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4l headswap valve spring questions |
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ncofab
AMC Fan Joined: Feb/12/2016 Location: edmonton Status: Offline Points: 29 |
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Posted: Dec/13/2018 at 9:39pm |
What is the max lift on the stock valve springs
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19686 |
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0.500" is max, but I'd go a little less than that, like 0.490". The Comp Xtreme cams have too much lift for the stock springs IIRC, and the Comp recommended springs are really for high rpm racing -- I consider them way too strong for street use. You will need off-road oil or a high pressure additive to run them also. Anything much over 300# per inch on valve springs is too much for regular oil. I think it's Crower that has springs around 312#, those are the strongest I'd recommend. Mopar Performance sells a performance spring for the 4.0L that is really just one of the V-8 springs. It's not a lot stronger than stock 4.0L springs, but is stronger... I forget the rating though. That's what I always recommend, and something like the Isky 256 Supercam (mild) or 262H (a bit more aggressive but still not bad, and works with all stock parts -- works with stock gearing, but would "like" a little more gear, like the optional ratios, 3.08 or better).
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Frank Swygert
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Pdok
Supporter of TheAMCForum Joined: Apr/03/2011 Location: Alabama Status: Offline Points: 1025 |
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Not sure what cam you're using, but the only springs i found that fit without machining were from Hughes. Those were the only ones that gave me the right install height, fit the hole, and gave me 280# of open pressure along with the correct closed pressure for my Comp x4 cam. Every other option required something to change that would cost me more money.
Comp tech support said i could go as low as 280 pounds on open pressure, instead of the 300+ on the card. Just be careful and do the math on installed height, pressures and spring rate, and you can always spend the extra money to go custom pockets and valves if you need to.
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76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.
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