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Sudden case of burning oil

Not sure if you did an oil change about the same time as the dizzy swap.... But in my experience with the sqaures, gas and diesel, every time I switched to synthetic oil I started shooting the blues. Switch back to conventional and it quit. :dunno:. Had I happen in 4 different trucks the same way. Just an idea if you did change oil
 
it actually was about the same time but I've always run either Brad Penn or Valvoline VR1 in this truck, Brad Penn in it now so nothing I haven't used before.
 
Well i finally got around to trying the new PCV valve. I think it helped some but its still smoking/fuming way more than acceptable. Decided I am going to check into the cost of doing a full reman on the heads before I invest that much effort in just doing seals.
 
In the end taking the heads off is not a bad idea,it is a lot easier to do valve stem seals on the bench rather than on the engine,and it would suck to have a head gasket fail a short time later,if you did it "in the vehicle"..(seen it happen before!)..

Also it isn't impossible for a valve to fail to stay seated while the valve spring & retainers are off,and drop into the cylinder..usually they wont drop in far enough to not be able to pull it back up,but it happens--the engine can turn over by the compressed air and let the piston go down far enough..

305's were noted for valve guide failures,and soft cams..sometimes an engine that loses a cam lobe on an exhaust valve will not be able to get rid of the exhaust fast enough,and it ends up by-passing the rings,and makes the crankcase build pressure up..

I saw one small block that guzzled oil,and it had the crack on the underside of the intake..its not common,but there are heat passages the exhaust gets forced thru when the heat riser or EFE valve is closed ,it forces the exhaust from one bank of cylinders to flow thru the passages casted into the intake,and warm the carb up,then it goes out the other bank of cylinders to the exhaust pipes..

This allows for better fuel vaporization and better cold start driveability...if a crack develops underneath,it can let exhaust gasses pressurize the crankcase,or a vacuum leak may suck oil in from the lifter galley...the cracks usually develop under the tin shield that is riveted to the intake..

Before you go that far,does this engine have stock valve covers ?--if so,nevermind,but if it has aftermarket ones,some had no provision for a crankcase breather unless you punched a knock out plug out of it,some also had the same thing needed to be done to put a PCV valve on the opposite valve cover..

An engine with no crankcase breather will build up pressure and or vacuum and suck oil past the rings ,oil seals,etc,and burn it rapidly..

I bought a few good running trucks that were advertised as "needs engine ,burns oil",and that was the only thing "wrong",they had put aftermarket valve covers on it and either didn't put a breather,or a PCV valve,or both,and the end result was excessive oil consumption..
I've had a few old small blocks that consumed multi-weight oils much faster than if I used SAE 30 or higher in them too--straight weight oils have higher flash points and wont get burned as quickly..

I had one truck that smoked on start up,I found out the vacuum modulator had its diaphragm fail,and it sucked ATF into the intake and burned it..I found that out when one morning it didn't want to go in drive right away,and checking the fluid revealed it was low enough to be "off the stick"..tranny also was taking forever to go into third and shifting harsh..

The '72 K5 I had,filled the brake booster up with brake fluid,the master cylinder leaked at the piston end into the booster..that made lots of foul smelling smoke every morning ..I had the brakes fail one day on my way to work,the master cylinder rear chamber was empty,and the front one less than 1/2 full,and it got airbound after some sharp corners..
 
Its an all original truck so the valve covers are stock. I have a breather in the passenger valve cover. Both banks start puffing a fair amount of oil about 1 minute after engine start and continues to do so for at least 15 minutes until full temp is reached.

I honestly think I ran it a little too hard when I was dialing the timing in. I revved it out past 4500 a couple times because it seemed like that's what it wanted to do at WOT. She's probably a little old for that kind of heart rate :D
 
Stock o-ring style valve stem seals are notorious for this kind of issue. GM stopped using o-ring valve stem seals and went to an umbrella style in the late 80's to early 90's. I'd get a set of those to install wether you take the heads off to do the repair or not. The nice thing is, the GM umbrella seals don't require machining the valve guide boss down like aftermarket seals do.
 
I used to sell a lot of "TOKE" brand umbrella style valve stem seals,they were able to be installed without machining the valve guides,they had a retaining clamp built into the seal..

I don't know if that company is still around,I think they were a local one here in MA,all the parts stores with machine shops used their products..

I recall a certain Oldsmobile valve stem seal would also work on Chevy's ,that were umbrella style and a "slip fit" over the valve guides..

Only thing I'd be worried about is if you do a valve job ,even just lap them in,might cause the rings to let blowby cause even more smoking..
I had that happen on a 305 from a Monza that was in my '71 GMC,
I wasted a weekend taking off one head,to replace a burnt valve,and after I got it back together with a fresh valve job on that one head,the cylinder that was dead due to the burnt valve evidently had gas washed the rings and it smoked so badly I couldn't drive it without getting pulled over..
I ended up buying a low mileage 350 off a friend's '75 El-Camino his wife totaled on an icy road..
 
