Rotor Timing on .90 and above. (closing side)

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Norm Doerr

Well-Known Member
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Apr 2, 2002
Messages
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What is the latest opinion on how far is too far to close the rotor on an engine? Rule of thumb used to be 60-65 degrees was good, anything above 70 degrees was "radical". Lets say the rotor is opened just past BDC ( for sake of discussion) Opinions, experiences, anecdotal stories? Asking for a friend who made a dumbarse mistake :)
 
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Norm what are you and Marty going to do with that Dyno?
Would be nice to have it put to good use and not just sit in the corner and collect dust.
 
I never messed with the closing timing. Never even checked it on my eng builds.
Now I do open the intake at BDC and have found that the eng will over rev much more at the end of the straits.
Not sure this would show up on a Dyno.
Don't think you will find any thing worth talking about messing with the closing.
I think eng stroke and rod length will have a lot to do with piston speed at a certain point in timing the closing point.
You would want to take advantage of all the slow speed dwell time you can before you close it.
 
I always figured mods to closing side helped with over-rev and closing side helped with torque..
 
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What is the latest opinion on how far is too far to close the rotor on an engine? Rule of thumb used to be 60-65 degrees was good, anything above 70 degrees was "radical". Lets say the rotor is opened just past BDC ( for sake of discussion) Opinions, experiences, anecdotal stories? Asking for a friend who made a dumbarse mistake :)

Hello Norm
I remember reading notes from Marty ,yourself ,Ackerman and others years,years ago and I would of figured you fellas would have timing numbers all sorted now..
 
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Hello Norm
I remember reading notes from Marty ,yourself ,Ackerman and others years,years ago and I would of figured you fellas would have timing numbers all sorted now..
For the most part we have/had good numbers and we started finding bigger gains in other areas so never revisited rotor timing in the test cell. In more recent years there has been discussion on opening sooner, nothing about the closing side. I screwed up cutting on some parts which prompted me to go fishing for new feedback on the subject. I am closing at 75, 70 is about as far as I have ever gone reliably, however that was prior to all the other stuff we messed with since. Thanks for your reply ;)
 
You can benefit from later closing. I believe it’s mainly because the amount of time that it’s ‘full open’ is increased and the engine breaths better. However most engines today are closing late enough for racing.
 
Really surprised it only has 10 replys. The answer will change with every boater you ask... What is stk rotor timing is the Question? HA. a superior performing engine you might see run...you can bet you ass its not on stk factory timing numbers. no use in changing any numbers on the engine unless you are at MAX Effort & plan to get it all.
 
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