V-12 Engine into 308 Build, over on Grassroots

At least you know it leaked there and not somewhere else!

 

Well, I know it leaked there for sure, but I don't yet know it if leaks anywhere else. Still waiting for the sealant to harden before finding out.

 

Ah, didn't catch the copper. It looked like the aluminum? Plate and O ring was it, thought it strange and wondered how you'd keep the flame front from torching the O ring.

You've got the cad files, wouldn't hurt to get a quote from cometic on MLS gaskets.. Just in case. I went thru so many different design changes and two mfg.. the head gasket issue was a royal PITA. Finally went MLS, problem solved. Still used a layer of aviation sealant though, block and heads just move too much.

Hadn't thought of using heat to set 518, always figured it was a time thing, a day or so. I have to check my inventory but I think there's a bottle of accelerant for it as well. Pricey stuff.

 

The heads are sitting just a little lower now and one is hitting the oil filter adapter and I can here a small leak right there.
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Bugger...
Ok went and looked. Loctite 7649, it's a primer to speed the cure of their anaerobic sealants.

 

Gahhhhh! That’s maddening isn’t it. Aside from this clearance issue, have you changed the amount of torque you’re applying to the heads with this new solution?

 

Its actually good I had to pull the head, a couple o-rings were not where they belonged
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Looking at it I'm thinking the no sealant shows the higher low areas
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This time I used 518 and it was WAY easier to assemble. after about 5 minutes I almost couldn't move the copper rings and the o-ring had no interest in popping anywhere so overall I feel a lot better this time. Leak test will be tomorrow to give the sealant time to set.
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no change to torque specs....its basically as tight as the bolts will stand.

 

Very interested in how 518 works in this application. Being thixotropic I wonder how it'll handle the thermal cycles and vibration.
R&D can be 'fascinating' and also drive one to drink!
Fingers crossed for you!

 

Strike 2. Gross leak out the side. When I got the heads off the o-rings stated put and looked. The issue appears to have been time, maybe it could be solved with technique, not sure. I coated the deck the shim, installed the shim copper and o-ring, then coated the top od the shim and head, assembled and torqued. It looks like the 518 began to set in the thicker areas that made contact as soon as I set the shim on and by the time I torqued it was too late for the material to flow and seal. Then it took forever to clean it all off.

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Hylomer blue on 1 head, hylomer M on the other cuz I didn't have enough of either. The copper ring and 0-ring stuck in place nicely and unlike the 518 I can see it oozing out a bit so even though it gets really thick really fast it does seem to flow like they say it should. The heat gun is on the gage plate, in a couple hours I can add pressure and see what I have.
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30 minutes so no gross leaks this time
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Nope, strike 3. It was 2psi this morning, I recharged it and it lost 5 psi in under 20 minutes so it blew out the hylomer somewhere. Luckily this is more like t-ball and I can swing until I get a hit. I'll need to think about what to try next but the spray stuff is on the list, I think its just copper spray paint so I worry it won't have enough thickness.

 

Damn..

While not cheap, pressure sensitive film could help with showing what's going on.

https://www.mcmaster.com/products/pressure-paper/

If memory and back of the envelope calc scribbles out 800-1200 max psi range.

I know you've cycled the heads on/off a fair bit. Most I could get was ~5 times before studs were stretched out. Possibly a yield issue with the studs?

Lastly... Bite the bullet and have cometic make MLS for you..I know.. Not cheap.

 

5 cycles? I did 3 last weekend alone

Remember I have the older M11, not the newer M10 which have the same torque soec so are under about 17% higher stress. I haven't noticed anything odd in the way they torque or that they lose torque or anything like that.

I'm not sure I can use MLS gaskets. My understanding is they require a flat deck and my liners were not set and machined with the deck.

