valve lash

Old 03-08-2012, 02:04 PM
  #1  
hotrod1994
Senior Member
EXPERT BUILDER
Thread Starter
 
Join Date: Jul 2009
Location: nekoosa wisconsin
Posts: 308
Default valve lash

does the valve lash of a cam effect the performance of it

i foud a cheaper cam with the specs as as the comp cam i was looking at but the lash on it is .026 intake .028 exhaust and the comp cam is .20 on the intake and .022 on the exhaust

what difference will this make? if any?

thanks -logan
hotrod1994 is offline  
Old 03-08-2012, 04:29 PM
  #2  
TheRabbit
Senior Member
RACING JUNKIE
 
TheRabbit's Avatar
 
Join Date: Jan 2007
Location: Augusta, Ga.
Posts: 2,276
Default

I've never run as much lash as mfg says to use. I only ran .015 on my little BBC.
TheRabbit is offline  
Old 03-08-2012, 04:55 PM
  #3  
roadkill2
Senior Member
RACING JUNKIE
 
Join Date: Jan 2012
Posts: 628
Default Re: valve lash

Originally Posted by mrbigtrucks
does the valve lash of a cam effect the performance of it

what difference will this make? if any?

thanks -logan
Depends on a bunch of things . . Tighter valve lash settings will lengthen duration (everybody knows that) but it also has to do with the lifters you use, the pushrod length and installed height . . Hot running expansion is the main reason for establishing a "General" valve lash setting and each engineer figures his own tolerances . . easiest way is warm it up and then measure what you have left . . work within those, being careful not to preload your cam/follower(lifter) or valve stem . . Probably ought to stay outside of .010+ . . both sides . . or . . just go with the instructions until you have the balls to screw with it and risk a slight misunderstanding . .

One opinion . . . .
roadkill2 is offline  
Old 03-08-2012, 07:22 PM
  #4  
TheYellaBrick
Senior Member
RACING JUNKIE
 
TheYellaBrick's Avatar
 
Join Date: Mar 2008
Location: Emmett, Idaho
Posts: 7,334
Default


"risk a slight misunderstanding"
I LIKE that term !
A kinder gentler way of saying "Catastrophic engine failure"
:cry: :cry: :cry: :cry: :cry: :cry: :cry: :cry: :cry:
TheYellaBrick is offline  
Old 03-08-2012, 09:50 PM
  #5  
olds48
Senior Member
RACING JUNKIE
 
Join Date: Sep 2007
Location: Montvale, VA
Posts: 1,431
Default

Cam companies have their reasons for establishing certain lashes for certain lobe profiles. We don't know why,but they do. And they are not going to do anything to make their cams make LESS power. That's their reputation on the line. You can loosen lash for less duration in the hopes for more bottom end power. Or tighten it up for more duration like stated before,for topend.But the effects are usually minimal,especially for the risk you are taking. Why did they specify that particular lash????....who knows,just go by it and you'll have one less worry.

But you asked "why" they were different,not if you can change the lash. Looser lash cams typically have a more aggressive lobe profile.Like faster opening ramps.
olds48 is offline  
Old 03-09-2012, 08:52 AM
  #6  
hotrod1994
Senior Member
EXPERT BUILDER
Thread Starter
 
Join Date: Jul 2009
Location: nekoosa wisconsin
Posts: 308
Default

ok thanks guys
hotrod1994 is offline  
Old 03-10-2012, 11:25 AM
  #7  
sbu
Junior Member
SHOW GUEST
 
Join Date: Jul 2008
Posts: 5
Default Re: valve lash

Originally Posted by mrbigtrucks
does the valve lash of a cam effect the performance of it

i foud a cheaper cam with the specs as as the comp cam i was looking at but the lash on it is .026 intake .028 exhaust and the comp cam is .20 on the intake and .022 on the exhaust

what difference will this make? if any?

thanks -logan
Yes the lash does make a difference, the tight lash will normally take away some of the low end performance, the tighter lash fools the motor into thinking the cam is bigger. Usually the lash will grow about 10 to 15thousandths. I never set lash out, only check hot and the if any are off , I change. Iam not the smartest in the world but have been drag racing and building motors both big and small block 500 inch SB and 815 BB, I am 67 and have been doing this for 48 years. So lash does matter, go by the cam card, it is a starting point and then play around with the valves lash, tighter about 5 thousandth and see if the motor slows down then loosen and see what happens, what ever change you make should show up in your 60ft times first. Hope this helps
sbu is offline  
Old 03-10-2012, 03:17 PM
  #8  
hotrod1994
Senior Member
EXPERT BUILDER
Thread Starter
 
Join Date: Jul 2009
Location: nekoosa wisconsin
Posts: 308
Default

ok so i should set the lash warm it up and check again and readjust if needed?
hotrod1994 is offline  
Old 03-11-2012, 06:56 AM
  #9  
markdunlap
Senior Member
DYNO OPERATOR
 
Join Date: Jan 2004
Location: central Illinois
Posts: 459
Default Valve lash

When I am initially set valve lash cold on an aluminum headed, iron block engine,
I take the cam builders hot specs and go .004" loose cold. When the engine is fully up to temperature and heat soaked for a little while, I recheck the lash and see what the difference from spec is. I correct it to spec.

I use the difference I saw warm to change the cold setting. Next time I check it hot again to see if it is right.

I don't vary hot lash from spec except to see if it is faster with .004" less or more lash seperately on the intake and then the exhaust.. Then I go back to spec. If I want to go faster, I go back to the cam guy and tell him the results and have a different cam ground for that combination.

On an iron head/block, I go .004" tighter cold and recheck hot.
markdunlap is offline  
Old 03-11-2012, 07:36 AM
  #10  
hotrod1994
Senior Member
EXPERT BUILDER
Thread Starter
 
Join Date: Jul 2009
Location: nekoosa wisconsin
Posts: 308
Default

ok thnaks
hotrod1994 is offline  

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -