Return to the home page...

Go Back   Moyer Marine Atomic 4 Community - Home of the Afourians > Discussion Topics > Overhaul

Reply
 
Thread Tools Display Modes
  #1   IP: 142.68.112.67
Old 12-07-2008, 06:25 AM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
Valve clearance adjustment - image

I couldn't find an image of the atomic 4 valve clearance technique, which is well described here in other posts, so I made up this. Is it correct? My understanding is that the clearance is maximum, the valve spring is fully relaxed and the valve is closed when the camshaft has rotated to that piston's TDC, and that both intake and exhaust valves at a cylinder are closed at the piston's TDC.

Also attached: the valve clearance adjustment worksheet I made up and Don reviewed a few weeks ago in another post somewhere here.

UPDATE #1: clearer image to show the clearance gap better. The valves are nicely diagrammed in Robert Staton's "Service and Repair Manual for Atomic 4 Marine Engine" (Seacraft Publications, Toronto, Canada).

UPDATE #2: the label "locknut" in the image below is wrong. It isn't a locknut, just the top of the tappet shaped to take a wrench. Hold the tappet with one wrench and twist the adjusting nut with another wrench. Takes some force to move that nut. See rest of thread.
Attached Images
  
__________________
1974 C&C 27

Last edited by rigspelt; 01-24-2010 at 05:45 AM. Reason: I incorrectly labelled "locknut"
Reply With Quote
The Following User Says Thank You to rigspelt For This Useful Post:
PWAusCal29 (07-01-2016)
  #2   IP: 71.254.108.203
Old 12-07-2008, 09:30 AM
ne57301 ne57301 is offline
Senior Member
 
Join Date: Oct 2006
Location: Maine
Posts: 36
Thanks: 0
Thanked 1 Time in 1 Post
I'll soon have the same question. Looking at the Tappet picture in Moyers Catalog I'm guessing 'B' but I'm not positive.
Attached Images
 
Reply With Quote
  #3   IP: 38.102.24.196
Old 12-07-2008, 11:01 AM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
Join Date: Oct 2004
Posts: 2,811
Thanks: 0
Thanked 183 Times in 124 Posts
Beautiful! Not to beg, but if you could remove just a bit more masking tape to expose the flat spots on top of the tappet, you'd have everything in your photo to illustrate making an adjustment in the clearance.

Don
Reply With Quote
  #4   IP: 38.102.24.196
Old 12-07-2008, 11:03 AM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
Join Date: Oct 2004
Posts: 2,811
Thanks: 0
Thanked 183 Times in 124 Posts
Quote:
I'll soon have the same question. Looking at the Tappet picture in Moyer's Catalog I'm guessing 'B' but I'm not positive.
The valve clearance is indeed the space between the top of the tappet and the bottom of the valve stem when that particular cylinder has the piston at the top of its compression (or power) stroke (commonly referred to as TDC). This would be "B" in your photo.

Don
Reply With Quote
  #5   IP: 142.68.112.67
Old 12-07-2008, 02:48 PM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
I spent a couple of hours practising finding TDC on each of the cylinders and measuring the present clearances.

How critical is it that the crankshaft be turned "to vertical"? Is it allowable to be a few degrees before or after perfect TDC? I found it hard to judge super precisely when the crank pins were vertical.

1. I think the crank pins are vertical on the end of the crankshaft just before the small triangle mark on the flywheel cover, not when the top pin is pointing at it. I think this is because the hole in the center of the flywheel cover does not appear to be centered over the end of the crankshaft. Could that be?

2. I measured the clearances for the I and E valves at cylinder #1 all the way through the #1 intake stroke after I first felt a puff of air in the #1 spark plug hole. I could swear that the clearances were slightly wider just after half way into the stroke than when the pins were vertical. Is this possible? Both valves should be closed during the compression stroke from BDC to TDC, and remain closed during the power stroke from TDC to BDC, right? If so, then would not the clearances on both valves be maximum from BDC through TDC to BDC at that part of the 4-stroke cycle?

3. The next stroke is power, when both valves should be closed anyway, so is it acceptable to err a bit on the side of going a tad too far past TDC?

