Benefit of tightening up exh lash...

Not a dumb question at all. I would not tighten the intake any more since it is already close. The tighter exhaust is where there is the most gain to be had. It will open the exhaust a bit sooner and will help with spoolup a bit. I would set it at .015 and leave the intake alone.

Zach
 
2007 5.9 said:
So in theory I should have no real issues setting lash at...008/.015??

There is no chance of hanging the valve open too long or opening it too soon as to have contact??
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Let us know how that works out.... may try that on my truck!
 
david_brown_mt said:
Maybe a dumb question, but I'm trying to figure out the math here.

How do I determine how much I can tighten up the lash without running into clearance issues?

I know how much the block was decked, and how much was taken off the head, and the piston protrusion. What else is there to take into consideration?

I have the 181/210 cam.

I don't ever get the EGTs over 1200F if that makes any difference.

Thanks for any suggestions
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When it comes to something this sensitive don't screw around with equations. Remove a valve spring, find yourself a very loose spring that will support the retainer (i.e. push the retainer up against the lock) and will be easy to press down on the retainer opening the valve with your hands. Reassemble the rocker arm and set it up with the lash you want. Rotate the motor over and where the intake valve is opening the and exhaust valve is closing push (most sensitive portion of 4 stroke motor to p to v contact, the overlap cycle) down and verify how much distance until the valve hits the piston preferably with a dial gauge. This will tell you exactly how much piston to valve clearance you have to work with no if ands or buts. Try multiple positions around intake opening exhaust closing to make sure you have plenty of clearance at all areas where valves are closest to the piston. Not sure what minimum recommended for each application so just ask Zach what he likes for his cams. A typical value is .100 but i've heard of seups using far far less!

Ofcourse Zach may be familiar enough to tell you if tightening the lash will give you problems or not which would make it easier on ya. Good luck!
 
Hamilton Cams said:
Yes, but it is hard to check while exhaust flow is around the exhaust valves. That is why the exhaust calls for more lash than does the intake to allow for growth. The intake doesn not see anywhere close to the same temps so they can use a different lash.

Zach
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I spot checked number one immediately after a 30 minute drive at 70 mph with multiple runs to 15 psi boost and 1100 max egts (did let truck cool down to 350 or so before shutting off as always). Intake was surprisingly about .002" tighter than the .009" I set it at cold and the exhaust was surprisingly looser at about .002" more than .020" I set it at cold. This suggests to me (would spot check other cylinders before drawing a conclusion) that tightening down the exhaust .010" on a stock cam would be fine.
 
I went from .020 to .015 on my 181/210 107c cam and it mad a huge difference. Spools my s-471 at least 100 rpm faster and seems to run smoother and quieter. The bottom is a little smokier and gained about 100 degrees on the pyro. I can live with the negatives for the quicker spool. I honestly think 100rpm quicker is an understatement.

Joe
 
NickTF said:
When it comes to something this sensitive don't screw around with equations. Remove a valve spring, find yourself a very loose spring that will support the retainer (i.e. push the retainer up against the lock) and will be easy to press down on the retainer opening the valve with your hands. Reassemble the rocker arm and set it up with the lash you want. Rotate the motor over and where the intake valve is opening the and exhaust valve is closing push (most sensitive portion of 4 stroke motor to p to v contact, the overlap cycle) down and verify how much distance until the valve hits the piston preferably with a dial gauge. This will tell you exactly how much piston to valve clearance you have to work with no if ands or buts. Try multiple positions around intake opening exhaust closing to make sure you have plenty of clearance at all areas where valves are closest to the piston. Not sure what minimum recommended for each application so just ask Zach what he likes for his cams. A typical value is .100 but i've heard of seups using far far less!

Ofcourse Zach may be familiar enough to tell you if tightening the lash will give you problems or not which would make it easier on ya. Good luck!
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Thanks, this is exactly the information that I was looking for! So if I find that I don't have sufficient clearance with a stock head gasket I'm guessing I should be able to get the clearance I need with a .020 over one then, and should be able to run tighter lash (I'll measure everything like you suggest so I have numbers to work with)
 
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very very interesting will be doing mine to .10 and .15 on the ex now thanks guys
 
thinking i am going to need to check the clearance first, the head has been decked twice now, just under .20 thous. total, and i am running a .20over gasket, if my calculations are right, should be right around stock comp. ratio/valve clearance, i guess i need to get a dial indicator and find out.... this is a interesting topic...
 
Ive had mine set at .010/.016 for a couple of months now, it spools up my 64 very nicely and the engine is much quieter too.
 
^ x-2! This is exactly what i set mine to and it spools the turbos like crazy off the line!
 
It is a nice little bump in power that I noticed while playing on the Dyno. It makes a little more egt due to the earlier opening exhaust but it does make more power. I noticed 12-15 extra hp on a few trucks I played with on the 181/210. If you are degreeing in your cam and checking clearances, DO NOT put in lighter springs if it is a 24v engine. It has been my experience that lighter/cheaper springs have a higher tolerance and vary in pressure more. THis will allow one to open earlier and higher than the other intake sice they both act off of the crosshead. THis will make your readings null and void. Just use your OE or performance springs.

Zach
 
how much higher egts?

and do you need to have oil on the rockers when you do this? the reason i ask is because mine are out, so whats better no oil or oil? id imagine oil but who knows? thanks
 
on some of the trucks I have done I noticed 50-100 degrees at WOT. Not a major bump at all. To be honest the in cylinder temps should not be affected at all. Since you are releasing the exhaust from the cylinder sooner after the combustion process is done, less heat energy has been transmitted to the cylinder walls, cylinder head and the piston, thus the small rise in the reading at the probe. Hotter air is bigger and the additional heat energy and bigger pule act to spin the charger sooner/harder.


Zach
 
sweet! thanks zach! one last question when adjusting them should there be oil on the rocker arms and bridges?
 
I went from .010 and .020 to .08 and .018. The only difference is A LOT more blowby......might need to do it again. argh!
 
Zach,

I did a search on this site and others about the change in the exhaust lash on the 2006-2007 cummins. Found a post by you saying you like to run .018 on the exhaust side of these motors with stock springs, cam, ect. With the material changes made to either the valve or seat is this .018 a good number to go by or would you say looser?

some say .015 to .030 on the exhaust is good others say .021 to .034 is what it should be.

I just set my 2006 to .010 intake and .020 exhaust ( before I saw the sticker on the valve cover for the .026 exhaust) the motor runs great! a lot less noise and the turbo spools faster. But I want to make sure I'm alright running .020 on the exhaust. Don't wanna burn a valve up.

Thanks
 
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