauge threadhttp://67-72chevytrucks.com/vboard/s...d.php?t=554511

11-18-2012, 12:11 AM	#9
LEEVON Moderator Join Date: Jul 2006 Location: Ozark, MO Posts: 4,893	Re: timing engine -what does it mean when engine is sucking air through exaust ports Valves are adjusted incorrectly. __________________ '86 GMC C30 Crew ~ '86 C20 Crew ~ '79 K15 Sierra Grande ~ '76 Blazer 2wd ~ '74K10 ~ '71 Cheyenne swb ~'50 3100 bagged ~ '80 Wife ~ Late model kids

11-18-2012, 09:46 AM	#10
Desert1957 Registered User Join Date: Apr 2009 Location: New Freedom Pa. Posts: 1,335	Re: timing engine -what does it mean when engine is sucking air through exaust ports Here is a Pic of a Dual Roller setup, but you get the idea. Also recheck the valve adjustment like suggested earlier in this thread, rotate the engine over (by hand) spinning the push-rods with your fingers for intial lash, then due your 1/2 or 3/4 turn preload. Desert

11-18-2012, 04:21 PM	#11
1LowToy Registered User Join Date: Nov 2009 Location: Sonora California Posts: 860	Re: timing engine -what does it mean when engine is sucking air through exaust ports I think you all thinking way too much. Turn the the crank in the proper direction and it should be exhausting through that port

11-19-2012, 06:50 PM	#13
1LowToy Registered User Join Date: Nov 2009 Location: Sonora California Posts: 860	Re: timing engine -what does it mean when engine is sucking air through exaust ports Thats the only way I know an engine will draw in air from the exhaust port. If he's using the starter then he has a boat cam that is designed to be rotating in the oposite direction. I.e. a boat with twin engines.



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