Here's what I found today:
1E .008 slight drag
1I > .008, < .010
2I > .008, < .010
2E > .008, < .010
3E .008 slight drag
3I .012 slight drag
4I .010 slight drag
4E > .006, < .008

I have not had the nerve yet do what appear to be the necessary adjustments.
__________________
1974 C&C 27

Last edited by rigspelt; 12-07-2008 at 03:02 PM.
Reply With Quote
  #6   IP: 142.68.112.67
Old 12-07-2008, 02:50 PM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
Here's how I think it works:

The tappet is an intermediary part between the camshaft and the valve.
The valve spring compresses when the cam drives the tappet up into the valve stem base forcing the valve open, and relaxes when the tappet drops down allowing the valve to close. The tappet falls a short distance away from the base of the valve stem (the clearance gap).
Valve clearance is the gap between the valve lifter (tappet) and valve stem, ensuring that the valve closes completely. Clearance too low: valve does not close completely, so engine performance suffers. Clearance too high: valves get hammered.

Compression stroke up, both valves remain closed and compression builds.
TDC: both valves closed, spark plug fires.
Power stroke down, both valves closed.
BDC: both valves closed.
Exhaust stroke up: the exhaust valve opens after BDC and then closes before TDC.
TDC: both valves closed.
Intake stroke down: intake valve opens after TDC and then closes before BDC.
BDC: both valves closed again.
__________________
1974 C&C 27

Last edited by rigspelt; 12-07-2008 at 03:22 PM.
Reply With Quote
  #7   IP: 71.254.108.203
Old 12-07-2008, 04:34 PM
ne57301 ne57301 is offline
Senior Member
 
Join Date: Oct 2006
Location: Maine
Posts: 36
Thanks: 0
Thanked 1 Time in 1 Post
How's this?

I think this pretty much answers that question!!

Randy
Attached Images
  

Last edited by ne57301; 12-07-2008 at 09:36 PM.
Reply With Quote
The Following User Says Thank You to ne57301 For This Useful Post:
TimBSmith (09-26-2020)
  #8   IP: 142.68.112.67
Old 12-07-2008, 04:44 PM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
Another wrinkle I haven't figured out yet. Just found this in a Universal manual for engines including the A4:

"b. Two types of tappet adjusting screws are used: one is of the self-locking type and the other has a locking nut for holding the adjusting screw in place. Before making the adjustment, this locking nut must be loosened and the adjusting nut held in place when it is retightened after the adjustment is completed."
__________________
1974 C&C 27
Reply With Quote
  #9   IP: 142.68.112.67
Old 12-08-2008, 05:13 AM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
Quote:
Originally Posted by ne57301 View Post
I think this pretty much answers that question!! Randy
Great photos! I'll get better ones when I get back to my boat, which I've moved from the driveway to an indoor shop for the winter. So now I have to drive to the boat.

Looks like we have different adjusting mechanisms on the tappets. I'm still uncertain exactly how to proceed with the wrenches. I wonder if I hold the lower locking nut while turning the adjusting nut? See my last post about there being two styles of tappet locking mechanisms in Universal engines.
__________________
1974 C&C 27
Reply With Quote
  #10   IP: 38.102.24.196
Old 12-08-2008, 08:21 AM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
Join Date: Oct 2004
Posts: 2,811
Thanks: 0
Thanked 183 Times in 124 Posts
I've never done an official "traverse" of valve clearances as you rotate the engine through TDC, but I would expect that the lower radius of the cam lobes have a slight dimensional variation that would explain clearances other than the official specification as you approach TDC from either direction.

As long as you line up the roll pin vertically (it's really one pin that extends through the front of the crankshaft), you should be OK. I've never noticed any variation in valve clearance if you vary a couple degrees from vertical.

Don
Reply With Quote
  #11   IP: 38.102.24.196
Old 12-08-2008, 08:24 AM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
Join Date: Oct 2004
Posts: 2,811
Thanks: 0
Thanked 183 Times in 124 Posts
Atomic 4 tappets are self-locking. You simply hold the top of the tappet with a 1/2" open-end wrench and turn the threaded part with another open-end wrench. Early engines have 7/16" hex-headed tappet adjustments, and later engines (circa mid-seventies) have 1/2" hex-headed adjustments in the tappets. From your photos, you appear to have the 1/2" variety.

Don
Reply With Quote
The Following 2 Users Say Thank You to Don Moyer For This Useful Post:
Hawkeye54 (01-28-2021), TimBSmith (09-26-2020)
  #12   IP: 69.162.193.30
Old 12-08-2008, 12:47 PM
lat 64's Avatar
lat 64 lat 64 is offline
Afourian MVP
 
Join Date: Oct 2008
Location: Fairbanks, Alaska
Posts: 1,964
Thanks: 39
Thanked 240 Times in 157 Posts
valve clearance

Hi all,
I think I should weigh in on twothree items here.

