In a 95 Suburban. TBI, non vortec.

In as little as 3000 miles, the passenger side rear plug, and the drivers side front three plugs will be all corroded over. I am guessing it is oil. The others are very clean.

Its been an issue since the thing was new, now at 100k. Other than that, she runs good.

Any ideas? I can post a pic of the plug if need be.

http://www.dieselplace.com/forum/uploads/8F3_one.jpg

http://www.dieselplace.com/forum/uploads/C62_three.jpg

http://www.dieselplace.com/forum/uploads/4CD_two.jpg

Mobil 1, cant see anything coming from the exhaust.......

I suspect leaky valve guides seals on that cylinder. On a modern engine, you have to burn a good bit of oil before you will see it in the exhaust.

But why would a valve be needing to hold back oil?

The rocker arms in the head have a lot of oil flowing thru them to lube the ball studs and the valves also run in this "pool" of oil. There is the actual gide in the head that the valve runs in and then there is a seal on top of the guide to wipeoff excess oil from stem and keep it out of combustion chamber. Since the intake posrt usually has a vacum on it excess oil can be sucked down guide and into chamber and foul plug with time. THe actaul guide could be worn too but seals are usually he first thing to go.

IIRC that engine has an O-ring on the valve stud thru the head.


It is most likely the exhaust valve seal.


I replaced mine in my 1987 350-TBI with unbrella type seals.......


Never had any problem since.


Does it puff smoke when you first start it up ?????


Thttp://www.dieselplace.com/forum/smileys/Confused.gifNY

No smoke that I can ever see. She does go through oil at 1 qt or so for 1k. I just guessed that thats how GM smallblocks work.

Thanks for the explanation.

So you would just have to take off the valve covers, and poke around in there to change the seals? How hard is it? Big job?

I would like to do it, I hate having to give it $5 of Mobil 1 all the time.

Thanks fellas

I removed the valve covers........you need to get the crank in position so the piston is top dead center of the cylinder you are going to change the seals in........both valves have to be closed.


Remove the spark plug and inflate the cylinder with constant air pressure with an adapter.


Use a valve spring compressor to depress the valve retainers and remove the "KEEPERS" with a small magnet.


Take the pressure off the spring, remove the spring and change out the seals......


Do only one valve at a time.


IIRC you can do several cylinders at one time before you need to rotate the engine..........it's been so long I do not know which one's anymore.


Good Luck........


IIRC parts were under $50.00 when I did mine a few years ago.





Thttp://www.dieselplace.com/forum/smileys/Big Smile.gifNY


Edited by: GMC-2002-Dmax

IIRC that engine has an O-ring on the valve stud thru the head.


It is most likely the exhaust valve seal.


I replaced mine in my 1987 350-TBI with unbrella type seals.......


Never had any problem since.


Does it puff smoke when you first start it up ?????


Thttp://www.dieselplace.com/forum/smileys/Confused.gifNY

An exhaust valve seal would not foul plug.

I removed the valve covers........you need to get the crank in position so the piston is top dead center of the cylinder you are going to change the seals in........both valves have to be closed.


Remove the spark plug and inflate the cylinder with constant air pressure with an adapter.


Use a valve spring compressor to depress the valve retainers and remove the "KEEPERS" with a small magnet.


Take the pressure off the spring, remove the spring and change out the seals......


Do only one valve at a time.


IIRC you can do several cylinders at one time before you need to rotate the engine..........it's been so long I do not know which one's anymore.


Good Luck........


IIRC parts were under $50.00 when I did mine a few years ago.





Thttp://www.dieselplace.com/forum/smileys/Big Smile.gifNY




This will work. Follow this advise http://www.dieselplace.com/forum/smileys/HiHi.gif

Maybe I could have been better with my choice of words.......


It's easy to understand if you have done it many times then explaining it......."KEEPERS" and seals and the like.





