Burning oil? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Big69C20 Toy · 10-02-2002, 02:28 PM

Hey fellas i just got back in town and well the truck is running alright but it's dogging on accel and kinda hesitating/chugging a bit. I've been trying to adjust the carb a li'l bit but nothings really working. I checked my oil and it's down to almost nothing, oddly enough i never noticed any smoke or anythign outa this truck but today i did when i gassed it the nice blue smoke.
The engine was rebuilt like 20k ago but i guess something's up. any thoughts on where to check for oil out of? the underside is clean, the seals aren't leaking either. I thought i might be sucking it up thru the pcv but that doesnt appear the case either unless my heads are getting so hot that the oil is vaporizing which it seems like it actually might be doing. I'm concerned about this but the truck has always ran fine.

I guess 3 months off for the truck wasnt a good thing

any thoughts on what i should check? i'm broke right now so a rebuild isnt exactly possible at the moment and like i said it was rebuilt recently by the guy i bought it from. Thanks in advance fellas

bigjimzlll · 10-02-2002, 02:33 PM

do you have an automatic? might check the vacuum modulator..some times it will suck up tranny fluid..if thats not the case..compression check time..

71GMC_3/4T · 10-02-2002, 03:02 PM

You could have bad valve guide seals, which would cause it to smoke on startup mostly.
If it has only sat for 3 months, it probably isn't stuck oil rings.
I'd be checking the PCV valve (it should rattle) and make sure you have a breather tube or breather cap on the other valve cover. If the guy that rebuilt it put aftermarket valve covers on it, he may have overlooked the fact that the air has to get in from somewhere. I looked at a ferdstang the other day for a buddy and while it was running, I pulled the oil filler cap off to listen to the valve train. It was very hard to pull the cap because the whole crankcase was under vacuum. He had put a rubber oil fill plug in instead of a breather cap.

Big69C20 Toy · 10-02-2002, 04:55 PM

Yep the other side has a breather, hooked right up to a spacer under the air filter. I suppose it could be valve seals but they all looked good last time i saw em and the thing doesnt smoke on startup or anything, only when i was gassing it earlier... kinda odd i think.

tom hand · 10-02-2002, 08:33 PM

Oil can only go two places, on the ground or out the tail pipe. Clean motor underneath and blue smoke says out the tailpipe to me. If the valve guides are not worn, valve seals will change oil consumption very little, mainly give you a cloud when you crank it. If you are running aftermarket valve covers with no baffles, the PVC valve can burn a lot of oil. Do a wet and dry compression test and you will know.

10-02-2002, 02:28 PM	#1
Big69C20 Toy Livin' it up. Join Date: Nov 2001 Location: Richland, MI Posts: 2,212	Burning oil? Hey fellas i just got back in town and well the truck is running alright but it's dogging on accel and kinda hesitating/chugging a bit. I've been trying to adjust the carb a li'l bit but nothings really working. I checked my oil and it's down to almost nothing, oddly enough i never noticed any smoke or anythign outa this truck but today i did when i gassed it the nice blue smoke. The engine was rebuilt like 20k ago but i guess something's up. any thoughts on where to check for oil out of? the underside is clean, the seals aren't leaking either. I thought i might be sucking it up thru the pcv but that doesnt appear the case either unless my heads are getting so hot that the oil is vaporizing which it seems like it actually might be doing. I'm concerned about this but the truck has always ran fine. I guess 3 months off for the truck wasnt a good thing any thoughts on what i should check? i'm broke right now so a rebuild isnt exactly possible at the moment and like i said it was rebuilt recently by the guy i bought it from. Thanks in advance fellas __________________ -Greg; Sold the 69 C20. It's off to a better home with more love! Now onto the 86 CUCV M1009; K5 blazer with 6.2L diesel, corp 10 bolt axles, Detroit locker in the rear, trutrac front, 3.73 gears, 35" tires.

10-02-2002, 02:33 PM	#2
bigjimzlll Senior Member Join Date: Dec 2001 Location: Redding,CA...USA Posts: 4,736	do you have an automatic? might check the vacuum modulator..some times it will suck up tranny fluid..if thats not the case..compression check time.. __________________ 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

10-02-2002, 03:02 PM	#3
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	You could have bad valve guide seals, which would cause it to smoke on startup mostly. If it has only sat for 3 months, it probably isn't stuck oil rings. I'd be checking the PCV valve (it should rattle) and make sure you have a breather tube or breather cap on the other valve cover. If the guy that rebuilt it put aftermarket valve covers on it, he may have overlooked the fact that the air has to get in from somewhere. I looked at a ferdstang the other day for a buddy and while it was running, I pulled the oil filler cap off to listen to the valve train. It was very hard to pull the cap because the whole crankcase was under vacuum. He had put a rubber oil fill plug in instead of a breather cap. __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO

10-02-2002, 04:55 PM	#4
Big69C20 Toy Livin' it up. Join Date: Nov 2001 Location: Richland, MI Posts: 2,212	Yep the other side has a breather, hooked right up to a spacer under the air filter. I suppose it could be valve seals but they all looked good last time i saw em and the thing doesnt smoke on startup or anything, only when i was gassing it earlier... kinda odd i think. __________________ -Greg; Sold the 69 C20. It's off to a better home with more love! Now onto the 86 CUCV M1009; K5 blazer with 6.2L diesel, corp 10 bolt axles, Detroit locker in the rear, trutrac front, 3.73 gears, 35" tires.

10-02-2002, 08:33 PM	#5
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Oil can only go two places, on the ground or out the tail pipe. Clean motor underneath and blue smoke says out the tailpipe to me. If the valve guides are not worn, valve seals will change oil consumption very little, mainly give you a cloud when you crank it. If you are running aftermarket valve covers with no baffles, the PVC valve can burn a lot of oil. Do a wet and dry compression test and you will know. __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS



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