Head Removed

[Harold R]

Starting to determine what needs to be fixed in the motor, so I took the head off......and was a little suprised. Is this the domed pistons I've heard about?

http://photos.cubfest.com/albums/userpics/10314/Humps.jpg

The lower end was tight and the motor held good oil pressure. It had just started to smoke a little under a load. I'm thinking the pistons are standard........they have an arrow pointing to "Front", and each piston is numbered. I was hoping a new set of rings and lap the valves, but the number 2 and 3 look real oily.

[John *.?-!.* cub owner]

This morning the link is pointing to a picture of the engine turned over showing sludge plugging the oil pump intake screen. The one you had yesterday was showing what appeared to be the IH Fire Crater pistons, which was their version of a domed piston.

[Bigdog]

I re-pointed your link HR.

[Harold R]

This morning the link is pointing to a picture of the engine turned over showing sludge plugging the oil pump intake screen.

Can't explain that. I think BD enlarged it for me.........but that oil pump screen photo belongs to someone else.

Never the less. Was the "Fire Crater" from the factory or replacement part. The reason I ask is because I need to order a set of rings for them but I need to know what size. It's been my experience if it's an over-size piston, the size over is usually stamped on the top. I've seen nothing but sequence numbers and a direction arrow "Front".

[Steve Butram]

HR, clean them up real good there should be a size on them. The fire crater piston was marketed by IH. But I don't know who was manufacturing them. Any manufacture of rings will work on the pistons

[George Willer]

Harold,

You will have to mike the cylinders before you order rings to know their exact size. The allowable ring end gap must be between .007" and .017"". As little as .003" cylinder wear will cause the ring gap to be out of spec as soon as the engine is broken in. I typically use the next size ring and carefully file the gaps to give .007" fit. I just did it again on the engine I'm preparing for the demo.

The pistons themselves are more forgiving and can be knurled to enlarge them to make up for wear.

[Eugene]

Yup on what George said.

Ifn that engine were mine I would do a major overhaul. If the engine doesn't need extensive machine work - It won't cost much more. And if it needs extensive machine work - Well, it's cheaper to do it right once.

Just my opinion.

Eugene