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Discussion Starter · #1 ·
Cylinder bored .030, new rod (piston set and rod bought from ISaveTractors).
All went together nicely. While setting cam and counter weight timing the piston must be at TDC. I used my dial indicator for this and discovered the piston actually protrudes ABOVE the cylinder by .025”. I never noticed where the original piston stopped at TDC. I haven’t installed the head gasket and torqued the head down to see if there’s any head-to-piston clearance issues but this seems abnormal to me. Should have high compression though!!

Is this normal and its good to go?
Or, should I use two head gaskets?

I did not compare old piston to new, nor did I compare rods other than a “yep, they look the same” in both cases.
Do I have a problem?

ron
 

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Personally speaking as a non-engineer, unless you are using a steel stamped head gasket, you should not have a lot of worry about the piston colliding with the head. Two thousandths of an inch is not a lot. May be that a piece of paper(newspaper is .0039" on average) is thicker... If you have a normal composition head gasket there should be more than enough clearance.
I would not stack head gaskets unless there was no other option. I do not think they were designed for stacking. I don't know how well the 'fire ring' metal edges would compact together to form a good seal.
tom
 

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Discussion Starter · #3 ·
Personally speaking as a non-engineer, unless you are using a steel stamped head gasket, you should not have a lot of worry about the piston colliding with the head. Two thousandths of an inch is not a lot. May be that a piece of paper(newspaper is .0039" on average) is thicker... If you have a normal composition head gasket there should be more than enough clearance.
I would not stack head gaskets unless there was no other option. I do not think they were designed for stacking. I don't know how well the 'fire ring' metal edges would compact together to form a good seal.
tom
tomw0 - that’s .025”, not .002”!
Ron
 

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I wouldn't stack head gaskets, that is begging for a blow out.

I presume this is the valves in the block style B&S? If so, before you final assemble, stick a couple of dabs of putty or modeling clay in the cylinder head where it is the closest to the piston at TDC, and bolt the head down to the block. You can do this without a head gasket but I'd use the old one for this purpose so as not to waste a new one. Rotate the crank by hand through a couple of strokes to see how close the piston gets to the head. My wild guess is that even with a 0.025" protrusion, you still have a lot of clearance. Best to check though.
 

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Discussion Starter · #5 ·
Yes, old flathead.

Truth be known, prior to setting up for the camshaft/counter balancer timing, I had installed the head without a head gasket to keep dust and such out. A couple of finger-tightened head bolts held it on. At one point I rotated the crankshaft and the piston did a hard stop against the head, so I already knew there was interference. I just didn’t know how much and just temporarily put the old head gasket in place with the two bolts. Then I got to the timing procedure, pulled the head, and put my dial indicator in place. That’s when I saw how much the piston protruded.

I will use the clay method to see if there is any clearance after torquing the head down. Not sure if I’ll use the new head gasket for this or not. There appear to be some differences in the head gasket structure and composition that could result in different thicknesses, hence possible clearances.

ron
 

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Discussion Starter · #7 ·
I did mike the two new head gaskets I have: one is .068“ thick and the other is .062” thick. Depending on how much they compress under torque there might be at least some clearance.

ron
 

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They will compress a little bit but it needs some room above the piston for any 'Stretch of the connecting rod and 'Flex' of the crankshaft at speed plus it needs a little bit of room for the exploding gas/fuel mixture to begin expanding to start to push the piston down in the cylinder.
'Stacking' a head gasket is usually not a good idea due to a possible 'Blow-out' but it has been done before on different occasions. Usually you would use a 'Metal' gasket and the stock gasket with the 'Graphite' coating on it instead of 2 separate stock gaskets.
There were places that made custom thickness head gaskets for them at one time. A lot of guys that build the engines for tractor pulling know of places to get the custom thickness head gaskets.
 

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Discussion Starter · #9 ·
They will compress a little bit but it needs some room above the piston for any 'Stretch of the connecting rod and 'Flex' of the crankshaft at speed plus it needs a little bit of room for the exploding gas/fuel mixture to begin expanding to start to push the piston down in the cylinder.
'Stacking' a head gasket is usually not a good idea due to a possible 'Blow-out' but it has been done before on different occasions. Usually you would use a 'Metal' gasket and the stock gasket with the 'Graphite' coating on it instead of 2 separate stock gaskets.
There were places that made custom thickness head gaskets for them at one time. A lot of guys that build the engines for tractor pulling know of places to get the custom thickness head gaskets.
Thanks. I’ll call the A1-Miller guy you suggested.
ron
 

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Oops. Don't know where I got that number from.
FWIW, I have read of head gaskets made from sheet copper. Hole punchers and tin snips can make a workable gasket.
Twenty five thousandths is a bit more than I would dismiss as negligible. The squish clay test should be telling, but you know the gap depends on gasket thickness.
I would check with the vendor. Depending upon availability, if you can't find another piston with a smaller wrist pin distance, you could machine the piston top as needed, or remove metal using a flat surface and abrasive paper. I expect the piston is aluminum, which can be removed, slowly, by hand as desired. It should not hurt anything as far as degrading the strength.
OTOH, you would get a bit better compression ratio. One that might even need the octane of our current fuel supply.
tom
 

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Discussion Starter · #11 · (Edited)
I pulled the crankcase this morning and shoved the piston and rod out so I could do some comparisons. I used the wrist pin to align the pistons and a straight edge across the tops - nope, piston wasn’t the problem. Using same wrist pin with the rods found the problem - my little Starret 6” straightedge laid across the crank journal showed a sliver of light under the new rod journal. I didn’t try to measure it but it was enough big to say definitively that the new rod is longer and the source of my problem. I guess I should reassemble the new rod and old piston and secure to crank pin. I pretty sure the old piston will protrude also. It’ll flop some because of the .030 over bore but it still should be obvious. The new piston/old rod combo should really prove the point.

