Piston hitting heads!

3twinridges

3twinridges

Well-known member
Finally got the last piston in, even though the EAB heads were NOS, I was still worried about them hitting the egge pistons. Sure enough, they hit.

I foil balled the valves and cylinder with the head torque down with a gasket and it wouldn’t turn over. Basically no clearance with a gasket which means I would have to remove about .05 of material, seems like a lot!

Thoughts on an 8BA head having enough clearance?

JB
 

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I ran into this once. It was just on the passenger side. I ran two head gaskets on that side. While not ideal, I ran it for thousands of miles like that.
 
3twinridges said:
Finally got the last piston in, even though the EAB heads were NOS, I was still worried about them hitting the egge pistons. Sure enough, they hit.

I foil balled the valves and cylinder with the head torque down with a gasket and it wouldn’t turn over. Basically no clearance with a gasket which means I would have to remove about .05 of material, seems like a lot!

Thoughts on an 8BA head having enough clearance?

JB
Click to expand...
571970
 
Are they hitting just in the middle of the dome? Some pistons have a constant radius dome. Some pistons have a "pointy" dome. In my experience, French pistons have the pointy dome. I have reduced the point by filing on my lathe and by just filing in situ on one occasion. If this your problem there is normally no problem with removing enough material to achieve the correct clearance.
If it is more general across the dome, maybe the heads have been previously milled and some different heads will do the trick.
 
I had this happen and used a grinder to grind a bit off the heads and double gaskets did the job. Poor folks. We ain't got much but we do have a shade tree... Lol. Chap
 
Sounds like a perfect opportunity to get in there and custom fit your heads for optimum "quench".
 
I made an improvised 'doming head' from old V8 parts on my 276 stroker build a couple of years ago. This did a good job of cleaning up and finishing the somewhat crude hand grinder work I did in sculpting out the bowls with an angle grinder. Not sure how to link parts of an old post into this one, or to interject some of the photos. Therefore until someone smarter than me can do that, go to my build thread '276 stroker from 35 years of parts' and go to page 13 is where the discussion on clearance/squish area/foil balls starts and maybe on page 15 or so I come up with this crazy apparatus. You would need an extra block and a few junk parts to construct one.
 
Look into cosmetic head gaskets, they have a wide range of thicknesses. Without a gasket, how much does the piston raise the head?
 
GB SISSON said:
I made an improvised 'doming head' from old V8 parts on my 276 stroker build a couple of years ago. This did a good job of cleaning up and finishing the somewhat crude hand grinder work I did in sculpting out the bowls with an angle grinder. Not sure how to link parts of an old post into this one, or to interject some of the photos. Therefore until someone smarter than me can do that, go to my build thread '276 stroker from 35 years of parts' and go to page 13 is where the discussion on clearance/squish area/foil balls starts and maybe on page 15 or so I come up with this crazy apparatus. You would need an extra block and a few junk parts to construct one.
Click to expand...
Page 13 > https://www.fordbarn.com/forum/showthread.php?t=336892&highlight=%27276+stroker&page=13


Page 15 > https://www.fordbarn.com/forum/showthread.php?t=336892&highlight='276+stroker&page=15
 
big deuce said:
Look into cosmetic head gaskets, they have a wide range of thicknesses. Without a gasket, how much does the piston raise the head?
Click to expand...
COMETIC Head Gaskets > https://www.cometic.com/materials/head-gaskets

Multi-Layer Protection

The thickness of the center layer can be changed to change the overall thickness of the gasket.

Thickness: .018, .019, .020, .021, .022, .023, .024, .025, .027, .029, .030, .031, .032, .034, .035, .036, .038, .040, .042, .043, .044, .045, .046, .047, .049, .050, .051, .052, .053, .054, .055, .056, .057, .058, .060, .062, .064, .065, .066, .067, .068, .070, .071, .072, .073, .074, .075, .076, .077, .078, .080, .081, .082, .084, .086, .089, .092, .095, .098, .100, .102, .104, .120, .124, .140


Additional Layers

With any cylinder head gasket design, additional layers can be added to increase active seal height. Clamping force, surface distortion, head lift, and other factors must be taken into consideration when determining the function and design of each layer.
 
Not against two gaskets, I am going to have to do that anyway to get enough clearance to measure how much I need to take off. I am still hitting with one gasket, so at least 0.050 in some places.

I am going to call the shop tomorrow to see if they can redome them. With the piston top profile and the right cutter, and depth to remove seems like you could get pretty close and have a nice uniform combustion chamber. Hopefully they have run into this before.

JB
 
When putting Edelbrock heads on one of my french motors, I found that the pistons just touch slightly at their peak point. I made a cutter to the shape of the piston and deepened the pockets in the heads. When doing this I found that those 4 pockets were not exactly parallel to the head and of slightly varying depth...
Here is a pic of my cutter. It is just a shaped HSS in the slot so I could make different cutters for other shapes, if needed.
 

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vincent said:
When putting Edelbrock heads on one of my french motors, I found that the pistons just touch slightly at their peak point. I made a cutter to the shape of the piston and deepened the pockets in the heads. When doing this I found that those 4 pockets were not exactly parallel to the head and of slightly varying depth...
Here is a pic of my cutter. It is just a shaped HSS in the slot so I could make different cutters for other shapes, if needed.
Click to expand...
572003
 
Talked to the shop today today and they can redome them, but they were afraid of final head thickness above the piston.

I talked to cometic and they can make a gasket for me, going to go that route. At least in principle it seems like the easiest fix. Going to bolt up a head tonight and get the thickness I need.
 
The OP states he has NOS EAB heads. I've seen new heads back in the day but I've also seen misrepresented ones too. Make sure the bottoms of the coolant exit ports have a fair clearance to the deck surface. I've seen them shaved all the way down to the coolant port bottoms.

The Ford pistons with a Merc crank as was mentioned, is another problem. The Merc piston pin bores are a good bit lower on the piston to get clearance right for a 4-inch crank.

Block deck height is another thing if they've been shaved too much.
 
rotorwrench said:
The OP states he has NOS EAB heads. I've seen new heads back in the day but I've also seen misrepresented ones too. Make sure the bottoms of the coolant exit ports have a fair clearance to the deck surface. I've seen them shaved all the way down to the coolant port bottoms.

The Ford pistons with a Merc crank as was mentioned, is another problem. The Merc piston pin bores are a good bit lower on the piston to get clearance right for a 4-inch crank.

Block deck height is another thing if they've been shaved too much.
Click to expand...

They are mercury pistons and I don’t think the heads have been shaved that much. I have a new set of EAB heads still in the crate and they haven’t been touched and they hit. I am going to put two gaskets on tonight to see what I have in clearance. I figure with two gaskets compressed at 50ft/lb I will be at 0.110 gasket height. If I get 0.030 clearance I can run a 0.086 cometic gasket.

JB
 
I was able spend some time on this. I torqued down two gaskets, best I could tell final compressed height of both gaskets came to 0.110 at 50 ft/lbs. Lowest clearing I had with aluminum foil balls was 0.068. So with an ideal 0.050 clearance, I could take 0.018 off 0.110 and run a 0.092 cometic gasket, which they have with a 3.250 bore size. My bore size is 3.2275 so I think that is fine also. Logic sound right?

That is for the passenger side, on to the drivers side.

JB
 
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