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By airman - 10 Years Ago
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I have ecz-c heads there stamped with 312 on the ends and I bought mummerts y284s cam and 105# springs, does anyone know how long the valve length should be from the factory, mummert said for me to ground them down 100 thousandths, the machine shop said theres no way we can go that far, theres not much there above the spring, maybe they've been ground before, how long should they be after they've been ground down? any info helps
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By charliemccraney - 10 Years Ago
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I don't know why you would grind that much off of a valve. When valve are reground, it's usually at the seat and I don't think .100" will be possible there. If you have to grind the top of the stem, then you probably have the wrong valve.
John may have been referring to the valve guides. The 284s cam has a good bit of lift and you need to ensure that there is clearance for the spring retainer. .100" sounds much more logical there.
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By miker - 10 Years Ago
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I think Charlie's right. From Mummert's site
"CAMS WITH MORE THAN .450" LIFT REQUIRE CUTTING VALVE GUIDES FOR ADDITIONAL RETAINER TO SEAL CLEARANCE. OVER .500" MUST CHECK PISTON TO VALVE CLEARANCE."
Y-284-S 2500-6200 284 236 .465 108 VS105 .018
I've got a 284 in my roadster. Great cam.
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By airman - 10 Years Ago
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ok, I guess I misunderstood john, that does make more sense, ill tell the machine shop thanks for the info guys
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By lyonroad - 10 Years Ago
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I've got the same cam so I too called John to find out how much to remove from the guides. He said (as best as I can recall) "a millimetre or so". This blew my mind as I didn't expect to be given a metric amount. Fortunately it was not the first time at the rodeo for the fellow that did the heads and he knew exactly how and what to check.
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By airman - 10 Years Ago
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Went back to machine shop and gave them specs on cam and talked to guy who does heads and he knows what to do, valve seat to retainer is what is needed shortened, he's going to shorten valve guides to allow for the lift of cam and install new springs, he did the head work last time I brought them in, he said he's very familiar with yblocks, let's hope so lol
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By lyonroad - 10 Years Ago
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Well he knows what they are. That's a good start in this day and age. You should be ok.
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By slumlord444 - 10 Years Ago
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Is this an issue with Mummert's aluminum heads?
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By Ted - 10 Years Ago
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slumlord444 (2/18/2015)
Is this an issue with Mummert's aluminum heads?
Not an issue with the aluminum heads as I’ve run up to 0.600” lift on those heads without having to touch the top of the guides. Retainer to guide clearance (with seal installed) is still checked on all heads though regardless of lift as you cannot assume anything.
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By Joe-JDC - 10 Years Ago
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On the flow bench with Mummert heads and stock valves, retainers and keepers, with valve seal in place, you can get about .670" lift before hitting the seal. When flowing the heads, it is necessary to carefully remove the valve stem seal, then you can measure flow to .800" with the stock retainers and keepers with checking springs. Joe-JDC
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