TOPIC: In-line inner water jacket exhaust baffle plate

Hi all,
Thought I'd share my experience/findings on a recent failure. First I start with a new plate and decked surface on the block I use only merc gaskets and the specified epoxy. I run a water pressure gauge and verify all is well before during and after a WOT run. I have several inline 6's from 57 up to 76. The two 1500's I run with this cover is a 74 on a 74 Hydrostream and a 76 xs on A 69 Switzercraft. I run them at WOT a lot for bursts of a few minutes at a time. Both of these have suffered an inner plate leak after meticulous assembly. It took a few seasons to happen. This past summer the 74 1500 failed. Upon disassembly the gasket was nearly intact, that is, it did not tear to pieceswhen the plate was removed from the block, so I got an unusually good look at the failure. The gasket actually burns near the ports, eventually to the point it ruptures at a thin spot and water leaks. You could see burned areas that had not gone through but would have soon. I need to stress this is NOT an overheat issue internals where perfect, my water pressure was solid and the Pistons would show lots of scuffingbetc. If cooling failed. II caught the failure ASAP as power dropped suddenly, (water suddenly squirting through) I shut down till diagnosis was done.
So my humble opinion is that the very hot exhaust gas hitting the deflectors on the baffle get it extremely hot, thus actually searing the gasket into a brittle cracking mess. This all exacerbated by my WOT fun. The baffle is not really in contact with the block, it is insulated thermally by the gasket so it's only a minimum of cooling water in contact with the backside to regulate the temps in the port area. Very little heat can actually transfer to the mass of the block from the hot baffle plate through the area of contact. The gasket just gets grilled like a panini on a hot plate.
If you look at the water flow in an in-line it goes to the outer exhaust jacket first, then from there it flows into the cylinder area and the space under the inner waterjacket cover. Under this inner cover one notices that the water does a serpentine flow passing by the ports last before being ejected. The water, by the time it gets to the port area has already absorbed quite a bit of heat so it's not cold water its hot water cooling at that point.
Normally I'd say the temps of the plate are not to extreme but prolonged WOT runs basically results in hot flames roasting that plate and the gasket eventually gives up the ghost. This process is probably happening on all of these just a lot slower when use is mostly at lower throttle.
I have conversed with some knowlegable people and an interesting thought was these gaskets might have been originally asbestos based and burning would not happen ( in these instances gasket failure probably was due to lack of cooling water/ impeller issues) now that asbestos is a no-no the gaskets are not as robust and Merc gave up development/ interest in these motors a long time ago to investigate a better material of today.
This all seems reasonable to me....but what to do? Make a better gasket? Or possibly use a high temp sealer and no gasket? It seems to me when properly done this is a perfect metal to metal with high temp sealer situation. Better heat transfer to block and no gasket to burn. Sealer is only holding against 10 or 15 psi water. The block and the deflector are both aluminum and will expand and contract together over temps do joint would not halve to take up relative movement. Hey I'm a Mechanical a Engineer and deal with this type stuff all the time.
Any thoughts out there? I am searching sealers now and came across Hylomar which looks like it was designed for such situations...any other ideas?
Randy

Good read. great possibility.

Randy,
I will be very interested in what you find if you select to use no gasket. I have also found the .030" light gray gaskets shattered and consequently leaking resulting in a piston melt.
I have been considering trying a thicker (.075")asbestos base gasket material I have located, but I have yet to proceed with this experiment.
I have recently been using the 'latest' gasket from Merc that has the dark tacky coating that I'm hoping will have better resistance to shuffling and heat variances in the tall L-6.
27-72142-1.
These assemblies have not withstood the test of time at WOT, etc yet.
Please keep me posted on any discoveries Randy,
Thom

Gents I struggled with this gasket on my inlines too. I personally think that the inner plate warps and pulls away from the diverter plate. Its a long plate subject to temp differences. I had reasonable luck with these gaskets but water intrusion continued to plague this engine . The really frustrating thing was there were times that the intrusion actually acted like a tuned pipe and the engine would gain 500 to 600 rpm at the top end. I would be in favor of no gasket with the appropriate sealant.