I agree with what you are saying there. Its now continuing to smoke a small amount all the time. Vacuum isn't where i'd like to see it at cruise speed so I think this engine is just tired. Even though I've been trying to keep this truck an original survivor, im growing tired of the drama and I think a crate 350 with a fitech fuel injection will be the next chapter.

Once thats all running and together, I might try a home brew rebuild of 305 just because it would be a good learning experience on an engine i don't particularly care about. But the reality is I'll probably just throw it in the corner of the garage and leave it there.
 
I'd try running thicker oil like SAE 30 or 20W-50,with some Lucas added to it,it'll reduce the smoking a lot..using 15W-40 diesel rated oil may help,if sludge has built up in the ring grooves or elsewhere,it's higher detergent (and higher zinc content) will clean the engine inside as you drive and help cam lobes live longer too..

I've seen quite a few older engines "reject" synthetic oil,they start smoking or leaking right away once it was used,and when regular oil was put back in the smoking and leaks stopped..I know they say that is a "myth" but in real life it does happen..

My theory is an engine run on regular oils for 100K+ isn't going to benefit any from thinner synthetic oil,if anything it will suffer..any damage has already been done by then,and a "looser" high mileage engine will usually guzzle thinner more slippery oil or start leaking it from seals..its a waste of money IMO on an old engine..

The Ford Contour I had with a 2.5 V6 started sounding horrible shortly after an oil change with Mobil 1,sounded like the timing chain tensioner lost its nylon--previously I had used the reccomended 5W-20 regular oil ,with zero noises...
I put 10W-30 regular oil back in it with a new filter and the engine quieted down as soon as I started it..
It had 140,000 miles on it,I figured a little thicker oil wouldn't harm anything..it didn't make any other noises after that..
I'm still leery of synthetic oils,I'd only use them in a new engine after break in..

One thing you may want to check if you haven't already ,is to ensure the oil return holes in the rear of the heads are clean and not blocked with sludge..oil can pool up there and get sucked past the valve guides..

I had a 350 in a 70 Impala that smoked like a tire fire when I got it--I pulled off the drivers side valve cover after having the #7 plug foul repeatedly,about 2 quarts of oil gushed out when the cover came off and there was a ton of sludge-- and I found about 100 aluminum foil seals they put on plastic oil quart bottles blocking the oil returns,evidently whoever added oil just shoved the bottle in with the seal still on it and squeezed it to pop it open and let the oil flow out,and most of them landed back there..once I used a shop vac and a hunk of hose duct taped to the crevice tool to suck out all that crap it stopped smoking completely..
 
The oil drains in the heads could very well be the problem. The passenger valve cover is leaking bad and its a brand new gasket last year. The driver side valve cover would be a challenge of its own. I think id have to destroy to remove it since it seems like someone glued it on.

The engine has excellent oil pressure with 10w-30 as it is so id be hesitant to try anything thicker.

Appreciate the advice but all in all, I'm just kinda done with the "trying things." I've given this 305 two and a half years of my time already and its not like the performance is even modest.

A month ago it was still running "good" despite being smokey but this weekend the power level seemed down again, and some spark knock came back.... no reason for any of it.
 
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The 305 never was a high performance engine,excepting maybe the HO versions they put in Firebird's and Monte Carlo SS's ,even those were lame compared to a 350 though..they were basically a all around "daily driver" engine with decent fuel economy,not so much a powerhouse..

It is likely yours is getting tired,pulling a nearly 3 ton truck around for a long time,that likely has highway gears..

Thicker oil will not raise the oil pressure much if at all once it is warmed up..what it will do is help seal around the rings and valve stems,and having a higher flash point,resist burning off as rapidly..this will allow you to keep using the truck until you decide what to do with the engine..without smoke screening or having to add a quart every 100 miles..

I have seen some "special" oil sold in stores that looks almost transparent that is touted to "completely stop all smoking"--and it does seem to work,a few used car dealers locally love the stuff (so they can sell a vehicle that smokes and have it go beyond the 30 day warranty without smoking,the scumbags!)..first time the oil gets changed ,an angry customer returns wanting to cut their throats!..

I like using Lucas,it seems to reduce oil consumption and smoking quite a bit,and it doesn't drain off overnight,so it starts up lubed the next morning..in the dead of winter though,it can become too thick and possibly cause hard starts or lack of lube the first few seconds after a cold start..best to use it when its above freezing only..
 
JoeliusZ28 said:
The oil drains in the heads could very well be the problem. The passenger valve cover is leaking bad and its a brand new gasket last year. The driver side valve cover would be a challenge of its own. I think id have to destroy to remove it since it seems like someone glued it on.

