Valve/Rocker/Pushrod Geometry

Wolfplace · Post by **Wolfplace** » Sun Aug 13, 2006 1:08 pm

Andy,
Very nice
I can see a real advantange although I am not sure it is any more accurate as what I feel we are shooting for is a narrow pattern.

But I can sure see where this would speed up the process.
Sure will beat crap out of removing the rockers, checking, adjusting, installing, rechecking, removing, installing,,

Ed-vancedEngines · Post by **Ed-vancedEngines** » Sun Aug 13, 2006 1:12 pm

Andy,
Another question for you.

Whose rocker arm and stand is that? I do not recognize it.
Ed

andyf · Post by **andyf** » Sun Aug 13, 2006 4:58 pm

That rocker arm is from RAS. I built the aluminum shaft supports. This setup is on a BB Mopar.

The tool is a simple idea. Just a block of steel welded to a retainer. Drill the hole for the dial indicator so it is on center with the roller wheel. I added a drilled and tapped hole for a set screw to hold the dial indicator tight. The tool only takes 30 minutes to make but it speeds up the process since it allows you to write down a number for the side scrub. After a few engines you can start to develop a "database" of scrub numbres so you'll be able to compare notes and see how different systems work.

Here is the link to RAS if you're not familiar with them. They are good guys to work with. They have some neat custom stuff and they are great for rebuilding arms.
http://www.rockerarms.com/

mach9 · Post by **mach9** » Mon Aug 14, 2006 2:00 pm

Andy,
If you built that fixture with a long flat tip attached to the indicator plunger for the roller to work against, would that allow the same fixture to be used on most any stem height/retainer combo?
Also, what is the average amount of side movement you see on a proper setup? Thanks! Nice fixture! MJ

andyf · Post by **andyf** » Mon Aug 14, 2006 3:07 pm

I'm not sure you need a different tip since most roller wheels are the same diameter.

That 0.080 indicated is a pretty good number for .550 lift. Scrub goes up with lift since the rocker arm arc is fixed. You can map it out on a piece of paper with a arc and a line and calculate the minimum possible scrub.

The only way to reduce scrub from the "perfect" setup is to use longer rocker arms.

andyf · Post by **andyf** » Fri Aug 18, 2006 11:30 am

I read the article in the Circle Track that just showed up. I didn't see anything in there that was new info. Basically just said to set up your rocker arms so they are perpendicular at half lift. The author didn't even mention the possibility of setting up the valvetrain to reduce wasted energy. (the minimize the product of scrub and force method that Chevy engineering recommends).

Post by **SchmidtMotorWorks** » Fri Aug 18, 2006 7:30 pm

andyf, Nice travel gauge!

I agree, when you can do it the 66% method might be better except i think it doesn't work in super high pressure engines like nitro stuff.

Bye the way, what rocker arm is that?

andyf · Post by **andyf** » Fri Aug 18, 2006 8:28 pm

Rocker arm is from Rocker Arm Specialist in Anderson CA. They are a great BB Mopar rocker arm. Investment cast SST with a bronze bushing. The guys at RAS make a lot of cool rocker arms, check them out some time.

www.rockerarms.com

devilbrad · Post by **devilbrad** » Sat Aug 19, 2006 3:59 pm

andyf wrote:Rocker arm is from Rocker Arm Specialist in Anderson CA. They are a great BB Mopar rocker arm. Investment cast SST with a bronze bushing. The guys at RAS make a lot of cool rocker arms, check them out some time.

www.rockerarms.com

Wow, I have never heard of them. I was looking into the Jesel shaft mount rockers for my Dodge Magnum motor, might have to contact these guys see if they would be interested in building a shaft setup for a Mag motor.

putztastics · Post by **putztastics** » Sat Aug 19, 2006 4:29 pm

There is a guy in SD that built LA shaft adapters for the Magnum heads. He's got all the engineering done but it didn't look like there would be a market so it stalled.

And I was trying to get RHS to offer their 360HPST iron Magnum replacement head with both Magnum roker pads and LA shaft stands and a dual LA/Magnum intake bolt patern but it looks like that is stalled right now too.

panic · Post by **panic** » Sat Nov 25, 2006 12:18 pm

steelcomp · Post by **steelcomp** » Mon Nov 27, 2006 12:02 am

I posted this some time ago on another similar thread. A (picture) says a thousand words. (Read...CompCams instructions on valve geometry stinks)

Also, how many times has anyone had to cut guide plates (on stud mounted set-up) and re-weld them to get the rockers over the valve tips??

Details, details....

Post by **Stevespeed** » Mon Nov 27, 2006 12:39 am

Steelcomp, I'll second that about guideplates-especially BBC. Maybe Isky should come out with adjustable like their SBC plates. Save lots of cutting and welding. Actually though, with the advent of sportsman shaft rockers, there is no need anymore.

idunno · Post by **idunno** » Mon Nov 27, 2006 8:48 pm

heres a short & sweet info page from Reed Cams
http://www.reedcams.com/rocker_arm_geo.htm

panic · Post by **panic** » Mon Nov 27, 2006 10:20 pm

How clever - it refers to one possible method as "correct".
Apparently Jessel, Warren Johnson, etc. aren't "correct", nor are many of the automobile manufacturers, who don't use the 50% lift figure...

Since now we know that there is only one possible answer to the question, I'll just remove all those mistakes I made.