Go Back  Offshoreonly.com > Technical > Do It Yourself, Boating on a Budget
Mercruiser 420 - Valve Adjustment >

Mercruiser 420 - Valve Adjustment

Notices

Mercruiser 420 - Valve Adjustment

Thread Tools
 
Old 06-15-2021 | 01:54 PM
  #1  
Thread Starter
Registered
10 Year Member
 
Joined: Jul 2014
Posts: 670
Likes: 117
From: Denton, MD
Default Mercruiser 420 - Valve Adjustment

Does anyone have the appropriate valve lash/adjustment for the Crane valvetrain on the 420 mercs? I am picking up my cylinder heads from the machine shop tomorrow and was hoping someone has the information handy. I am reusing the stock rockers, lifters, pushrods, etc.
distantthunder is offline  
Reply
Old 06-15-2021 | 04:25 PM
  #2  
SB
Registered
20 Year Member
 
Joined: Nov 2004
Posts: 14,068
Likes: 3,668
From: On A Dirt Floor
Default

Crane has always stated 3/4 to
one turn therefore half to three quarter is fine too

Last edited by SB; 06-15-2021 at 04:29 PM.
SB is offline  
Reply
Old 06-15-2021 | 05:19 PM
  #3  
Thread Starter
Registered
10 Year Member
 
Joined: Jul 2014
Posts: 670
Likes: 117
From: Denton, MD
Default

Originally Posted by SB
Crane has always stated 3/4 to
one turn therefore half to three quarter is fine too
Thanks SB! I hope your summer is going well buddy.
distantthunder is offline  
Reply
Old 06-15-2021 | 11:01 PM
  #4  
Griff's Avatar
Charter Member # 55
25 Year Member
Charter Member
Super Moderators
 
Joined: Oct 2000
Posts: 20,232
Likes: 2,482
From: Omaha/LOTO
Default

Adjusting them before you install the intake manifold is easier to see/feel 0 lash. 3/4 turn is about perfect for Crane cams and will give about .040 of preload.
Griff is offline  
Reply
Old 06-16-2021 | 07:53 AM
  #5  
Thread Starter
Registered
10 Year Member
 
Joined: Jul 2014
Posts: 670
Likes: 117
From: Denton, MD
Default

Originally Posted by Griff
Adjusting them before you install the intake manifold is easier to see/feel 0 lash. 3/4 turn is about perfect for Crane cams and will give about .040 of preload.
https://www.youtube.com/watch?v=8ROU7D-6meY
Thanks Griff, great to hear from you!
distantthunder is offline  
Reply
Old 06-20-2021 | 08:54 AM
  #6  
Registered
 
Joined: Sep 2012
Posts: 523
Likes: 38
From: new baltimore mi
Default

spin push rod ,,tighten rocker till cant spin push rod..then 1/2 ....3/4 turn...
flashgordon is offline  
Reply
Old 06-21-2021 | 09:06 AM
  #7  
Registered
10 Year Member
 
Joined: Feb 2012
Posts: 265
Likes: 16
From: Omaha, NE
Default

Originally Posted by flashgordon
spin push rod ,,tighten rocker till cant spin push rod..then 1/2 ....3/4 turn...
That would be too tight.

Loosen, then tighten while spinning pushrod between fingers. Stop when you feel the pushrod has begun to feel resistance as it touches lifter and turn to desired lash.
Cory H is offline  
Reply
Old 06-30-2021 | 08:37 AM
  #8  
Registered
 
Joined: Sep 2012
Posts: 523
Likes: 38
From: new baltimore mi
Talking

Originally Posted by Cory H
That would be too tight.

Loosen, then tighten while spinning pushrod between fingers. Stop when you feel the pushrod has begun to feel resistance as it touches lifter and turn to desired lash.
well,,best way run motor motors till hear rockers are loose,,,then tighten,,,but it makes a big mess running motor with out covers..,,but i stand corrected tighten till u feel drag on push rod,,then tighten..
flashgordon is offline  
Reply
Old 06-30-2021 | 08:41 AM
  #9  
F-2 Speedy's Avatar
Platinum Member
Community Builder
10 Year Member
Platinum Member
 
Joined: May 2012
Posts: 11,418
Likes: 3,938
From: Midwest & T-Rock
Default

If their Morels almost a full turn down..........
F-2 Speedy is offline  
Reply

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 On
Pingbacks are On
Refbacks are On



Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.