ITT: Shim Under Buckets; When and Why? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


General Miata Chat A place to talk about anything Miata

Reply
 
 
 
LinkBack Thread Tools
Old 02-19-2015, 12:02 AM   #21
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

Quote:
Originally Posted by Chooofoojoo View Post
I used some go no-go feelers on my test-assembled head. Cleaned bucket/shim interface real good with brakleen. Lobe positioned 180* from shim surface for measuring. Hope I did it right.

Sooo at any rate, as I'd like to keep this thread about SUBs as possible : Are there reduced wear characteristics of running SUBs? Decreased chances of valve float would help keep valves happy. Which is the wear item in the BP valvetrain, Cam or lifter?
Less valvetrain weight is the "advantage" of running shim under bucket, also if done right it can't "spit a shim" out as the factory setup can. But in reality, the only way it's going to spit a shim with a shim over bucket (factory) setup is if it floats the valvs.

Less weight, thus: less HP to drive cams, less wear on cams, for the same spring stiffness, better valve control as less weight to accelerate. Can now rev higher since valvetrain has better control.

Downside is cost and time to do it.

FWIW, I run the double heavy springs, and have revved to 8,800 and not spit a shim. So if you're goal is only 7,400, I wouldn't say you "need" them, but less valvetrain weight is ALWAYS nice so if you want it, do it, but I'd run the heavy double springs before converting myself.
patsmx5 is online now   Reply With Quote
Old 02-19-2015, 12:03 AM   #22
Junior Member
 
guttedmiata's Avatar
 
Join Date: Sep 2012
Posts: 438
Total Cats: -3
Default

Going from SOB to SUB and titanium retainers saves right at .75lbs. Retainer savings is more than the lash caps weigh, so I'm guessing the ztech conversion wouldn't save quite that much without the retainer swap as well.
guttedmiata is offline   Reply With Quote
Old 02-19-2015, 12:04 AM   #23
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

So I already have titanium retainers, but I believe steel keepers, so for me going to the ztech shim under bucket would be more like say, 0.2-0.3 lb savings? Sound right?
patsmx5 is online now   Reply With Quote
Old 02-19-2015, 12:08 AM   #24
Junior Member
 
guttedmiata's Avatar
 
Join Date: Sep 2012
Posts: 438
Total Cats: -3
Default

Quote:
Originally Posted by patsmx5 View Post
So I already have titanium retainers, but I believe steel keepers, so for me going to the ztech shim under bucket would be more like say, 0.2-0.3 lb savings? Sound right?
Ztech isn't SUB. No shims would be the point. You'd have to tip your valves or the bucket stem to get lash correct. So whatever the weight of your current shims is would be your savings.
guttedmiata is offline   Reply With Quote
Old 02-19-2015, 12:10 AM   #25
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,797
Total Cats: 248
Default

Ok that makes sense. Sorry I didn't realize that, it's obvious I guess if you think about it... So considerable savings then, since shim is probably 30+% of the weight if I had to guess. Hmm....
patsmx5 is online now   Reply With Quote
Old 02-19-2015, 12:16 AM   #26
Goin Innnnn!!!
Thread Starter
iTrader: (7)
 
Chooofoojoo's Avatar
 
Join Date: May 2014
Location: Denver, Co.
Posts: 460
Total Cats: 40
Default

@guttedmiata: Great point about feeler measurement. Certainly something to consider. I bought an extra shim on the thick side in case.

Good info guys. I've been convinced on it's merits. With new cams I will surely end up running SUBs or Zetec depending on base circle diam. of new cams.
Chooofoojoo is offline   Reply With Quote
Old 02-19-2015, 03:01 PM   #27
Elite Member
iTrader: (5)
 
Join Date: Oct 2007
Location: Canton, Ga
Posts: 1,707
Total Cats: 19
Default

thought I'd add my cost here for sub conversion:

~$200 for lifters from mazdacomp
$100 in shims.
$300 in labor for machining each shim. Of course I got a valve job, deck, etc from the machine shop for another $300, basically a whole rebuild top end rebuid.
Stealth97 is offline   Reply With Quote
Old 03-16-2015, 09:11 PM   #28
Senior Member
iTrader: (2)
 
Join Date: Sep 2009
Location: Edmonton, AB, Canada
Posts: 1,177
Total Cats: 27
Default

Quote:
Originally Posted by patsmx5 View Post
Ok so I have a valve grinding machine I built, I can tip valves, removing 1/2 a thousandth with decent accuracy. I have aftermarket supertech valves. Can I do this? Is it basically just keep tipping the valve till it's short enough to use these lifters? And are you serious about the 3/4 lb part?!

Can I see pics of the machine you made? I'd love to be able to grind my own tips. Is there a temperature to keep them under, is there a hardened layer that only allows so much material cut ?
Landrew is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
1994 Spec Miata Race Car SM/SM2/SSM For Sale Quinn Cars for sale/trade 6 10-23-2016 08:58 AM
LucaCarMods's Boosted Dutch Miata Build! LucaCarMods Build Threads 11 02-14-2016 07:13 AM
Wilwood Corrado bracket measurements Neilv Suspension, Brakes, Drivetrain 3 09-12-2015 10:46 AM
Annoying little leaks AlwaysBroken Engine Performance 5 09-06-2015 01:53 AM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 08:37 PM.