valve spring and camshaft question

jerry S

New Member

Sep 3, 2003

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52.22N 5.12E

Feb 1, 2006

#1

• Feb 1, 2006

• #1

how much lift should your springs be rated above the lift of your cam? Is there any hard and fast rule?

The reason I ask is that I was told by somebody who purports to know that I am couritng disaster with my valve springs having only .38 of clearance.

I have Edelbrock RPM Performer cylinder heads. They came fully assembled and the have a max valve lift of .576. My cam's specs are as follows:

ADV DUR: INT 297, EXH 308
LIFT: INT 538, EXH 534
DURATION AT .50 DEGREES: INT 236, EXH 242 @ 108 centerline

Should I be worried and replace these springs as a prophylactic measure or am I within spec?

 

milner351

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Jun 12, 2002

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The Motor City

Feb 1, 2006

#2

• Feb 1, 2006

• #2

You could always call the edlebrock tech line, or look up on the edlebrock website to be sure.
I'm pretty sure my twisted wedge heads had max lift called out in the spec sheet.

 

LMan

Founding Member

Aug 10, 2002

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Mom's basement

Feb 1, 2006

#3

• Feb 1, 2006

• #3

Most cam cards have the recommended spring set listed right on them. Compare that recommendation to what you have now...

 

jerry S

New Member

Sep 3, 2003

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52.22N 5.12E

Feb 1, 2006

#4

• Feb 1, 2006

• #4

LMan said:

Most cam cards have the recommended spring set listed right on them. Compare that recommendation to what you have now...

Click to expand...

I have the cam card and know the recommended springs but cannot determine what springs Edelbrock used with my heads. I have taken Milner's advice and have asked for their opinion.

thanks.

jS

 

jerry S

New Member

Sep 3, 2003

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52.22N 5.12E

Feb 1, 2006

#5

• Feb 1, 2006

• #5

Edlebrock replied (awesome turnaround) and provided me with the specs on the springs. (120 lbs @ the seat and 320 lbs open) which seem to be within crower's specs for the cam shaft.

 

rbohm

Founding Member

Apr 12, 2002

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tucson,az

Feb 1, 2006

#6

• Feb 1, 2006

• #6

as i recall, the difference between max allowed lift and coil bind is something like .010", and if your springs allow .576 with your cam only pushing .538, you have plenty of room before you get into coil bind. max lift always allows for coil bind clearance.

 

brianj5600

Active Member

Sep 19, 2003

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Middle TN

Feb 1, 2006

#7

• Feb 1, 2006

• #7

Some companies list coil bind. You need to be about .060" from that. Max lift is exactly that. Meaning .576" max lift means you can run .576" but .577 is not advised.