Low Power: Stuck valves?

Al

Al

Member
I'm getting my A back on the road after about 2 years of storage with no use, had some fuel issues and have drained tank, cleaned lines, cleaned carb of all the junk.

She starts quickly now, but idles rough (and loud) and greatly reduced power when driving.

I'm thinking maybe some of the gunk founds it way to gum up a valve or two, does that reasoning seem sound? If so, how would I verify and fix?

Can I address and correct this through the valve cover or will the head have to be removed?

Or is there something else that's likely to be the cause?

Thanks
 
Al said:
I'm getting my A back on the road after about 2 years of storage with no use, had some fuel issues and have drained tank, cleaned lines, cleaned carb of all the junk.

She starts quickly now, but idles rough (and loud) and greatly reduced power when driving.

I'm thinking maybe some of the gunk founds it way to gum up a valve or two, does that reasoning seem sound? If so, how would I verify and fix?

Can I address and correct this through the valve cover or will the head have to be removed?

Or is there something else that's likely to be the cause?

Thanks
Click to expand...


Do a compression test, quick way to answer stuck valve question, and then a leak down test. Will tell you if you have valve issue, compression issue, or bad head gasket.


If valve issue perhaps remove the valve access cover, hand crank or starter with the ignition off, and observe the valves. Quickest way to an answer instead of shot gunning and trying possible remedies for stuck valves. Would also give you the opportunity to clean out the valve area, and possible gunked up oil passages.


Until you do some diagnostics you will not know if the head has to be pulled.


May want to drop the oil pan and clean it out, put in fresh oil.
 
Had the same problem recently. Compression was good. Sucked Marvel Mystery Oil through the vacuum wiper line and problem went away. Think one or more valves were sluggish rather than stuck. Might try the MMO before serious disassembly.
 
Same here !!! Marvel mystery oil through the vacume line is a good way to lubricate sticky valves . Four ounces of Marvel mystery oil to every ten gallons of gas is always a good thing . Removing the head should always be a last resort . The results of removing the model A head can end up with wrung off studs in the block . If a person hasn't ever had to remove a broken stud , it can end up having to remove the engine and take it to a machine shop .
 
Smell gas in tank and compare with new fresh gas from a name brand station if it smells funky get it out of the tank.

Cheap discount stations generally buy the gas that the fuel terminals are selling to purge their tanks to prepare for the summer season.

Choice of station is important as this is the time of year that they change from winter gas to summer gas and you do not want to get another load of winter gas that will vapor lock until you use it up.


Buy some fresh gas if gas in tank is more than 6 months old.

Drain tank and add fresh gas.

Old gas can gum up valves quickly.



Click here to read about gas change over ...

https://www.eia.gov/todayinenergy/detail.php?id=11031
 
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Purdy Swoft said:
Same here !!! Marvel mystery oil through the vacume line is a good way to lubricate sticky valves . Four ounces of Marvel mystery oil to every ten gallons of gas is always a good thing . Removing the head should always be a last resort . The results of removing the model A head can end up with wrung off studs in the block . If a person hasn't ever had to remove a broken stud , it can end up having to remove the engine and take it to a machine shop .
Click to expand...

Follow his advise. Sometime we assume the worst. Try the easy fixes first.

If it ran good two years ago, it will most likely do it again.

MMO in the gas. We use it every time gas is added. Enjoy.
 
If you have stuck valves it is much easier to remove intake / exhaust manifolds to get to valve guides than removing the head.

NOTE do not use WD40 for this ... as I have seen WD40 turn to a glue when heated above 400 degrees or so.
 
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I also agree with first trying MMO.


Recently, I had a Model A that had been sitting for many years and the new gas with ethanol had dissolved some varnish in the tank and coated the valve stems and they stuck.


The engine would hardly run at all. I removed the spark plugs and shot carb cleaner at the open valves. Was able to get enough valves freed up and the thing to run good enough that MMO thru the vacuum fitting on the intake and in the gas resolved the problem.


Do not start to take things apart until you try other easier remedies.


I am a very lazy mechanic and only take things apart as the last resort.


My opinion and experience,


Chris W.
 
+1 on MMO. Have about 250 miles on my new engine and it started making some noise and missing at idle. Didn't have any MMO but dumped about 6oz of 2-stroke oil in the gas and after a 10 minute drive it was silent and idling smoothly. Next tank of gas I forgot to add oil and the noise and idle miss came back. Must have some tight/sluggish valves.
 
I haven't had stuck valves since I started using MMO several years ago.
As mentioned, give it a try and do the easy things first.
Head removal is always the last resort.
 
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