Does anyone know offhand what the angle from vertical the exhaust valve stem is canted in the cylinder head? I believe the 216, 235, and 261 engines all have the same valve geometry. I can remove a valve and use a close-fitting steel rod in the guide and a combination square to measure the angle it makes with the head gasket surface, but I'm hoping someone can short-stop the process with some accurate info. Thanks! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
OK- - - - -thanks! I'm building a setup to replace the rocker shaft and rocker arms with stud-mounted roller bearing rocker arms and pushrod guide plates, and the studs for the exhaust rockers need to match the angle of the valve stems to keep the geometry correct. The item that replaces the rocker shaft will be a solid steel bar 3/4" thick by 1 1/2" wide, mounted to the same stud holes in the head as the rocker arm stands. Rockers will be for a big block Chevy with a 1.7:1 ratio. This setup will be used on the engine I'm building with MOPAR roller lifters running on a Corvette/261 camshaft. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I would guess that the pivoting stud for each rocker would be placed along a diagonal line between the pushrod center and the valve stem tip (on the steel bar), and the rocker arm will follow this axis as it oscillates.
Panic has the idea- - - -draw a line between the pushrod hole and the valve stem, and elongate the hole in the head so the pushrod can tilt a little. Install the threaded stud into the steel support plate that replaces the rocker shaft centered on the line, and use a guide plate to keep the roller rocker from pivoting off the tip of the valve stem. Use an 11/32" lash cap on the top of the valve stem to give the roller tip on the rocker a little more diameter to roll across, and use a pushrod the proper length to control the sweep of the roller across the lash cap. It's the same sort of geometry exercise we used to do when installing roller rockers with different lift ratios on round track race engines. I'll be using MOPAR roller lifters on a Corvette/261 camshaft and adjusting the cam timing with offset Woodruff keys or broaching extra keyways in the cam gear to get the opening and closing points right on the cam lobes. I'll open up the hole in the cam gear to be a very snug slip fit instead of a press on the cam, and attach the gear to the cam with a center bolt. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
... mounted to the same stud holes in the head as the rocker arm stands. Rockers will be for a big block Chevy with a 1.7:1 ratio. This setup will be used on the engine I'm building with MOPAR roller lifters running on a Corvette/261 camshaft. Jerry
Now you got my attention. That sounds really intriguing. Not sure if they are any help, but here are some drawings I have laying around.
I'll also be shortening the tip of the stovebolt intake valve to lower the profile of the intake valve train, leaving just enough height above the split locks to secure the lash cap in place. The roller lifters are available in either mechanical or hydraulic versions, but the prototype engine will probably run the mechanical type. Getting the early blocks drilled for a hydraulic lifter oil gallery is going to be a bit of a challenge. Might as well use the KISS principle to chase the R&D gremlins off! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
My circle track "claimer" engines used to be famous (or maybe infamous) for what I could shoehorn inside a "stock appearing" engine. Like Smokey Yunick used to say- - - -"It's only cheatin' if ya get caugt!" LOL! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
When the chief tech inspector at the Merced California dirt track retired after 20-something years, the track owner hired the biggest cheater at the place, and made him the new tech guy. He knew all the tricks. It was tough to slip anything past him! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
My Dad had a theory about building things, particularly hot rod related stuff. "First, you build something that won't work. Then you build something that works, but it's so butt-ugly you're ashamed of it. On the third try, you make something that works, and looks good!"
I've got an addition to that comment- - - - -you make, and correct enough mistakes building the first one that the second working model takes half as much time, and looks better! I'm getting ready to start whittling metal on the second rocker stud support rail in a couple of days. There was quite a learning curve on the first one! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Speaking of mistakes- - - -the three mounting holes between the stud support bar and the cylinder head were about 1/8" off sideways. Gotta press fit some plugs into them and re-drill them correctly. Once all the dimensions are correct, I'll make a mirror image piece to support the rocker arms for the other three cylinders. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I understand that "exact" is the object. However, Barton makes some really $$$ rocker arms for the Gen-2 Chrysler 426 hemi engine, which have some side-scrubbing of the rocker roller on the stem tip as the valve opens (the rocker's oscillation path isn't in the same plane as the valve stem and guide). This is apparently insignificant, even in these high power, high RPM, high spring load engines.
Since this project might serve as a pattern for a friend with some CNC equipment to make a small run of the system, it's important for the protoptype to be as exact a fit as possible. The OEM stovebolt valve gear is getting a bit scarce, and if I can come up with an alternative using off the shelf parts, I believe it might benefit more than just myself. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Next question- - - - -is the intake valve exactly vertical, or is its guide angled a little? I've heard a specification of a 6 degree tilt on the intake valve stem- - - - -yes or no? Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Thanks! That's probably not enough tilt to require another milling cut on the protptype stud support bar I'm making, but it will be good information to provide to the CNC guy when and if I decide to commission a few production pieces. Now it's just a matter of getting a running "lab rat" on the treadmill for some dyno testing! Thanks! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Welllll- - - - -I made up a checking jig that centers in the valve guide so I can evaluate the tilt of the intake valves. Yes, it will be necessary to do some milling to assure the rocker arm stud is parallel to the valve stem. No biggy- - - -that's why I'm taking my time and trying to do it right the first time! Once I get all the preliminary work done, it won't be much of a challenge to turn out some exact copies of the stud rail on a CNC mill. The intake studs will need to tilt a little bit in the opposite direction of the ones for the exhaust rockers- - - -sort of a "porcupine head" stovebolt! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
