More lessons learned, one of them for a second or third time.

A compression test can identify a problem in an engine, but it can also give you false confidence that you have a good cylinder.

Sometimes I think it was my purpose in life to make mistakes so I could warn others NOT to do the same thing or come to the same conclusions.

In about 1998, I bought a 1990 GMC Sierra pickup from a Salesman at the local Kent Chevy Dealer. He told me it was his Father In-law's truck, it was absolutely flawless (show Room condition) with 46,000 miles on it.

After my purchase, (private sale), I realized I had an oil burner, it's just another used car Salesman story, pretty obvious that he was dumping his oil burner on me. I couldn't see anything coming out of the exhaust, so I thought I might as well drive it and see if it got better or worse (it was spilt milk at this point). The oil consumption was less of a problem for me, because I really don't drive that far or that often, with the exception of visits to our off grid locations, one being a 120 mile round trip, and the other being around 250 miles.

I'd use a quart round trip to Cowiche, and as the miles added up, pretty soon it was two quarts, then you couldn't pour it in often enough.

Then one day it was too much to ignore, I heard the engine ping under light acceleration, and saw a puff of black smoke with each ping. The ECU noted the ping via the knock detector, and retarded the timing...(great for good  mileage) and the ping was canceled. Noting this, I found a place to really stomp on the truck and noted the steady stream of smoke out the exhaust. I got 50,000 miles out of my oil burner before it was time to pay the price for buying from a used car Salesman that used too much Cologne. Looking back, I think he had a gold necklace and an open shirt, are these bad signs? I'm not sure... but I made the mistake of falling in love with a Truck.

Pulling the spark plugs at 95,000 miles revealed 7 plugs with great color, and a lone oil fouled plug in number one cylinder. This is where the story gets interesting (IMHO). The compression test showed all cylinders reading 175-180 pounds, with all plugs pulled and throttle plate open, I thought this was excellent news.

New plugs, New rotor, and rotor cap, (needed it anyway), still bad, added new spark plug wires... No help...

I dropped in to see Jerry Wright who I regard as an expert, he started rebuilding things at eight years old in his Dad's small engine shop. That's where he started... He's also built engines that won in their class at Daytona!  He's a Mechanic's Mechanic. Jerry verified his  thoughts regarding my problem with a GM mechanic friend and passes along the following. "We see GM 350s with valve seals bad, and burning excessive oil all the time, if it's not that, it's probably an intake manifold gasket defect allowing oil into the intake of number one cylinder, there's always a chance it's something else, but the odds are high, it's one of these".

With that info, I bought some valve stem seals from NAPA and thought about how I would change them. After looking at my SEARS screw in compression tester (VERY NICE), I noted that the quick coupler that connected the gauge to the hose that screws into the spark plug was the same as that on my shop air hose. A quick check revealed that I could use this to apply air to the cylinder from my compressor line and hold the valves closed under pressure. I then used a spring compressor to remove the keepers, springs and get to the valve seals. Sure enough, they were like little pieces of crumbly carbon. They came out in pieces.

Mike McCandless (owner of Auburn Auto Machine) warned me that DIYers often install the new seals wrong, they put them on the valve stem and them slide the compressed spring over the stem and push the seal from it's groove down the stem. I tried it this way and sure enough, it's a bad idea. Trying to place the seal above the compressed spring is a pain, but it results in a correct installation. This causes me to wonder how many persons have installed these wrong and created an even bigger oil burner!

With the new seals installed in number one cylinder, I ran the truck around the block and found the same problems, maybe it was slightly better, but the ping and the smoke was still there.

I remembered Jerry's stories of stuck oil rings, usually caused by lack of oil changes, I used two cans of GM's top end cleaner, even poured some into #1 cylinder and let it set... NO immediate HELP.

At this point we have two possibilities, the intake manifold has a leak where oil is sucked into number one intake runner, or this cylinder is unable to control the oil. How does one determine which one?

We know the intake manifold is easy to pull compared to rebuilding the engine, but is there a way to prove what's going on for sure ??? Mike McCandless suggested I do a leak down test, "might try and identify a problem before you attempt to fix it."  Derek Smail, (a mutual Friend and Motor Head) agreed to drop by with a quality test set up and provide his expertise.

Derek looked at number three cylinder and exclaimed "Shoot! this looks like a cylinder out of a custom engine! Text book perfect. Moving over to cylinder number one he found a major leak down through the pan! We pulled the dip stick and could feel the air across finger tips. This was NOT the news I was looking for.