Thttp://www.dieselplace.com/forum/smileys/Embarrased.gifNY

Me, I always called them "retainers" but you have the base description down without getting too complex. http://www.dieselplace.com/forum/smileys/Big Smile.gif

Sounds a tad complicated.......

My luck, Ide open the valve cover, try to take off a spring, and have about 50 small parts shoot across the garage.................

Sounds a tad complicated.......

My luck, Ide open the valve cover, try to take off a spring, and have about 50 small parts shoot across the garage.................



Not really, there are only about 5 at most per valve not counting seal. (spring, a one or two piece spring cap or hood, and two half moon retainer clips) If you rent or buy a sping compressing tool and have air compressor with a cylinder adaptor it is really pretty straight forward and fairly easy.

So you all think it would be the intake valves? Seems like the exhaust valves would be hot enough to burn the oil/blow it out the exhaust before it got a chance to drip on the plugs...

What would a mechanic charge for something like this?

How many valves are there? One intake, one exhaust per cylinder?

Should I do them all, or just the 4 leaky ones?

Tx

I would at least do all of the intakes. There is usually a vacum in the intake port and oil from leaking seals will be sucked in with incoming fuel mixture and be it worst are part throttle cruising. Any oil on exhaust valve would tend to be consumed in hot gases present in exhaust port and since the port generall has a positve pressure in it in relation to crankcase it would tend to leak a lot less than intakes. Some leakage is needed to lube valve guides but not enough to foul plugs or use more than a quart of oil ever 2 to 3000 miles.

Thnaks Snowman

What would you guess on price?

Still trying to decide wether or not to DIY........

Thnaks Snowman

What would you guess on price?

Still trying to decide wether or not to DIY........




I would venture to say that it would cost 5 times as much or more to farm it out than doing it yourself. Parts are cheap, they would kill you with labor costs. Parts minus tools should be well under 50 bucks

Hmmm......

I just called a mechanic I know personally, and hes a big chevy guy. He seems to think that it would be the rings before the valve seals......

I do not see any smoke at startup. He told me that this is a sign of valve seals.

The things got 100k on it. Maintained fairly well. Not synth oil from the start, but not crap either. I do recall a time or two that I would idle it on a steep hill, and see the oil gauge drop to 0. I added oil ASAP, and went home and changed it. Never let that happen again.....

I am just thinking that if it were the rings, it should be happeneing on all cylinders. Not just some of them.......

I took a look, and it seems to have a little puff of oil on startup. So maybe it is the seals.......

Would NAPA have all of the parts I need?

Napa would have them and valve guide seals are classic problem with some GM 350's. You mechanic friend is not well versed. If your engine has been fairly well maintained, 200,000 miles or more is reasonable for a set of rings (350's are not known for ring problems either) but you can be diligent in maintainace and still have valve guide seal problems. They (the seals) seem to last longer in cool environments and have a shorter life span where engine gets hot a lot (hotter than normal at time)

Thanks snowman, Ill get the parts and do it this weekend....

Im guessing that the intake valve is on the left, and the exhaust valve is on the right?

I hope that all of this oil down there hasnt built up a big deposit on the valves.......

How hard is it to drop a valve into the engine....???http://www.dieselplace.com/forum/smileys/Embarrased.gif

Actually it goes "Ex In In Ex Ex In In Ex" on a Small Block Chevy as I recall without a head in front of me at the moment. Edited by: snoman

Any special type of seal to get, or just replace exactly what came out?

http://www.dieselplace.com/forum/smileys/Confused.gif


Thanks snowman.....I like to ask a lotta ?'s before I screw it up.....http://www.dieselplace.com/forum/smileys/Big Smile.gif

Any off shelf replacement will work for this application. No need to get exotic on this fix. Ask NAPA guy what he recommands.

Thanks!

Git-R-Done!

I got the parts....and I took off the valve cover.

I plan to use the rope method instead of air to hold the valves up. I just want to make EXTRA sure that I dont drop a valve into the chamber.

When I fill the chamber with rope and turn it, does it matter which valve (intake or exhaust) opens first? I guess that I can look by the position of the valve stem.

