tappet clearance limits

Forum Members,
Was running the R2 Cat on Tuesday I noticed a complete miss when running. When repairing it two years I noticed the tappet clearance was quite over tolerance by about four times. Would have adjusted the tappets to correct clearance but the adjusting screws and locks appeared too corroded to adjust. Is it possible for an engine to miss because of too much clearance between valves and rockers? The miss does not have the same sound as a missing plug. Any and all thoughts are welcome.
Mr. T. Minnesota

Mr T,
In my experience, when you have a valve that is too tight, or not closing completely, you're gonna have a miss, and possibly a burnt valve eventually. Same goes for a tappet that is too loose, or not opening the valve, you're gonna have a miss, but not a burnt valve.

HTH,
Roger

Sounds like the rocker shaft assembly isn't getting enough oil up to it.

I dealt with an engine once where the shaft was rusty bone dry and eating itself to death. I ordered a new used shaft assembly and put it on, but no way could I get oil to it through the designated channels.

So what I did was T in a line from the out-side of the oil filter canister that I had installed and made the appropriate point of entry through the valve cover. It worked like a charm and still is 10 years later.

Cheers,
T

I would say 4 times the normal intake clearance would affect the running and likely wouldn't sound the same as a spark miss.
If you think about it the intake valve in that cylinder would not be open for as long as it should. So the piston would not draw in a full load of air/fuel. That would affect the strength of the explosion - kinda like a firecracker with only a 2/3 powder charge. Not quite a dud but not a full bang.
Likewise if it is not exhausting fully that would also reduce the explosiveness of the fuel/air charge.

"When repairing it two years I noticed the tappet clearance was quite over tolerance by about four times. Would have adjusted the tappets to correct clearance but the adjusting screws and locks appeared too corroded to adjust."

Reading that statement, you did not "repair it", in any conventional sense of the term.

Or you would have dug into it and determined what was causing such a big gap.

Rough/rusted cam lobes eating the tappets/lifters would be the prime suspect. Or, as the other guy said, the rocker arms and shaft are tearing each other up.

Bob,
You are correct, I did not need to repair it, I did not attempt to adjust it because the adjusting mechanism appeared too rusted and corroded. All other components were worn, but not to the point where they would need repair. I did not attempt to adjust them because if I broke one, finding a replacement on a '41 Cat is just about impossible. Finding rocker arm studs were luckily found in California by accident, lucky me I appreciate your observation. I plan to open the Cat up again and carefully attempt adjustment of the set screws.
Mr. T. Minnesota

Tall T,
The rocker arm assembly has lots of oil. I observed it running before replacing the rocker arm cover. Thanks for the reply.
Mr. T. Minnesota

Glad to hear that Mr. T.

Guessing that this is applicable advice, what I would have done if the lock nuts would not let go is to use my favorite and proven rust penetrant, a long-ish handled ratchet, a 6-point socket and a firm yank just to break them loose -- or a 6-point box end and a small hammer.

P.S.
speaking of my favorite penetrating fluid, Amsoil MP, here are two photos of my old sizzor jack that I serviced yesterday. that brown runoff out of every joint was instant as soon as I worked the jack up and down twice! This is how de-rusters are SUPPOSED to work regardless of how people stick to their favorite brand no matter what.

it is sold as a metal protector, not rust remover. displaces water, leave a film to protect the metal. I lie CRC sp 350 which works the same way. One is probably not any better than the next. None work if you don't use them.

I've always wondered why they stressed the Metal Protecting part over it's rust ability but it matters not.

The proof is in the pudding and I've been getting this kind of de-rusting action with it for 30 years.

Show me some similar INSTANT action with your favorite juice.

Speaking of CRC.
their "Power Lube" is also great for cutting rust
But the final (METAL PROTECTING) film gets gummy over time.
Amsoil MP DOES NOT ever oxidize!

that's precisely why "metal protection" as in stable and non-oxidizing is also super important -- hence the name, "MP".

By the way, you are dead wrong about how it is marketed or
what it is "sold as".

Here's the write-up and it has ALWAYS been sold as all of the above.

_________________________________
[b:96e367eca0]MP Metal Protector[/b:96e367eca0]
High-Performance Spray-On Metal Surface Protectant
Displaces water and protects metal surfaces from rust and corrosion. Provides a light film that prevents metal-to-metal contact. Excellent for use on guns, hinges, squeaky mechanical objects, electrical systems and more. [b:96e367eca0]Penetrates existing rust buildup.[/b:96e367eca0] Also dries wet electrical systems.

AMSOIL Metal Protector (AMP) is a high-performance, easy-to-use spray-on product that lubricates, displaces moisture, [b:96e367eca0]protects against corrosion and penetrates to free rusty parts.[/b:96e367eca0] It does not form gum or sludge.
____________________________

Also, written right on the present U.S. can:
FREES RUSTY PARTS

cheers,
T