A few degrees off of dead center is ok to adjust valves, you are all the way on the back side of the base circle of the cam at this point. Many auto valve-adjusting procedures call for doing more than one at a time, in those cases the cam must be quite a few degrees off of dead enter when they are measured. I would do them one at a time of course, like you are.

There is both a minimum AND a maximum. Stay in the range that is specified for valve clearance (eg. .010 to .012 or whatever.) Too tight can let the valves stay open when the engine gets up to temp and hot gases flow past the valve seat and then the valve starts to burn.
Too loose and it just makes lots of noise and beats up the valve tip. Rigspelt covered this, but it's important.

Also make sure you adjust them at the proper temperature. Some engines, like the old ford 292 v-8, must be at near operating temp for valve adjusting( Yes, it's very painfull. ) Others, mercedes diesel comes to mind, need to be ice cold to get it right. Check the spec.s for A-4.

Finally, it is good practice to practice. Adjusting valves is almost a black art on some engines like the old Datsun L-16 types. On those darn things the lock nut would actually stretch the adjuster screw so it would never be the same thing twice. Get lots of experience for what it feels like to do this on the bench if you can. so when you are laying in dirty oil with a battery terminal poking you in the ribs you can be efficient and accurate adjusting the valves. I always "run the rack" more than once if I can to check my work. there always seems to be one or two that mysteriously get missed or change clearance with just a few turns of the crank

Russ
p.s. Great pics
__________________
Whiskeyjack a '68 Columbia 36 rebuilt A-4 with 2:1

"Since when is napping doing nothing?"

Last edited by lat 64; 12-08-2008 at 11:10 PM. Reason: typos
Reply With Quote
The Following 2 Users Say Thank You to lat 64 For This Useful Post:
GregH (01-27-2021), TimBSmith (09-26-2020)
  #13   IP: 142.68.102.108
Old 12-11-2008, 05:47 AM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
I posted a sketch of how the crank pin, piston position, valve state and distributor rotor position relate to each other during a part of the A4 four stroke cycle here: http://www.moyermarine.com/forums/showthread.php?t=2930
__________________
1974 C&C 27
Reply With Quote
  #14   IP: 142.68.102.108
Old 12-13-2008, 04:16 PM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
Help: Should adjustment nuts be so tight?

I tried adjusting the gap today on the valves. I put a 1/2" wrench on the lower "locking" nut, which spins freely, and a 7/16" wrench on the upper adjusting nut. Should it be so hard to turn that upper nut when holding the lower one fixed? I don't see a way to back off the so-called locking nut, turn the adjusting nut, and retighten the locking nut. Doesn't make sense to me.

My tappets look different from the ones ne57301 shows in his photos in this thread. See a clearer picture of mine below.
Attached Images
 
__________________
1974 C&C 27

Last edited by rigspelt; 12-14-2008 at 06:26 AM. Reason: Incorrectly labelled "locking nut"
Reply With Quote
  #15   IP: 70.211.230.229
Old 12-13-2008, 08:33 PM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
Join Date: Oct 2004
Posts: 2,811
Thanks: 0
Thanked 183 Times in 124 Posts
You're likely simply not turning the upper nut (at the top of the adjustable part of the assembly) with enough force while holding the top of the tappet. The lower 1/2" wrench position is actually the top of the tappet, not a locking nut, as you're calling it. You can turn the tappet freely with a 1/2" wrench as long as you're not holding the upper nut with a second wrench.

Don
Reply With Quote
  #16   IP: 142.68.116.35
Old 12-14-2008, 05:27 AM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
Quote:
Originally Posted by Don Moyer View Post
You're likely simply not turning the upper nut (at the top of the adjustable part of the assembly) with enough force while holding the top of the tappet. The lower 1/2" wrench position is actually the top of the tappet, not a locking nut, as you're calling it. You can turn the tappet freely with a 1/2" wrench as long as you're not holding the upper nut with a second wrench.Don
Thanks for helping Don.

UPDATED: In the image below:
A - a smooth round metal part that "taps" the base of the valve stem and pushes the valve up. A, B and C are all one part: the adjusting nut.
B - adjusting nut that takes a 7/16" inch wrench.
C - These threads are part of adjusting nut B. They turn into the top of the tappet D.
D - The top of the tappet, fits a 1/2" wrench.

