valves siezing in guides

[fizz]

Finally finished my top end overhaul, fresh bore, pistons, guides, springs, keepers on my 1945 chief. Started right up, but had an intake leak so took it back apart and installed new Viton seals. Went for a ride and went about a half mile, engine just shuts down like electrical short, started up after a few minutes, went home, started checking it over, tried again, same thing. Did this several times, generally did it on acceleration, sometimes would pick up again after coasting, sometimes not, but would start again after a few minutes. Yesturday a buddy of mine who is a pretty good engine tuner, adjusted the carb, took it for a ride, and everything was hunky dory. Said he thought I was too lean and it was causing the valves to sieze up. I did have the carb at the base settings per the manual. I did do a pressure check on the manifold after installing the new seals. Live and learn, I guess.

[T. Cotten]

A coupla questions, Fizz!

First, forgive me, I am always compelled to ask,..
Did you bubble-test with a regulated 12-15 psi air supply?

Next, how did you configure your manifold assembly to accept O-rings?

....Cotten

[kitabel]

A valve refusing to close completely disables that cylinder instantly, doesn't sound like it from your description. Normally I would expect normal behavior from the good cylinder and severe misfiring from the bad one.
A carburetor without an accelerator pump (all Linkert) will have slow or bad snap response if it's lean.
A useful test (if it repeats): compression test will show very low on the bad cylinder as long as the valve is stuck, and a big jump if it frees up.

[T. Cotten]

..
A carburetor without an accelerator pump (all Linkert) will have slow or bad snap response if it's lean.

That's worth a new thread all by itself, Mr. D!

Accelerator pumps are "highly over-rated".

....Cotten
PS: Attachment is from the 1943 Armored School Handbook

[tfburke3]

I only have experiece with Linkerts except for an 80 with an 1 1/2 SU long gone .
The lack of a mid circuit is discussed in Jimmoshersperformanceindian web site.It's an interesting read,and since he uses AFR ,temp sensor measurements and a dyno I think his results are worth considering.
His 4 LSP records on his Scout also in my opinion add to his credability.He does endorse the CV and sells the adapter kit but I dont think that changes his results.
Which is all academic for me because Im sticking with the linkerts,except for two Schelblers waiting to be tried on next projects.
BTW my favorite carb was the holley 2barrel on my 54 ford with a side mount glass float bowl.

Tom
Tom

[T. Cotten]

Tom!

Out of respect for Fizz, we really aught to spill carb design theory into a different thread.

Fizz could be facing anything from elektrikal grief (like a key switch or a condensor), to the worst scenario suggested.

It is best that he diagnose one small step at a time.

....Cotten
PS: There are no bad carbs, just badly worn ones, or anachronist replacements: Why not fuel injection?
I wish somebody 'here' had a testbed Chief and a handy dyno (albeit only as good as its dynomeister...)

I've got contestants.

[fizz]

Cotton, I made a block off plate where the carb bolts to the manifold with a threaded hole for a pipe nipple which connected To my paint gun regulator, set to 12psi, I did not fit o rings, just had the viton seals installed, then tested for leaks with soapy water. I did detect leaking at the guides, but not at the manifold, so I considered it good. Did I do that correctly, as I thought I interpreted the instructions that came from Enfield correctly.
I also thought that one valve hanging up would only cause one cylinder to shut down, and it definitely shut down abruptly, and believe I have an electrical gremlin there somewhere

[T. Cotten]

Fizz!

The Enfield Racing seals are molded PEEK, not viton.

Beware of some aftermarket nuts with improper inside bevels that can cause mass-produced seals grief.
(The last failed set across my benches had nuts with 58° and 62° bevels, when they should be 60°.)

...Cotten

[fizz]

Cotton, I am interested on your opinion of the PEEK seals. It is interesting that you should mention the manifold nut, as I cracked one like a cub bear with boxing gloves, when I found the leak initially. I acquired new ones from Greer, but it sealed, and if it remains leak free, all is well.

[T. Cotten]

Fizz!

Greer's nuts are excellent.

As far as PEEK seals, I pioneered its use: http://virtualindian.org/9techpeek.htm
(Please note that my prices went up in eighteen years...)

That was published before it became obvious that mass-production was impractical, as nearly all vintage manifolds are worn upon the spigots, and even new reproductions didn't match.

The material is phenomenal, when properly fitted.
Reuseability depends very much upon the finish on the manifold's spigots.
Like any seal, an occasional snugging of the nuts is prudent, particularly after the first few heat cycles. Over-tightening should be avoided.

Other than the nut bevel issue, the only two failures reported to me on Chiefs both had oiling issues, that apparently spiked temperatures near 600°F.
Most folks would notice.

....Cotten

[kitabel]

If you are actually losing only one cylinder (for whatever reason) the spark plug, piston, and head temperature of the "good" cylinder will rise quickly since it's carrying the entire load, and will be prone to heat (not lubrication) -related seizure. Be careful!
Complete secondary electrical failure (no spark at all) kills the motor dead, but weak spark may continue to fire the cylinder with the lower cylinder pressure (in psi) especially at low throttle openings (and go dead at WOT). After a few seconds, the working pipe will be hotter and of course louder (the cold cylinder will just release compression when the exhaust valve opens, not combustion).

[fizz]

Engine is killed dead abruptly when it happens. I suspect a short in the lead from the coil to distributer, in the tube that contains the spark plug and coil wires, as that was the only other thing that got fiddled with. It works perfect now, but will investigate this weekend. 73 year old wire.