The big thing is measure, measure, measure. Cam companies have a tendency to be "optomistic".
| Slant Six Forum https://slantsix.org/forum/ |
|
| mechanical valve lash effect on actual valve lift https://slantsix.org/forum/viewtopic.php?t=56933 |
Page 1 of 1 |
| Author: | DadTruck [ Fri Jan 16, 2015 7:47 am ] |
| Post subject: | mechanical valve lash effect on actual valve lift |
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? |
|
| Author: | Doctor Dodge [ Fri Jan 16, 2015 8:09 am ] |
| Post subject: | |
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 |
|
| Author: | DadTruck [ Fri Jan 16, 2015 8:22 am ] |
| Post subject: | |
Quote: advertized" cam readings
not asking about duration,,asking about the effect of lash on lift at the valve |
|
| Author: | sandy in BC [ Fri Jan 16, 2015 10:18 am ] |
| Post subject: | |
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.... |
|
| Author: | slantzilla [ Fri Jan 16, 2015 10:21 am ] |
| Post subject: | |
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. |
|
| Author: | SlantSteve [ Fri Jan 16, 2015 11:27 am ] |
| Post subject: | |
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. |
|
| Author: | DadTruck [ Fri Jan 16, 2015 11:56 am ] |
| Post subject: | |
Quote: actual lift was cam lift minus lash
thanks for the replies,, that makes sense to me,, so I was checking,,, |
|
| Author: | nm9stheham [ Fri Jan 16, 2015 6:21 pm ] |
| Post subject: | |
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..) |
|
| Author: | slantzilla [ Fri Jan 16, 2015 9:55 pm ] |
| Post subject: | |
The big thing is measure, measure, measure. Cam companies have a tendency to be "optomistic".
|
|
| Author: | DadTruck [ Sat Jan 17, 2015 6:26 am ] |
| Post subject: | |
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... |
|
| Author: | SlantSteve [ Sat Jan 17, 2015 11:26 am ] |
| Post subject: | |
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... |
|
| Page 1 of 1 | All times are UTC-08:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|