This whole unit spins freely if no wrenches are attached.

Hold D with a 1/2" wrench and then turn B with a 7/16" wrench with enough force to move it. First time I did it, I was surprised by the force it took to move the adjusting nut.
Attached Images
 
__________________
1974 C&C 27

Last edited by rigspelt; 01-23-2010 at 04:07 PM.
Reply With Quote
The Following User Says Thank You to rigspelt For This Useful Post:
TimBSmith (09-26-2020)
  #17   IP: 142.68.116.35
Old 12-14-2008, 06:19 AM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
Wait - I think I see it.

I had a good look through the images I took yesterday. This one shows a valve being pushed up by the tappet. The clearance of course is zero. Now I can see the part under D, labelled E in this image. It is the tappet, and I can see that D is a part of E, shaped to take a 1/2" wrench. So, of course the tappet would spin freely as it rides on the cam. Since this arrangement has no locking nut mechanism, and then of course it would take some force to turn adjusting nut B in order to change the clearance. A, B and C must be one part, and D and E the second part, correct?

I'll go back and edit the images above to change the name from "locking nut" to "top of tappet", but I would like confirmation that my penny finally dropped, and the amount of force it takes to turn adjusting nut B while holding top of tappet D is indeed fairly high. (UPDATED: Confirmed.)
Attached Images
 
__________________
1974 C&C 27

Last edited by rigspelt; 01-23-2010 at 04:07 PM.
Reply With Quote
  #18   IP: 38.102.24.196
Old 12-14-2008, 08:13 AM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
Join Date: Oct 2004
Posts: 2,811
Thanks: 0
Thanked 183 Times in 124 Posts
The tappet is built in two parts: the tappet itself with flat spots on each side of the top to accommodate a 1/2" open-end wrench and a threaded part (we've been calling it the adjusting part) which has a hex-headed top. To adjust the clearance between the top of the tappet assembly and the bottom of the valve stem, you hold the top of the tappet with one wrench while turning the hex-headed adjusting nut at the top of the threaded part of the tappet assembly with a second wrench.

The threaded part of the assembly is designed to fit tightly (self-locking) into the top of the tappet so there is no lock nut required. You only have to turn the threaded (or adjusting part) up or down within the tappet to make an adjustment. I still believe that you simply aren't putting enough muscle on the wrenches. Sometimes the threaded part of the assembly turns quite tightly within the tappet.

Don
Reply With Quote
The Following User Says Thank You to Don Moyer For This Useful Post:
TimBSmith (09-26-2020)
  #19   IP: 142.68.125.62
Old 12-14-2008, 09:13 AM
rigspelt's Avatar
rigspelt rigspelt is offline
Afourian MVP
 
Join Date: May 2008
Posts: 1,187
Thanks: 0
Thanked 19 Times in 17 Posts
Quote:
Originally Posted by Don Moyer View Post
I still believe that you simply aren't putting enough muscle on the wrenches. Sometimes the threaded part of the assembly turns quite tightly within the tappet.
Don, that explains it. Thank you for your patience.

UPODATE: All 8 done and double checked. Thanks all.
__________________
1974 C&C 27

Last edited by rigspelt; 12-14-2008 at 05:16 PM.
Reply With Quote
The Following User Says Thank You to rigspelt For This Useful Post:
TimBSmith (09-26-2020)
  #20   IP: 68.104.64.227
Old 01-19-2010, 02:56 PM
roadnsky's Avatar
roadnsky roadnsky is offline
Afourian MVP
 
Join Date: Dec 2008
Location: Lake Mead, NV
Posts: 3,104
Thanks: 24
Thanked 467 Times in 309 Posts
Question COLD or HOT?

I'm resurrecting Rigs' old thread to ask...

Should the valve clearances be adjusted COLD or "WARM"? (at operating temp)
I'm about to dive in to the adjustment.
The engine runs fine, but I have no idea when this was last done and that gasket sure looks old!
__________________
-Jerry

'Lone Ranger'

1978 RANGER 30
Reply With Quote
  #21   IP: 64.231.97.154
Old 01-19-2010, 03:19 PM
67c&ccorv's Avatar
67c&ccorv 67c&ccorv is offline
Afourian MVP
 
Join Date: Dec 2008
Location: London, ON
Posts: 1,559
Thanks: 4
Thanked 9 Times in 9 Posts
Quote:
Originally Posted by roadnsky View Post
I'm resurrecting Rigs' old thread to ask...