I was looking at the motor can you make a thicker plate. Harley Davidson uses a gasket with a printed o ring seal between the rocker box and head that lets the two metals expand at different rates and withstands the heat. If you could make a thicker plate incorporate a o ring in the plate that way you could have metal to metal for heat transfer

Keep ideas and comments flowing....yoooohoooo Conrad (milk dud) where are you....?

charles wrote:

I was looking at the motor can you make a thicker plate. Harley Davidson uses a gasket with a printed o ring seal between the rocker box and head that lets the two metals expand at different rates and withstands the heat. If you could make a thicker plate incorporate a o ring in the plate that way you could have metal to metal for heat transfer

Worked HD motors decades and diff expansion rates always been a problem scrubbing gaskets to death. We used Permatex Hi Temp red gasket sealer the crankcase 1/2's. But this new stuff might be a workable sealer with no gasket. A copper gasket might be a better app here (heat transfer) but you would probably have to make one..heck, you guys know more than I do.

Anyway the new stuff..

I would be reluctant to use anything copper between two aluminum plates, the galvanic action would be problematic. If I was using a sealant style gasket I would use the high temperature sealant used in natural gas appliances. High temp and no galvanic.

the product that I used for metal to metal was a yamabond sold by Yamaha there is another product that is very similar that I used but can't remember the name worked in Harley shops for over 30 years been over 15 years since I worked in one Thom I lived in your area in the early 70's worked for the Oly hd and worked for Masoth automotive machine shop
Charles

I try Indian Head Gasket Sealer. it was used for head gaskets back in the day. might do a better job . I use it for sealing crankcases.

Here is a link to a product Master Ed Mc suggested, but has not tried.
It looks very interesting to me.
www.copaltite.com/sealants/liquid-form-sealant/copaltite-liquid-form-5-oz-tube.html
Has anyone had any experience with this product??
doc

Seems like a workable product Doc, but wow, its PRICEY!

Thom, I would say Master Ed has nailed this one. Cures at 300 degrees and runs up to 1500 degrees, withstands high pressure steam and chemicals. PERFECT. Yup the tube is pricey but if you can spend 64 bucks once and not have to tear an engine back apart again then its money well spent.

As I was scouring the bowels of the Interwebs for something suitable, I found a good discussion on the surface finish requirements for something like this, vs. what you'd need for a gasket.

They were saying that if you went metal-on-metal without a gasket, you'd have to have a very fine finish on both surfaces. Such that you'd probably need to have the block skimmed-cut flat (Thom does this anyway and my old machinist did the same for Many Moons before he went to the Big Machine Shop in the Sky).

Then you'd have to work over the water jacket cover as well.

I don't really see any barriers to doing it this way, then sealing with something like Copaltite. It really is Da Schizz!

If you wanted to use a gasket, you need a rougher surface so the gasket can't "walk" between the block and cover. Maybe that's part of the problem with gaskets being spit out; too smooth. The metal surfaces don't "bite" into the gasket.

Plus I'd imagine the Hi-Temp RTV used in the past might be a wee bit slippery; you know how that silicone is between the fingers, slick!

I have used Loctite 518 anaerobic gasket dressing in the past, and never had a failure with that. But, haven't ever had one run at WOT for long periods, which certainly would require a very stout gasket, super-sealer, or both.

I would venture that a either a metal-to-metal joint, or a thicker, more durable gasket (asbestos or something like Mr. Gasket header material), sealed with Copaltite, would be pretty much bulletproof.

Now we just need someone to experiment, eh?

