Valve springs question

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1938dodge

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Biloxi Ms
I’m doing a fresh up on my LA 318 just purchased the SPD 25 cam with new lifters and push rods.
My question is I have a complete set of P4120249 springs that have been sitting in my garage for a while now.
With this new cam and everything else being stock should I use these springs or stay with the original springs?

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That spring looks to have very thick wire, meaning it has a lot of tension. I am only going by the pic.

Is the cam a flat tappet? if you want it to last, use the lightest spring that will control the valvetrain at max engine rpm expected.
 
with those springs rated for .430~.500 lift and the cam at .410 lift it's kind of a borderline call.

i'd err toward something a little lighter, it's not like you're gonna be revving its balls off anyway.
 
The stock 340 spring would be my call.
 
1938dodge said:
I’m doing a fresh up on my LA 318 just purchased the SPD 25 cam with new lifters and push rods.
My question is I have a complete set of P4120249 springs that have been sitting in my garage for a while now.
With this new cam and everything else being stock should I use these springs or stay with the original springs?

View attachment 1716160734

View attachment 1716160735
Click to expand...
203°/.410 You could use a stock Melling spring. Their 340 spring is #466434 (recommended for their MTD-1 and 2 cam which is their versions of the 340 cam.)



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Last edited:
PRH said:
In the MP engine manual, the specs for the P4120249 and the factory 340 spring are identical.
Click to expand...
If this is the case ^^^^^ then run those you have!
 
Not sure if at your spring pressure it is that critical, but rust on a spring is BAD. Creates weak spot where rust is.
 
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