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By mikeT - 3 Years Ago
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Hi! I have my heads back from the machine shop. G heads that I added posts too with Stainless valves for a 289 1.94"
my cam is a Clay Smith .465" lift 236 duration at 0.050"
My valve springs are at 130# on the seat 290# valve open. The installed height is 1.68". Will I be ok running this spring pressure? I can change to + .050" valve locks to lower the pressures if needed?
its going in a fenderless hot rod truck with 5 speed manual trans
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By 55blacktie - 3 Years Ago
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Is .465 lift before/after subtracting lash? If you didn't subtract lash, I would recommend less spring for your application. What's the max rpm, and how often will you see it? I would look at a 1.75 installed height. Do you know the spring rate?
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By miker - 3 Years Ago
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Those specs look a lot like Mummert’s 284 cam. IIRC, that’s what’s in my F code clone. The spring pressures he shows are in your area. I don’t wind mine that high, figuring the boost takes care of it. But if it’s one of John’s cams, call and ask.
I don’t like excessive spring pressure or the rpm’s that require them. I’m a street guy and don’t want the additional wear and stress.
http://www.ford-y-block.com/valvetrain.htm
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By 55blacktie - 3 Years Ago
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Miker, you're using a 108 LSA cam with a supercharger?
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By miker - 3 Years Ago
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I can’t remember if it’s the 108 or if I had it ground to something else. The car and all the records are down south and I’m north for Christmas. But with a centrifugal that makes very low boost below 3000 rpm, and set to only make 6-7 lbs at 5000, I don’t think it’s a huge concern. I would not do something like that with a modern centrifugal or a positive displacement blower.
But I do have an OT car with a positive displacement 7lb boost blower on a stock motor. It makes well over 1hp per cubic inches on a very conservative rear wheel dyno. I think the lobe center discussions on boosted motors are often biased towards dyno/racing results, and I’m strictly a street/drivability guy.
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By Ted - 3 Years Ago
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It’s the over the nose pressure that will wipe out a camshaft and your over the nose pressure is good. You want just enough over the nose pressure to keep valve float at bay while not so much that the camshaft or tappets have wear issues. Having adequate seat pressure is necessary to ensure that the valve does not bounce on the seat when it closes so you are good in that respect. I have successfully run up to 420 lbs. of over the nose pressure on the Ford Y without any issues so the 290 lbs. number is adequate for your combination. Not to be left out of this discussion is the overall quality of the camshaft and lifters which must be able to handle whatever pressures you want to use.
You did not give the measurement for the coil bind. A minimum of 0.060” of spring compression remaining is desired after full valve lift is achieved.
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By mikeT - 3 Years Ago
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The cam is a clay smith and the lifters are comp cams.
Hopefully they are good quality?
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By 55blacktie - 3 Years Ago
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A representative of Topline Hylift Johnson confirmed that the Comp Cams Y-block lifters are made by them. Clay Smith said the same about their Y-block lifters, and Ted said that Isky's Y-block lifters are also made by Topline Hylift Johnson. Therefore, I bought the Comp Cams lifters from Scroggin Dickey in Texas, but the lifters haven't been installed. I recall Florida Phil saying he is running the same Comp Cam lifters without complaint.
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By RB - 3 Years Ago
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As far as springs, check Mummert's site he lists the pressures for the various spring that match his cams.. Your Clay Smith is probably close to one of his.. My advice is to run the lightest spring you can get away with . Unless you are turning 5000 rpm stockish springs should get the job done
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By 55blacktie - 3 Years Ago
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Your stated cam specs are the same as Mummert's Y-284S, which has an rpm range of 2500-6200. I have to assume that your engine will see 5000+; otherwise, another cam should have been selected. Clay Smith does supply Mummert's cams.
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