Slant *        6        Forum
Home Home Home
The Place to Go for Slant Six Info!
Click here to help support the Slant Six Forum!
It is currently Sun Jan 05, 2025 8:28 pm

All times are UTC-08:00




Post new topic  Reply to topic  [ 11 posts ] 
Author Message
PostPosted: Fri Jan 16, 2015 7:47 am 
Offline
Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3830
Location: Indianapolis
Car Model:
does mechanical valve lash subtract from actual valve lift?

for example Oregon cam grind 819 lists .291 lift at the cam and .437 lift at the valve with 1.5 rockers,, when applying the .010 valve lash setting, would the actual valve lift be .427?

A .010 loss of lift is not much,, but there are cams listed with .018 and .025 lash,,

if there is a loss of lift associated to lash, I should be able to add that back in when determining how much lift a given valve spring can handle,,
is that right?


Top
   
 Post subject:
PostPosted: Fri Jan 16, 2015 8:09 am 
Offline
Guru
User avatar

Joined: Sat Oct 12, 2002 11:22 am
Posts: 3740
Location: Sonoma, Calif.
Car Model: Many Darts and a Dacuda
The "advertized" cam readings we are given are taken at some checking lift / lash reading... trouble is that we may not be given that checking lift value. ( or the checking lift(s) are different then that actual running lash(s)
This is the main reason why the cam industry started using the "at .050 of lifter rise" checking standard.

As for advertized numbers you see... all you can do is call the manufacturer / cam grinder and ask if they know the actual checking lift / lash they used to get the cam numbers you are reviewing.
BTW
This also applies to the checking lifter diameter... the same profile will "look" a little different when checked with different diameter lifters .
DD


Top
   
 Post subject:
PostPosted: Fri Jan 16, 2015 8:22 am 
Offline
Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3830
Location: Indianapolis
Car Model:
Quote:
advertized" cam readings
not asking about duration,,

asking about the effect of lash on lift at the valve


Top
   
 Post subject:
PostPosted: Fri Jan 16, 2015 10:18 am 
Offline
Board Sponsor & SL6 Racer
User avatar

Joined: Fri Nov 08, 2002 4:48 pm
Posts: 5835
Location: Burton BC canada
Car Model:
Less lash ,,,,more lift.


The thing is ,,,there is a ton of variables (pushrod length will come soon) that can change the numbers.

The trick is to take their numbers and get close. Then you use lash and pushrod length ( and 12 other secret things) to get the maximum effect.

Check all clearances at zero lash and its hard to go wrong....

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....

Image


Top
   
 Post subject:
PostPosted: Fri Jan 16, 2015 10:21 am 
Offline
Board Sponsor & Moderator
User avatar

Joined: Thu Oct 17, 2002 7:27 pm
Posts: 14530
Location: Park Forest, Illinoisy
Car Model: 68 Valiant
I have always believed that actual lift was cam lift minus lash. If you put a dial indicator on the valve you may find out advertised lift is even less than advertised. I found that to be true with my Racer Brown and Mopar cams.

_________________
Official Cookie and Mater Tormentor.


Top
   
 Post subject:
PostPosted: Fri Jan 16, 2015 11:27 am 
Offline
Turbo Slant 6

Joined: Wed Jun 13, 2012 4:39 am
Posts: 519
Location: Australia
Car Model:
I'd be more concerned about the loss of lift with rocker ratio. The slant rockers can vary in ratio somewhat. Also,if you have stiffer springs and stock push rods deflection may be an issue? But to answer your question, I always seem to find that lash is subtracted from the advertised lift.


Top
   
 Post subject:
PostPosted: Fri Jan 16, 2015 11:56 am 
Offline
Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3830
Location: Indianapolis
Car Model:
Quote:
actual lift was cam lift minus lash

thanks for the replies,, that makes sense to me,, so I was checking,,,


Top
   
 Post subject:
PostPosted: Fri Jan 16, 2015 6:21 pm 
Offline
Turbo Slant 6

Joined: Sun Jun 01, 2014 10:27 am
Posts: 548
Location: Waynesboro VA
Car Model:
Since you are asking about max lift, with lifter on the toe of the cam, I can't see how lifter radius effects that. Since the lash is measured at the valve tip, how can the actual lift not be max lift - lash? (Excepting rocker ratio and geometry variations..)


Top
   
 Post subject:
PostPosted: Fri Jan 16, 2015 9:55 pm 
Offline
Board Sponsor & Moderator
User avatar

Joined: Thu Oct 17, 2002 7:27 pm
Posts: 14530
Location: Park Forest, Illinoisy
Car Model: 68 Valiant
The big thing is measure, measure, measure. Cam companies have a tendency to be "optomistic". :lol:

_________________
Official Cookie and Mater Tormentor.


Top
   
 Post subject:
PostPosted: Sat Jan 17, 2015 6:26 am 
Offline
Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3830
Location: Indianapolis
Car Model:
Quote:
actual lift not be max lift - lash? (Excepting rocker ratio and geometry variations..)

as stated by some one else previously

actual valve lift should be: (lift at the cam - lash) x rocker ratio,,,

that would not include part geometry errors and deflections...


Top
   
 Post subject:
PostPosted: Sat Jan 17, 2015 11:26 am 
Offline
Turbo Slant 6

Joined: Wed Jun 13, 2012 4:39 am
Posts: 519
Location: Australia
Car Model:
Quote:
Quote:
actual lift not be max lift - lash? (Excepting rocker ratio and geometry variations..)

as stated by some one else previously

actual valve lift should be: (lift at the cam - lash) x rocker ratio,,,

that would not include part geometry errors and deflections...
Not quite the correct sequence .... Actual lift is lift at cam x rocker ratio- lash...small difference but will have an effect. I agree with the post about lifter diameter,it can't effect lift,but duration is another thing all together.....


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 11 posts ] 

All times are UTC-08:00


Who is online

Users browsing this forum: Bing [Bot], Semrush [Bot] and 5 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited