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Valve spring pressure and a Stipe cam A question on valve spring pressures for a new Stipe B340 cam.
History... I have a reground cam in the diamond B in my Fordor, modern valves, new (10 years ago...) stock springs, with pressed in guides. Few other tricks, but it's still pulling at 85mph on the sat nav with no sign of valve float - I make that about 3300 with the gearing and tyre size. The Tourer has the same grind on the cam with 1.7" inlets, and the stepped push in guides that Snyders sell, with stock springs. I've taken it to 3300 rpm on the rolling road where the power starts dropping off. So - I'm putting together a new B engine with a Stipe B340 cam, 1.7" inlets, and the Snyder type guides. Will the stock valve springs suit, or do I need something with a little higher pressure? I don't want to knock the cam or seats out for the hell of it, and so far I've had no noticeable valve float with my previous ground cams? Or have I and I couldn't hear it above the wind noise...? |
Re: Valve spring pressure and a Stipe cam Charlie Yapp sells spring spacers to bring seat pressure up to what's recommended in Jim B's book. They're not expensive. Look them up on the Secrets of Speed website.
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English Fordors are faster :)
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Re: Valve spring pressure and a Stipe cam Nice picture. I must have washed it.
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Re: Valve spring pressure and a Stipe cam Contact Bill to be sure. I recommend 60 lbs. on the seat with my mild performance cams, more on racing cams.
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Re: Valve spring pressure and a Stipe cam I had a conversion with Jim Brierley back in May 2013 about higher spring pressures for my Stipe 330 cam. The installed pressure of a Model A valve spring is about 50 lbs at 2.340 inches(that's with one piece guides). With .330 inches of lift, the spring pressure is 75 lbs. That's a spring rate of about 75lbs/in. for the stock springs. I have found springs with slightly higher spring rates (116lbs/in) that are exactly the same size (1 inch OD by 3 inches high) as the stock Model A spring. This spring has as installed pressure of 76 lbs and 114 lbs pressure at full lift. Jim felt that was a good spring for this application. They are sold by "Hardware Products Company"(https://www.hardwareproducts.com/stock-springs) in Chelsea, MA. The spring part number is 14079. Listed price is $5.75 each with a minimum order of 10 pieces. I've been running them since 2014 (4000+ miles) with no problems.
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Re: Valve spring pressure and a Stipe cam Thanks for the reminder Al !
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Re: Valve spring pressure and a Stipe cam The spacers that Charlie Yapp sells (Scalded Dog Speed Parts) are 3/16 inch thick machined rings that have an ID that matches the OD of the standard two-piece Model A valve guides. I did not achieve the 60 lbs. of seat pressure recommended by Jim Brierly with stock (new) valve springs and Charlie's spacer. I found that I needed another 3/16 inch spacer to get the installed spring pressure to 60 lbs. I made spacers out of 3/4-inch black iron pipe to get the additional 3/16 inch that I needed. One good thing about the Yapp spacers is that they can be installed between the block and the valve guide; that is above the step in the original or Snyder's original style guide. This drops the guide relative to the ports and (IMO) provides the opportunity for additional flow through the ports.
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Did you check out Iskendarian for springs ? They have a good reputation for consistency and quality of their V8 flathead valve springs. I've used them on our four A/B , and they work well. I've only used them for higher performance engine work and they are in Los Angeles, close by. |
Re: Valve spring pressure and a Stipe cam Hardtimes, no I didn't check out Iskendarian. The spring I bought from Hardware Products were very consistent in pressure. I wasn't looking for a high performance spring, just something slightly stronger then the stock spring. And at 5.75 each, they were a bargain.
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Re: Valve spring pressure and a Stipe cam 40, that's a good point. I remember reading that Mr. Don Snyder came from a spring manufacturing background. He began making Model A seat springs to get where he is now. He may have some input on this fatigue issue.
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Re: Valve spring pressure and a Stipe cam We may want to ask Don Snyder the source of the springs he sells. The Hardware Products site has another spring that has the same specs as the standard Model A spring. It's PN is 14078. I guess we could put that fatigue question to the Hardware Products people.
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