Rockerblock I.C.--Something a little different-

[Brian Rupnow]

One valve down, and one to go. Both intake and exhaust are the same. The stem on these valves are almost ridiculously long, at 1.537", but once they are set into place in the cylinder head they look about right. The actual guided part of the valve in the valve cage is quite long. I turn these valves down to about 0.128" in 3 stages to keep from having a lot of deflection to deal with. The hardest part of the entire valve is to keep from turning the stem undersize. The last 0.003" or so, I work down to size (0.125") using 220 grit carborundum paper.

[Brian Rupnow]

Chuck, I've been very lucky on my last 2 or 3 engines, the valves sealed right away with no problem. I don't really know what I'm doing different now, compared to my first few engines, but whatever it is I hope I keep it up!!---Brian

[Brian Rupnow]

And that's the second valve finished. I'd have been done sooner, but I had to run across town to my sons house and look after a sump-pump emergency. Tomorrow I'll machine a set of "keepers" and drill that tiny 0.040" cross hole in the valve stems that allows a cross pin to hold the keepers and springs in place.

[Art K]

Brian,
Things are coming along nicely.
Art

[Brian Rupnow]

The time has almost arrived to make my rocker arms. I wasn't totally happy with the original design, as there was no good way to lock the adjusting bolt which sets the valve lash in place. So--this morning a couple of hours were spent redesigning the rockers. I'm happy with what I've came up with. I have to attend a birthday party for youngest grandson at noon, so I may not get any actual machining done today.----Maybe---

[Brian Rupnow]

Those rocker arms look like monsters. They aren't really, they are only a bit less than 2" overall length.  I will probably attach two 1/4" plates together and do the side profile, which is where most of the work is, then separate them and do the top profile, thinning them out to 3/16" in the center.

[Brian Rupnow]

YOWZAHHH---we got rocker arms!!! I had forgotten that today was a holiday. I got ready to travel to my office across town this morning and good wife said "where are you going? It's a holiday today."---So, today I machined the rocker arms I redesigned yesterday. There is a lot of work in those rascals. I spent most of today making them.

[crueby]

Victoria Day, correct?  Glad you found out before getting there and wondering "Where IS everyone?"

Rockers look great!

[Brian Rupnow]

It's the twenty fourth of May
I'ts the queens birthday--
If you don't give us a holiday
We'll all run away.
Yes, that one, I guess. Once you progress to this retirement lifestyle, every weekend is a long weekend. I have a heck of a time keeping the holidays sorted out.

[crueby]

It's the twenty fourth of May
I'ts the queens birthday--
If you don't give us a holiday
We'll all run away.
Yes, that one, I guess. Once you progress to this retirement lifestyle, every weekend is a long weekend. I have a heck of a time keeping the holidays sorted out.

After retirement, sometimes it is "is this a weekend? What's a weekend?!"

[Brian Rupnow]

Made a mistake--Kissed a snake--ah, POOP!!! I totally screwed up the design of those rocker arms. I can't even see a decent way to modify the existing ones and "save" them. As for some idea of what I did wrong, look at the drawing I posted. The actual part of the rocker arm or the adjusting screw that contacts the end of the valve stem should be almost dead-nuts in line vertically with the pivot hole in the rocker arm. Pulling it away off center like I show in the 3d cad model means that instead of an almost vertical up and down movement, which is what you want to have acting on the valve stem,  it "swipes" across the end of the valve stem as it pushes it down. This produces undue wear on the end of the valve stem and also tries to make the stem bend sideways as the rocker rocks up and down. I will have to make new rocker arms, and probably have to make an adjustment to the height of the rocker pivot tower. Fortunately this hasn't cost me any money.--Just the best part of a days work. One more thing to file away in my mind about what you can and can not do when designing these little engines.-That's what I get for working on the queens birthday!!!--Brian

[cfellows]

Why don't you just reverse them and put a roller in the slot to bear against the valve stems.  Put the allen head screws in upside down and insert the short push rod into the hex hole of the screw.  You can even drill out the hex hole so it's round.

Chuck

[Jasonb]

What chuck said, better to have the rollers or a rounded surface against the valve and a pocket (screw head) for teh pushrod to go into, This is how the bobcat/jaguar is done. Flipping them upside down would bring teh surface of teh roller about on ctr line of the pivot

[Brian Rupnow]

To give you some idea of what I'm talking about, the dotted line indicates the optimum position for the rocker arm pivot, in relationship to the end of the valve stem. Arranging it this way gives the absolute minimum of "side movement" on the end of the valve stem when the rocker arm rocks.

[Jasonb]

Yep thats what we are talking about too, you will also need to redrill pivot hole 0.125" to the side which should just work