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I am just about finished with my restoration, and the engine has suddenly developed an issue. I have less than five miles on the truck. Engine rebuild within the past 9 months. I am not the best when it comes to trouble shooting, so I'd appreciate anyone weighing in to make sure I'm going in the right direction.
226 6 cylinder, completely stock. Fresh rebuild that included everything.
About two months ago I started the engine up and about 20 seconds after starting it began to make a tapping noise. The tap would go away if you increased RPM, but would come back as soon as it got close to idle. I was working on other projects so I just didn't run the engine much other than to move the truck in and out of the garage, occasionally driving around the block. The symptoms stayed pretty much the same, although once or twice it never made any tapping.
Now that the other projects are done, I decided to dive into the issue today. I started the truck and after 15 seconds or so the tap started just like before. I drove around the block once and it acted the same way as before. I then went a little further down the road and the tapping got a little louder, and it was staying through the higher RPMs. It seemed to be robbing power and affecting the smoothness of the engine. I made a few recordings when I got home. The tap is a little sporadic but it stays mostly consistent. The tap is also in unison with the puffs recorded at the tail pipe. I held my hand against the tail pipe so that you could hear the exhaust easier. Sometimes the tap will go away for a few seconds, but it always returns at some point.
My initial fear was that I was hearing a rod or wrist pin knock. However, removing the spark plug wire from the cylinders one at a time has no effect on the sound. The fact that the engine is running a little rough, and that the tapping matches the odd exhaust puffs makes me think that it is a valve issue. The noise seems to be coming from around cyl 4-6, but it is hard to tell.
The next step that I'm planning on doing is a compression test and then removing the valve covers. Before I go tearing into anything, does anyone have any ideas? Does it seem like the right direction? Thanks!
While typing that out I remembered the “paper test”.
I just went out and tested it and the exhaust grabs the paper back and forth at the tail pipe, so I’m fairly confident that I have a stuck valve. I think I'll hook up a vacuum gauge tomorrow just to confirm. The amount of clicking/tapping noise still has me worried.
Try drizzling some MMO or Seafoam down the carb while running at ~1500 RPM (don't overdo it, the stuff smokes like crazy!)
I think you're likely right, a sticking valve.
I was able to confirm the diagnosis the day after I posted the question. I wanted to wait until it was all back together before I said it was completely solved though.
No 6 exhaust valve was seized as I suspected. I pulled the head and spent an hour working the valve out of the guide. It was the first time I’ve been completely inside the the engine bay straddling the engine, and hopefully my last.
After getting the valve out, I discovered the reason for the sticking. The assembly lube had dried out and turned to a hard resin. Even though I only had an issue on No 6 so far as I knew, I decided to pull all the valves and inspect. It was a little annoying to pull the manifolds, but I’m glad I did. Three other valves were starting to stick, 2 exhaust and 1 intake.
I cleaned all the valves and guides thoroughly and reassembled using only motor oil. I’ve never had an issue with the Sta-Lube Engine Assembly Lube on any other flatheads that I’ve built. However, I will stick to using oil on the valve stems from now on. Even though it says it’s good for valve stems, I definitely think oil is the only choice.
All in all, it cost about $150 in gaskets and one exhaust valve. It’s frustrating that it was something that shouldn’t have been an issue to begin with, but it’s also good that it wasn’t anything “mechanically” wrong. The truck is back together and running as smoothly as ever. All’s well that ends well I suppose.
I don't care how careful you are, there's always something that gets you. Glad you got it fixed and it wasn't worse. Now what are you going to do with all your free time? What's next?
Which Sta-Lube Engine Assembly Lube did you use? (they make several) I've never heard of such a thing. Glad you got it fixed! I know all too well the pain of working over those big fenders...
Which Sta-Lube Engine Assembly Lube did you use? (they make several) I've never heard of such a thing. Glad you got it fixed! I know all too well the pain of working over those big fenders...
LOL...I like how Ross really gets “into” his work.
Several years ago my BIL helped me put on heads I bought from Dennis, Pinto Plumber. The heads are heavy as you know. And the 53-56 trucks have the fender support rods making it very difficult to put the head in place. My BIL who is short, sat in the engine bay. I handed the head to him and he put it in place.
Which Sta-Lube Engine Assembly Lube did you use? (they make several) I've never heard of such a thing. Glad you got it fixed! I know all too well the pain of working over those big fenders...
LOL...I musta looked like that the other day when I was replacing wires on the beam switch, and I’m 6’5” tall.
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