So when I take the tension off of the spring, if there is nothing to hold the valve up, it will just fall into the chamber?

http://www.dieselplace.com/forum/smileys/Geek.gif

Tx.

THe air method is much better really and if you are worried about dropping a valve you can rotate crank with a breaker bar to TDC the piston in the cylinder you are working on (which you should do anyway)

Managed to get one bank done in, oh, 6 hours.............

Had some snags, but Im done. What a PITA.

Anyway, I put it all back together, and started her up, and now I hear vauge clicking. Seemed to quiet down the longer she idled. Anything to worry about?

I hope I adjusted the valves right. Kinda screwed the rockers down to about where the rest were.

I had a hell of a time just getting the valve covers off. Thats why I dont think Ill even be able to do the Passenger side one.

No fun.

On the clicking, it may clatter for a bit. When setting those rockets I would start engine at a slow idle and loosen each one (one at a time) until there is a steady tap then slowly tighten until tap first disapears than add 1/2 to 3/4 a turn to it and go to next one. Some will use up to 1 turn but I find the a little less seem to work a bit better and it less suseptable to lifter "pump up" if you over rev engine sometime.

If you start it up with the valve covers off, wont you get an oil bath?

Not at a slow idle but you will lose some but not a "flood" of it. It is best to do with a warm engine. They do make clips that you can put on to limit leakage out od rocket assembly while doing this but since this a is a on time deal you can do without them. Make it a two person job and have someone turn engine on and off as needed if you need to reposition yourself or need a break.

The best way is if you have an old set of covers........cut the tops off re-install them and use those for the adjustments.


While idling the truck, back each one off till the clacking get's louder then slowly turn the nut in until the clacking stops and then depending on "WHO" you talk to they need some pre-load.


I have alway gone around 1/2 turn in for the preload and it seems to have always been fine.


Thttp://www.dieselplace.com/forum/smileys/Clown.gifNY

The best way is if you have an old set of covers........cut the tops off re-install them and use those for the adjustments.


Nice trick if you do that a lot. The clips work good too, I used to have some years ago but no longer do and I am not sure where they went.

Acually, it seems to have solved itself. No more noise after a 40 mile drive. (Yay) Acually drove better, but I think I had a vacuum leak at the throttle body. I replaced the o ring there. Seems to have helped.

I dont think Ill get around to doing the other side. Im not even sure I can get that valve cover off. Theres a lot of stuff over there. Took me 10 minutes of toying around with the drivers side one to get it off.

Then, the first cylinder I did, I used rope. Im all done, and I go to take the rope out, and it would NOT come. I kept turning the flywheel, and pulling the rope, nothing. I screwed with this for about 30 minutes, and was about to get the head pulled, when it finally came out.

When I put them back together, I brought the piston to TDC (as best I could tell) and then cranked down the rockers until the pushrod stopped spinning, and then I did another 3/4 turn.

The bank that I did had 3 of the 4 plugs that were fouling up. The holes in the seals were a lot smaller in the seals that I put in. I hope this solves the problem. When I was doing this, I had a spring compressor, and managed to loose a spring, and retainer and that other part. I found the spring, but lost a retainer. http://www.dieselplace.com/forum/smileys/Ermm.gif I went down to a local machine shop, and talked to a nice dude that gave me a retainer. He tells me that what Im doing might solve the problem.........Im hoping it does. Then maybe Ill get around to the other bank.

One last thing....As I was reading through some info that came with the seals, I saw that you are supposed to add that little o ring after you get the springs back on. (without the keepers) I did it before. It pry slid down the valve stem, but I hope they popped back into place. They dont seem to be of any real use anyway. Those big valve seals should catch all the oil headed down there anyway.

I strongly recommand that you check and set lifter preload as stated above. If you have one wound too tight it can lead to premature lifter or lobe failure.

I am confidant that this will fix most of your fouling problem. Usually (but not always) when you have ring problems it is on all cylinders, not just a few.