I will be using hydraulic roller lifters in a blown DeSoto Hemi. I'm wondering what sort of spring pressure (open and closed) I will need. The engine will only have 3-4 pounds of boost, and NEVER see over 5,000-5,500 RPM, and no Drag Strip use. Valve lift is .375, duration is 268/268, 236/236 @ .050. The dual springs I have are 110 lb closed, 240 lb open...out of a 57 345 Adventurer engine. Thanks, guys...
You can't go wrong with the Cam MFG. recommendations or just buy the complete cam kit with all the parts. That way there is no question as to whats correct in the event you have any problems.Usualy with todays lift and duration it's easy to screw up in the seat pressure area so I say do it right the first time.
Talk to a cam grinder who knows Hemis......Donny at Herbert Cams? Those springs will not be enough for a juice roller.....hell, the'yre not really enough for a similar solid cam. Sure you're not going to RPM the engine but springs will also often drop 10-15lbs after break in and stabilise there. PS are you sure that cams lift is .375" and not .475" ? .375" lift seems real low for a 235 deg @ .050" cam. Rat
Apparently Ray is not up to speed with the EarlyHemi engines and the availability of parts. No Problem. Tony, although big springs are sometimes needed on roller cams, I say you are in the ball park albeit a bit light. I might look at 125 closed / 275 open. I would not go over 300#. Since this is a street package why not check the Big 3 and see what they are using on the current crop of roller cammed engines? Your operating range is similar to what we see in factory 'hot-rods'. You can then decide if you have a good number or need to go bigger. My $0.02 .
If the lift is really that small you need a very stiff and very short spring, installed loose. 130 seat + 350 open = 220 lb. change in only .375", or 587 lbs. per inch deflection.
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