Limiting blowby? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

greasemonkey · 11-30-2002, 11:19 AM

My 350 engine has pretty bad blowby out of the breather cap. It doesn't burn a lot out of the exhaust that you can see by revving it up real good, but I add a quart every couple hundred miles. Is there any way to limit the amount of smoke coming out of the breather by using a heavier oil or something? I use 10W-30 now. I hate sitting at a stoplight on a sunny day and seeing this nice cloud of oil smoke floating from my grille or escaping from the cracks in the hood. I am still waiting to buy a new crate engine and rebuild this one. Thanks for any help.
John

mikep · 11-30-2002, 12:52 PM

Your rings are shot. You shouldnt be using 10-30 in it anyway. Old worn out small blocks in warm climates like heavy oils . You can buy yourself some time using 20W-50 or straight 40 weight

Gordo · 11-30-2002, 02:44 PM

Your engine is probably tired, but be sure that the PCV and the crankcase breather assembly is functioning. If you dissconnect the hose from the PCV valve while the engine is running, it should stall the engine, if not the system may be plugged up or restricted. The crank case breather cap/tube should be clear and connected to the air breather.

ChevLoRay · 11-30-2002, 07:56 PM

I have a little bit of blow-by on my truck, but I am using a breather cap on the right valve cover, instead of the plug and pipe that routes the blow-by gasses (smoke) to the air filter housing.

Routing it to the air filter housing won't make the blow-by go away, but will surely gunk-up the carburetor and air filter housing. If anyone doesn't like the occasional smoke that may come out from under my truck, they can pass me or go a different direction. It doesn't matter to me.

Oh, I am using 30-wt oil, and the blow-by is less than when I was running 10W30. I am also going to put a can of Restore in the crankcase with my next oil change, in December. I don't know if the claims are true, or not. I'll find out.

bigjimzlll · 11-30-2002, 09:00 PM

You need to run a pcv valve(positive crankcase ventilation)..it creates a vacuum in the crankcase,which is important, for all seals and gaskets(rings included) run a hose from full manifold vacuum to a pcv valve in a valve cover..and a breather on the other valve cover..full race engines will even run a vacuum pump hooked into the crank case...it wont hurt performance..

Jim

11-30-2002, 11:19 AM	#1
greasemonkey Registered User Join Date: Dec 2001 Location: Pace, FL Posts: 2,155	Limiting blowby? My 350 engine has pretty bad blowby out of the breather cap. It doesn't burn a lot out of the exhaust that you can see by revving it up real good, but I add a quart every couple hundred miles. Is there any way to limit the amount of smoke coming out of the breather by using a heavier oil or something? I use 10W-30 now. I hate sitting at a stoplight on a sunny day and seeing this nice cloud of oil smoke floating from my grille or escaping from the cracks in the hood. I am still waiting to buy a new crate engine and rebuild this one. Thanks for any help. John __________________ 1942 Master Deluxe 1969 C/10 1985 Blazer CUCV 1987 Jimmy 2004 Tahoe 2005 Silverado 1500 2005 Silverado 3500

11-30-2002, 12:52 PM	#2
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	Your rings are shot. You shouldnt be using 10-30 in it anyway. Old worn out small blocks in warm climates like heavy oils . You can buy yourself some time using 20W-50 or straight 40 weight __________________ No truck :-(

11-30-2002, 02:44 PM	#3
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	Your engine is probably tired, but be sure that the PCV and the crankcase breather assembly is functioning. If you dissconnect the hose from the PCV valve while the engine is running, it should stall the engine, if not the system may be plugged up or restricted. The crank case breather cap/tube should be clear and connected to the air breather. __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist. Last edited by Gordo; 11-30-2002 at 03:43 PM.

11-30-2002, 07:56 PM	#4
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	I have a little bit of blow-by on my truck, but I am using a breather cap on the right valve cover, instead of the plug and pipe that routes the blow-by gasses (smoke) to the air filter housing. Routing it to the air filter housing won't make the blow-by go away, but will surely gunk-up the carburetor and air filter housing. If anyone doesn't like the occasional smoke that may come out from under my truck, they can pass me or go a different direction. It doesn't matter to me. Oh, I am using 30-wt oil, and the blow-by is less than when I was running 10W30. I am also going to put a can of Restore in the crankcase with my next oil change, in December. I don't know if the claims are true, or not. I'll find out. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

11-30-2002, 09:00 PM	#5
bigjimzlll Senior Member Join Date: Dec 2001 Location: Redding,CA...USA Posts: 4,736	You need to run a pcv valve(positive crankcase ventilation)..it creates a vacuum in the crankcase,which is important, for all seals and gaskets(rings included) run a hose from full manifold vacuum to a pcv valve in a valve cover..and a breather on the other valve cover..full race engines will even run a vacuum pump hooked into the crank case...it wont hurt performance.. Jim __________________ It's called "drag racing" if they called it "tic..tic..WHAM!..BANG! F*&K!!!", they'd have to keep the magazines under the counter with the other men's publications click the clicky to join the site.... http://67-72chevytrucks.com/vboard/payments.php 67 lwb..first hotrod in 25 years..540 best ET is 9.45 @ 141.44 Anderson,CA

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