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this weeks engine labs news letter on valve lash.
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mark tucker
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PostPosted: Fri Jan 30, 2015 9:11 am    Post subject: this weeks engine labs news letter on valve lash. Reply with quote

this is an excerpt for this weeks engine labs newsletter,sponcered by mahle.you can look it up to see the rest if you wish. this is the method I have used for 40 years and I refer to it as the preload method.go figure Ive always done it right.fast and easy
"When setting the lash, be sure the feeler-gauge blade is parallel to the valve tip surface or a false reading could result.
This procedure is generally called the EO/IC method, which stands for exhaust opening/intake closing. Working with the first cylinder turn the engine until the exhaust valve starts to open. That indicates that the intake valve is resting fully on the cam base circle and can be adjusted. Then turn the engine over until the intake valve is just about to close. That means the exhaust valve is ready to be adjusted. Simply repeat this process with all remaining cylinders"
In the pics that go along with this they show the valve depressed about .200" "thus preload"and sure your on the right part of the lobe
It also gos on to say checking/adjusting lash is just that a check.if everythings right it will require little to no adjustment.
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andy198712
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PostPosted: Fri Jan 30, 2015 9:16 am    Post subject: Reply with quote

I'll try that next, as mine has no dizzy it makes things trickier.

So you want the valve about .2in from being closed? Which is about 5mm

Cheers mark
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Quokka42
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PostPosted: Fri Jan 30, 2015 2:37 pm    Post subject: Reply with quote

That method has been around for a long time.
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Last edited by Quokka42 on Fri Jan 30, 2015 3:54 pm; edited 1 time in total
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slalombuggy
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PostPosted: Fri Jan 30, 2015 3:34 pm    Post subject: Reply with quote

The bottom of the lobe is where you want to set your valve at, you don't need to increase your lash at all it doesn't matter if it's lower than at crank TDC, The lowest part of the lobe is the lowest part of the lobe independent of where it is compared to crank TDC. On cams with long duration, different lobe separation, split lift and durations the bottom of the lobe base will varie when compared to TDC. I always set my lash using the method mark describes as I have long durations and different lobe separation than most cams. It's the only way I can be sure the valves are fully at rest.

brad
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Quokka42
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PostPosted: Fri Jan 30, 2015 3:58 pm    Post subject: Reply with quote

No, it isn't. Set your lash at TDC. Due to manufacturing tolerances, which will have no effect on an engine set correctly, the bottom of the lobe might be far enough below that the valves will be open at TDC - not good.
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PostPosted: Fri Jan 30, 2015 4:26 pm    Post subject: Reply with quote

Quokka42 wrote:
No, it isn't. Set your lash at TDC. Due to manufacturing tolerances, which will have no effect on an engine set correctly, the bottom of the lobe might be far enough below that the valves will be open at TDC - not good.


I have set valves at the lowest cam point, and then some valves are slightly open at TDC when the explosion is going on - very bad! This was a very common problem with the Ford Courier, you could make them quite but you burnt ever valve. Cam Base Circles are exactly not round, you want your valves completely shut with the proper clearance when the Spark goes off. That is why some cams make more clatter that others.
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Dan Ruddock
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PostPosted: Fri Jan 30, 2015 4:37 pm    Post subject: Reply with quote

I check the base circle run out on every engine I build and if the cam has a lot I won't use it.

Dan
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Bajaman65
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PostPosted: Fri Jan 30, 2015 4:40 pm    Post subject: Reply with quote

Dan Ruddock wrote:
I check the base circle run out on every engine I build and if the cam has a lot I won't use it.

Dan


X2
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mark tucker
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PostPosted: Fri Jan 30, 2015 6:22 pm    Post subject: Reply with quote

andy198712 wrote:
I'll try that next, as mine has no dizzy it makes things trickier.

So you want the valve about .2in from being closed? Which is about 5mm

Cheers mark
.200 from when the exhaust opens you adjust the intake valve next to the exhaust. then rotate untill that intake is about .200 from closing, then adjust that exhaust. move on to tne next cylinder.never look at any degree marks or dist.simple and fast. remember exhaust opening and intake closing (EO/IC)
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Boolean
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PostPosted: Sat Jan 31, 2015 3:26 pm    Post subject: Reply with quote

A cam with so much runout that the valve may be open somewhere on the base circle, and still have correct lash somewhere else will end up in the bin in my garage.
I adjust at the bottom of the lobe, and check that the runout is reasonable.
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Quokka42
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PostPosted: Sat Jan 31, 2015 4:32 pm    Post subject: Reply with quote

It doesn't need to be a lot, and it doesn't have to all be in the cam itself. Running clearance is about 2 thou at the valve, and it may be less as things wear, divide that by the rocker ratio and you will see that you have two choices - be another fool who throws away a lot of money trying to find the "perfect" parts then prays it works, or do it the way the engineers designed it, which has been working for 80 years. This is why such people hate engineering - in reality nothing is ever perfect and instead we design to specified tolerances and allow for these. Some buy expensive, amazingly accurate tools, but don't understand their use and go chasing rainbows.
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Mad Manx
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PostPosted: Sat Jan 31, 2015 5:09 pm    Post subject: Reply with quote

Boolean wrote:
A cam with so much runout that the valve may be open somewhere on the base circle, and still have correct lash somewhere else will end up in the bin in my garage.
I adjust at the bottom of the lobe, and check that the runout is reasonable.


Lets get 'Real' 95% of the DIY engine builders on this site would never even think about - or have the knowledge to check cam base circle perfection. Most are just wanting to put an engine together with the least amount of problems and when it come to adjusting their valves they follow what the books say. I have seem many production engines with .002 -.005 difference when rotating the crank 20 degrees Confused
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Dan Ruddock
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PostPosted: Sat Jan 31, 2015 5:37 pm    Post subject: Reply with quote

Mad Manx wrote:
Boolean wrote:
A cam with so much runout that the valve may be open somewhere on the base circle, and still have correct lash somewhere else will end up in the bin in my garage.
I adjust at the bottom of the lobe, and check that the runout is reasonable.


Lets get 'Real' 95% of the DIY engine builders on this site would never even think about - or have the knowledge to check cam base circle perfection. Most are just wanting to put an engine together with the least amount of problems and when it come to adjusting their valves they follow what the books say. I have seem many production engines with .002 -.005 difference when rotating the crank 20 degrees Confused


X2 and that is one of the reasons you see hp VW's going down the street sounding like a bucket of ball bearings.

Dan
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