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225...it dies!
https://slantsix.org/forum/viewtopic.php?t=63662		 Page 1 of 2
Author:  GregCon [ Sun May 26, 2019 7:00 am ]
Post subject:  225...it dies!
As a companion to my earlier thread of a few days ago...

The 225 was running great. I had about an hour of total run time on the engine, maybe a little more. I drove down the street a half mile, then turned around to go home when it started running very rough, as if a few spark plugs had exited the confines of their dwelling. I was pretty sure I had tightened them down, however. I rolled home, did some poking around, and ..... under the valve cover I noticed one of the fancy new pushrods (#6 Exhaust) was no longer where I had left it. Nor was the lifter.

I did some further checking, quite sure I had more or less tightened the rocker assembly as planned. Then I noticed the exhaust valve itself was still down, even though nothing was pushing it down. I pretty much knew what had happened by now.

After removing the cylinder head...sure enough, the valve was stuck open. I took off the spring and was able to tap it out with a mallet and could see the guide had run dry of oil which led to the usual galling of metal.

When I had discussed the head work with the machine shop, they recommended new silicone seals. I told them they 'could' use them but was just as happy with the stock umbrella seals...I didn't care if the engine used a little oil if it kept the guides lubricated. We agreed they would use the stock seals...but when I picked up the head I noticed they had used the silicone seals after all. I didn't complain, figuring I was being too fussy and that the seals they used would be OK. Well, they weren't! lol.

I haven't looked at the other valves but I am guessing the exhausts will all be in bad shape. My plan is to go back with new valves and stock seals....

Attachments:
No. 6 valve lr.jpg
No. 6 valve lr.jpg [ 115.51 KiB | Viewed 7468 times ]
#6 Ex valve seal.JPG
#6 Ex valve seal.JPG [ 151.54 KiB | Viewed 7469 times ]
Author:  Badvert65 [ Sun May 26, 2019 8:24 am ]
Post subject:  Re: 225...it dies!
I have used those type of seals on big block Mopars with no issues. I actually have those style valve seals on my race engine, but I haven't started it up and broken it in yet.
I would be curios to know the root cause of your issue.
Author:  Reed [ Sun May 26, 2019 8:51 am ]
Post subject:  Re: 225...it dies!
My brother had those style of seals installed on a slant head he ran on the street for a few hundred hard miles. No problems.

I would be interested to see if the rocker arm shaft was installed in the correct orientation. Pre 77 or 78 rocler arm shafts can be installed upside own with the rocker arm oiling holes pointe the wrong way. This leads to much less oil reaching the rocker arms and dribbling out onto the valves. I suppose it is possible that this caused oil starvation and the galling you have in the valve stem.

THIS THREAD, while not specifically about rocker arm shafts, does have some pictures and information explaining proper orientation of the rocker arm shaft oiling holes an why the shafts must be installed with the oiling holes oriented correctly.
Author:  GregCon [ Sun May 26, 2019 9:10 am ]
Post subject:  Re: 225...it dies!
The shaft is correct, and there was plenty of oil up top. On this engine, I had grooved the cam journal and ensured all the passages were 'wide open'. When I primed the engine, lots of oil was flowing on the rockers even with minimal pump RPM.

I've used these seals too, but (from memory) a V8 has a shorter guide. And I have only personally used them with bronze guides, not iron. All I can say is the seals fits so tightly that I don't see how any oil gets down the stem...it's like a wiper (spring loaded to boot) that will remove almost all oil from the stem.
Author:  Dart270 [ Sun May 26, 2019 1:54 pm ]
Post subject:  Re: 225...it dies!
I have used Teflon seals that looks like the ones you have and never had a problem. I would suspect they set the guide clearance too tight?

Lou
Author:  slantzilla [ Sun May 26, 2019 2:20 pm ]
Post subject:  Re: 225...it dies!
I personally don't like those seals, especially on the exhaust side. I tend to run no seals on the exhaust side and umbrellas on the intakes.
Author:  GregCon [ Sun May 26, 2019 7:19 pm ]
Post subject:  Re: 225...it dies!
I didn't measure the guide clearance...but it felt good and of course the machine shop said it was 'right'. The problem happened right where you'd expect - the bottom of the stem on the thrust side. It's easy to imagine the oil being less there, the load the highest, and the heat from the exhaust helping cook away the oil.

I didn't mention before but these guides are iron (not bronze) replacements that have the rifle groove running down them, which is meant to provide better oiling. Of course, if they don't get any oil it doesn't matter if the groove is there or not.

I guess my gut feel is what it always has been....the silicone seals are too effective and don't let enough oil by. I mean...they are wiping the stem very efficiently, especially when new.

I'll be interested to see what the other valves look like. I might pull them tomorrow if I get in the mood though I kinda prefer to let the machine shop do it so they can see for themselves.