Cheers...........ed

The cure would be difficult, I found a similar material needing no high temp cure but for a similar application and withstands up to 250C which is over 500 F

hylomar.com/hylo-wp/wp-content/uploads/2013/10/Hylomar_Aerograde_TDS_issue_8.pdf


Sorry not sure how to hyperlink it, but you can copy and paste
I'm the guy to do the experiment! I am also looking into a high temp gasket, if I make the print of the gasket, which I can do, II found a place that will water jet cut high temp material of my choosing, there are very good substitutes to asbestos now.
That said I like the notion of no gasket........Hmmmmm it's winter so lots of time for more comments and ideas...
Randy

Hi all,
So status update on this. I have chickened out on the no gasket approach the only way I'd do that is to have a thicker exhaust baffle machined but, that would be pricey. The next approach is to have a better gasket made. I have made a 3 d model of one from which I made a blue print. I am in process of selecting a material to water jet cut out a new gasket. ..........HOWEVER.....the plot has thickened....
We were snowed in yesterday (mandatory road closures) so I wandered down to kill some time in the "engine room" I had some 700 Merc block to tear down to make one good one BUT my attention soon went over to the 1500's. I have several bare blocks ranging from 73 to about 77 all the distributor style, some J blocks in the mix. I was sizing up my gasket model for correct fit when I stumbled on there are many variations on how Merc ran the water flow to cool the area under the baffle, there were different drilled passage configurations, some of you may already know this but I didn't so I'll share what I found.
First I'll say Merc must have been well aware of the weakness as they were making changes. I would also surmise the later the block the better the solution. I'll detail the three variants I found BUT does anyone have a very late in line 6 ADI block they can look at? This most likely has the best solution in cooling water path.
The variations are in how Merc gets the water to, and out of, the area under the exhaust baffle. They all cool the outer water jacket ( the big cover on the side) and around the cylinders the same way.
Here is how they do that:
First: Water enters from the bottom of the block from the water pump and is directed through a passage in the block to the space under the outer waterjacket and the inner jacket so this area gets cooled first.
Second: From there the water goes though several drilled hole passages to the area around the cylinders, so this area gets cooled second.
Third: Water flows out of this area from the top of the block through a passage towards the front of the block and then flows down though a narrow water passage in the block to the bottom and exits.
For ease of understanding the water is directed to first pickup heat in outer jacket (exhaust heat here). then that warm water cools the cylinder area. Then this still warmer water flows down through the block near where the block halves meet and exits, it is easy to see water flow is concentrated (logically) on the exhaust side of the block.
Now some portion of this water flow needs to be directed to go into the area under exhaust baffle plate water jacket and then exit out. Here is where the variations come in.
A digression:
Keep in mind water flows from higher pressure to lower pressure, so highest pressure is at water entry and lowest at water exit and decreases along the way so each of the three areas have succsessively lower pressures but water FLOW is the same. The volume (flow) of water moving through the block is somewhat determined by how much can escape, the pressure is built up because the water pump can pump in more than what can escape. The higher the pump can pump the greater the pressure and to some degree this increases flow, but there is a relation of diminishing returns, that is if the pressure is doubled, flow will increase but will not anywhere near double. Water FLOW is what cools.
Back to the motor, in general the three areas outlined above have bigger water entrances than exits so although each area is at a lower pressure than the one prior, each is under pressure and again each sees the same flow, now that said, some of this flow needs to be diverted to go under the exhaust baffle plate water jacket area and then exit out, here is where the variations come in.
The early blocks have passages drilled to split the water flow out of the inner and outer waterjacket area between water going to the cylinder area as described above and going through the area under the baffle plate. The drill holes are such as to favor flow into the cylinder area. So this is how the baffle plate area gets its cooling water,
The water exits from the baffle plate area through a drill hole connecting it to the CYLINDER area...THIS IS THE PROBLEM!!!! There is a very small pressure differential to get water to FLOW under the baffle plate area. As pressure in the system increases that is, pump output goes up, (in our inlines this happens as RPM increases) a strange thing happens under the baffle plate...water FLOW decreases, worst case scenario for our poor gasket, maximum heat (high exhaust) and minimum cooling water flow.
WHY is this so? Both of these areas are fed from the same source, the outer water jacket area, but the paths to the cylinder area is much larger than to the baffle area so at some point as water input increases (think RPM) the water pressure in the cylinder area becomes marginally higher than the baffle area So water no longer can flow from the baffle area to the cylinder area so cooling essentially goes to zero at higher RPM under the baffle plate. This area gets very hot very fast and I would not be surprised if water here starts to boil, this steam locally spikes the pressure and our poor baking gasket blows out.
Merc's better idea as seen on later versions is to feed the baffle plate area through a drill hole directly from the same place that the bottom of the block gets water, that is nearly directly from the waterpump, then this water exits from under the baffle plate through a drill hole to where all the water exits the block. This means the baffle area sees the highest input pressures and the lowest exit pressures which maximizes flow over the whole RPM range AND this flow increases with RPM!!!! Best case scenario!!! So they split the water flow essentially at the pump input into two flows, one goes through the baffle plate area the other through the three areas described above.
The third variation I saw is an interesting one and was most likely an attempt to be able to drill the blocks with both options but this particular one was pluggedvsonthe better option was the cooling path.
The motor I just had the issue with cooled the early, inferior way. I can change flow by re drilling but the castings are ever so slightly different so I'll need to press in tube so the baffle area will go to the block base without breaking into the cylinder area. The later blocks have a casting bump way down in the bottom cylinder area at the base of the cylinder so the hole does not break through. I can block off the original supply holes and can drlill through for the water exit as this will be similar to what was done on the third variation done for both options.
I am now wondering if the inner jacket problem was solved with the later blocks better cooling loop when a good gasket was used. Everyone's experiece would help. The better method is easily seen looking at the bottom of the block, there is a tiny drain hole, about 1/16 in dia near the exhaust outlet and right near that there will be a 5/16 hole that is drilled at an angle into the wall between the exhaust ports.
Has anyone had the baffle problem on the ADI 115's? the other thing I noticed is the distributor blocks where the crankcase haves bolt together will have the better cooling for sure if it's the style that has no nuts for the bolts, the block is cast a little different and has tapped holes...have you seen this failure on this style??
Chime in please....all this goes for the early 1150's too.
Randy

