Piston hitting heads!

[3twinridges]

Some quick photos of the above!

JB

[petehoovie]

Originally Posted by 3twinridges

Some quick photos of the above!

JB

[95476]

I bought a set of Cometics for a project. They are super expensive but worth the long wait and $$$.
I ended up changing heads though.

[3twinridges]

I hear you on cost, but it’s really not bad. I was going to have to buy 4 new gaskets anyway as I wouldn’t trust reusing these with all the fitting.

The driver side ended up being the same with my smallest quench gap being 0.068, so 0.092 for both sides.

JB

[GB SISSON]

All in all, looks like you came up with a good solution. We are fortunate that there is a company making gaskets of this nature for an engine family that is coming up on a hundred years old.

[petehoovie]

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Originally Posted by 3twinridges

I hear you on cost, but it’s really not bad. I was going to have to buy 4 new gaskets anyway as I wouldn’t trust reusing these with all the fitting.

The driver side ended up being the same with my smallest quench gap being 0.068, so 0.092 for both sides.

JB

[richard crow]

if you have used merk pistons there is no reason the pistons are above the block as they say something is wrong in demark

[3twinridges]

Originally Posted by richard crow

if you have used merk pistons there is no reason the pistons are above the block as they say something is wrong in demark

Richard they are Egge L991 mercury pistons. I think the reason they didn’t hit in the last build is because I used 8BA heads.

JB

[GB SISSON]

All those tin foil balls brings back the angst I was feeling when doing the same thing 18 months ago. I had to carve into the heads and carve some more, The machinist had told me he decked the block just a bit because of a flaw. While it wasn't really apparant to me, others here with more experience pointed out that the pistonns were indeed protruding, 'pop ups' they said.. I perservered and got a quench area that satisfied my online coaches. Fact is I could not possibly be happier with the power this thing has. For me it's actually more about the torque/hill pulling ability. You will be amazed what the extra bore and stroke particularly if you are installing it into the same vehicle like I did. In other words you will be rewarded greatly for the time and money spent on this engine.

[tubman]

I have gone through this entire thread, and I see a couple places where the O/P says he has Mercury pistons. I don't see which crank he is using, but it has to be a Mercury crank to have this kind of problems. Since Merc pistons have the pins located 1/8" higher to make up for the increased 1/4" stroke, they would be 1/8" low in the bores at TDC with a Ford crank.

Could the O/P definitively identify which crank and pistons he has?

[Scotty's 52 F3]

@tubman He's got a thread on the FTE forum as well for this build. Said he has a 4" Merc crank, ground 10/10, .040 over bore on the block with Egge L991 mercury pistons and an EAB cam.

[tubman]

Originally Posted by Scotty's 52 F3

@tubman He's got a thread on the FTE forum as well for this build. Said he has a 4" Merc crank, ground 10/10, .040 over bore on the block with Egge L991 mercury pistons and an EAB cam.

OK. Good, as I was getting a bit confused.

Thanks.

[3twinridges]

4” mercury crank, egge mercury pistons, EAB heads

JB

[tubman]

I'll go on record by saying this should be approached with head work rather than double or fancy, expensive thick gaskets.

[3twinridges]

Originally Posted by tubman

I'll go on record by saying this should be approached with head work rather than double or fancy, expensive thick gaskets.

The shop can do it, they were just worried about taking .0.040 out of the quench area on the head, potentially weakening it there given the heat and compression. How thick is the head above the piston?

The cometic gaskets were ordered today.

JB

[tubman]

I've seen a bunch of cut up blocks so folks could measure cylinder wall thickness and port wall thickness. Surely someone has cut up a few heads. You've got the gaskets coming, so that's done. I would have cut up a junk head to see exactly where I was. I just don't like the idea of a thin deck and a non-standard gasket.

I'm sure it will work; good luck with your project.

[tubman]

Sorry for getting all involved in this, but I am having some serious problems with what's going on here. The first thing I have to ask myself, is how did this problem (the piston being at least .040" proud of the cylinder) come about? There are only two ways I can think of that can cause this. The first is there's something funny going on with the crankshaft, rods and pistons. I would think this would be highly unlikely, which leaves my second choice, that the block has been decked excessively. Since no flathead ever left the factory with an ideal .050" quench, the decking must have been .060"-.080". Given the notorious thinness of flathead decks, I would be very wary of this block.

If any of you can come up with a flaw in my logic, I'd like to hear it so we can put the O/P's mind at ease. The way things stand now, I believe it is imperative to find out what the actual cause of this situation is and not just throw a "band-aid" (yes, that's what it is) of non-standard thick gaskets at it. I'd at least want to sonic check the deck to find the actual thickness.

This sounds like it's a high class, high buck build that deserves to done right, not finished with a patch. If someone else can tell me what's causing this, lets hear it. If this were my engine and my money, I know I'd sure like to be sure I know exactly what's going on.

[38 coupe]

For different reasons I asked the group here about head thickness and doming to fit. The findings from some very helpful members was there should be enough thickness above the piston. The thread is here: https://fordbarn.com/forum/showthread.php?t=325380

[Mart]

If the engine will not run without oversize head gaskets there must be something wrong. I'd be more inclined to see where the error is. Once the anomaly is identified, Then a decision can be made whether to correct it or to live with it and compensate with the thicker gaskets. The things that could be wrong are crank stroke, rod length, Pistons with incorrect height above the pin, pistons with incorrect dome shape, block deck height and head being skimmed or incorrectly cast. There may be other things but that is enough to be going on with.

[cadillac512]

Originally Posted by 3twinridges

The shop can do it, they were just worried about taking .0.040 out of the quench area on the head, potentially weakening it there given the heat and compression. How thick is the head above the piston?

The cometic gaskets were ordered today.

JB

The EAB heads are .260"-.275" thick in the dome area. I cut mine .040" with no ill effects and have driven it another 15K miles since.