Engine experts - odd issue with setting the valves.

[Code54]

I looked around cant seem to find any threads on my current valve issue.
1979 FJ40 2 F motor - ran decent with no known issues except I had to replace the gas tank due to rust. Do to the rust in the tank we decided to clean the carb well so while it was off thought it would be worth checking the valves.
We attempted to set the valves several times and they will not stay in spec.

Here is what is happened (sorry I may not have the best description)

Turn the fly wheel to the TDC marking on the fly wheel in the viewing window.

Now we set the valves following this chart (We are doing them COLD)

Once we did the yellow, we rolled the motor around to the TDC line and then did the pink valves.

Roll the motor 1 revolution to TDC and check the yellow - Valves are off (normally #3-9). The one was over 6 thoundsant loose.

Roll the motor again to check pink, again 1 or 2 substantially out of spec.

Roll the motor again 1 revolution and not the one that was 6 thoundsant off is now back in spec.

We have done this several times with the same results over and over. I understand that normally you sent the valves, roll the motor over and one or two may be a hair off so you reset them. Then mostly they stay in spec and your done. I can not get them to stay in spec.

After the first try with these results, we pulled the center tube with all the rockers and cleaned everything, making sure they all move freely. We put it back on and torqued every bolt at least three times following the pattern listed in the manual to make sure they were dead on.

That is when we reset the valves and again had the above results.

I did find one slightly loose stud that was also bent a bit but replaced it.

I am looking for any info on what could be causing this or what we are missing/doing wrong. As I mentioned, it ran okay, but when we checked the valves, a few were good and tight, so we figured no big deal, just set them and have been going in circles ever since.

Thank you

 

[charliemeyer007]

Have you tried setting the valves while its idling? Look at the adjustment and lock nut threads - some people wrench that down like it is Jesus nut on a helicopter main rotor - stretched threads can cause issues.

I like my valves set on the loose end of clearance, better to hear them than burn them. I do them in firing order not the method you use. All plugs out, and only pulling on the metal fan to position the piston - no turning the engine backwards.

Give it a good hard Italian tune up before adjusting things. What are the compression #'s

 

[pb4ugo]

Were you on TDC on the compression stroke when you started adjusting the yellow valves?

 

[fjc-man]

It’s quite possible some lobes on the camshaft are worn. Unfortunately the best way to check would be to pull the oil pan and visually inspect from underneath.

 

[rlong]

Were you on TDC on the compression stroke when you started adjusting the yellow valves?

I’ve never used that table, I’ve seen it, I just prefer to do #1 at TDC (watch the. Intake valve fully close plus a little). And just go through the timing order the same way ; 45 years (from my original factory F engine manual).

They should not change, and even with worn cam lobes I would not expect changes; I have to assume your using the table wrong and are starting or ending 180 deg. out (remember two flywheel revolutions to get back to TDC). Just do it the old factory service manual way, and see if that solves it.

 

[Chamba]

I've always set mine with the engine idling. My step dad taught me that way on my '76 40 when I was 16 back in '85 and I've been adjusting them that way on 2Fs ever since: .008" intake, .014" exhaust. I never even look them up anymore.

That's why there are 'hot' and 'cold' numbers I believe. Hot for running, cold for not.

 

[pb4ugo]

I’ve never used that table, I’ve seen it, I just prefer to do #1 at TDC (watch the. Intake valve fully close plus a little). And just go through the timing order the same way ; 45 years (from my original factory F engine manual).

They should not change, and even with worn cam lobes I would not expect changes; I have to assume your using the table wrong and are starting or ending 180 deg. out (remember two flywheel revolutions to get back to TDC). Just do it the old factory service manual way, and see if that solves it.

When I ran a stk 6 cyldr I never set valves using a chart like that or have it running. I always would adjust going thru the firing order. Back in the day i would adjusted the hydraulic lifters on a sbc while it was running. What a mess. Later I figured there has to be a better way. The factory wouldn't do it this way. Then I found a similar chart for a Chev V8 or I'll just go thru the firing order starting with #1 cyldr at tdc on the compression stroke then rotate the crank every 90* to adjust the next cyldr in line.

