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Good morning guys, been forever since I posted a new topic but this one's got me stumped. Last winter I built up a 265 Spitfire engine for my B4b, used an edgy cam, shaved head, and heavy truck manifolds for now. Ran like a Swiss watch. I parked it in fall just before the snow started but usually light it up every month or so. I've noticed that when I start it, #1 exhaust valve keeps hanging open, usually it will come free on it's own accord once it warms up but this time no dice. Had to pry it back down with a screwdriver, and it stuck again immediately. Even tried running it and being the valve spring. Darn thing just sticks up, and makes it sound like a messed up Harley! Has anyone seen something like this before? 

 

Josh

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I've found it to be something of a weak point on the flatheads. Valve stem lubrication is not the best aspect of these motors. Especially on a new rebuild with tight tolerances, cold, damp weather, and hung valves are fairly common.

Generally, after a few hours in service, this will stop happening.

Suggestion for now is to get lots of lubrication down the valve stem, removing the head if necessary, so that the stem is not sticking. Check to make sure the spring is not broken.

Add an oil additive such as CamGuard which will leave a nice film on the moving parts. You may want to play with oil viscosities a bit to see if that will help.

 

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New engine with tight stem clearance. sticky valve..worse in a unheated garage.

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Agree with all the other posts.  The exh guides have a recess in top of the guide.  The main purpose of that recess is to retain what little oil splashed into the valve area to lube the exhaust.  Intakes have that recess down to prevent that very thing. 

 

I think you can reach the valve stem with an oil squirt from an aerosol can with the little tube extension. With the spark plug removed and the exh valve open.  Probably not important what type of oil you use,  just soak it well before storage.  And, add one of the magic gas additives to aid valve lube to the gas.  Marvel Mystery oil is one, or ATF works for me.  That should help until you get enough miles on it to free things up.

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The exhaust guide counterbore is up to protect the valve stem from carbon build up and also to help prevent exhaust valves from sticking.

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Give it a shot of Marvel Mystery oil down the carb, and run some in the gas.   We've had to do that for years with our flattys-they sit too much. 

 

Edited by MBFowler

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100% agree...Marvel Mystery was what brought my rebuild back to life as well. I had all new guides/valves, pistons and rings and after the truck sat for a year during some body and interior modifications, I lost almost all my compression...I let it soak for a few days with MM, then ran some down the carb, in the fuel and in the oil...no more issues and back to 120-130 psi hot on all cyl’s.

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I've seen these stuck so bad that they've pushed the valve guide up out of its original position.  Still have that engine-truck sat for years outside, but it ran great when it was parked!  I bought a 46 2 ton dump a few yrs back.  Got a deal on it because it was running on only 5 cyls.   When they delivered it he started it on the trailer, I choked it off on MMO and a short time later I heard it clunk.   Started it back up-hitting on all 6.   Sometimes you get lucky, and sometimes the bear bites you.

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Yes, Marvel Mystery oil is good.  I've used it in the gas for top cylinder lubrication.  Even poured some down the spark plug holes and the carburetor.

 

For long term storage, I use a can of fogging oil. 

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This is the best topic I seen on the flatly had the same problem. I’m going to try Kroy  oil

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I had this same problem the first few years after I got my truck together. It always seemed to rain a lot between uses and every time I'd try to start it up it would crank funny and be very hard to start. I quickly realized that sticky valves was the problem. Once I would finally get it to start it would run rough for several minutes then gradually smooth out. I tried adding MMO to the gas, when I'd remember. I can't say if that really helped or not. I have not experienced that anymore in the past few years, so maybe it had something to do with it. Or things are just wearing in now.

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Thanks for the thoughts guys, I was kinda figuring it had to do with getting damp and probably rusting up the stem. I'll have to try the marvel mystery oil, or I've got some outboard fogging oil in the garage. The big pain in the rear is that it's the exhaust valve, so it just keeps blowing back through the intake! Funny how that works...

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I put about 4oz of MMO in my gas tank every other time I fill up. It really helps with the fuels we have these days. We have a winter fuel formula here in SoCal that makes for harder starting if I forget to dose it with MMO. My daily driver has a 230 that I revived rather than doing a full rebuild. I change the oil about every 2000 miles and use MMO in the fuel. Over 20k miles and it does not smoke or let me down ever.

Jeff

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4 hours ago, 41/53dodges said:

Thanks for the thoughts guys, I was kinda figuring it had to do with getting damp and probably rusting up the stem. I'll have to try the marvel mystery oil, or I've got some outboard fogging oil in the garage. The big pain in the rear is that it's the exhaust valve, so it just keeps blowing back through the intake! Funny how that works...

Odd that the sticking open exhaust valve causes " blowing back through the intake!":blink:

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Nope, already popped the side cover off to check! That was my first thought as well. Best I can figure, the exhaust charge from the other cylinders pressurizes the one with the stuck exhaust valve through the whole cycle, including intake. It seems to blow back and pollute the charge for #2 as well, because that cylinder goes down at the same time but maintains spark and compression.

Wierd eh?

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If that's the case you have some pretty high exhaust back pressure that needs to be addressed. Maybe its because the heat riser flap is vertical? #1 exhaust valve is the first valve from the front of the block.

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Heat riser flap was staked in the open position, since the spring was gone. Trucks got 2.5 ton school bus manifolds, so 2.5" straight back exhaust and a glasspack. But that does make me wonder if a mouse might have climbed up in there and built a home...

Thing doesn't sound constricted when it runs on all 6, but definitely food for thought... 

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They're not a whole lot different from standard truck manifolds, but the intake is a tiny bit bigger and the exhaust is a huge 2.5" 4 bolt dump. Would be very good for a turbo... Here's a picture from when I finished the motor 

IMG_20190315_065038.jpg

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I got the same manifolds on my 251 in my power wagon.  I've got an industrial 251 in my truck though. Yours has the heat riser valve, mine does not.  I'm thinking of modifying it as it would help in winter startup and driving.   

 

I also need to drill a couple of extra holes in the intake manifold for the windshield wipers and brake booster

Edited by thisoldtruck

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Nice looking engine.

Yep... all the 1-1/2 ton up use the 4 bolt 2-1/2"  exhaust manifolds for better breathing...the intake is basically a car intake..🙂

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Pretty much! I think I measured like a whopping 1/32 difference in the intake bore. Which I why I've got an Ellis intake on hand, whenever I find all the stuff to get it together. 

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1 hour ago, 41/53dodges said:

Pretty much! I think I measured like a whopping 1/32 difference in the intake bore. Which I why I've got an Ellis intake on hand, whenever I find all the stuff to get it together. 

That 1/32" is probably all it takes to turn one of these engines into a roaring beast........😂 There has to be times when we all dream of just a few more ponies. I have a few steep hills on my commute where I thin even one more would help

Jeff

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