Intermittent sticking valve

Mark's 37

Mark's 37

Senior Member
My 37 221 V8 has what I think is an intermittent sticking valve. It drops a cylinder about every 4 or 5 seconds at idle. The vacuum gauge is otherwise steady but drops on the same frequency. Compression is good and uniform across all cylinders. This is a rebuilt engine with one piece guides, new valves, springs and adjustable lifters. Engine has about 4000 miles on it. Removed the intake and had a look, adjusted the valves which were not too far off. Nothing visually out of place. I think either a sticky valve/guide or a lifter hanging up intermittently. I am trying to determine which valve is the problem child. Any suggestions on how to find the offending valve?
 
Mark's 37 said:
My 37 221 V8 has what I think is an intermittent sticking valve. It drops a cylinder about every 4 or 5 seconds at idle. The vacuum gauge is otherwise steady but drops on the same frequency. Compression is good and uniform across all cylinders. This is a rebuilt engine with one piece guides, new valves, springs and adjustable lifters. Engine has about 4000 miles on it. Removed the intake and had a look, adjusted the valves which were not too far off. Nothing visually out of place. I think either a sticky valve/guide or a lifter hanging up intermittently. I am trying to determine which valve is the problem child. Any suggestions on how to find the offending valve?
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Hi Mark, can't help locating the "offender", but I can give you this: when we come across anyone in the beginning or the middle of a fresh build we tell them to install bronze-lined guides. I can all but guarantee you'll NEVER experience any "hung" valves anymore!

Thanks, Gary in N.Y.

P.S. Whether or not this is your issue the lined guides are really a must-have in the build regardless! We're literally still doing hundreds every year and have been for a very long time now, stainless valves and the bronze guides, never look back!
 

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^^^x2. Add a pint of MMO to the crankcase with 5W-20. And a pint to a full gas tank for good measure. Jack E/NJ
 
GOSFAST said:
Hi Mark, can't help locating the "offender", but I can give you this: when we come across anyone in the beginning or the middle of a fresh build we tell them to install bronze-lined guides. I can all but guarantee you'll NEVER experience any "hung" valves anymore!

Thanks, Gary in N.Y.

P.S. Whether or not this is your issue the lined guides are really a must-have in the build regardless! We're literally still doing hundreds every year and have been for a very long time now, stainless valves and the bronze guides, never look back!
Click to expand...

Thanks Gary,

This engine was machined and left unassembled by Don Canepa in Watsonville, Ca. years ago after he passed away. The guides (black) were from Mac's as I remember when I put it all together. Can I change the guides to yours using the existing valves?

Mark
 
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I started getting a little flutter on the vacuum gauge at idle about 3000 miles after the build. Ran some MMO through the intake and the problem cleared up. I now add 4 oz of MMO to each tank of gas and the problem has not come back at over 4000 miles.

I was a MMO skeptic and now am a true believer.
 
If you haven't done it already, I'd try the MMO treatment. Regarding the bronze-lined guides, I'd have installed them in my engines in a heartbeat if I had known about them when I built my last two engines. That being said, the only sticking valves I have ever encountered in a flathead V8 were two in a 41,000 mile '50 Ford that had been put in a garage in 1954 after a tree fell on it in a storm. I pulled it out in 1989, and got it running and it had two stuck exhaust valves. The improved guides will solve your problem for sure, but since it is a fresh assembled engine, try the MMO first. You have nothing to lose.
 
Ill fifth or sixth this.


MMO every spring here. I get it idling and pour it down the carb till it almost chokes out. Smokes up the garage some. Maybe some in the the tank too. New-ish rebuild, valves have settled in now.


Not sure about this totally, but.... fuel when these engines were made and up to the 70s had lead in it. Lead was used to lube the upper part of the engine (as my understanding). No lead in fuel today. So on a L head (valves in block) maybe it could use some help. Just a thought.



.
 
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You want to put in the bronze liners as well as a seal on the intake valves, our 33 just did a 2000 mile trip towing and used maybe 1/16 on the dipstick.
Lawrie
 
If you still need to find the cyl . Remove one plug wire at a time and run , if it's not that cyl it'll drop even more when the bad one acts up . Yes it's time consuming but it'll find it usually . It works best when the bad cyl acts up on a regular occurrence.
 
Tinker, yes bronze liners ,(Klines ) and a small seal on the inlet valve stem.
Easy job, good results
Lawrie
 
Ggmac said:
If you still need to find the cyl . Remove one plug wire at a time and run , if it's not that cyl it'll drop even more when the bad one acts up . Yes it's time consuming but it'll find it usually . It works best when the bad cyl acts up on a regular occurrence.
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To do the same test, I've taken a long stout screwdriver (with a good insulated handle) and placed it between the top of the plug and the head. This shorts the plug and the cylinder will drop out.

For those smarter than I am. Am I doing anything bad with this test?
 
^^ Ok if you have exposed plug connectors. If later type, fully covered plug caps, you wouldn't be able to do this.

If you do this, it is a good idea to touch the screwdriver to ground on the head before touching the exposed plug lead.

Mart.
 
Today I added MMO to the gas tank, 5 ounces, then changed the oil with 5-20 Mobil 1 with about a quart of MMO. Fired it up and let it warm up then poured about 3 ounces of MMO slowly down the carb. Still an irregular fluttering but not as pronounced. I tried to upload a video of the vacuum gauge with the engine idling but couldn't get it to load on this page. I am cautious about putting too much MMO into the carb because of worry about fouling the plugs. I drove it about 4 miles afterward. I will put a few more miles and see what happens. The symptoms changed somewhat as it is more fluttering with a small cylinder drop intermittently. Not right.
 
Looks lime that won't work, but I would let it go a little longer. Maybe it's a faulty valve spring?
 
Mark's 37 said:
I tried to upload a video of the vacuum gauge with the engine idling but couldn't get it to load on this page.
Click to expand...


IMHO I would imagine you would have to post the video to youtube or some hosting site like that and then just put the link in this thread? I think Ryan has file size restrictions on this forum? If you don't know how u can try to email me the file and Ill do it for you, I don't mind...Pm for email info.
 
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