Author Topic: Shaved some tenths off  (Read 3817 times)

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blykins

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Re: Shaved some tenths off
« Reply #15 on: November 08, 2021, 11:55:26 AM »
I hear what you are saying about the overlap. I did not consider that.
Never cared for the subjectivity of “ when the exhaust rocker begins to move”. If I supply the cam card may the number of degrees of before and after TDC be calculated so that I could continue using my degreed balancer? Or is that just as subjective as EOIC ?

Thanks for humoring me.

The subjectivity is correct though and really infallible.  It's what I use on *very* high end race engines.

Think about how it works:

When the exhaust valve is opening, you can set the intake valve.  The reason for that is because when the exhaust valve is opening, the power stroke has just occurred for that cylinder.  There is literally ZERO possibility that the intake lifter is anywhere besides on the base circle of the cam at this point. 

When the intake valve is closing, you can set the exhaust valve.  The reason for that is because when the intake valve is closing, the engine is on compression stroke of that cylinder.  Again, there is literally ZERO possibility that the exhaust lifter is anywhere besides on the heel of the lobe. 

If you use the TDC method, especially with a larger cam, you have room for error, because there is a remote chance that one valve is not all the way shut or is beginning to open.

With both valve covers off and a remote starter, you should be able to roll through the entire valve setting scenario in just a brief moment.   Solid cams are even easier because you just use a feeler gauge as a GO/NO-GO gauge and you can check it immediately.  Hydraulic cams are a little tougher because you essentially have to start from scratch and reset it in order to check yourself. 



Brent Lykins
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blykins

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Re: Shaved some tenths off
« Reply #16 on: November 11, 2021, 10:00:54 AM »
FWIW, I just set the lash on an FE this morning.  Cam is decently healthy, a solid roller at 260/272 @ .050", 109 LSA.  Good bit of overlap. 

There was .002" difference between the EVO method and the TDC method.  Setting a valve at a tight .018" with the EVO method, I rolled through and got the engine at TDC (not overlap, but compression) and checked it again.  Couldn't even get an .018" or a .017" in there.  A .016" finally slid in. 

You may think that .002" isn't a lot, but on a solid cam, that's enough to manipulate duration.  A .002" difference also can mean a lot in scenarios with short travel hydraulic lifters and aluminum heads, or *especially* all-aluminum engines, where lash/preload can change by .015".
Brent Lykins
Lykins Motorsports
Custom FE Street, Drag Race, Road Race, and Pulling Truck Engines
Custom Roller & Flat Tappet Camshafts
www.lykinsmotorsports.com
brent@lykinsmotorsports.com
www.customfordcams.com
502-759-1431
Instagram:  brentlykinsmotorsports
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6667fan

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Re: Shaved some tenths off
« Reply #17 on: November 11, 2021, 03:49:01 PM »
Nice real world comparison example.
Good stuff.  Thanks.
JB


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Stangman

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Re: Shaved some tenths off
« Reply #18 on: November 11, 2021, 08:01:46 PM »
Hmm didn’t know .002 would be enough to know a difference in duration. Good to know. That cam sounds healthy what is it going in and what would the RPM range on that be.

blykins

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Re: Shaved some tenths off
« Reply #19 on: November 12, 2021, 05:57:59 AM »
Hmm didn’t know .002 would be enough to know a difference in duration. Good to know. That cam sounds healthy what is it going in and what would the RPM range on that be.

It's in a 465ci Tunnel Port engine.
Brent Lykins
Lykins Motorsports
Custom FE Street, Drag Race, Road Race, and Pulling Truck Engines
Custom Roller & Flat Tappet Camshafts
www.lykinsmotorsports.com
brent@lykinsmotorsports.com
www.customfordcams.com
502-759-1431
Instagram:  brentlykinsmotorsports
YouTube:  Lykins Motorsports