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AKRA motor not meeting duration min

C

cking

Member
Have an AKRA motor that is 2 to 3 degree's below the .200" duration check minimums on both the exhaust and intake. What's best way to fix this issue?
Is this common as motor wears?
Everything else on motor is well within specs. Increasing the duration a few degrees would you expect that to help or hurt performance?
Thanks for any insight.
 
Where is it failing the test? At the push rods or at the valve retainer?

Edit: on second thought the only way for it to fail that test is with a worn out cam. If the cam isn't lifting enough it should fail in both places. I think there is some +/- written into the rules, but you are probably in the market for a new cam.
 
alvin l nunley said:
You don't measured degrees in .000", you checked duration in degrees of rotation, not in .000". I'm a little confused by your post!
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In order to check duration on a cam you first must determine the points of lift in the cam (which are measured in .001) AKRA has prescribed two lift check points for duration, being .050 lift and .200 lift. I have seen in tech many times that the .050 lift duration pass and the .200 lift duration fail, but not on the min side of duration,
 
I have 79 degrees of intake duration at the .200" lift. AKRA rules is 81-88 on the intake at the .200" lift correct?
I have 90 degrees of exhaust duration at the .200" lift. AKRA rules is 92-99.
I am within the duration limits at the .050" lift checks. Also I am around 2 thousandths below the max lift checks. These checks are off the push rods.
 
OK - I thought most NKA cams had more duration, not less. I have no idea though.
So is there no easy way to increase duration slightly without changing cam? Would adding a little lift with the rockers help add duration also?
 
Checked some NKA profiles and this cam is profiling like an NKA. Was sold motor as an AKRA but believe it has NKA cam. I assume I will need to replace cam. Thanks for the input above.
 
cking said:
OK - I thought most NKA cams had more duration, not less. I have no idea though.
So is there no easy way to increase duration slightly without changing cam? Would adding a little lift with the rockers help add duration also?
Click to expand...
yes anything that adds lift also adds to duration. Are you at the max lift rule yet?
 
cking said:
I have 79 degrees of intake duration at the .200" lift. AKRA rules is 81-88 on the intake at the .200" lift correct?
I have 90 degrees of exhaust duration at the .200" lift. AKRA rules is 92-99.
I am within the duration limits at the .050" lift checks. Also I am around 2 thousandths below the max lift checks. These checks are off the push rods.
Click to expand...
The current AKRA rule on duration states : duration checks for the intake and exhaust lobes (taken off the pushrod) intake duration of 219 degrees @ .050 lift/86 degrees @ .200 lift. Exhaust duration of 222 degrees @ .050 lift/97 degrees @ .200 lift. All checks will allow +2/-5(minimum duration checks effective 3-1-2016)
So with the current -5 your cam is out of spec, I’m not sure that you have a NKA cam most likely just a heavily worn cam.. do you know the age of the cam/engine ?
 
Copy from NKA site
40.4.26.3: Duration taken from pushrod. Intake duration of 221 degrees at .050 lift and 88 degrees at .200 lift. Exhaust duration of 224 degrees at .050” lift and 99 degrees at .200” lift. Camshaft tolerances: +2 degrees with no minimum duration check

so with the NKA rule you are more out of spec with this rule than AKRA with the no minimum
Hope this helps you out.... replace the cam, pm me and I can give suggestions if you like
 
Petty Race Engines - Thanks for input. Dynocams lists their cam information.
Their CL4 cam states it is NKA legal and has 79.90 degrees duration at .200" lift. The cam I have profiles about exactly the same as a CL4. I don't have a copy of the NKA rules but your NKA specs don't meet dynocams CL4 (NKA cam specs). This used motor has about a season on it and was told AKRA motor.
 
cking said:
Petty Race Engines - Thanks for input. Dynocams lists their cam information.
Their CL4 cam states it is NKA legal and has 79.90 degrees duration at .200" lift. The cam I have profiles about exactly the same as a CL4. I don't have a copy of the NKA rules but your NKA specs don't meet dynocams CL4 (NKA cam specs). This used motor has about a season on it and was told AKRA motor.
Click to expand...
I just looked up that profile as well and confirms 79.90 @ .200, so that questions my search on the NKA site, however if your engine is actually a AKRA, just make sure that you are within specs, ported heads and such do not cross party lines
 
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