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Extremely Fluctuating Valve Clearance
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Anky1978
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PostPosted: Mon Sep 20, 2021 5:04 am    Post subject: Extremely Fluctuating Valve Clearance Reply with quote

Hi all,

Before you read any further - I bought my '72 Bug in 2011, and I've always been bad at setting the valve clearance. I don't know why, but it's a job I can never seem to get right. This last time, I swore I did it 'by the book' - and while I've got a quiet motor that idles and cruises nicely - I've lost a significant degree of power, and the whole car shudders when accelerating in 3rd and 4th.

Here's the process I followed:
    > Rotate engine to TDC using the #1 mark on the distributor;
    > Adjust #1 (front right) to 0.006" (0.15mm), to the point where a 0.008" (0.20mm) won't slide through - tighten the nut and double check;
    > Rotate the engine counterclockwise 180 degrees, then do the same for #2 (rear right);
    > Rinse and repeat for #3 (front left) and #4 (rear left).

I swore I did this last time - but when I looked this time - I had valve clearance in excess of 0.5" (12mm) on some cylinders! I couldn't have gotten it that wrong. No wonder I couldn't hear myself think in the cabin, but at least I could keep up with traffic.

Because it was so off, this time I adjusted the points to 0.16" (0.4mm) on my 009 single vacuum-advance distributor, static timed it to 5 degrees ATDC (that's where the notch on my wheel is, and 7.5 degrees BTDC gives me grief), and adjusted the carburetor.

I swear going to burn valves...I'm at begging / breaking point - what am I doing wrong?!
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Dougy Dee
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PostPosted: Mon Sep 20, 2021 5:16 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

.500-1/2"-12mm valve clearance! Wow!

Tighten the 2 nuts that hold the rockers to the heads.
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PostPosted: Mon Sep 20, 2021 6:24 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

There are thousands of posts and topics on a step by step process, so I won't go into the things that you are doing right, but there are several you could be doing wrong.
Use the timing mark in the distributor as a guide to see what cylinder your on, but use the crank pulley at TDC and BDC when doing the actual valve adjustment (#1 in the distributor should point to the little notch, as well as the corresponding cylinder that is firing...that's not to say that the distributor drive gear was put in 180° out, or just incorrectly all together). If you have never double checked to ensure you are actually at TDC on number 1, pull a spark plug and stick a pencil down the hole. If you are in fact on TDC, and both valves are not compressed, you should feel the piston right at the top of the combustion chamber with the pencil.
You can static time all you want to get to what you think is a happy timing number, but you should be timing your motor with a timing light at ~3000rpm (full mechanical advance on your distributor) with the hose removed from the carb and the port plugged up. Time to ~30-32 degrees BTDC, and then just let idle land where it wants. This will also make sure that the mechanical portion of your distributor is advancing correctly. Then hook your vac hose back up. You can also pull a vac on the end of the tube to make sure that the vacuum portion of the distributor is advancing as well.
Point gap in your distributor is important as well. This could go out of spec real quick if the lobe and point ramp are not lubed.
Also, always make sure you're adjusting valves on a stone cold motor. You can't go out for a drive and then adjust valves on a warm motor.
As far as the valves going out of adjustment, it sounds like you are adjusting them at different points of the rotation of the motor. If you were going to drop a valve, they tend to expand...not contract as you are describing with your huge valve clearances. You're just measuring at the wrong point when you do your adjustment, and then measuring again at another wrong point when you check them.
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PostPosted: Mon Sep 20, 2021 8:50 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

If you’re going to confirm TDC for number one cylinder, using the distributor as a guide, do NOT use the notch. After aligning your crank pulley’s TDC mark (or dimple) to the crack in the crankcase, confirm that you’re on number one cylinder by confirming that the tip of the distributor rotor is pointing toward where the number one plug wire plugs into the distributor cap. Lift the cap and locate where the number one plug wire is inserted into the distributor cap. Take a marker and draw this location further down on the side of the distributor body. When your pulley TDC mark is lined up at the case, if you are at TDC for number one cylinder, the rotor will be pointing at the mark you just made on the distributor body.

If the distributor rotor is pointing 180 degrees from the mark you made, then you are at TDC for cylinder number three. If this happens, turn the crank clockwise to line up the TDC mark again to the crankcase crack. Your distributor should be pointing in the vicinity of the mark you made on the distributor.

