Thread: Boring Harley cylinders...what size lathe do I need

I'm not sure Michael. Is a hawk available in chrome?

They are usually made of plywood here in the UK but plastic is making inroads.

John S.

Aluminum here, though they have gotten thinner over the years. My first (hawk) from 30+ years ago is still fairly flat, later ones bend down around from center and take a crown after minimal use.

The real question is, do they use a mill or lathe to put the circular grooves in?

smt

I don't understand "bolt-up torque."

Those jugs are pulled down, via four nuts, onto
studs that are projecting out of a flat face,
which is the crankcase surface.

My bmw jugs look pretty much the same, and
are snugged down to a flat one piece machined
surface.

As long as the underside of the mounting flange,
and the surface it is being bolted to, are
both flat to within a thou or so, nothing
in the jug is going to move when that force
is applied.

Or am I missing something here?

My first approach at cleaning up a jug was
making a fixture that went into a 10 SB machine.

Seemed like too much work so after that I went
to a specialty shop that bored and honed with
a sunnen. Cheap at twice the price.

Jim

jim;
a Harley cylinder is bolted down as you said.
however the head is pulled down by 5 bolts which puts a strain on the upper cylinder flexing it so thats the reason for the torque plates.

having said that ive bored lots of shovelhead and some panhead cylinders before i started using torque plates and have never had any returned for reasons related to boring or any other reason.

i havent bored any Blockhead cylinders.

the biggest problem i did see on HD engines using hydraulic lifters was the person wouldnt let the lifter bleed down after adjusting the valves then they would cycle the engine thru bend a valve and crack a valve guide and usually the head also.
i love home schooled mechanics they will keep you in business, at least for a while.

i dont mind adjusting valves on Shovelheads so i use solid lifter adapters and dont have the bleed down problem...jim

What I found with the old style cylinders is, the thin area that protrudes into the case flares out about .002" when the four nuts are tightened, an area about 2" down from the head bolts will bulge in about .001". At least use a torque plate on the bottom of the cylinder, otherwise the piston will tend to rock at the bottom of the stroke causing the rings to wear a groove.
Its good to use the same type of gaskets with the torque plates, but use new ones on assembly.
One problem I encounter on pan/shovel hydraulic lifters is, often an after market cam is used. These cams develop their lift by grinding down the base circle of the cam. This causes the lifters to drop below the oil holes in the tappet guides, starving the lifter. The top oil groove on the lifter can be widened upward to help with that.

benesesso did mention a good point, years ago I was shocked to find a knucklehead cylinder grew by almost an eighth of an inch at top operating temp- no wonder HD adapted the hydraulic lifters to their machines.

Typical cylinder growth is about .060", lifters compress at cold .100".
The top motor mount is designed to flex.
One of the most interesting things is, how the oil is returned in the 1999 and earlier big twin engines.

Cylinders growing an eighth inch.......come on get real.
If that were true the compression ratio would drop about four to five points,and you would need magic pushrods also.

Donie:
i seem to recall that the late Casey LaRue used to market a gage for adjusting Shovelhead lifters and the gap was 1/2" before bleed down is that about right?
how is the oil returned on the Blockhead im guessing it doesnt drain VIA the cast in return gallery like the Shovel?...jim

No, .125 growth on those old small bore iron cylinders.
CR was probably 6 or 7 to 1 0n a thirties knuck?
And the magic push rods were the hydraulic lifters- that's why HD bought the GM lifter design in the first place.
Of course this is all "hanging around in old shops" talk- I sure don't have a testing rig.
Anyone know the real measurement?

Zach

Ah, a torque plate for the *top* of the head.

That makes more sense.

Jim

tooljim, the blockheads and twincams drain from the the head via a straight hole along the edge of the cylinder into the crankcase compartment, very much like the early panheads that had the hydraulic lifter in the top of the pushrod 52 and earlier off the top of my bald head.
I remember those adjusting tools, but never owned one.
Jim rozen, on Hardly old Ablesons its the base of the iron cylinders the distort the most, the BMWs probably less prone to these problems. I have always wanted a BMW.

Found a photo of torque plates,
http://s170.photobucket.com/albums/u...rqueplates.jpg