Should the valve clearances be adjusted COLD or "WARM"? (at operating temp)
I'm about to dive in to the adjustment.
The engine runs fine, but I have no idea when this was last done and that gasket sure looks old!
I would go with the cold specs myself - mainly due to what one man thinks (or due differences in operating tempuratures of various engines) is "warm" enough.

Plus, it is a lot harder to get burned this way!
Reply With Quote
  #22   IP: 68.104.64.227
Old 01-19-2010, 08:31 PM
roadnsky's Avatar
roadnsky roadnsky is offline
Afourian MVP
 
Join Date: Dec 2008
Location: Lake Mead, NV
Posts: 3,104
Thanks: 24
Thanked 467 Times in 309 Posts
Quote:
Originally Posted by 67c&ccorv View Post
I would go with the cold specs myself - mainly due to what one man thinks (or due differences in operating tempuratures of various engines) is "warm" enough.

Plus, it is a lot harder to get burned this way!
Thanks 67...
When pulling the carb and cables today to get to the cover, I realized the answer to my own question.
COLD...
Because I won't have a way to run the engine with the carb off!
DUH!
__________________
-Jerry

'Lone Ranger'

1978 RANGER 30
Reply With Quote
  #23   IP: 71.118.13.238
Old 01-20-2010, 01:51 PM
Dave Neptune Dave Neptune is online now
Afourian MVP, Professor Emeritus
 
Join Date: Jan 2007
Location: Grove, Oklahoma
Posts: 5,035
Thanks: 711
Thanked 1,289 Times in 839 Posts
Question Oil splash??

Don, I am definately an old school mechanic as I grew up adjusting all sort of valvetrains, some adjusted hot some cold and quite a few running. I always prefered the results on older engines when adjusting while running which brings me to this question.
How messy (spray & splash) is it if you attempt to run with the cover off to check the "running clearance"? I have always had a copuple of extra noises in my valvetrain (not to worried it's been there for 25 years for me @ 3 valve adjustments) that I think I could possibly eliminate if I could check while running.

Dave Neptune
Reply With Quote
  #24   IP: 216.70.184.248
Old 01-20-2010, 02:36 PM
roadnsky's Avatar
roadnsky roadnsky is offline
Afourian MVP
 
Join Date: Dec 2008
Location: Lake Mead, NV
Posts: 3,104
Thanks: 24
Thanked 467 Times in 309 Posts
Dave-
So, obviously, you have good access to the valves without removing the carb?
There's no way I can on my boat. Between the Indigo PVC and the carb.
(Plus my Shift Cable)

I'm going after mine mainly to change that very old looking gasket.
I'd think trying to do the clearances while the engine was humming along would really get messy.
__________________
-Jerry

'Lone Ranger'

1978 RANGER 30

Last edited by roadnsky; 05-18-2019 at 08:18 PM.
Reply With Quote
  #25   IP: 38.118.55.125
Old 01-20-2010, 02:40 PM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
Join Date: Oct 2004
Posts: 2,811
Thanks: 0
Thanked 183 Times in 124 Posts
Dave,

There's hardly any splash at all when running the engine with the valve cover removed. However, if you go that route, you might consider using the 1/4" - 20 studs in our online catalog (product number OVAL_14_418 in overhaul/valves) to replace your 1/4" - 20 bolts. It's much easier to install the valve cover over the ends of the studs than to find the holes in the block when reinstalling bolts through the valve cover.

The warm clearance for the valves are: .008" for intake and .010" for exhaust valves.

Regards,

Don
Reply With Quote
Reply

Thread Tools
Display Modes

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Valve Adjustment Jim Mac Overhaul 5 02-04-2015 10:51 AM
valve adjustment schedule MikeB.330 General Maintenance 4 06-30-2008 08:19 PM
Valve Adjustment Clarification HOTFLASH General Maintenance 1 10-27-2007 10:01 AM
Valve lifter adjustment anglosax General Maintenance 1 03-13-2007 08:24 AM
Valve adjustment Banyan Day General Maintenance 1 02-14-2005 07:53 PM


All times are GMT -4. The time now is 01:39 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.


Universal® is a registered trademark of Westerbeke Corporation

Copyright © 2004-2024 Moyer Marine Inc.

All Rights Reserved