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ashman40
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PostPosted: Mon Sep 20, 2021 10:28 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Anky1978 wrote:
Here's the process I followed:
    > Rotate engine to TDC using the #1 mark on the distributor;
    > Adjust #1 (front right) to 0.006" (0.15mm), to the point where a 0.008" (0.20mm) won't slide through - tighten the nut and double check;
    > Rotate the engine counterclockwise 180 degrees, then do the same for #2 (rear right);
    > Rinse and repeat for #3 (front left) and #4 (rear left).

I swore I did this last time - but when I looked this time - I had valve clearance in excess of 0.5" (12mm) on some cylinders! I couldn't have gotten it that wrong. No wonder I couldn't hear myself think in the cabin, but at least I could keep up with traffic.

Your steps above sound correct. The only step that I might question is how you determine you are at #1 TDC at the end of the compression stroke. The #1 plug wire notch on the distributor should not be trusted until you confirm it is oriented correctly. For a good running engine, confirm the #1 spark plug wire is installed over this notch. If you are uncertain (for example the engine has never run) you should confirm #1 TDC at the end of the compression stroke using #1 valve movement. Rotate the crank CW until you see the #1 intake valve open and then close. The intake valve closes at the start of the compression stroke. Rotate the crank approx 180deg more and the TDC mark will line up with the case split. This is TDC at the end of the compression stroke for #1 cylinder. The distributor must now deliver a spark to the #1 spark plug. This is done by placing the #1 spark plug wire into the post over the rotor tip. It doesn’t matter if you THINK this is the correct position or not. The #1 cylinder is at the end of the compression stroke and the distributor MUST deliver a spark to the #1 spark plug. If the rotor is point to the #1 plug wire notch, GREAT! If it is not, add a paint mark or permanent marker mark on the distributor so you now know where #1 plug wire should be installed.

0.5” is no small change in the adjustment. Can you tell if the adjusting screw in the rocker arm has moved? Was the lock nut loose? Has the push rod bent?
The gap between the rocker arm and the valve stem is adjusted when the rocker arm is not pressing on the valve. If you mistakenly adjusted the valve while it was pressing on the valve, you would need to loosed the adjuster a great deal to get the clearance. The adjuster screw would be barely extending thru the rocker arm at all. Can you post pics of your rocker arms showing how much of the adjuster screw is passing thru the rocker arm or how much is still sticking up above the rocker arms?
Here is a pic showing one rocker that is obviously adjusted different from the other three just based on how much of the adjuster screw is exposed above the rocker arm. This suggests something is wrong with that rocker/valve.
Image may have been reduced in size. Click image to view fullscreen.



Anky1978 wrote:
I've lost a significant degree of power, and the whole car shudders when accelerating in 3rd and 4th.
<…>
Because it was so off, this time I adjusted the points to 0.16" (I think you meant 0.016” here) (0.4mm) on my 009 single vacuum-advance distributor, static timed it to 5 degrees ATDC (that's where the notch on my wheel is, and 7.5 degrees BTDC gives me grief), and adjusted the carburetor.

Your power loss is likely because you have set your ignition timing wrong.
First off, I’m not aware of a “009” distributor with a vacuum advance. I’ll conceded that an SVDA distributor (034/205) is similar to a 009 with a vacuum advance, but they are not the same thing. What model distributor are you running?

Your ignition timing should be based on the distributor you have installed… not based on the crank pulley or the engine you have. If you are running a different distributor you need to adjust your timing to reflect that distributor.
5ATDC idle timing is only used with a DVDA distributor at idle with the vacuum retard system removing 8-12deg of timing. You are assuming that idle timing and static timing are the same. In many cases they are, but for engines running a DVDA distributor, they are not. If you were to set the idle timing to 5ATDC on a DVDA distributor and then shut off the engine and checked the static timing you would find it to be around 5~7BDTC. Static timing any distributor to 5ATDC means you are as much as 12deg retarded in your ignition timing. No wonder you have no power.

What problems were you having with the static timing at 5~7BTDC? Also, where have you connected your distributor’s vacuum advance hose? If you connected the hose to the wrong port on the carb the vacuum advance may be advancing the timing at idle. The SVDA/DVDA distributor’s vacuum advance is connected to ported vacuum on the carb so at idle there is no vacuum. If the vacuum hose were connected to intake vacuum at idle, the static timing of 7BTDC would be increased to 17-20BTDC at idle. This is not a timing problem but an installation problem. Post pics of your carb and distributor.

Adjust your ignition timing based on the model of your distributor. If necessary, add notches to the crank pulley to support the distributor you have installed.

