i need to plug cylinder drain holes for a 4 1/2 stroke crank. whats the best way to do that? thanks
I expect that you're drilling into the case and through the lower cylinder for oil return? If yes, use a 3/8" O.D. steel tube about 0.750" to 0.781" in length to divert the oil to the case under the cylinder base gasket.
Quote from: 1stop on December 10, 2020, 02:57:51 PM
i need to plug cylinder drain holes for a 4 1/2 stroke crank. whats the best way to do that? thanks
With the 4.5" stroke oem shovel barrels, the oil ring often cut over the oil hole and you had an oil burner. If that's what you are doing here's a fix I have used.
Assemble the barrels onto the engine using mechanic's blue to the ring pac so you can see where the oil ring stops. It is generally at or just cutting the drain hole in the cylinder wall.
Clean the oil gallery and barrel throughout. Depending how much it cuts into the oil hole you have the option of passing a long drill bit down from the top until it shows right through in the barrel. If the ring pac just barely cuts over the top of the drain hole you may not have to do that but you still can. The purpose is to try to lower the hole bottom a bit and cover the top where the rings pass over.
Weld the hole up with brass. I have used a length of round stock down the3 gallery to back the hole and prevent the brass from filling the galley of tight. Make sure you don't leave a large humped deposit behind. A fine large diameter stone on a drill or sanding barrel on a dremel done carefully works well. Your fingers are good to about .001 but a dial gauge is better. Carefully bring the welded area down to the cylinder surface ending with fine emery on your finger tips if necessary.
Re-drill the hole to make sure you haven't plugged the gallery. Using a smaller bit drill into the brass at the "lower part" of the hole but not high enough to catch the level your oil rings tracked the blue to in the barrel at the oil hole.
Hone the cylinder surface lightly to confirm the brass is conforming to the cylinder surface profile and not going to interfere with the rings. Again, a dial guage is nice. Ideally it will be perfect as though it was always there.
The rings will not wear the brass away because the cylinder wall is supporting the ring pac from both sides. All you really need is the rings to not pass over any part of the open oil gallery hole. It's easy enough to mock up and check before and after.
I can tell you this works well and on your next oversize you will barely be able to tell you did it.
Piece of brake line.
so just put a piece of tubing in to block off hole in bore? maybe chamfer hole in bore and run it? thanks for replies
0.375" OD tubing, lots of strokers running around like this.
S&S 51-1043 instructions lay it out for you.
S&S 51-1043 (http://images.rolliesspeedshop.com/pdf/SS91-9012.pdf)
Quote from: Ohio HD on December 11, 2020, 09:14:09 AM
0.375" OD tubing, lots of strokers running around like this.
:up:
To be clear, the method I tried to explain was something we came up with the year that S&S made their first stroker flywheels. (very early 1970's) George Smith sent my buddy Robyn Gray 4 sets of wheels on spec for trial. Three were 4 1/2" stroke and one set was for me.
While we were mocking up using the drive side case (timkins) to check piston to piston and scraper clearance we noticed witness marks from the oil ring just cutting over the oil hole. The rear cylinder was usually the culprit but could be both. We shared the info with George. Our fix was as I described or the alternative seemed to be 3 sets of door stops. It simply became the way it was done to us. Part of the reason was to retain the oil feed to the cylinder wall (even though IIRC the early pans did not have that feature). S&S obviously moved the oil drain hole in their barrels but we were poor and always used scavenged OEM. The OEM barrels could be bored well beyond .060 but we stopped there because pistons were hard to source beyond that.
Brazing the oil drain has been around a long, long time. With Iron Head Sportsters you have no other choice. With the Shovel you could use the tube, much much easier.
Truett and Osborn (http://www.truettandosborn.com/Oilholerelocation-xlweldingbrazingmethod.htm)
HA HA well the early 70's wasn't like yesterday. Sometimes it feels that way though. When we were trying to nail down our approach one of the others suggested the brass. Knowing how sharp he was / is I don't doubt he knew it was done before. He just never said anything and we trusted him enough to try it. As said, it worked perfectly.
My understanding is that the reason the oil drains into the side of the cylinder wall was so the piston would "seal it off" 1/2 way on the down stroke when the crankcase is being pressurized, and uncover it on the up stroke when the crankcase is going into a vacuum. This is supposed to pull oil out of the rocker area on the upstroke, and not push it back up there on the down stroke.
By the way, my 4-5/8 Ironhead had the drain holes relocated as KD described.
-JW
That's the first time I heard that reasoning / description. It does make sense with a common crank pin. We also would open up the side of the crankcase vent hole in the timed spool to accommodate the extra pressure and duration from the longer stroke.
Shovel head step by step from the experts.
Rest In Peace Bonnie Truett, August 13, 2018.
Truett and Osborn (http://www.truettandosborn.com/Oilholerelocation-sleevemethod.htm)
Yeah, I think the pre-evo motors tended to pump too much oil into the heads. If you re-route the oil return back into the crankcase directly (as opposed to the stock method of into the cylinder walls), you may want to consider this trick. I did this to my Ironhead, may do it to my Shovelhead at some point. You drill & tap the top end oil fittings at the engine case to accept Keihin carb main jets, and restrict the top end oil a bit.
[attach=0]
-JW
AAAAAaaaaaaaaaaaaaaa!
The extra oil that goes to the top is used to cool the valve springs!
If the designed amount of lube is not delivered the bushings may not get proper lube.
There is an orifice in the exhaust rocker arm that delivers oil to the valve springs.