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How much does moving the cam affect peak rpm?

General engine tech -- Drag Racing to Circle Track

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Bill Chase
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Re: How much does moving the cam affect peak rpm?

Post by Bill Chase »

mt-engines wrote: Wed Nov 18, 2020 4:16 pm I've seen valve lash change rpm more so than specifically changing intake centerline.
Was this a hydraulic roller where you see the gains/losses?

I am using one of Mike's cams. nothing radical276/280 adv 228/232 @ 50 576/576 110 lsa installed at 107icl exhaust 113 icl. I just degreed it where the card said to, and set the lash 1 turn past zero lash with the delphi ls replacement lifters. Given the fact that I want this engine to be as strong as possible from idle to 6000 would looser or tighter lash help? new 385 sbc, afr 195 street ports and shaft rockers from scorpion racing. as is it started right up, is very quiet, got oil up top almost instantly when priming. I was actually surprised at how quiet it was at idle for a first start of a new mill.

Think going looser would help? I read a lot of conflicting info on these lifters being used in the gen 1 880 roller block. many lash at 1?2 turn past zero lash, yet others have went 1.25 turns past zero. and still others have said set preload for them the same as you would in the ls block. if running a little looser would help it rev easier off of idle, or tighter I would be all for that.
tenxal
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Re: How much does moving the cam affect peak rpm?

Post by tenxal »

treyrags wrote: Fri Nov 20, 2020 6:34 am If anything that will favor keeping the peak below your target 6000 rpm and might boost your low range torque slightly.
It may or may not. I've seen where retarding the cam shows increased low end torque.
treyrags
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Re: How much does moving the cam affect peak rpm?

Post by treyrags »

tenxal wrote: Fri Nov 20, 2020 7:42 am
treyrags wrote: Fri Nov 20, 2020 6:34 am If anything that will favor keeping the peak below your target 6000 rpm and might boost your low range torque slightly.
It may or may not. I've seen where retarding the cam shows increased low end torque.
Agreed. But most of the time it will go that direction. Unfortunately there is no rule of thumb that is 100%.
Orr89rocz
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Re: How much does moving the cam affect peak rpm?

Post by Orr89rocz »

Doesnt it depend on how close the cam is to being “correct” for the application and desired performance? If cam was spec’d right it should do the power and rpm you want and moving it a few degs shouldnt change much. If its out in left field moving it may show greater changes. At least thats what i have read and makes sense to me

Kinda like lash changes on a solid roller
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