If you cannot identify your distributor or it is an aftermarket distributor with questionable tolerances… adjust the ignition timing so that the mechanical advance does not take you above 28-32BTDC at ANY rpms. This is done by disconnecting and plugging the vacuum hoses so the distributor’s vacuum advance/retard is disabled. Rev the engine while you watch the timing marks under the strobe timing light increase. Once the timing marks stop increasing set the total initial + mechanical advance to 28BTDC (you can work up from here). 28-32BTDC is the safe upper limit for mechanical (rpm-based) timing advance. The (SVDA/DVDA) distributor’s vacuum advance work on top of this baseline for mechanical advance.
If you don’t have a degree pulley or an advanced timing light where you can adjust the pulse of the light… you will need to add paint/pen/pencil marks on the crank pulley for 7.5BTDC, 28BTDC and 32BTDC.
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Anky1978
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PostPosted: Mon Sep 20, 2021 8:40 pm    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Thank you all for your very thorough responses! I took my newfound knowledge and tackled the car again this morning, and made some interesting finds.

First Things First - TDC

I took all of your advice, and rotate to the #1 firing position, lined up the crank wheel dimple with the crank case, watched for no movement on #1 arms, watched for movement on #3 arms, and stuck a pencil down the #1 spark plug - felt the piston - and watched it rise and fall. The dimple is correct.

Note the 5 degree ATDC notch.

Image may have been reduced in size. Click image to view fullscreen.

#1 Intake Pushrod Came Loose

Image may have been reduced in size. Click image to view fullscreen.

This would explain the power troubles; I was only firing on three cylinders. After reading Ashman's post, I realised that this adjuster screw was screwed far further in than the others - so far that it mustn't have had enough bite on the thread to hold the nut in place.

You'll note that the intake rocker arm will even disconnect from the pushrod when there is no screw, whereas the exhaust arm doesn't.

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

Damaged Pushrods
The valves seemed to be lined up identically, so I took off the rocker arm and inspected the pushrods. I noticed that the intake pushrod is slightly shorter than the others, and every one of them has a strange spike at the end of them, along with some metal shearings. The rocker arms look okay.

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

Perhaps I placed them the wrong way around, but I don't remember that little spike when I put them in - and one shouldn't be shorter than the others. These have only done about 1,500 miles.

Bonus - The Other Side, and the Distributor

Image may have been reduced in size. Click image to view fullscreen.

The other side looks okay comparatively, but haven't tried adjusting it again.

Image may have been reduced in size. Click image to view fullscreen.

The distributor, as requested - I thought it was a 009.

The Verdict

So, I understand that pushrods may need replacing, however:
    > What could have caused this in the first place?
    > What other damage could have been done?
    > How would one go about detecting any such problems?
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ashman40
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PostPosted: Mon Sep 20, 2021 9:41 pm    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Wow! Some crazy things going on here! Shocked

First off... the notch in your crank pulley is 7.5BTDC... not 5ATDC.
The crank pulley rotates CW when the engine is running. As the pulley rotates, that notch lines up with the case split BEFORE the TDC dimple reaches the case split. If the spark fires for #1 spark plug and the strobe flashes to show the notch lined up with the case split it means the #1 spark plug is firing BEFORE TDC. The notch represents a BTDC timing mark.
The only stock pulley with a dimple and a single notch CW from the TDC dimple was a 7.5BTDC notch.
A 5ATDC notch would be CCW from the TDC dimple along the lip of the crank pulley. The 5ATDC notch would line up with the case split AFTER the TDC dimple had rotated past the case split.

The spikes at the end of your push rods... I've never seen that before! Crazy! Shocked I suppose if your valve gap was set too wide the push rods could have been pounded into the cups in the rocker arms and they formed into the oil hole in the cup? You will definitely need a new set of push rods. You should also check that nothing is stuck in the holes of the rocker arms.


After you removed the rocker arm assembly, did you lay a straight edge across the top of the 4 valves? Without the rockers in place, all 4 valves should be closed and resting at exactly the same height. A straight edge across the tops will show this. If any are higher or lower than the others it could indicate a valve that is stretched, a valve seat that has sunk into the head, or something is preventing the valve from fully closing. Investigate any valves that are not even.

