The Most Intricate Mechanical Job: Replacing V8 Engine’s Valve Stem Seals

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There are some jobs on our 1965 Clark Cortez motorhome that I admittedly wanted to put off like the replacing the passenger’s and driver’s side ball joints because I knew they would be a pain before L and I even started. The other job we probably should have done earlier but didn’t was this one—replacing our V8 engine’s valve stem seals.

I guess the three main reasons why I’d pushed this aside was because of the following:

• This job would more than likely immobilize our Cortez for a good while.
• Replacing the stem seals would be most uncomfortable and awkward because of the Cortez’s engine bay design.
• This job is unknown territory of course for L because she is learning about mechanics as we restore our RV but also for me because I have never done this job either. (PS—For anyone watching our stem seal YouTube videos, you get extra credit points for leaving a comment that says the correct number of times I say something along the lines of “I’ve never done this job before!”)

Here’s a side note, too, about how much I learned to avoid this job: My dad and I once went through the effort of swapping out an entire engine instead of just changing the valve stem seals! And the swap made me late for a blind date, and my mum had to take me because my car wasn’t finished, and she hit her van’s roof on a low-level car park. (No, Americans—it’s not a parking lot!) And the date was … er, dull!

To some of you, my words won’t show how dreaded replacing stem seals are, so fear not! I shall educate you! (And for those who know—yea … Wish us luck!)

Valve stem seals stop oil that is in the top of the engine from going down the shaft of the valve stem and into the combustion chamber (which is where fuel and air ignite). If these seals crack or disintegrate and oil enters the combustion chamber, the fuel and air mixture is contaminated, which leads to poor engine performance and poor fuel economy.

To replace the seals, we need to dig deeper into our engine than ever before. There are eight cylinders, and each of those cylinders have two valves—an intake and an exhaust.

With each of those cylinders, there’s different parts holding up the valve, including a valve stem seal, which is what we needed to replace … and we needed to replace sixteen in total.

We were given the hint that the stem seals on our 360 LA V8 engine needed to be replaced early on when I saw a blue tint to the exhaust smoke …

When I tried to explain to L that different colors of exhaust smoke show different problems (blue means the engine is burning oil, so the stem seals are likely cracked; white means water is getting into the combustion chamber, so the head gasket likely failed; and black means the engine is over-fueling, so the carb is not adjusted correctly), L stubbornly maintains—as she so eloquently puts it—“Smoke is smoke colored.” That lass is technical sometimes!

Regardless of what she says, our smoke was most definitely blue, so leaking valve stem seals were likely the cause, especially as our compression test revealed our engine was healthy. All of this meant this job could be put off no longer!

At the start, L announced she wanted to be the lead mechanic, so I quickly set her to work pulling the valve cover off, removing spark plugs, and rocker shaft, along with any other parts that would get in the way.

Next, L started cleaning and removing loose debris—flakes of paint and rather nasty lumps of old oil. The nice part was since L took charge, she was the one who got dirty!

Next, it was time to start the job. We decided to begin at Cylinder Eight’s exhaust valve, which was closest to us on the passenger’s side at the rear of the engine.

At this point, L had never seen this far inside an engine , and was super excited, but I was super nervous …

From here, we used the traditional, and somewhat sketchy method of stuffing a load of rope into the cylinder before tightening the spring compressor around the spring assembly.

With much panic, swearing, and fiddling, we carefully removed the top hat, spring, and retainer assembly, crossing our fingers that the value wouldn’t drop into the combustion chamber because if that happened—well, let’s just say, we’d be having a rather bad day! The good news is that the valve barely moved when we cautiously took off the old stem seal.

The old seal looked to be in okay condition, but there was some confusion because our new seal looked completely different from the one we had just removed. This made us jump to the intake and take off that seal, which also looked slightly different than the new one.

After researching, we learned our new seals were for a newer 360 LA engine, but (more importantly) they were backwards compatible, meaning they were a newer design for a newer engine but would work on our older engine. Feeling confident, we replaced both the exhaust and intake stem seals at the same time.

Then we put everything back together.

One cylinder down—seven to go!

Next up was Cylinder Six …

and this is when we were rewarded with our first failed seal …

The exhaust was knackered, proving the job was needed, and I wasn’t imagining the blue tint to the exhaust smoke!