Randy,
I have an '88 115 L-6 bare block I'll pull out and check.
doc

Randy,
Can you point out in one of the attached pictures which water passage you are asking about?
Doc

Hi Doc,
Thanks for posting on this. I don't know how to mark them up on my iPad. I'll try and bring them into my widows computer. In the mean time I'll try to post some smaller file size pics of the earlier block two variations.
The 1150 you have there is cast different on the underside near the exhaust outlet so Merc did change something here. With the gasket in place it's hard to see how holes might be drilled but whe I get my pics up you'll see what to look for on yours. Interesting to note gasket is in much worse shape around exhaust ports even on these later versions.
Randy

Randy,
While digging through some exhaust extension plates (EEP) today, I noticed something interesting that might come into play on this issue.
I found that the top half of an EEP that only has a single cap-screw securing it to the lower half of the EEP has a much greater restriction at the water exit point than the EEP that uses (2) cap-screws.
Interesting too is that the single cap-screw EEP water intake looks like it would allow more water to enter the base of the block from the water tube than the (2) cap-screw EEP that allows the greater exit volume. Kinda bass-ackwards me thinks???
doc

The auto parts company I used to work for had a box of aircraft hylomar, it all went bad since it was there since the 70s but the guys that used it really liked it. Maybe take a trip to the airport and look at a head gasket no water in an aircraft motor but lots of temp swings and a lot are still flying so development isn't dead, tried to do a google but not finding much.

Permatex Permashield is their version of Hylomar and is readily available:

www.amazon.com/Permatex-85420-Permashield-Resistant-Dressing/dp/B007VIGCJW/ref=sr_1_2?ie=UTF8&qid=1423096274&sr=8-2&keywords=hylomar

Very interesting topic! Newby here trying to learn how to use this Site. I tried to post a reply but it said wrong code.

