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Besides clipping the valves for clearance, no one mentioned(or I missed it) anywhere about cutting the exhaust valve to 1.900. I agree with BG..old school cams should be set up the old school way. I run a Crane R290 in my 477 and it's clipped with 1.900 exh valves. It wouldn't work(clear) any other way even with moving the cam timing around.




Hi,
I ran the old R290 (I still have it)years back also, I assembled the motor with out pistons and rods, with everything just the way it would run and checked it that way, I back cut the intakes and clipped the exh diameter till I had about .050 between the valves at full overlap.
Russ



Yep
Thats what were are shooting for at least .040+ I know guys run them closer, I also know those guys service there engine a bunch more frequent also. I bet they dont go season, after season without refreshing the heads etc...Being a bracket engine, a few seasons with hundreds or runs..Guide clearance gets loose .003-.004 or so, and the bottom see's .008-.010 movement..kaboom. Its probably no big deal to those guys, if they kill a piston, or knock the head off a valve..they have deep pockets..I dont however..

The heads and valves are over to the machine shop now. He said the margins on these new valves were super thick and were +.080..He is going to gauge the clearance, then cut the margin down to about .040-.050 backcut the valve again, and see what he gained by doing this..If he gets a desent return he will do them all. I will then mock it back up and measure actual clearance between the valves during over lap.. We are looking for .040 minimal, or he will sink the exh valve some to achieve what I want...


The one cam I have is probably a 1970 Crane grind that has a narrow 104 LSA..I might try it in this long stroke engine just too see what and how it runs, just for experience. As for the .290-.300 I may not be able to get those margins, but I wished I had them. If it worked back then, it will work now..no matter how out dated it is. I have several intakes,cams, and I plan to just have fun, and test some parts out..

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