Valve Lift
Valve Lift
(OP)
Good Morning
I need to check total valve lift on some racecar engines. I understand how to check lift with a dial indicator but there are varying opinions on this method being acurate. My fixture will screw directly into the rocker cover mounting holes, so I would not have a problem with the magnetic base moving.
The reason I need to check this at the valve is the rule states "maximum .500 lift at the valve. So a cam ground for lets say 498 lift with a 1.5 ratio rocker arm would go over the maximum with a 1.6. Obtaining rocker arm ratio can be time consuming to do acuratley.
I need to be able to check this after a saturday night race with some sharp engine builders looking on so I want to be fair and acurate.
Any help would be appreciated.
Thanks
I need to check total valve lift on some racecar engines. I understand how to check lift with a dial indicator but there are varying opinions on this method being acurate. My fixture will screw directly into the rocker cover mounting holes, so I would not have a problem with the magnetic base moving.
The reason I need to check this at the valve is the rule states "maximum .500 lift at the valve. So a cam ground for lets say 498 lift with a 1.5 ratio rocker arm would go over the maximum with a 1.6. Obtaining rocker arm ratio can be time consuming to do acuratley.
I need to be able to check this after a saturday night race with some sharp engine builders looking on so I want to be fair and acurate.
Any help would be appreciated.
Thanks





RE: Valve Lift
Cheers
I don't know anything but the people that do.
RE: Valve Lift
Thanks
RE: Valve Lift
RE: Valve Lift
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RE: Valve Lift
RE: Valve Lift
As previously mentioned hydraulic bleed down can be a problem.
I would check more than one cylinder as astute racers might leave #1 legal, but cheat on the rest.
Regards
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RE: Valve Lift
I think I am going to build a jig to measure rocker arm ratio so that if someone bucks on my test procedure I can measure at the lifter and do the math.
Thanks for all the help. You folks are great.
RE: Valve Lift
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Valve Lift
If room into lifter galley is hard to obtain for this method or you want the 'all inclucive' measurement. Use the current push rods and rockers, replace the race valve springs with test springs of about 10lb force so the lifters do not bleed down during the check. Mount magnetic dial indicator to flat stock attached to valve cover bolt holes. This way ALL the valve train parts and hard to calculate angles are included. Remember in all the math you attempt to use for rocker arm ratio, the contact point on the tip of the rocker changes the ratio (roller rockers excluded) as it sweeps the valve stem. Effective measurement point will move approx 1/4" depending on cam lift and several other 'circular relationships'.
RE: Valve Lift
With all types the effective ratio changes as the valve and the pushrod may not both be perpendicular to the axis of the rocker arm at mid lift.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Valve Lift
RE: Valve Lift
RE: Valve Lift
RE: Valve Lift
Have fun screwing the air chuck into the still smokin hot race engine to keep the valve from dropping
ISZ
RE: Valve Lift
But in real life I have the same obstacles but alot more stuff in the way. So the racecar engines are alot more fun.
Thanks for the help.
RE: Valve Lift
Norm