Diesel valve adjustment

All U Get

All U Get

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Oct 2, 2008
3,810
Pearson/ 530 Strafford, NH
Hi Rodd,

I was going through some maintenance items and wanted to check the valve clearances on our Perkins 4.236. Several valves have more than the 0.012 in clearance so I thought it would be easy to adjust. However, I found the locking nut to be tighter than I can turn with an 8 inch box wrench. Should I use a breaker bar, pipe extension, or some other means to loosen those nuts? We’ve never had any adjustments checked since 2011.
 
jon hansen

jon hansen

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May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
well, i feel for you. so, i can only tell you what i would do. first kroil. let it sit for some time. then heat. heat gun or torch. the i would use one of these 1/4 in. drive impact wrenches with slowly increasing the tork pressure . no room for a driver? breaker bar.

'heat the nut'/ will be your friend

good luck, jon
 
All U Get

All U Get

.
Oct 2, 2008
3,810
Pearson/ 530 Strafford, NH
I’ll use some PB Blaster, since I have that aboard. I do have an impact drill, but I was saving that for last resort.
 
jon hansen

jon hansen

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May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
i like blaster too. i'm thinking heat, lots of heat, would be my choice. then impact wrench. it really comes down to 'there are no other options'.
 
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IStream

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Nov 14, 2013
200
Catalina 50 Seattle
jon hansen said:
try and secure the rocker while you apply the pressure, i'm thinking
Click to expand
This. You will damage or break the rockers if you apply excessive torque. Can you get an open end wrench around the rocker head to counter the torque you're applying to the nut?
 
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kloudie1

kloudie1

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Nov 6, 2006
10,017
Hunter 34 Mandeville Louisiana
I agree, an open end wrench over the end of the rocker so you can counter the force you are using to release the locknut.. Be very careful to not bend the rocker arm.
 
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All U Get

All U Get

.
Oct 2, 2008
3,810
Pearson/ 530 Strafford, NH
D039D573-A95E-4B8A-ACC1-73C4880E58F9.jpeg

I don’t think I can get a wrench between the arms to hold one in place.
 
Claude L.-Auger

Claude L.-Auger

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Dec 14, 2003
1,414
Hunter 34 Lake of Two Mountains, QC, Can
Hi Tom, a simple Google search with the caption: Adjusting valves on Perkins 4-236 brought a lot of info, among which the attached. I understand why you can't put a wrench between the arms, but as in the attached picture you could use a heavy flat blade screwdriver. Holding it with Vise-grips should provide enough holding power for you to unscrew the nut after you've let the PB blaster do its job. If screwdriver has a square shank you could even use a small open-end wrench on it. Hope it helps.
 

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Morgan donor

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Sep 17, 2012
104
Morgan 383 Fairhaven, NY
Get a six sided quality socket, put it on a breaker bar. Push firmly down on the socket with the palm of your left hand, while pushing on the breaker bar with your right hand. Keep the angle between the socket & bar as close to 90 deg. as possible. Push the bar in progressively increasing pulses (w/o letting "slack" back into the parts). If that doesn't work and you have a 3'rd hand available - rap the breaker bar with a hammer. Most important is to press down on the socket so it doesn't slip off.
PB Blaster won't help much as the part lives in oil and won't be rusted.
 
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kloudie1

kloudie1

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Nov 6, 2006
10,017
Hunter 34 Mandeville Louisiana
'nother option is to remove the rocker arm shaft from the head.. (only 4 bolts?) then the rockers can slide for access to hold them so they don't get bent.. Break all of 'em loose while ya have access then bolt the shaft back on and proceed.. don't remove the pushrods and take care that when ya bolt the shaft back on the pushrods are seated as ya slowly tighten the shaft bolts..
 
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jon hansen

jon hansen

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May 25, 2012
4,338
john alden caravelle 42 sturgeon bay, wis
i'm a 'heat it up with a say a heat gun' guy. get those molecules more active. then a impact wrench.
i have has success this way with stubborn car suspension nuts.
i like impact wrench over breaker bar as the forces are more inline with the parts.
i'm just sharing what has worked for me in the past.

i've been doing the valves on my motorcycles forever. i feel for you

good luck
 
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Maine Sail

Maine Sail

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Feb 6, 1998
11,697
Canadian Sailcraft 36T Casco Bay, ME
Just be very careful applying too much pressure. They really should not be that tight? I've done a lot of valve adjustments over the years and while I have had to buy custom wrenches for some (Mercedes), I've never not been able to not break a nut free as they are continually bathed in oil.. Odd for sure.. I also agree with the others that if they are that tight you want a 6 point socket so you don't round them over..
 
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I

IStream

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Nov 14, 2013
200
Catalina 50 Seattle
Allan12210 said:
How about a T-handle socket wrench? Should balance out the load on both sides but give the torque you may need. Available at Harbor Freight.
Click to expand
Not quite sure what you mean. Excessive torque applied to the lock nut is the issue as it could bend the arm. Unless I misunderstand, whether that torque is applied from one or both sides of the socket doesn't make a difference to the rocker arm.
 
RoyS

RoyS

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Jun 3, 2012
1,742
Hunter 33 Steamboat Wharf, Hull, MA
I cannot see how penetrating oil will help as these are bathed in oil all the time. I would try a small electric impact wrench with a six point socket. In my experience impact wrenches are less likely to damage (strip) an overtorqued threaded connection than a long handled wrench for a given amount of required torque. Some way of applying a counter torque on the rocker would be nice but probably not required with an impact wrench. Having said that, removing the whole assembly, as suggested above, to get better access to the rocker arm is a good idea.
 
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cagreen75

cagreen75

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Nov 6, 2017
77
Catalina 30 5611 Stratford, Ct
I have been working on engines professionally for over 40 years and have adjusted many valves just like the ones you show in the picture and those nuts can be very hard to break loose. The reason these nuts are so tight is that they are machined to much tighter tolerances than your typical nuts and bolts. This higher quality machining causes the threads to match much closer making them have more contact between the threads. Forming threads in this way allows the absence of lock washers without the fear of the fastener loosening. You can really crank on those nuts with no fear of bending or breaking the rocker arm. It is typical to hear a fairly loud cracking noise when they break loose which is nothing to worry about. If you can't get them loose with a wrench an impact gun should work. It is important that these nuts are tight after adjustment and you must recheck valve clearance afterward as the adjustment will change when you tighten the locknuts.
 
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All U Get

All U Get

.
Oct 2, 2008
3,810
Pearson/ 530 Strafford, NH
Thanks for the insight, I didn’t get any nuts to budge so I put the cover back on for another week.

In order to chip in on the effort of restoring the economy, I asked the service manager to put adjust Perkins engine valve clearances on the list.
 
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