Hmm, this is odd

[JayJay]

Last week I pulled the cylinder head on my '31 to replace the head gasket. Broke a stud (discusssion on that last week) but that got resolved. Got the head back on, started up, sounded funny. Like it wasn't running on all the cylinders at idle. Hmm.

Pulled the plugs. #1 and #2 look fine. #3 was wet. #4 was OK. Hmm.

Did a compression test. Prior to the head gasket replacement I had good compression - low 90s on #1, mid 80s on #2, 3, and 4. After the head gasket replacement I had the same on #1, 2 and 4, but ZERO on #3. Hmm.

During the compression test I could hear chuffing coming out the carb when #3 had the spark plug hole blocked by the compression tester. I confirmed that I could feel it, also.

So I figured I had a stuck #3 intake valve. How that would have happened I don't know. Pulled the head again, and the valve seems to be working fine. So I figured maybe during the cleaning of the top of the block to get a good surface for the new gasket I got a bit of crud into the #3 intake seat (I used a scraper followed up by a small ScotchBrite wheel on my angle die grinder). I could not see anything obvious, and a towel didn't turn up anything. Hmm.

So my plan at this point (which I'd love for you folks to shoot holes in) is to remove the #3 intake valve and inspect it and the seat. If they look OK I thought I'd Dykem or lap it to assure it's making full contact. Based upon the excellent compression readings I'm loathe to pull any more valves, except that I might get ambitious and install some adjustable lifters since I don't think there are any in there now.

Any thoughts or comments? Thanks.

JayJay

[johnneilson]

IMHO, you have half of the troubleshooting done, now pinpoint it.
if you have access to a leakdown unit, test #3 for the cause or the culprit.
if you do not have one, just get an adaptor for the sparkplug and put some air pressure on it, doesn't need much #30 will show you where it is leaking.

and yes, it sounds like the intake, but you might find another issue that can be resolved at the same time.

J

[Y-Blockhead]

Ya'll didn't pry off the head by sticking wedges in there, did ya? Maybe you bent a valve. Easy to do.

Installing adjustable lifters is quite the job since you have to pull the cam...

[JayJay]

Originally Posted by johnneilson

IMHO, you have half of the troubleshooting done, now pinpoint it.
if you have access to a leakdown unit, test #3 for the cause or the culprit.
if you do not have one, just get an adaptor for the sparkplug and put some air pressure on it, doesn't need much #30 will show you where it is leaking.

and yes, it sounds like the intake, but you might find another issue that can be resolved at the same time.

J

I do have a leakdown unit but didn't think to use it before I pulled the head. Shows what tunnel vision will do for you. Dang. Thanks for reminding me to take it a bit slower next time.

[JayJay]

Originally Posted by Y-Blockhead

Ya'll didn't pry off the head by sticking wedges in there, did ya? Maybe you bent a valve. Easy to do.

Installing adjustable lifters is quite the job since you have to pull the cam...

No, I didn't use wedges. When I do have to rely upon wedges I only use them across the corners, preferably on the piston side, and avoid the valve area. I'll certainly check for a bent valve but I can't think how that would have happened.

Oh - lifters come in from the cam side, not through the oil galley? I guess if I'd looked at what the lifter looks like that would have been obvious. Doh. I plan to pull the engine sometime this winter and do a complete reseal, that would be the time to pull the camshaft and install the adjustable lifters.

[Benson]

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Originally Posted by JayJay

Last week I pulled the cylinder head on my '31 to replace the head gasket. Broke a stud (discusssion on that last week) but that got resolved. Got the head back on, started up, sounded funny. Like it wasn't running on all the cylinders at idle. Hmm.

Pulled the plugs. #1 and #2 look fine. #3 was wet. #4 was OK. Hmm.

Did a compression test. Prior to the head gasket replacement I had good compression - low 90s on #1, mid 80s on #2, 3, and 4. After the head gasket replacement I had the same on #1, 2 and 4, but ZERO on #3. Hmm.

During the compression test I could hear chuffing coming out the carb when #3 had the spark plug hole blocked by the compression tester. I confirmed that I could feel it, also.

So I figured I had a stuck #3 intake valve. How that would have happened I don't know. Pulled the head again, and the valve seems to be working fine. So I figured maybe during the cleaning of the top of the block to get a good surface for the new gasket I got a bit of crud into the #3 intake seat (I used a scraper followed up by a small ScotchBrite wheel on my angle die grinder). I could not see anything obvious, and a towel didn't turn up anything. Hmm.

So my plan at this point (which I'd love for you folks to shoot holes in) is to remove the #3 intake valve and inspect it and the seat. If they look OK I thought I'd Dykem or lap it to assure it's making full contact. Based upon the excellent compression readings I'm loathe to pull any more valves, except that I might get ambitious and install some adjustable lifters since I don't think there are any in there now.

Any thoughts or comments? Thanks.

JayJay

I believe problem is with #3 Exhaust valve


Since # 3 and #4 use the same intake port ... If it was an intake seems to me that the noise would also be in (port # 3 AND port # 4 )not just # 3?

Aint't so? ,,,, Or maybe they were smoking POT again in the last TENT I visited!

Contact high don't ya know?


Updates are in Blue text ...

[Benson]

I would be looking for a tight valve clearance on Number #3 exhaust valve.

Especially if this is a Model B camshaft.

Which might have been the problem that led to the replacement of the head gasket.

[JayJay]

Originally Posted by Benson

I believe problem is with #3 Exhaust valve


Since # 3 and #4 use the same intake port ... If it was an intake seems to me that the noise would also be in port # 4 not just # 3?

Aint't so? ,,,, Or maybe they were smoking POT again in the last TENT I visted!

Contact high don't ya know?


Updates are in Blue text ...