In another vein, I used the Sealed Power head gasket, which is a modern Teflon type gasket that happens to be the identical part as offered by Fel Pro. I'm not overly impressed with the gasket. It clearly states 'do not use sealer' on it. In the lifter rail areas, I did use some silicone to prevent the usual rail leaking - and it was working flawlessly, dry as a bone. But on one of the water jackets, I could see that some water had oozed out and made its way between two cylinders and even gotten a little rusty. I doubt this would have caused any issues, but it's still not what you like to see.

Attachments:
head gasket.JPG
head gasket.JPG [ 88.22 KiB | Viewed 7394 times ]
Author:  Joshie225 [ Sun May 26, 2019 8:01 pm ]
Post subject:  Re: 225...it dies!
Positive seals are good on intake valves which are relatively cool and have vacuum to help draw in the oil. They do keep oil out of the combustion chamber. Good for a race engine. The exhaust sees little, if any, vacuum and runs hotter so it needs more lube. In this context is easy to see why exhaust umbrella seals are shorter than intake umbrella seals. My 1956 Dodge hemi wasn't built with valve stem seals on the exhaust side as the stems are essentially horizontal. Oil does not run down the stems and pool on the tops of the guides.

That valve needs to be replaced as the stem surface is rough and will tear up the guide.
Author:  GregCon [ Mon May 27, 2019 4:46 am ]
Post subject:  Re: 225...it dies!
Oh, trust me, it will get all new exh valves!

I'm kinda wondering how new guides, if needed, can be installed given the head already has had new guides installed.
Author:  Joshie225 [ Mon May 27, 2019 6:18 pm ]
Post subject:  Re: 225...it dies!
Quote:
Oh, trust me, it will get all new exh valves!

I'm kinda wondering how new guides, if needed, can be installed given the head already has had new guides installed.
They will drive the old ones out, new ones in and ream them to size.
Author:  Louise76 [ Tue May 28, 2019 3:33 pm ]
Post subject:  Re: 225...it dies!
What am I missing here? On piston aircraft engines, (granted: air cooled), the valves are located horizontally, and only the tip of the stem gets oil at the rocker arm. In fact, if oil gets between the valve neck and the guide, it cooks and cokes up the guide, causing severe valve sticking and engine failure. Those seals on the Slant valves appear to me to be installed to keep the oil out of the guide, same as my airplanes. Airplanes burn 100 LL, which is 100 octane "Low-Lead" fuel. The lead in the fuel is the ONLY thing lubricating the valves. No oil. Confirmed today by the Tech Support desk of a major aircraft engine manufacturer. Cylinder head temps run about 350* F to 420* F for hours of cruise power at 65% to 75% rated power. I wazz told that when automotive went to unleaded fuel, the valves needed to be made out of a different (harder) material due to almost NO lubrication: hence the "peanut head" Slants in 1975. (liquid cooled). You engine builders- your thoughts??
Author:  GregCon [ Tue May 28, 2019 3:39 pm ]
Post subject:  Re: 225...it dies!
I won't comment on the whole airplane stuff other than to say it has its own nuances.

It's interesting you mention exhaust temps around 400F. On this engine, while I was letting it run for other reasons, I took a bunch of readings with my infrared gun and the exhaust manifold was running right around 400F at each port. That, of course, is idling.

The bottom line...as I see it...is valve stems need oil if they're gonna last. I'd rather burn a little oil (a little) than have issues related to not enough oil.
Author:  Louise76 [ Tue May 28, 2019 4:12 pm ]
Post subject:  Re: 225...it dies!
Cylinder head temps in cruise around 400*F. Exhaust temps at idle around 400*F, and 1100*F to 1400*F in cruise.
Author:  Reed [ Tue May 28, 2019 6:56 pm ]
Post subject:  Re: 225...it dies!
Quote:
What am I missing here? On piston aircraft engines, (granted: air cooled), the valves are located horizontally, and only the tip of the stem gets oil at the rocker arm. In fact, if oil gets between the valve neck and the guide, it cooks and cokes up the guide, causing severe valve sticking and engine failure. Those seals on the Slant valves appear to me to be installed to keep the oil out of the guide, same as my airplanes. Airplanes burn 100 LL, which is 100 octane "Low-Lead" fuel. The lead in the fuel is the ONLY thing lubricating the valves. No oil. Confirmed today by the Tech Support desk of a major aircraft engine manufacturer. Cylinder head temps run about 350* F to 420* F for hours of cruise power at 65% to 75% rated power. I wazz told that when automotive went to unleaded fuel, the valves needed to be made out of a different (harder) material due to almost NO lubrication: hence the "peanut head" Slants in 1975. (liquid cooled). You engine builders- your thoughts??
What material are airplane engine valves and valve guides made of? THe same materials as used in slant sixes?
Author:  Louise76 [ Tue May 28, 2019 7:54 pm ]
Post subject:  Re: 225...it dies!
I doubt it. I used to know, but would now need to research that. Some are sodium filled. The cheap ones start at around $100.00 each.
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