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Old 10-25-2019, 12:16 PM   #1
djuby1
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Default Number 8 Exhaust Valve sticking

This summer the the No. 8 exhaust valve started sticking while going down the road on several tours this past summer. The problem is intermittent but seems to be happening more each time and stays stuck longer. I use Marvel oil additive in the gas and I use zero ethanol gas. Several buddies have suggested spraying a lacquer remover into the No 4 cylinder to remove the varnish on the exhaust valve. Has anybody had this issue and what was your remedy for the sticking valve?
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Old 10-25-2019, 12:24 PM   #2
ryanheacox
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Default Re: Number 8 Exhaust Valve sticking

Lacquer thinner is great at dissolving stuff so might be worth a shot. Definitely worth trying that before taking stuff apart. MMO usually seems to do the trick for most people but maybe you have more varnish than most. Whats the history on the engine?



I've only ever had issues with valves sticking on engines that hadn't run in a long time. Exercising the valves with WD-40 always freed them up.
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Old 10-25-2019, 12:31 PM   #3
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Default Re: Number 8 Exhaust Valve sticking

I only have four exhaust valves in my model a ?
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Old 10-25-2019, 12:33 PM   #4
J Franklin
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Default Re: Number 8 Exhaust Valve sticking

You might also have a weak or broken spring.
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Old 10-25-2019, 12:34 PM   #5
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Default Re: Number 8 Exhaust Valve sticking

Time for some Bardahl..."Frees sticky valves"!
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Old 10-25-2019, 01:23 PM   #6
Werner
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Default Re: Number 8 Exhaust Valve sticking

Hallo Djuby,

do you know "Valve Clean" from Liqui Moly? I recommend trying this.

Note: MMO max. 3 ounces per 10 gal.
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Old 10-25-2019, 01:23 PM   #7
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Default Re: Number 8 Exhaust Valve sticking

start the moto put some Rislone (oil additive to clean sludge etc)in intake at high revs let carb suck it in until it kills engine let it sit for 15 min..try it again. works on intake valves...in your case remove #4 plugs pour some this stuff in plug hole with ign off crank moto and let it sit for a while..
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Old 10-25-2019, 02:00 PM   #8
Patrick L.
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Default Re: Number 8 Exhaust Valve sticking

About the only good thing I can say about WD40 is that it has worked good for sticky valves. Thru the plug hole it can be sprayed at the valves, [not just in the hole]. I remove the side cover and spray the stem. Turn the engine over to make sure its unstuck. I also think mixing ATF with the fuel helps keep them free.
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Old 10-25-2019, 02:12 PM   #9
Dick M
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Default Re: Number 8 Exhaust Valve sticking

HHHUUUUMMMMMMMMMMMM!!!
I thought everyone knew that a Model A engine has 8 valves and number 8 valve is an exhaust valve. Guess I was wrong....
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Old 10-25-2019, 02:29 PM   #10
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Default Re: Number 8 Exhaust Valve sticking

ive allways added a bit of 2 cycle oil to the fuel to help a sticky one
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Old 10-25-2019, 04:12 PM   #11
Werner
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Default Re: Number 8 Exhaust Valve sticking

Incidentally, this is a disadvantage of unleaded gasoline. Each outlet valve shaft moves in the so-called "mixed friction area". The lubrication of these valve guides allows only lead, no oil survives these extreme temperatures!
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Old 10-25-2019, 05:00 PM   #12
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Default Re: Number 8 Exhaust Valve sticking

or instead of using snake oil you actually pull the head and valve cover,find the root cause and save yourself potentially huge issues from a broken spring or a broken guide..
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Old 10-25-2019, 05:48 PM   #13
Magicbox51
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Default Re: Number 8 Exhaust Valve sticking

How does one narrow it down to a particular valve that is sticking? Diagnostic equipment?
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Old 10-25-2019, 05:56 PM   #14
Purdy Swoft
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Default Re: Number 8 Exhaust Valve sticking

The main reason that I avoid removing the head is the risk of broken head studs

A quick and easy way to get snake oil of choice to the valves is through the vacume line with the engine running .

I disconnect the vacume line from the firewall .

I either bend the original vacume line for the procedure or make up another vacume line so I don't have to bend the original .

With the engine running .

Connect one of the vacume line to the vacume port on the intake manifold .

Stick the other end of the vacume line in the bottle of the snake oil .

The vacume of the engine will pull the snake oil right in to the valves and stems.

Sometimes valves are so tightly stuck that more drastic action is necessary.

I have in some cases removed the valve spring on the stuck open valve .

I then break out the vise grips with the round gripping area.

Sometimes I remove the manifolds so that I can spray penetrant on the valve stem above the guide through the intake or exhaust port .

I then carefully grip the mushroom end of the valve stem with the vice grips .

No need to grip the valve stem with enough pressure to scar up the mushroom . It WON'T be stuck tight enough to require that much pressure .

Move the vice grips left and right while spraying penetrant on the upper and lower valve stem .

Pretty soon the stuck valve will loosen up enough That you can remove the vice grips.

I then reach in with my hand and continue to turn and push the valve up and down until the valve moves to my satisfaction .

I then reinstall the valve spring and side cover .

If it works out , the valve will be unstuck without removing the head

There is no risk of the HORROR of a broken head stud .
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Old 10-25-2019, 06:21 PM   #15
Synchro909
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Default Re: Number 8 Exhaust Valve sticking

Quote:
Originally Posted by Dick M View Post
HHHUUUUMMMMMMMMMMMM!!!
I thought everyone knew that a Model A engine has 8 valves and number 8 valve is an exhaust valve. Guess I was wrong....
All we have here is a poor choice of words.The heading of this thread "Number 8 Exhaust Valve sticking" implies that the sticky valve is the exhaust valve for cylinder #8.
Let's not get 'em in a tangle over it.
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Old 10-25-2019, 06:33 PM   #16
Patrick L.
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Default Re: Number 8 Exhaust Valve sticking

Quote:
Originally Posted by Magicbox51 View Post
How does one narrow it down to a particular valve that is sticking? Diagnostic equipment?
Air, leak test
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Old 10-25-2019, 06:34 PM   #17
Patrick L.
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Default Re: Number 8 Exhaust Valve sticking

Exhaust valve in cylinder #4 I believe is called valve #8.
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Old 10-26-2019, 06:42 AM   #18
Tom Wesenberg
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Default Re: Number 8 Exhaust Valve sticking

A can of Sea Foam in the oil, and another in the gas should fix it.
Just a can in the oil fixed a long time stuck hydraulic lifter in an Olds in less than 5 miles driving.
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Old 10-26-2019, 09:33 AM   #19
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Default Re: Number 8 Exhaust Valve sticking

Not arguing Purdy,just don't understand..the horror of a broken head stud is worse than the horror of a broken valve guide?. I'd be as happy as a clam if a chemical fixed the problem but an assumption is made that the valve is sticking.Assumptions can lead to expensive lessons,finding the root cause of the issue negates assumption.
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Old 10-26-2019, 10:02 AM   #20
Purdy Swoft
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Default Re: Number 8 Exhaust Valve sticking

Because the broken stud must be removed without causing damage to the cast iron threads in the block

. The valve guide is held in place by the valve spring .

With the valve spring removed , the guide is easier for me to remove than a broken stud .

.Sometimes the head has to be removed , no matter what .

I just try to avoid removing the head unless it is absolutely necessary .

I'm not trying to be a smartazz .

I have seen that Railcaarmover knows his stuff .

This is just my preferred method and why .

Last edited by Purdy Swoft; 10-26-2019 at 01:13 PM.
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