EJ22, planes, HG, what is a fly cut?

[steptoe]

Hope the title draws interest.

Got talking to a fella at the LPG pump just then, amused my Brumby was on LPG, more so when I told him of my EA82T also on LPG. He knew subie engines - for planes and has an EJ22 SOHC in his winged beast. Got onto EJ25 and their HG issues they develop. He has a fix and has had for many years on many engines to stop weeping HG's

A .020" 'fly cut' on the block around the bore. I get the gist but not complete understanding and did not want to hold him up in the mozzie environment, he's travelling, works for an overseas aeronautical engineering company and lives in an area I know and visit - so another time maybe.

I have gogled fly cut but not got best understanding results yet so thought should share in here first - and maybe Disco has a good few words to say on the topic. I imagine it is a recess to help gasket sit in place and seal?

Also designed his own fuel injection system for his plane. His back up fuel system in case efi goes to crap is a 5lbs pressure pump pumping fuel through a jet into the airstream - aloows him to set throttle to suit fuel suply for - a safer landing than no power at all !!

[Point]

that's the first time I've heard of a fly cut on the block. To my knowledge a fly cut is the recess cut in the piston crown to allow room for the partially open valve. Most pistons have a recess from factory cast in, however bigger cams requiere bigger reliefs to be cut.

As far as the block goes, or to improve headgasket sealing, you use what is called an 'o' ring, where they cut a groove in the head or block, and fit a wire in the groove. This then increases the crush on the headgasket.

[discopotato03]

Yes I'll give this a go though don't forget I'm 22 yrs out of old fitting and machining trade - it didn't pay .

My take on fly cutting is using a small single point cutting tool out on a limb so to speak and buzzing around in circles in a wide enough arc to machine or "deck" the full width of the head or block/engine case .
These days I believe machine shops use a large diameter disc with ganged carbide tipped cutting tools because it speeds up the process .
To "fly cut" or "deck machine" a casting means to re create a flat surface square to the table of the generally vertical milling machine its clamped down to .

What your airy plane friend is possibly talking about is machining one or more fine shallow grooves in the blocks deck face to form a mechanical lock between itself and the head gaskets fire rings .

Sick with cold on days off so I'll ramble on .

I seem to remember later EJ engines having open deck blocks/cases and if thats true then you can run into problems with the unsupported tops of the cylinders moving around and breaking the seal between the gasket and the block or head/s . Honda people have been having this drama for years and use all kinds of weird ways to support the tops of the cylinders within the block . I seem to remember seeing a pic of steel rods cut to length and pressed into machined faces between the cylinder and the other side of the surrounding water jacket in the open deck block .

No doubt there is some reason for making open deck blocks but its not a outright performance based one . Again from memory Subaru deliberatly made the 22B cases closed deck to avoid these problems .

Forgot to add that normally once a head gaskets fire ring moves its a failure because it relies on the crush tension between the head and block so once they move the crush and seal is gone and they leak badly .

Up in the sky there is no roll over to the curb so he wants do do everything humanly possible to have a reliable engine .
One of the reasons why EA81s are so popular with Gyro Copter Man , see Mad Max 2 , is that they are light compact AND reliable . They may not be a power house for 1800cc's but they have a gear driven cam and a simple pushrod and rockerised valve train and if kept in good order is virtually bullet proof . The are pretty under stressed and I guess simplicity is bliss . Performance wise its the heads that let them down a bit but better ones are or were available .

Wanted new throat , cheers A .

[Gannon]

No doubt there is some reason for making open deck blocks but its not a outright performance based one . Again from memory Subaru deliberatly made the 22B cases closed deck to avoid these problems .

I have a feeling that it comes down to ease of production. Closed deck blocks are cast with a cast that must be destroyed to be removed, open deck means the cast can be removed and reused.

[tony]

My father had a mate who had a type 25c? I think, bugatti, about 1925, he bought it new, it was a lovely little car, had a magnificent note from the exhaust when revved, a real pants tearer.
anyway the machining on that car was so good it had no gaskets, in the head or sump, sealing was by the fit of the parts.
It was voted the best preserved bug in the world, had never raced or crashed, completely original. when he died (about 35 years ago) I believe it went overseas.