Your comment about push rods that can be removed or not removed with the adjusting screws removed... this is not necessarily indicative of anything. At the bottom of the push rods are the lifters which ride on the cam lobes. If both lobes for a cylinder are at their lowest point, both lifters will be the same height and the push rods will extend the same amount (minimal extension). But if the cam lobes are in lift, the push rods will extend out different amounts for that cylinder. So if you rotated your engine so #1 cylinder was at the end of the compression stroke to adjust the valves... both push rods should extend out the same amount (minimum extension). But all three other cylinders will be in some other stroke and the cam lobes will be lifting lifters/push rods and opening valves by different amounts. These pairs of push rods would never be even. Just removing the adjuster screws does not determine if the push rods will be at the same extension. If you were saying that the cylinder pictured was at the end of the compression stroke and yet both push rods were not even... I would suggest that it was actually NOT at the end of the compression stroke and one of the cam lobes was lifting the push rod.


You still have not identified the model# of your distributor. Look for numbers stamped into the body. Usually this is on the side facing the front of the car and you will need a mirror to see them. That looks like an aftermarket SVDA distributor, but there were still different models. Some have no markings.
Normally, SVDAs are adjusted to 7.5BTDC @idle with hoses disconnected. But there were some SVDAs that were adjusted to TDC. I just installed an aftermarket SVDA in a buddy's engine and we had to set the idle timing to 2BTDC to keep the max mechanical advance at 28BTDC. This illustrates that aftermarket tolerances cannot be relied on.
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Anky1978
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PostPosted: Tue Sep 21, 2021 12:03 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

As always, a response worthy of a textbook on schooling wannabe mechanics such as myself. Laughing Thank you for your time and patience Ashman!

Duty called me away from the bug today, but I’ll get back at it - this weekend at the latest. I’ll order some new pushrods on the off chance that that’s all I need to replace.

In a brief response:
    ATDC - Yep, my mistake here is testimony to my [lack of] mechanical and engineering skills.
    Valve Height - Didn’t get to check that, but will do so by this weekend and will report back.
    Rocker Arms Without Adjustment Screws - Makes sense, but one of the rods is definitely shorter than the others, which is probably due to poor adjustment and it getting bashed around (compressed?). The weird thing is, those spikes were on the lifter side! Hoping there’s no damage from the metal filings in the pushrod tubes?
    Distributor Model - Sorry, I just dumbly photographed what was there thinking it’d be obvious to the world. I have a lot to learn from you folk!

I’m so eager to get this sorted, and learn how to do this properly because it’s always been a nightmare for me!
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PostPosted: Tue Sep 21, 2021 5:36 pm    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Just an update for anybody who may be experiencing, or will experience, and issue like mine - a call to a classic VW workshop has revealed that I used cheap aftermarket pushrods.

Like Ashman, the lead mechanic had never seen the spikes before - and was even more perplexed by the fact that they were on the lifter side. The only thing he could think of was that although they were junk - they were machined with a tight core, and they got bashed out by the poor adjustment of the valves.

Alternative theory is that the lifters are junk too and have pitted - but I don’t want to disassemble just yet, so I’ll replace the rods (hopefully with VW originals if I can find them), replace the oil, and readjust the valve clearances.

I don’t think the valves should have stretched as it’s a new motor that hasn’t been driven far, but I’ll double-check and post an update this weekend.
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PostPosted: Wed Sep 22, 2021 6:26 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

If you get stock aluminum push rods, the valve gap is set at 0.006".

If you get all-steel (chrome moly?) push rods, the valve gap is set at a "loose zero" (no play but you can rotate the push rods).

This is because the aluminum push rods expand at a different rate than the steel cylinders. They expand more. As the engine heats up they take up the 0.006" so that a hot engine actually runs with near zero valve gap. All-steel push rods will expand at the same rate as the steel cylinders so no extra gap is needed.

If you are uncertain, check your push rod bodies with a magnet. Aluminum doesn't attract a magnet. The tips of the push rods are almost always steel.
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PostPosted: Wed Sep 22, 2021 6:27 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Anky1978 wrote:
Just an update for anybody who may be experiencing, or will experience, and issue like mine - a call to a classic VW workshop has revealed that I used cheap aftermarket pushrods.


Welp, good to know that you were likely adjusting them correctly. I can't believe the culprit was crappy pushrods that were playing the accordion game Laughing
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that fucking thing looks like it drove through a J.C. Whitney catalogue and hit everything on the way out Laughing
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PostPosted: Wed Sep 22, 2021 6:48 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

I have never seen pushrod ends deform like that. Were they made of Playdough? It appears like the oil hole would have been completely closed off seeing as they deformed into a point!
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Anky1978
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PostPosted: Fri Sep 24, 2021 1:46 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

It’s absolutely mind boggling. I just don’t understand the physics; you can see that the lifter ends have compressed, but the rocker ends are fine:

Image may have been reduced in size. Click image to view fullscreen.
Image may have been reduced in size. Click image to view fullscreen.
Image may have been reduced in size. Click image to view fullscreen.
Image may have been reduced in size. Click image to view fullscreen.

