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Master Fabricator
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1,780 Posts
Discussion Starter #1
Ok, I am not a math major, so I have so ask.

My cam is a .440 lobe, 1.7 rockers. Gross lift is .748 with zero lash. I want to know how to calculate the gross lift with lets say .026 lash?

Right now I am getting .738 with .026 lash.

Thanks.
 

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EFI/N2O JUNKIE
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17,080 Posts
Gross lift is .748, net lift is .748 - .026 = .722. You should be able to check this with a dial indicator on the retainer. Now, during running all bets are off if you can't control spring motion (lifters lofting off the ramp of the cam and going higher than the net lift and possibly even the gross lift) OR pushrods flexing and not allowing the net lift you observed with the dial indicator.

Now, I could be completely wrong, I am no engine builder, but I have assembled some heads in the past and never had any problems.
 

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Registered
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1,365 Posts
also a lot of rockers dont deliver thier true lift that they should on paper, whether it be more or less

Exactly! x 2 I have done alot of testing with rockers with the same ratio and they were all off, except shafts. Which one depends on how close they get you to the actual ratio. Always best to measure actual lift with an indicator at the valve after rocker ratio, against spring pressure and current pushrod. You will be surprised, you def get what you pay for with rockers.
 

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Master Fabricator
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1,780 Posts
Discussion Starter #5
Hmm... Well I got the Crower 1.7 Stainless rockers. I would have thought they would be on the money.

I am testing with checking springs right now, so maybe they have the difference built in for when the actual springs and pushrods are on. That would explain the additional lift I am getting.
 
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