I have some observations to share (just typed a big long reply but got code error, lol) so i want to make sure i am using the Site correctly before attempting another reply! Any way to recover my previous draft/reply? THX!

In late '72-early '73, Mercury made some significant changes to block design (one change was how it bolted to the mid section)and i think they also made changes in the EEP at that point. From my observations: blocks made from '73 on, had the water inlet hole at the base of block that goes under inner baffle, like-wise they had the "cross-over" hole that connects the exhaust water jacket with the water jacket that's under the cylinder cover. Not until late '77 did they add that hole (at bottom of inner exhaust water jacket that connects to the water exit port that runs beside it.) And it wasn't until late '77 when they started making the pee stream come from the top of block, all blocks i have seen pre '77 pee came from cylinder cover below #3 cylinder, '77 on the pee stream came out from top of block.

3 things about this, really draws my attention: the little connector passage between the inner exhaust water jacket and the water jacket under cylinder head cover, that passage is right at the very top of block. Look right at the top of block, (spark plug side of the oiler hole for upper main bearing)pre '77 had just a casting support rib, then they added a thicker, rounded boss and drilled into the water jacket under cylinder head cover to pee the water. That tiny connector passage exits into the cylinder head area just below the new pee hole location. This is a critical area! Another area of concern to me is: the hole they drilled at bottom of inner exhaust water jacket, into the water exit jacket that runs beside it, this hole is facing in the oncoming exiting water. Does this somehow create a siphon, like-wise, the connector passage at the top, does the water flow out of the cylinder head area suck water out of that tiny connector passage and directly into pee stream??

Here's some more info: i just disassembled my '78 1400 (demoted from 1500 because of introduction of V-6 150) this motor was leaking badly from under inner exhaust jacket. I was able to get all bolts out without any breaking. When i got the inner cover off, it was warped like a banana (low in center, raised on ends)i got a new inner baffle plate and gasket from Mercury, the gasket had the name of the gasket material manufacturer (interface Solutions) so i googled them and got the phone number. I called them and ask them about the gasket, and if i should use a sealer etc. The man told me NOT to use a sealer, he said that gasket material was designed to adhere to a clean metal surface. He said, :if you use a sealant, the gasket will never adhere as designed, he said all your doing is mashing that gasket between the sealer, might as well be "filler" at that point, plus the gasket cannot be compressed as designed because the sealer will let it squish out from under mating surfaces. The new gasket material is rated at 500 degrees F.
Somehow, gotta improve water flow.

