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Proper valve springs for cam

mayhem

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OK, so I'm ready to purchase valve springs & need some knowledgeable opinions.

Engine is a 500" Indy Maxx alum block, 10.5:1 CR, 426-1 CNC 285 Legend heads, 426-3 intake drilled & plumbed for EFI & 4500 throttle body. Car is a full frame all steel '72 Challenger, D60 (gear selection pending) on leaf springs, 727 w/manual valve body, 3500 stall (for now). Car will be primarily street driven w/minimal turning (lol).

The cam is a hyd roller: 236/240 @ 050, 564/555 lift & 112 LSA. My guidance from Rich Nedbal's book is 130-165# on the seat & 280+ open. I'm looking at 2 different springs at the moment: (1) [email protected] on the seat & [email protected] open with 1.135 bind, 0.755" max lift or (2) [email protected] on the seat & [email protected] open with 1.175 bind, 0.665 max lift. Either of these make sense or is there a better spring out there & why? Thanks in advance for any assistance.
 

Steve340

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A hydraulic roller is more like 330 to 375 open pressure. There are a lot of variables to take in to account with valve spring selection.
 

Chryco Psycho

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Ramp speed can change the spring rates at the same lift , more pressure is needed to keep everything stable with faster ramp speeds , the cam MFG is who I would be looking to for advice they designed the cam & will know what pressure is needed . The first spring you listed seems extreme , why have the range to lift .755 if the cam is running .200 less lift , excessive pressure is no good just as much as not enough pressure .
Another thing to look at is the rocker arms you plan to use are they recommended for the spring pressures , I far prefer bushed rockers over any needle brg type as the contact surface is far greater , I have seen the rocker shafts worn into the needle brg pattern as they don't move very far , some alum arms may be recommended for the pressures but the life can be short on a street engine .
You probably will need thicker all pushrods also , Smith Bros in Bend Oregon can help you with those & they offer overnight service .
The last thing to remember is you will need a bronze dist / oil pump drive & fuel pump pushrod against the roller cam if you are going to use a mechanical fuel pump , if you use iron the cam & gear will eat each other up same with the pushrod .
 
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