DIYers need to take note, Mike's advice is something to keep in mind no matter how many times we re-learn it!.... identify the real problem before you spend money trying to remedy the symptoms.

And there were more lessons once the engine came apart.....

Intake gasket looked properly installed (no leaks)

Three cylinders and combustion chambers look real good, zero ridge at 95,000 miles.

Number one looks oil soaked, huge ridge in top of cylinder wearing at the bottom and front of the cylinder.

Build up of deposits are found on all cylinders on back side of valve and lower stem, this indicates the seals are no longer as effective. I would think that an investment in new valve seals should be made at 80,000 or greater miles on a Chev 350 of this Vintage.

I would also think water injection could help control these deposits, and that enabling the system when pulling hills or loads would be beneficial in other ways. If you choose to replace valve seals, investigate the new Teflon Seals and how to properly replace them. If you saw these deposits, you'd wonder how much air could flow at the higher RPMs, come to think of it, my truck is kind of a dog mid range and higher up.

This engine may have left the factory with a defect, But manufacturer's are pretty careful in this stage of assembly, and the folks doing it are usually skilled, so what happened ???

.40 over should clean up the wear in cylinder one, we'll see.

It was time to check in with Jerry Wright, compare notes, return his power steering pulley puller, and tell him the story.  Jerry smiles, (there's not too many stories he hasn't heard). He tells me the story of a customer who brought in a car with 40 some thousand miles on it that was worn out. The cylinder wall taper was worse than some 300,000 mile motors. Jerry said had asked the owner.... "what had happened to the thermostat ?? the owner replied " I take them out of all my rigs, darned things cause nothing but trouble". Jerry looks upwards and shakes his head.... "What's really amazing is we also see high mileage engines with perfect cylinders, you can still see the cross hatch in the cylinders, this is why you change your oil, and you do it often".

With this story told, Jerry recalls my efforts to pass emissions at 60,000 miles or so.. "didn't you find it running cold ?" I thought back.... "Yes!" I remembered the gauge reading low and how I thought it was just a gauge problem or something. I had put it off till I didn't pass emissions. (another lesson?) when I did take the thermostat out, I found it stuck open, I put a new one in and the gauge read as expected.

Considering that number one gets a shot of cold water out of the pump, it may be affected by the lack of a thermostat more than the others. If I pull the other head and find the front cylinder having more wear than the others, will this confirm this? Maybe it depends on who's expert you're talking to?

The lesson for DIYers... even that ole Lister needs the proper operating temp.  If you don't make up your own, order one of mine, and get that engine up to operating temp fast and keep it there!

And now I wish to thank my friends, I have learned so much from them and life would be far harder without them. Not enough room to mention them all.

Jerry Wright owner (Mazda's only) Kent, WA 253-854-9601, simply the best mechanic I know.

Mike Mcandless owner (Auburn Auto Machine) Motorhead and custom engine builder, older American engines, and newer stuff too. Mike   253-735-5267.

Derek Smail, (he's Insane).... Mega Horsepower Custom Snowmobiles. Derek has experience with turbo two strokes and big (NA) cubic inch triples. Truly insane sleds for speed freaks. 253-640-2100, Covington, WA.


A final Note, talked with Dale Green, (a well known NW engine builder), added some valuable insight into what happened to this engine. First he said We were probably right about the cold water taking out cylinder number one. This problem is often seen in 350 small block marine applications where temp control is NOT adequately maintained. Number one cylinder shows tremendous wear, others are OK.

He had more insight into what I'd call premature valve stem seal failure. Dale said these throttle body engines were run pretty lean, they run HOT and coke the seals. If you can get to the fuel mixture, you might correct this and increase the longevity of this engine. Another problem is the exhaust valves, they fail prematurely because of this lean condition.

I would imagine that GM had some Federal Government dictates to meet, and had no problem selling us a short lived engine to meet the specs.

I can't imagine how much crap goes into the Atmosphere once these valve seals go to hell, but I'd be tempted to say this engine could pollute far more in later life than if it was set up to run a little cooler (richer) from the very beginning. 

It all has great entertainment value doesn't it? the FEDs tell the Auto Manufacturers how to paint cars, and the paint falls off. They tell them what the emissions will be, and you pay more and get half the mileage before you haul it off to the dump. 

Water injection might be far more valuable than we know, this could lower temps during higher loads, and extend life.  Of course, fixing the fuel mixture would be the proper fix, but it could also void the warranty of a newer vehicle, and maybe they could fine you out of your house?


All the best, always learning....

George B.