Glad someone else is adding to the observations. atomant what I do on long winded posts is to copy it then go back sign in and paste it, you will time out and lose everything if you don't do this, I learned that the hard way. I am curious about the gasket you have, all the ones I have are black and a tad glossy, maybe there is a later gasket made of improved material now? There is no markings at all on the ones I have, they are Merc ones but from a few years ago.. I did make an accurate model of the gasket which can be used on either a water jet or laser cutter to make a new one of higher temp material. Most of what I see for materials are rated at about 500 F so I am now thinking this may have been done by Merc already, can you post a pic of your gasket? FYI I have no luck posting pics here, always comes back file too large, aggravating for sure but I don't know the trick.
Doc, brilliant obsevations on the intermediate and tuner plates!!! As far as the exhaust intermediate plates I have a two bolt on the motor with two bolt tuner plate to match. I can't look at that, boat in storage, 5 feet of snow. I do have two bolt intermediate plate and a single bolt tuner plate loose I did look at but, ultimately can't compare one matched set to the other. But it would seem outlet size could effect system flow if too small.
Back to the blocks.. My suspicion is that the flow under the baffle is too low, and further complicating is the water jacket is seperated so there is a smaller physical volume surrounding the hotter port area. In any of these blocks although Merc changed how the water enters and exits I don't see why they make it flow around in the u shape, it leaves a very small space of water under the port area, it would seem by the time that water gets to the end of this portion it's gotta be blazing near boil hot, like a small pot of water would boil before a large one
Early blocks have water flow up over the top then down past the port and exit at the bottom into the cross hole to the cylinders, later blocks the water enters from the bottom flows past the ports up around the top and exits low on the other side. Granted it's better this way as its direct cold water from pump entering but still little water is actually in that space under the ports.
Soooooo here is my idea....opinions/ thoughts please..... it looks like a hole could be drilled at the top of the baffle area into the exit jacket area ( I have junk block to try) and then the thin wall making the "u" could be machined down making a larger volume in contact with the ports. Water would need to enter at the bottom and then it would flow up, through the whole baffle jacket area, much like what is done on the cylinder side.
On the earlier blocks I think only the top hole would need to be drilled and the wall kicked down. The cross hole connecting the baffle area to the cylinder area could be left as is....Water would flow between the cylinder water jacket and the baffle area depending on which had the higher pressure but overall, water escapes through the top of the cylinder area or top of the baffle area to the exit jacket. This is pretty much the same size exit scenario as seen on the later blocks but flow and distribution would be better, so I don't believe the pump output would be insufficient. On the later blocks the original outlet hole should be blocked and the wall kicked down, water comes in from pump area to either the cylinder side and baffle side , flows up and then escapes into the exit baffle. In this scenario I actually think the earlier blocks might have an edge as there is more holes for water entry and it would promote flow around the bottom cylinder on the cylinder side of the motor.
What say you smart folks??

Randy, first I have to make a correction...the new gasket material is rated for only 350 degrees F. It looks like it has more graphite in it. The material comes from Interface Solutions and is numbered N-8092 InterFace only makes the material (someone else cuts it).
I don't have a clue as to the exhaust temp in the port area, but I am willing to bet it's more than 350F.
So, to me, I think the first thing is to try to get an idea of what temp we're talking about because I have reviewed all types of high temp gasket material and the highest I found is around 900F with sustained temps of 550F.

Now lets talk about the inner baffle plate itself:
I read a very interesting article where the guy said, "the inner plate high-centers/raises in the middle"..this starts all the problems.
So when I removed my plate, I started with the bottom bolts and worked to the top, when I got about 1/3 way up, my plate started raising up at the bottom...when I finally got plate off, it was warped like a banana (concaved in the center and raised at the ends. Well, I thought to myself, "this plate sure didn't high-center, it's 1/16th low in the center"!
WELL come to find out, the guy didn't mean it high-centers in the middle on the horizontal plane, it high-centers in the middle from the top down (on the vertical plane! I took a steel rule and layed it across my plate from side to side, the rule touched the outer edges of the plate but it was 1/16th low in the center from top to bottom.

SO, with that in mind, I got to thinking! I bolted my plate back on (clean block surface, clean plate)and I took a "tongue" type feeler gauge and went to the mating surface right at the ports...I could slide the .010 gauge right into the water jacket area, all the way from top to bottom!
What's happening is: the heat is tempering that aluminum plate right in the center where it extends the exhaust ports..plate gets hot, it warps and pulls up from gasket, allowing water to get in, and exhaust gasses to exit past weak areas. SO, now we know whats happening with the plate.

I received my new plate from Mercury. HOWEVER, now that I know exactly what happens to the plate, I decided to re-use my old plate! WHY?? because now my old plate is tempered...it has been through many heat cycles..and I believe this, no 2 parts "know each other" better than the originals that have been mated since it was assembled. The original plate is true to this block. Even though it is warped up on the upper and lower ends (and middle in the center top to bottom) it is still the mate to this block. I have more explaining to do.