The engine has excellent oil pressure with 10w-30 as it is so id be hesitant to try anything thicker.

Appreciate the advice but all in all, I'm just kinda done with the "trying things." I've given this 305 two and a half years of my time already and its not like the performance is even modest.
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Run it hard until oil consumption gets enough that you feel you have to do something about it.

I had the original 305 in my first K5 (an '83), which I bought more than a decade after it was made, and it may have had the factory oil in it. Joking, but barely. Engine got me across the US, and a few more years of driving around the West, before I decided the body was too far gone to waste the time on restoring it, and sold it running.

Well before selling it, I decided one day to replace the valve cover gaskets. When I pulled the valve covers off, you could barely make anything out around the coked up oil. I'm surprised oil was getting to the pan honestly. I broke that junk up, got out what I could, taking minimal care not to circulate the junk back through the engine, put it back together, and it continued to run fine.

It was pretty darn slow with the 3.08's, but holding it in 2nd at least made it feel like it had some power. Would have sucked towing anything, but with slightly better gears it wouldn't have been terrible. Not bad enough to replace it just to replace it. And heck, since I didn't care what happened with it, I wasn't concerned with beating the heck out of it.
 
I am probably going to top it off with some Lucas for now since its going to be some time before i start the engine swap project. I think its using close to a quart every 250 miles or so.

dyaeger thats basically what I plan on doing. Just to keep up with the pace of traffic the four barrel is open frequently on this screamer haha. And despite all the oil burning and lack of power the truck has, I really have no doubt it would get me across the country and back if i needed it to. Its tired out but its far from dead.

I also unfortunately have the miserable 3.08 gears and I can tell they make the engine worker harder than it should have to.
 
Say what you will of the 305's, but if nothing else, they seem to hold together really well. Probably because they don't make enough power to break anything.
 
I think towing is about the only way you'd kill one. Towed a 2000 pound trailer on the highway last year and it wouldnt have surprised me if the manifolds were glowing red, it was working hard... steady half throttle on small grades.
 
Speaking of glowing red exhaust manifolds--

Years ago,my brother had a near mint '77 Monte-Carlo,that had the original 305 in it--it was the last year of the "big" ones,and it had 3:08's...the car went well over 150,000 miles without ever doing any engine repair,other than tune ups and oil changes..never even needed a fuel or water pump,and the valve covers had never been off it..it was always garaged by the original owner and kept up nicely..
Older man had owned it..

My brother drove it all over new england,NY,etc,without any issues..kept it several years..
Eventually it began puffing a white cloud on a cold start,especially after it sat overnight or longer--but it still didn't use oil or foul plugs..

Then it was becoming evident the cam may have started losing a lobe,and back then (early 80's),GM had issued a recall covering "soft" camshafts on certain vehicles,and that car was among the ones covered,so my brother bought a new cam,lifters,timing kit,and gaskets and did the work himself (he was working as a GM tech at a dealer at the time)..GM covered all the parts and labor,which almost exceeded what he bought the car for..

He sold the car to a friend not that long afterwards..
One night we were at a night club partying,and the friend who bought it got quite drunk--and at closing time,he went out to the Monte-Carlo and got in it,started it up,and turned the A/C on (it was a hot muggy summer night)--and he promptly passed out cold--with his foot right to the floor on the gas pedal!..car had power windows and door locks and the doors were locked..

Some patrons came back in the club and said "hey,there is a guy in a yellow car outside that is out cold ,and the engine is screaming wide open!"..

We ran outside,sure enough it was my brothers friend!..the engine was screaming wide open,and we could see both exhaust manifolds were turning reddish orange,along with part of the Y pipe,and we feared if we couldn't wake him up,he'd either die of CO poisoning,or the car would start on fire..by then it had been winding out a good 5 minutes straight at least..

We had been drinking too,and weren't sure what to do,I do not recall if we ended up smashing a window to get him out,or if the cops came and did it for us,I do remember a cruiser showing up,and everyone made a beeline for their cars and they all took off
!..
We opened the hood and the exhaust manifolds looked like a pair of halloween pumpkins glowing in the dark!..we shut the car off,and it started dieseling,and it went on for a good minute before it finally stalled and spit smoke out of the carb..then it peuked coolant out of the overflow tank..
We let it cool off awhile,and I think the car was left there until the next day..
I don't remember if the friend got hauled away by the cops,or was taken home by someone else..

It still started right up and ran just as well as it ever did,according to the new owner too...:eek:..if it was mine,it would have chucked a rod out the block in less than 30 seconds probably..some guys just have good luck..:screwy:..
But it shows a 305 can take some abuse without coming apart,even if they aren't the greatest engine GM ever had..
 
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