Everything was going extremely smoothly, too … until L managed to flick one of the small retainers out of sight while reassembling the intake valve assembly, which scared me half to death! Fortunately, the retainer had just slipped around the valve stem, so L quickly recovered it, and my heart rate calmed. Here are pictures to better showcase our range of emotions:

Soon after, the intake seal on the same cylinder was underway, and before we knew it, Cylinder Six was finished …

but this is when our work took a slightly sketchy turn!

When putting the rope into Cylinder Four, more and more rope kept going in until the cylinder took all of our rope—that was five feet!

Here’s when we did something we both do not advise anyone to do: We risked moving forward. We shouldn’t have because if the valve fell into our engine, we would have been in serious trouble … but we did because we didn’t have more rope, and we were ready to progress in this job …

First up was the exhaust valve, so we compressed the spring, removed the retainers and spring, then … the valve dropped—as did my heart and bowels!

Fortunately, there was just enough rope in the cylinder to stop the valve from falling into the cylinder, and I quickly got a magnet on the valve to rescue it. The valve sat literally flush with the top of the valve guide. Basically, if valve went any further, we would not have been able to grab it. No pictures here as I was panicking and fully expecting it to drop further. Somehow, our crisis was averted, and the valve seal was replaced by holding the valve secure while re-installing the spring and retainers.

Feeling brave stupid, we decided that if the exhaust valve was safe then the intake valve would be too. The proverb is “Fortune favors the brave,” and this piece of wisdom was definitely true for us. Not only that, but we found another split valve seal.

Moving on to Cylinder Two, and we were starting to get more efficient, experienced, and confident, but after what happened with the rope in Cylinder Four we got a much longer rope because we weren’t willing to take the same risk again!

With the last two stem seals replaced, our passenger bank was done—and it was around this time that all seemed well in the world … until we set about re-installing the rocker arm shaft, and there is no other way to say it than the truth: S*** hit the proverbial fan! (However, let’s be honest that this is standard really when working on the Cortez.)

With everything re-oiled, repositioned, and finger tight, we grabbed our torque wrench to finish the job. I started working across the shaft, tightening the bolts down to sixteen foot-pound and skipping every other bolt to evenly distribute pressure—two clicks to signify the bolt is torqued, then the next bolt and two clicks, then next bolt and so on until I moved to the last bolt … which kept tightening without any clicks.

I remember saying, “I’m sure this doesn’t feel right,” and I should have stopped, but instead I gave another turn and SNAP—the bolt sheared inside our engine’s head.

At this point, I was gutted and extremely frustrated with myself because I knew something wasn’t quite right but I naively carried on, leaving us in this situation. At the time, I felt like this was worse than the clutch saga we’d previously ended up in because if we could not get the end of the bolt out, we would have had to remove the head of our V8—basically, disassemble our engine.

What was even more frustrating is we had promised L’s uncle that we would move the Cortez because it was stuck directly in front of his livestock trailer, and of course he needed to take cows to the market the next day.

Our work had looked so positive at the start … up until the bleeding bolt. Insult to injury, mate!

With it clear our Cortez was not going to move, we had to call L’s uncle back to the farm to tow us so we were dropped off between Chicken Houses Three and Four. L pointed out that the tow and spot was a gutting move because this is where we started … and three years later—when we were so close to finishing off our mechanical jobs—this is where we ended up.

For me, I wanted to douse the thing in petrol, light it, and walk away.

Fortunately, saner minds prevailed, but with time getting on, the light fading, and temperatures plummeting, we called it a day.

The next morning, L felt sick (possibly due to being outside in below freezing weather!) so, after deliberating what our next move should be, we agreed that I would return to the Cortez alone to take apart the dash area above the engine to give us and our power tools better access.

With that job done and the weekend soon over, I updated my Cortez thread on Retro Rides, writing about what happened and my plan to get us out of this situation. Here’s what I determined: Because the bolt sheared at an angle, I would flatten the top of it using a Dremel, make a small pilot hole with the Dremel, drill a hole for the extractor, smack the extractor in with a hammer, and then screw the bolt, out. Easy, right?

