Somebody please check my valve spring math
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Somebody please check my valve spring math Alright, 918 beehive springs coil bind @ 1.140". Now if the springs are installed @ 1.740" with a .628" lift cam at max lift the spring is compressed to 1.112" which is .028" lower than coil bind. If I install these springs @ 1.800" that will put me at about .032" above coil bind. First of all, is this correct. Secondly, if it is right will I be okay to run up to 7K rpm with the valves setup at 1.800"
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Originally Posted by wicked_95z
Alright, 918 beehive springs coil bind @ 1.140". Now if the springs are installed @ 1.740" with a .628" lift cam at max lift the spring is compressed to 1.112" which is .028" lower than coil bind. If I install these springs @ 1.800" that will put me at about .032" above coil bind. First of all, is this correct. Secondly, if it is right will I be okay to run up to 7K rpm with the valves setup at 1.800"
Yes that will be fine in terms of installed height and room to coil bind. The 918's can coil bind lower than 1.140" so check them before you install them and even at a tight clearance they work fine.
I would just be worried that its not enough valve spring for them, 130lbs on the seat is a little weak for most stuff going to 7000rpm.
Bret
I would just be worried that its not enough valve spring for them, 130lbs on the seat is a little weak for most stuff going to 7000rpm.
Bret
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Just so I understand completely. What is the difference between seat pressure and open pressure?? Also, installed height is inversely proportional to seat pressure correct??
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Seat load = (Free length - Installed height) X stiffness
or if the load is only given at 1.8"
Seat load = Load at 1.8" + (1.8 - Installed height) X stiffness
Open load = Seat load + (Installed height - valve lift) X stiffness
So as the installed height decreases, seat load increases. Since stiffness is for the most part linear, the open load will go up by the seat pressure increase.
For 918's, stiffness = 313 lb/in, load @ 1.8" = 130 lb
So for your installed height of 1.74"
Seat load = 130 + (1.8-1.74) X 313 = 148.78 lbs
Open load = 148.78 + 0.628 X 313 = 345.344 lbs
or if the load is only given at 1.8"
Seat load = Load at 1.8" + (1.8 - Installed height) X stiffness
Open load = Seat load + (Installed height - valve lift) X stiffness
So as the installed height decreases, seat load increases. Since stiffness is for the most part linear, the open load will go up by the seat pressure increase.
For 918's, stiffness = 313 lb/in, load @ 1.8" = 130 lb
So for your installed height of 1.74"
Seat load = 130 + (1.8-1.74) X 313 = 148.78 lbs
Open load = 148.78 + 0.628 X 313 = 345.344 lbs
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Originally Posted by skipperbisket
so Bret speaking in ls1s what would be the most suitable seat pressure for a hyd cam with mild to high lift and still keeping those higher rpm ranges?
Originally Posted by wicked_95z
Bret, what pressure do you recommend for seat and open for a .606 and .628 cam and 15psi.
Thanks guys for the calculations, good info
Thanks guys for the calculations, good info
Depends on the lobe, the rest of the parts in the system and the RPM range.
Bret