The only thing I can think of is that lifters are junk too, and I’ve worn a hole in them (I don’t know how else the pushrods could still “work” otherwise). I tried as best I could to get a photo down the pushrod tube, but it’s hard to tell anything. It does look like there’s a pit in the lifter?

Image may have been reduced in size. Click image to view fullscreen.

Please tell me I’m looking at the wrong thing…I really don’t want to pull the crank case apart…again…
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PostPosted: Fri Sep 24, 2021 1:33 pm    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Did you take the rocker assembly apart and clean out the oil passages? Did oil come out when you removed the valve covers? If the oil cant get to the parts things wear fast with those pressures generated by the valve springs.
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PostPosted: Fri Sep 24, 2021 1:52 pm    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Well the lifter has to have a hole in it because that's how the oil gets into the pushrod. It's like the pushrod rods were so soft, they deformed into the oil hole in the lifter.

Your pictures are showing up really small though. It's hard to see them. At least on this phone.
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PostPosted: Fri Sep 24, 2021 8:37 pm    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Starbucket wrote:
Did you take the rocker assembly apart and clean out the oil passages? Did oil come out when you removed the valve covers? If the oil cant get to the parts things wear fast with those pressures generated by the valve springs.

Yep! Cleaned them out good. The rods had plenty of oil on, in, and around them by the looks of it.

Quote:
Well the lifter has to have a hole in it because that's how the oil gets into the pushrod. It's like the pushrod rods were so soft, they deformed into the oil hole in the lifter.

Oh. I feel like a goose. In my mind, I was thinking of the flat end of the lifter (the part in contact with the camshaft). I never really looked at the inside of a lifter before.

I think we can safely say that the main problem is lousy pushrods - so cheap and useless that they compressed into the oil holes of the lifter. I’ll replace with second-hand originals if I can, otherwise I’ll just buy the best aftermarket I can. Really wish I had upgraded my cam when I had it out; solid rods seem like a nice idea…

Quote:
Your pictures are showing up really small though. It's hard to see them. At least on this phone.

Yeah, it’s weird - I don’t know why but it seems to be a quirk with the site I uploaded them to (Img.bb). If you open them as a new tab or window, they come up big.
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PostPosted: Sat Sep 25, 2021 4:15 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Try posting your photos to the Samba gallery.
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PostPosted: Sat Sep 25, 2021 8:34 pm    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Were the lifters replaced on that side? Were the lifters drilled for pushrod oil? Did the drilled passages actually connect?

I would think that even poor quality pushrods wouldn't do that if they were receiving any lubrication.

And all that crap is in your engine now. I'd pull it apart.
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PostPosted: Fri Oct 15, 2021 10:55 pm    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

Just a bit of an update (late, I know, but Melbourne in Australia is *still* in lockdown, and our postal service is having a heart attack processing mail).

I managed to get my hands on some second-hand good quality OEM VW pushrods. Upon comparing them with the ones I bashed around, there’s a good 3mm or 4mm extra length - which explains why I had that crazy valve clearance.

I drained the oil, stuck magnets everywhere, got out all the crud, shoved the pushrods in, put the rocker arms on, and set to adjusting the valve clearance.

Because the luck of the Irish skipped a generation, I’m still having strange issues…

Now, I can correctly set the lash on about 4 valves. Of the other 4, 2 of them move - even seemingly as much as the correct ones - but I can’t get a feeler gauge down them. For the other 2, they don’t move at all. These are sporadic 2, like intake on #1, intake on #2, exhaust on #3, and exhaust on #4.

Followed the guides over and over and over again, and the process is right. Valves don’t seem to be stretched, it runs sort of okay, but hesitates when cold, then backfires when it gets warm…what now?!

Maybe I missed some metal that got stuck in the lifter? Maybe the arms are worn unevenly? Maybe the lifters are stuffed? Valves are buggered? I have no idea.
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Igpoe
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Joined: February 24, 2019
Posts: 853
Location: South Boston, VA
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PostPosted: Sat Oct 16, 2021 4:51 am    Post subject: Re: Extremely Fluctuating Valve Clearance Reply with quote

For the sake of your sanity, take the motor apart, find the problems and repair it properly after a serious cleaning. Just saying
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