Benefit of tightening up exh lash...

2007 5.9

2007 5.9

West Coast Dyno Modifier
Joined
Jan 14, 2008
Messages
1,927
Zach,

I bought a 181/210 107LSA last year and set it up at .010 and .020, and I am looking to tighten up the exhaust down to .015.

What benefits or compramises might I encounter from doing this??

Any other lashes you recommend to run?? Maybe tighten up the intake??

I have a local diesel guru that told me to tighten the lashes up to ..008 and .015...any thoughts??
 
It changes your duration. Think about it, you have to take up the lash before the valve opens, if you tighten it up, it stays open longer.
 
I been running .010 & .015 on mine forever with stock cam. It did seem to help, but not anything to brag about, just made the engine quieter. LOL
 
I believe I was told I could run a tight as .006 and .018 on an F1 cam.....

I've wondered about this stuff myself....

Down falls / Risks is my man main concern...
 
I've always ran the minimum spec from the FSM, believe its .006/.015

Keeps everything much quieter.
 
Yeah, I understand that people do run their lashes tighter than stock settings or on the very min settings...but I am more concerned with Zach's settings in relation to his cam.

I basically want to know what if any power/spool up can I expect, what is the min lash for his 181/210 cam for both intake and exhaust...

I dont want to open them up too soon or hold them open too long that I might have an issue with piston/valve clearance.

Moreover I want to know the tighest settings I can run, so I can dyno document on my truck if there is any real world difference...or if its just a urban legend...

Thanks for the replys though guys!!!:rockwoot:
 
cummins724 said:
I been running .010 & .015 on mine forever with stock cam. It did seem to help, but not anything to brag about, just made the engine quieter. LOL
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Been running .010/.010 on a stock cam for a few years, lights the charger 100 rpm's or so sooner but I know the piston clearance, I could go to .005/.010 if I wanted to, same with the new motor lots of room to play with tuning.

Jim
 
Jim Fulmer said:
Been running .010/.010 on a stock cam for a few years, lights the charger 100 rpm's or so sooner but I know the piston clearance, I could go to .005/.010 if I wanted to, same with the new motor lots of room to play with tuning.

Jim
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100 rpm is very impressive. I might try that out.:Cheer:
 
I changed mine to .07 and .16 on my stock cam and it made a very noticable difference in spool up.
 
I may have to play with it a bit too.....This hot weather has slowed things down a bit...
 
been running .006 .018 for 8K miles now... made a turbo change at the same time so I don't really have a fair spoolup comparison but engine sounds smoother @ 2K rpm then it did at .010 .020

Lavon
 
I have only dyno tested .010/.020 and .010/.015. On our 107 and a few others we picked up around 12-15 hp due to the earlier spool. This is from opening the exhaust a little sooner and releasing pressure out of the cylinder to spool the charger sooner. On our 105.5LSA it didn't do as well because the overlap was already the most the engine wanted, more overlap netted a few more ponies up top but less down low. On our new line of cams we run them at .015/.022 this puts all of the valve events exactly where I want them and makes the most power. I have tried .010/.020 and lost 16hp today on our 183/220.

I guess it is relevant to the profile you are running. On CR's they already have such a tight LSA, more overlap from tighter lash doesn't do a whole lot. Also, the hotter an engine runs the more lash that will be eaten up by the valves growing. On hot engines I would not go less than .015 on the exh. and .008 on the intake. I think it is great that people are starting to question cams and valve events, there IS a lot of untapped power to be had in that neck of the woods.
 
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??
 
Hamilton Cams said:
I have only dyno tested .010/.020 and .010/.015. On our 107 and a few others we picked up around 12-15 hp due to the earlier spool. This is from opening the exhaust a little sooner and releasing pressure out of the cylinder to spool the charger sooner. On our 105.5LSA it didn't do as well because the overlap was already the most the engine wanted, more overlap netted a few more ponies up top but less down low. On our new line of cams we run them at .015/.022 this puts all of the valve events exactly where I want them and makes the most power. I have tried .010/.020 and lost 16hp today on our 183/220.

I guess it is relevant to the profile you are running. On CR's they already have such a tight LSA, more overlap from tighter lash doesn't do a whole lot. Also, the hotter an engine runs the more lash that will be eaten up by the valves growing. On hot engines I would not go less than .015 on the exh. and .008 on the intake. I think it is great that people are starting to question cams and valve events, there IS a lot of untapped power to be had in that neck of the woods.
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Zach, do these motors lose lash as they get hot? This is the exact opposite of what happens in aluminum gm ls motors and other iron motors i've had experience with. I guess it would be easy enough for me to pull a valve cover and varify my lazy self lol.
 
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
 
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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