Help with engine issue!!!!

[robertahegy]

Valve lifter float is possible with any hydraulic valve lifter. I never run my engine past 1400 during warmup. Wait until you see some increase in oil temp before doing any kind of high speed engine testing. If you are doing this on a really cold day, maybe put it off till it warms up to 35-40 degrees F.

Also as mentioned earlier, set your carb mixture per the engine instruction manual. This should be done at operating temperature and you should see a 25-50 rpm rise from idle as you pull the idle cutoff, just before the engine dies. Idle should be set about 650-700 rpm. If you see no increase, you are lean and need to turn the mixture screw out. An increase above 50 or so indicates you are too rich and need to turn the screw in.

All these adjustments and tests need to be done at operating temperature. Cold weather has an adverse effect on testing due to the difficulty in getting the engine properly warmed up without abusing it. Do your testing and adjustments when conditions are right. Rushing into the air before you and the plane are ready often results in one of those first flight engine failures, either on takeoff or landing.

Better to be on the ground wishing you were in the air, than in the air wishing you were on the ground.

Best of luck resolving your issues,

Roberta

[tacchi88]

Can't say that I have ever heard of valve lifter float in more years than I care to admit to. However, there is such an item as valve lifter bleed down clearance, which may not have been addresses in this overhaul. The Lycomings we fly, have bleed down clearances that must come between .028 and .080. with the lifter colapsed at TDC. Too tight or too loose will not necessarily cause the mag drop experienced in the begining of this thread. It will, however, cause future damage ranging from burned valves, to cam wear, and a number of other maladies.
There is not enough information regarding the causes of the problem, and in effect, the problem can be any number of things.
If the magnetos were set as closely as possible it should give a reasonable mag drop, which can be as much as 150 rpms and considered acceptable (and questionable), 200 is out of the box. It the engine can be started, E gap is close enough, at which time, assuming spark plugs, wires, point gap are in order, the engine would be able to give a satisfactory drop. They ain't rocket science.
And true, do not fly until the engine at least passes the simple mag check
T88

[mahlon_r]

Originally Posted by collinsj57@adelphia.net

Its missing on both, spoke with A&P and he thought it might be that the oil was not hot enough, said the lifters are floating becuase they are not draining the oil fast enough.

Never heard of this, any comments.

Thank all for the great feed back.

John

John , Don't think it's lifter float unless like the others suggested the cold valve clerance is way way off. I would run up to 1800 plus and let it run poorly for a while. After the run then check for a cold cylinder, this will tell us if one cylinder is misfiring or if it is multiple cylinders misfiring. If it is a single cylinder we know to hone in on it and see if we can find why that one will not run above 1800 rpm, like valve clearance, valve springs, intake pipe obstruction, single cylinder mixture problems i.e. something common to only one cylinder...... If it is multiple cylinders, it might be carburetion, valve timing(very easy to get wrong on an H2AD did this engine run OK in a test cell after the overhaul?) muffler/exhaust issues i.e. something common to all cylinders.
Good Luck and Happy New year,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."

[Vern]

Your tips on valve timing for the model 76 engine which you said was 'very easy to get wrong on an H2AD'?

Happy new year!

[osxuser]

Valve float is possible, but it would be happening all the time, not just when you do a mag check. Also if you CHT's got up to 450, there is NO way your oil wasn't hot enough. Did you confirm all your plug wires are going to the correct cylinders? Swapping one set could cause pretty much what you have happening.

[mahlon_r]

Originally Posted by Vern

Your tips on valve timing for the model 76 engine which you said was 'very easy to get wrong on an H2AD'?

Happy new year!

Hi Vern,
It a visual, parallax type thing. The H2AD doesn't have a separate accessory housing but rather an integral one to the crankcase. So being able to see the timing marks clearly is hard and thinking they are lined up when they are not can be easily done. you can always check the valve timing after assembly by checking valve overlap on number two cylinder with number one at TDC compression.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."

[Alschief]

Did you resolve the problem?

AL Smith

[collinsj57@adelphia.net]

Net Yet but I will be working on it today, I will let you know.

Thanks

[collinsj57@adelphia.net]

Thanks all for your wonderful input. Reset the mag points this morning and installed the two $5 nuts I ordered which fix the Caps in place. Mounted and timed to engine. Mag drop 50 -75 RPM both mags and no more missing . Looks like if the weather is ok I will be making first flight tomorrow.


Thanks again !!!!!