This Can Not Happen

[Steve Pierce]

There is a high and low spec for dry tappet clearnace, you install longer or shorter pushrods to adjust. Helps to have a stash of different let's when building up an engine or doing an engine swap. Every engine I have ever assembled I remember the rings were numbered top to bottom and the top of the ring as well.

[wyandot jim]

Steve,
I'm sure you are correct on this. Been awhile since I did the engines. Now have a severe case of CRS.

[mmoyle]

What is the opinion on proper break in procedures for seating the rings? I've read both continental and lycoming breaking procedures... After each read I come away with.... Doesn't sound like it'll guarantee seating the rings. I've spoke with a couple guys who recommend running a rebuild just long enough to check for leaks....then push the engine during the first flight. That fits my experience with non aviation engines. Start...check for leaks...shut it down...button up everything....strap it down to a dyno or push the engine hard enough to smoke the brakes. Never once had a come back....


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[Steve Pierce]

If new cylinders they break in very fast because of the new processes making everything more round. I run a newly rebuilt engine long enough to warm it up and check for leaks. I then wait till it cools completely, usually overnight. I then taxi to the runway and take off. Shallow climb, don't go very high to keep a high manifold pressure. I run it hard verying the rpm every 15-20 minutes. Also run a cruise prop rather than a flat, climb or Borer prop for high manifold pressures.

[Gilbert Pierce]

Jim

Reground rocker arms and camshaft, resurfaced case halfs, reground valves and seats all change the original dry tappet clearance.

The Continental hydraulic lifter will only keep a proper clearance within a clearance band of 0.030" to 0.110.
Outside that band it may hold the valve open or rattle; after the lifter has pumped up.
You adjust that by measuring the dry tappet clearance and if out side that spec you bring into to spec by adjusting the push rod length. Push rods are available in various lengths to accomplish this.

We use to accomplish this on Chevy engines with adjustable rocker arms. Screw the rocker arm down until it held the valve open and the engine missed and then back it off until it clattered and then leave it half way in between. This was done with the engine running and spitting oil on you. I have Chevy rocker covers with top cut out to accomplish this with less mess.

[wyandot jim]

We use to accomplish this on Chevy engines with adjustable rocker arms. Screw the rocker arm down until it held the valve open and then back it off until it clattered and then leave it half way in between. This was done with the engine running and spitting oil on you. I have Chevy rocker covers with top cut out to accomplish this with less mess.

Yep
Thanks again Gilbert,
The Stroker 383 Chevy we built up for Son's Camaro has solid lifters and I did the same thing with an old valve cover. I also had a boat with 327 solid lifters in it. Yep makes a mess. Hyd. in a car snug them up and the put a turn on them and they are done

Here is a story for you. My neighbors brother who retired from Tulsa Engines was here in OCT. Son and I were talking to him about adjusting the valves on the SNJ's 1340. He sad even though the book says adjust to .010 it very seldom can be done. be happy with .015. When hot the clearance will be from .080 to.120.

[mmoyle]

If new cylinders they break in very fast because of the new processes making everything more round. I run a newly rebuilt engine long enough to warm it up and check for leaks. I then wait till it cools completely, usually overnight. I then taxi to the runway and take off. Shallow climb, don't go very high to keep a high manifold pressure. I run it hard verying the rpm every 15-20 minutes. Also run a cruise prop rather than a flat, climb or Borer prop for high manifold pressures.

Thanks....


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[gliderman]

on Lycoming engines the hydraulic valve clearance is .028 to .080. as Steve says you just put longer or shorter push-rods in to get this clearance......

[mmoyle]

Does anyone offer unfinished push tubes for the O-320....As in one end is induction welded in place...the other end isn’t...for a custom fit then rosette weld the fitted end? Sure wish Lycoming had minimum and maximum valve stem height specification... I have eighty thousandths to play with if I adjust the valve stem height on the exhaust valve...as in the rotator cup...if that’s what it’s called is 0.206” deep... from the valve stem to the valve keepers are 0.287”.....I’d like to redo the rocker arms as well...but my machine will not to the radius on the valve end.. it will reface the valve stem end to a spark out mirror finish. Also discovered four push tubes same length...the others I can guess...can’t find my 11-12” micrometer...haven’t used it in 20 years...can’t remember the last time I used it or loaded it out....actually....had to fit within 0.002” a 11.25” diameter double roller bearing with internal thrust on a big rod mill...that was...well..20 years ago.


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[Steve Pierce]

Have not seen open ended push rods. I have a good collection of pushrods to choose from. Got lucky on Thursday and the two push rods removed left the correct amount of clearance between the rocker and the valve after cylinder change.