Good thoughts, Benson, and thanks. Could be I wasn't clear in my description. #3 is the only cylinder affected, it's blowing its compression stroke somewhere. And I believe I heard and felt it coming back through the carburetor, which would indicate an intake valve. Yes, I suppose if I had been looking for it I would have heard the noise in #4 since #4 is on its intake stroke when #3 is on compression, and that would mean both intake valves were open at the same time. But, if it was the exhaust valve I don't think I would have felt the "puff" coming out the carburetor. I'll check the exhaust valve as well. (Wish I'd used the leakdown kit, that would have nailed it down!)


I'll check clearances on all the valves. I have no idea what the camshaft is. The engine is 0.080" overbore, there's one head stud helicoil, and there have been valve seat inserts installed. I suspect it's been rebuilt at least a couple of times.

[Benson]

The reason that I brought up camshaft is that the ORIGINAL UN REGROUND Model B camshaft used different lifters and valve clearances are about .015 and 0.022.

Note engine damage will result if you mix / match the wrong lifters,
(UNREGROUND) camshafts and clearances between A and B engines.


Model B Lifters are longer (0.030) AND have a larger diameter (0.070) heel.

These clearances do not apply to a reground camshaft using an original Model B camshaft as a core!

In that case you must use the cam re-grinders clearances.

As a result people see the exhaust clearances at .022 and reset them to .015!

Result is leaky valves when engine gets very hot and eventually burned exhaust valves.

[Y-Blockhead]

Didn't you say the engine was running previously and you replaced the head gasket? I don't see how the valve clearance changed just by changing out a head gasket.

Did I miss something?

[JayJay]

Originally Posted by Y-Blockhead

Didn't you say the engine was running previously and you replaced the head gasket? I don't see how the valve clearance changed just by changing out a head gasket.

Did I miss something?

Nope, you are correct. I just figured as long as I was in the oil galley I'd document what the clearances are. I can't see any valve involvement in changing the head gasket, that's what has me a bit perplexed. Like I mentioned, I was around the tops of the valves cleaning off the block surface, but other than that, no valve involvement.

[Benson]

My point is / was that maybe the exhaust valve was too tight before the gasket was replaced and that is what caused the problem that the gasket was supposed to fix that is low compression on #3.

Sorry I missed the part in post one about the compression before gasket replacement

"low 90s on #1, mid 80s on #2, 3, and 4."

[jack backer]

When I was with Caterpillar they stopped us from using scotch brite discs on die grinders for cleaning heads and decks, they cited metal loss as their reason. Roloc bristle disc were mandated, and work well.

[nkaminar]

As others have mentioned, check the valve clearances first. After that you can use kerosene or even water to see if the valve is leaking. Pour a teaspoon amount around the valve seat and see if it seeps into the intake or exhaust ports on the engine. (You have to have the manifolds off.) If you have a leak, you can do a quick valve grind. You will be looking for a uniform pattern on the valve face and seat.

It is possible that the valves are sticking when running and not when the engine is stopped for your inspection. The sticking can be a sluggish valve. People have had success using MMO to free up valves either by squirting it down the valve stem or in the fuel or oil or all three.

[JayJay]

Originally Posted by nkaminar

As others have mentioned, check the valve clearances first. After that you can use kerosene or even water to see if the valve is leaking. Pour a teaspoon amount around the valve seat and see if it seeps into the intake or exhaust ports on the engine. (You have to have the manifolds off.) If you have a leak, you can do a quick valve grind. You will be looking for a uniform pattern on the valve face and seat.

It is possible that the valves are sticking when running and not when the engine is stopped for your inspection. The sticking can be a sluggish valve. People have had success using MMO to free up valves either by squirting it down the valve stem or in the fuel or oil or all three.

Thanks, I had that thought of intermittent sticking valves as well. I'm going to pull the #3 valves and inspect them anyhow so I'll clean up the stems while I'm at it.

[JayJay]

Originally Posted by jack backer

When I was with Caterpillar they stopped us from using scotch brite discs on die grinders for cleaning heads and decks, they cited metal loss as their reason. Roloc bristle disc were mandated, and work well.

Good to know for the future, thanks.

[JayJay]

Well, I'm going to close this one out. Y-B wins the prize - #3 intake valve is visibly bent (you can see it when you rotate it around in its port), and its clearance was about twice the clearance of the other three intake valves. Plus, once I got the spring keeper off, it was sticky in the valve guide towards the bottom of its travel.

Now, how a valve gets bent during a head gasket change I don't know. But I'll get a new one, a new guide, and install next week after I get back from visiting the grandkids this weekend.

I'm going to start another thread on valve clearances, and I'd appreciate all your input on that one too.

Thanks for everyone who contributed here.

JayJay

[kenny1930]

Valve Bent, When I remove heads I like to put a stud in the spark plug hole #1 and #4. I also look to see if any valves are up in these cylinders. The reason is that the stud could rest on the edge of the valve and bend the shaft. This method of removing the head has risk, so pay attention. Have Fun!

[bobbader]

Kenny, Please go further in your explanation of putting studs in #1 & 4 spark plug holes. This means what? Studs that have the same thread size as the spark plugs so they will push the head off by exerting pressure against the block surface in the valve chambers of these 2 cylinders???? Not understanding the process you're suggesting. Thanks

[JayJay]

Originally Posted by kenny1930

Valve Bent, When I remove heads I like to put a stud in the spark plug hole #1 and #4. I also look to see if any valves are up in these cylinders. The reason is that the stud could rest on the edge of the valve and bend the shaft. This method of removing the head has risk, so pay attention. Have Fun!

Good point. In fact, I use the adapter rings in holes #1 and #4 to lift the head, and I bent #3 intake. So no involvement. Still trying to figure out how that happened.