A worn cam isn't going to make the gap change thru each revolution of a solid lifter cam on the compression stroke. The gap should remain constant regardless.

 

[CruiserInProgress]

I looked around cant seem to find any threads on my current valve issue.
1979 FJ40 2 F motor - ran decent with no known issues except I had to replace the gas tank due to rust. Do to the rust in the tank we decided to clean the carb well so while it was off thought it would be worth checking the valves.
We attempted to set the valves several times and they will not stay in spec.

Here is what is happened (sorry I may not have the best description)

Turn the fly wheel to the TDC marking on the fly wheel in the viewing window.

Now we set the valves following this chart (We are doing them COLD)
View attachment 4185681

Once we did the yellow, we rolled the motor around to the TDC line and then did the pink valves.

Roll the motor 1 revolution to TDC and check the yellow - Valves are off (normally #3-9). The one was over 6 thoundsant loose.

Roll the motor again to check pink, again 1 or 2 substantially out of spec.

Roll the motor again 1 revolution and not the one that was 6 thoundsant off is now back in spec.

We have done this several times with the same results over and over. I understand that normally you sent the valves, roll the motor over and one or two may be a hair off so you reset them. Then mostly they stay in spec and your done. I can not get them to stay in spec.

After the first try with these results, we pulled the center tube with all the rockers and cleaned everything, making sure they all move freely. We put it back on and torqued every bolt at least three times following the pattern listed in the manual to make sure they were dead on.

That is when we reset the valves and again had the above results.

I did find one slightly loose stud that was also bent a bit but replaced it.

I am looking for any info on what could be causing this or what we are missing/doing wrong. As I mentioned, it ran okay, but when we checked the valves, a few were good and tight, so we figured no big deal, just set them and have been going in circles ever since.

Thank you

I had a similar experience with my resurrected 79 2F recently, after putting around 5k on the road, so I'm curious what you come up with.

I adjusted valves cold using that handy chart, several times getting inconsistent results on several valves each time I turned the crank. Not a huge difference, maybe a couple thousandth, but enough that I noticed.

So, I tried the running method, thinking I should be around .002" tighter when hot. Again, inconsistencies vs the cold method on some valves. And, I did a number on my .008" feeler gauge.

In order to get it back on the road, I got as close as I could, being careful not to run any too tight. I'll try it again and take better notes when I have more time.

Perhaps coincidentally, my compression checks done at the same time were also a bit inconsistent.

I never know if these things are tool-related, skill-level related, or worn parts related, so I'm kinda used to inconsistent or unexplained results and move on.

About the "worn parts related" angle, there are several components that make up and add up to a specific tappet gap (cam lobes, lifter surface, uneven rocker/valve surfaces, etc). My 79 most likely has some or all of those factors.

Still, I am very curious what you find.

 

[Code54]

Have you tried setting the valves while its idling? Look at the adjustment and lock nut threads - some people wrench that down like it is Jesus nut on a helicopter main rotor - stretched threads can cause issues.

I like my valves set on the loose end of clearance, better to hear them than burn them. I do them in firing order not the method you use. All plugs out, and only pulling on the metal fan to position the piston - no turning the engine backwards.

Give it a good hard Italian tune up before adjusting things. What are the compression #'s

I have not got compressioin numbers yet, but we can do that.
We did not try it ideling as the carb is still off, and figured it should be simular to cold, just slightly difference clearances. Would that make a difference?
Everyone says it should never float in and out of spec, but it sure does. Ugh

Were you on TDC on the compression stroke when you started adjusting the yellow valves?

Yes Sir.

Maybe we can pull the pan and see if we notice anything, I have a new gasket to install anyway.....

Thanks for the ideas and if anyone has anything to add, please do!