1500 is what I was thinking pressure might hit.....and while I was stacking 20k+lbs of patio stones I don't need but my wife got for a great price the last couple days it occurred to me that in my new design there is nothing supporting the o-rings between the cylinders so when I get it to pass the bench test and installed in the car, it will blow out the orings when it starts. Then I though I could make the copper rings taller and yield them on assembly to mostly seal, but then the hoop stress will be 6-8 times their yield stress so getting this setup to pass a bench leak test is a pointless exercise I think.

 

5 cycles? I did 3 last weekend alone

Remember I have the older M11, not the newer M10 which have the same torque soec so are under about 17% higher stress. I haven't noticed anything odd in the way they torque or that they lose torque or anything like that.

I'm not sure I can use MLS gaskets. My understanding is they require a flat deck and my liners were not set and machined with the deck.

1500 is what I was thinking pressure might hit.....and while I was stacking 20k+lbs of patio stones i don't need but my wife got for a great price the last couple days it occurred to me that I should be thinking about hoop stress and haven't been...those copper rings will be 6-8 times their yield stress so getting this setup to pass a bench leak test is a pointless exercise I think. I need to think about this a little more.

In happier news, the trans shaft now has threads so the ring nut fits, thank you Sean
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Cometic makes an MLS for the proud liners for us. They can do it, just need the technical specs data etc.. the guy to talk to is Bill Majetich, may or may not have the spelling right on that.

 

Why is it some type of conventional head gasket is not being used?

And how much liner protrusion does it have?

 

If I understand correctly you have said the head sealing problem is flexing of the head or block, or both? I may have missed if you tried a gasket and sealant, I would expect some crushing of the gasket would help.

Is a girdle on the crank and or valve train/ heads an option to eliminate some deflection if it’s the root cause?

 

It appears to have been tried with custom Reinz gaskets from Cometic. Attempted both dry and sealed with Aviation sealant, no go. As you have pointed out, that head is likely flexing way too much as is its nature with this head. I would think the head would need to be stabilized to keep it square with the deck. I know some head gaskets have strips of metal at the side edges, and sometimes the top edges to keep the head square. The current solution being attempted is clever and I hope it works, if it doesn't then I think working with Cometic for an MLS solution would be next. I just hope he can get the thing sealed, very neat bit of engineering and fabrication and it would be a shame if it all didn't work out cause the heads won't seal.

 

I was using custom composite head gaskets. Custom because because TR head on a 400 block is not standard, at least not the way I did it. I left 5 studs in the original locations which means the head id offset about 1mm or 1.5? I forget, form the standard location relative to the bore, and that allows larger intake valves. So custom head gasket

There in no protrusion....there was at one time but not now which is kind of scary.

I think the next attempt I will remake the 0.05" think alum shim to butt right up to the copper flame rings and remake those with 0.063" material so they are crush washers and forgetthe rubber orings. If I leave them 0.08" wide like they are they should crush at around 9k lbs. the WOT combustion load on the head is going to be 10k-13k lbs maybe and the bolts usually deliver about triple that. so the rings should crush down to the shim.

 

If the head is flexing when torqued to a flat surface there are serious problems not related to it. Put something solid under it like a solid fire ring and can guarantee it will flex and leak.

 

I have seen Ferrari engines seal with no liner protrusion but those were not engines with high pressures. Does this engine have rubber O rings sealing the liners to the spigots? If it used Orings you have a real issue. They compress under load of an installed head and you in reality have recessed liners.

Cometic makes composite head gaskets in different thicknesses. The thick ones seal better. They have more comprehensibility to seal over the uneven surface of a deck with wet liners and heads with a low level of rigidity.

 

I had not thought to ask about thicker gaskets... I will look in to that.

Yes orings, but I put sealant on and the liners didn't lift as far as I can tell....I'll check that tonight to be sure though

 

I already have the thickest version, .059"

 

You have rubber orings under the liners and statically it has zero liner protrusion?
I dont see how its going to seal.
Id take it apart and deck the block a few thousandths.