See, even if you use a new plate, the new plate is still going to temper and move, just like the original...then you're right back to the same problem!
I got a really nice, new flat file, I fastened my old plate down to a piece of 2 X 4 stud...I layed the file perpendicular to the plate and started taking good long strokes from top to bottom (lol, the file was cutting on the outer plate flange, but never touching the middle area). I delicately rasped the plate gasket surface until the file just started touching the center area. I never tried to cut the banana warp out of the center (remember my plate was also concaved in the middle on the horizontal plane)I purposely did that because even though the plate lifted at the top and bottom edges, that warp is critical because when the motor does come to temperature, the block and plate will "know" exactly how each other is going to expand...all I did was level the plate surface from side to side. I installed the plate back on my block, took feeler gauge and tested...I can't get that gauge (.001) between any of the mating surfaces...so now I have a good tempered part, great mating surfaces..all I need is a good gasket!

Thanks for the tip on the (copy/paste). I decided to do it in short segments for ease of reference.
I am still reviewing your ideas on improving the water flow. Which brings me to another thought: the cylinder cover, I barely feel any heat in that area (seems it's alot less than on the exhaust covers)therefore, by increasing water flow under the baffle, I don't think it would compromise the cylinder head area...

Facts of what I observed with my plate: when I bolted my plate back on (original as removed, just cleaned), and used feeler gauge around exhaust port mating area)..i had an increased opening between the block and plate mating surfaces (to be exact, the mating area at the bottom of the exhaust ports)...now, when I tried to put feeler gauge between the mating surfaces at the top of the exhaust ports, it wanted to go in some spots, but for the most part, it was sealed..alot better than at bottom of ports....point is: the heat is occurring at the bottom of the exhaust ports..right there in the center...top to bottom, the whole way down...LOL, this whole topic makes me think of another topic!..Is this over-heating problem, the reason we can't run more than 21 degrees timing advance??? they blame it on fuel..i have some scuffed and burned pistons from some boneyard stuff...im going to examine them to see where this scuffing and such happened...food for thought..

Here is what I found researching max EGT we could be talking about the top reaches of any of these solutions, maybe someone needs to install an EGT gauge to see the curve, probably why they inject water and stuff to cool it down in planes.

"It is not uncommon for gasoline engines to have EGT's between 1400-1650 degress at WOT.. I run a dyno for a living and 1600+ is common for newer engines at WOT above 4000 rpms. The manifolds will start glowing red around 1400 degrees, at 1650 degrees they are cherry red, at 1900 degrees they are transparent red!"

Great write-up atomant!
doc

firstfibre, I remember 'back-in-the-day' when I drove a crew bus up on the steep gravel roads to the logging sites, the exhaust manifolds on the 350 Chevy engine would be cherry red. Pretty amazing what those cast exhaust manifolds went through.
doc

Thanks Dr...I think it's great we can all get together and talk about this. I am sure, no single one of us has the whole answer. I've learned a lot from everyones input! You just have to take the (bits an pieces) and form your own game plan. Heck, who knows, maybe I bolt my plate back on and when it comes to temp, maybe it cracks...I don't know for sure.
This is a great case of "critical thinking"...don't try to over-think it, but go with what its showing you..but ya have to be smart at the same time...I guess, LOL!
We gonna talk about this water flow under that cover next!

Yes Doc, when I was young my buddies dad worked for Champion and we used to hang in the pits at all the races in Cali, early 70's those things would glow and you couldn't believe they would hold together, then bang and pieces of blower would rain down, maybe it's a problem that can't be fixed, only controlled till failure but I can't believe Fond du Lac doesn't have any research data on this with all their racing.

Any thoughts on opening up the exit points of the cooling system a bit more??
I realize typical water pressure on an open ended systems doesn't get very high, but is it free flowing everywhere that it needs to??
If I open the exit points more - will it simply free flow everywhere it already is and in doing so actually create even less flow at the inner water-jacket - if its exit volume is restricted - resulting in even higher heat and greater likelihood to distort?
If I figured out how to open the exit specific to the inner water-jacket,....Would a faster flow keep the area cooler???
doc