Well, over the next few days, more and more people suggested using a left-handed drill bit over an extractor …

They had two main reasons: The extractor would likely cause more problems by snapping (which, I have to say, I’ve used extractors in the past and had varying levels of success). They also recommended the left-handed drill bit because it spins the opposite way of a right-handed one, so it has a left-hand spiral because it spins anti-clockwise. That means—instead of a regular drill bit turning the bolt further into the engine—a left-hand drill bit would spin the bolt out. I’d never tried a left-hand drill bit, but it seemed brilliant.

The following frigid weekend, L and I headed back to the Cortez together, taking a quick diversion to our nearest Harbor Freight store. (For those outside of the U.S., Harbor Freight sells all kinds of tools (spanners, drills, sockets, hammers, more), car parts (lights, winches, tow bars, still more), hobby machines (lathes, drill presses, milling machines, and more), and loads of other random items. I should also add Harbor Freight items aren’t the best quality, but they are cheap and often do the job … but it is worth mentioning we do not recommend buying their torque wrenches—just ask L!

But we needed a set of left-hand drill bits quick, as I reminded L.

At the Cortez, we were greeted with our magnetic work tray, which was frozen and showed not only that temperatures were bloody freezing but also that, yes, our roof apparently still leaks.

Moving into place perched over our engine, we were ready to fix our problem.

I claimed the fix would either be a five-second job (though in my mind, I was thinking it was either going to be a five-second job or a five-week job, depending on what happened).

Meanwhile, L, being her usual pessimistic self, was not convinced.

Really hoping that I could prove her wrong, we moved to fixing our problem, starting by removing all rocker shaft bolts (except the sheared one) and removing the rocker shaft. I quickly got out the Dremel and a small ball-nose end mill, flattening the visible sheared part of the bolt inside the head of the engine. Next, we picked a suitable sized drill from our new kit, tightened it into the drill and put it against the face of the bolt.

Then we both held out breath … and I gave the drill trigger a cheeky squeeze … and the drill barely cut into the top of the bolt before it caught, and the end of the bolt came whizzing out of the hole! Huzzar!

And that was it! It was below 32 degrees Fahrenheit (or below 0 degrees Celsius, if you measure temperature sensibly), so we decided we’d end the day right there—go home, get warm, and enjoy our Saturday!

Meanwhile, with the snapped bolt still fresh in our minds, I made the decision to purchase a new set of suitable Grade Eight bolts to lock down our rocker shaft moving forward, as well as a new and lovely Titan torque wrench from Summit Racing.

L again: I try not to call out specific companies because we aren’t paid to advertise for them, but, damn—Titan (and Summit Racing), you deserve this because we love you! Thank you for offering a top-notch torque wrench that we fully endorse!

With those purchases made and our passenger’s side rocker shaft properly torqued down, we were ready to tackle our driver’s side engine valve stem seals …

In the end, after all the fuss of doing the passenger’s side seals, the driver’s side was a walk in the park—an uncomfortable walk but a walk in the park nonetheless.

There was one major “Oops!” during the driver’s side—and I’ll fully place the blame on L but forgive her because what happened could have happened to either of us while working …

While reassembling the intake valve on Cylinder Three, L somehow managed to drop the top-hat of the valve assembly … “drop” as in it vanished! We looked for ages in the freezing cold to no avail before giving up and going home. I purchased a replacement … which turned out to be wrong (no surprise!). Then one morning, I made a final effort to find it—I drove the farm early, and armed with a magnet-on-a-stick, I spent ages in the grass looking for the top-hat. Every pass with the magnet came up empty, though. In one last ditch attempt I returned to the engine bay and somehow some way … I found it! Nestled between the transmission and clutch slave cylinder bracket, the top-hat sat as if it was waiting for me!

So, the rest of our new seals were installed the next weekend. The better news is we also found another failed intake seal on the driver’s side, so all stem seal replacements should certainly help (if not stop) our engine from burning oil while running.

 With everything back together smoothly, L was one happy little beast!

I cannot hold back from commenting in a third spot: Just know your favorite Englishman had this dorky smile on his face, too—he was just behind the camera!

From here, we double checked all rocker shaft bolts were torqued down properly, and then our job was done!

From here, I’d love to tell you that after completing this intricate work, I confirmed our smoke-colored smoke issue was resolved … but that’s not how Cortez jobs go. With the valve covers back on the engine, we instantly jumped to refreshing our cooling system! Why? That’s our next story …

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