Jyrki..............are these the same width as stock rockers?.........and let me know what your decision is on the helicoil........
Thanks, and they look great!
Jyrki..............are these the same width as stock rockers?.........and let me know what your decision is on the helicoil........
Thanks, and they look great!
Last edited by Jyrki; 03-15-2012 at 01:12 AM.
I'm going to make the steel shaft stands slightly narrower, and use hardened steel shims between the rocker and stand. But I can't design my stands yet. First I need to get my head back from the welder, and let the porter find out what the max lift would be like. The imaginary line drawn through the center of the shaft and the center of the roller tip, must be perpendicular to the the valve, at mid-lift. So there is no correct stand height that works for everyone. It depends on the valve lift and the valve stem length.
These rockers won't work with stock valve guides, unless you either shorten the guide or use longer valves. For instance, the 320 stock cam has .348" valve lift with stock 1.5 ratio rockers. Swapping a set of 1.65 ratio rockers will increase lift to .3828". The retainer hits the valve guide at .400" lift. That leaves a .0172" margin, which is not enough. Add some factory manufacturing tolerances = destruction. You can't just swap the rockers, but you need to pull your head and shorten the guides, even with a stock cam, not to mention reground cams. Also, these rockers are going provide a lot more oil to the springs, so installing teflon seals on the intake valves would be advisable.
If I'm getting the message right, the public interest is dependent on whether the adjuster thread is helicoiled or not. My machinist isn't very enthusiastic about additional handiwork, so obviously this is something that I should perform. I'm going to find out what it takes and how much it costs.
I think for my use, the addition of a helicoil to the threads in your roller rockers isn't a must do requirement. However, for those who will be racing a straight 8 such is a valid concern. You've designed the rocker arms for use with stock pushrod adjusters. And we've brought up the issue of frequent adjustments using solid lifters. It is my experience adding a helicoil will prevent premature wear of the threads in aluminum bearing against a hardened steel bolt or screw. You're going to make adjustments of a steel screw threaded into an aluminum rocker which has a pushrod/solid lifter/cam lobe bearing on the adjuster end resisting valve spring pressure of 75 to 100 lbs through a 1.65 to 1 rocker arm rato. Helicoiling the rocker arm threads is a wise choice. In the aviation industry all steel bolts threaded into aluminum components are via helicoils. I was a US Navy jet engine mechanic, test cell operator, and SOAP lab operator. We always commented to folks, there's no parking lots at 20,000 feet.
You can always let folks who want them install helicoils themselves, how you like them apples?
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I don't understand your machinists concern with extra work with the heli-coil. All that has to be done is use a different drill and a STI tap inplace of whatever the hole is drilled and tapped to now. And if rigid tapping on the cnc, whatever brand he is using there is no time difference. And if need be you supply the heli-coils and install your self. The tool is between $30-$60 u.s. and helium coils are less then $1 each. And super easy to install. I use them all the time when we do aluminum.
40limited, I like your last plan - let the shop drill and tap for the helicoils, but furnish the inserts loose. That way, there are no additional shop operations, and yet you still avoid any potential alignment problems that might result from home installation.
Ray
I'll be out of town for a couple of days, but I will check with the helicoil stuff soon.
The rockers will be helicoiled. I have not yet got any verification if these rockers would fit the smaller engines. I'm going to look for a 248 to take some measurements.
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