Oh, I set up the dial indicator again before pulling new piston/rod and more carefully measured the protrusion, then double checked with straight edge and feeler gauges. Actual protrusion was .032”. Also placed chunk of clay on piston top and torqued head down with old gasket, which I’d miked at .060” thick. Two/three rotations and disassembled. Used knife to gently cut through clay and feeler gauges to approximate clay thickness at cut. Best I can say is that it was obviously thicker than .020” but not quite .030”. Either way that’s not as much clearance or squish area as I’m comfortable with. And those numbers match up with the .032” protrusion and .060” gasket.

So, calling vendor tomorrow morning after I’ve done the remaining checks above.

Thanks for all the suggestions and warnings. A new rod will be the way to go. I’m counting on this one being a fluke. My old rod was fine but the new one was cheap enough to get just to tighten up the big end clearances a scooch.

ron

edit: Yep, old rod/new piston was about a sheet of 20 lb paper thickness above cylinder at TDC. New rod/old piston stuck up close to same amount as new rod/new piston. I didn’t bother measuring-all I needed was to confirm that the new rod is the problem- and it is.
ron
 

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Good detective work!!
Now, hopefully a rod of the correct length can be procured.
 

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Discussion Starter · #13 ·
Oops. Don't know where I got that number from.
FWIW, I have read of head gaskets made from sheet copper. Hole punchers and tin snips can make a workable gasket.
Twenty five thousandths is a bit more than I would dismiss as negligible. The squish clay test should be telling, but you know the gap depends on gasket thickness.
I would check with the vendor. Depending upon availability, if you can't find another piston with a smaller wrist pin distance, you could machine the piston top as needed, or remove metal using a flat surface and abrasive paper. I expect the piston is aluminum, which can be removed, slowly, by hand as desired. It should not hurt anything as far as degrading the strength.
OTOH, you would get a bit better compression ratio. One that might even need the octane of our current fuel supply.
tom
The hot rod shows seem to like spraying copper on new head gaskets before installation. I’ve wonderEd exactly what the spray was bu haven’t found anything that looked right in Autozone and such.

A little higher compression would be good but my current setup puts piston and head way too close.
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There was(is?) a product sold in auto parts stores called Copper Coat, or Kopper Kote or similar. I think it was available 'brush in can' and later as a spray-on product. It was used as a 'soft filler' that was deformable enough to fill or partially fill those small scratches on heads and blocks to get a better seal.
I did not use it. Nothing against, but it was not free and extra dollars for a product that may not be necessary was not in the budget.
Some have used regular aluminum colored(silver) paint. Some used 'any color' paint. Can't say I have done either.
I remember seeing someone cut a fully Cu gasket from a sheet of copper, normally used as flashing. It is deformable when torqued, and should conform as well or actually better than a sheet steel fulll metal head gasket. IMO. It is a softer metal and easier to displace than the steel is.
I wonder if the rod supplied was for another application, or someone measured incorrectly. Could be that it was 'close' in the dimensions, and no one had complained, so it was supplied whenever your style/size was requested. It could have been installed previously in other engines with no difficulty and if problems arose, they could have been blamed on ... who knows.
tom
 

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Discussion Starter · #16 ·
There was(is?) a product sold in auto parts stores called Copper Coat, or Kopper Kote or similar. I think it was available 'brush in can' and later as a spray-on product. It was used as a 'soft filler' that was deformable enough to fill or partially fill those small scratches on heads and blocks to get a better seal.
I did not use it. Nothing against, but it was not free and extra dollars for a product that may not be necessary was not in the budget.
Some have used regular aluminum colored(silver) paint. Some used 'any color' paint. Can't say I have done either.
I remember seeing someone cut a fully Cu gasket from a sheet of copper, normally used as flashing. It is deformable when torqued, and should conform as well or actually better than a sheet steel fulll metal head gasket. IMO. It is a softer metal and easier to displace than the steel is.
I wonder if the rod supplied was for another application, or someone measured incorrectly. Could be that it was 'close' in the dimensions, and no one had complained, so it was supplied whenever your style/size was requested. It could have been installed previously in other engines with no difficulty and if problems arose, they could have been blamed on ... who knows.
tom
i

That’s the stuff I couldn’t remember!
I do have some sheet copper around somewhere but I never miked it for thickness. Pretty sure it’s not over .032” but I’ll sure check if I can find it.

I talked with vendor and he’s emailing mailing label to return the rod. He said he’ll pull ten from stock and compare. Also said he’s sold a bunch (I think he said hundreds) of these over the last few years and no returns so I’m thinking this was just a fluke size among the rest. Anyway, I’m dead in the water til a rod returns. If I needed the tractor for immediate work I’d put the old rod back in but that’s not the case. And, he did not try to shift blame to his supply. He said the rods were made by a supplier using his company’s design specs. I appreciated that.

Ron
 

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Discussion Starter · #17 · (Edited)
An update on rod status:

The vendor pulled ten rods from stock and compared them to mine as well as to his specs. All matched mine and specs, so it wasn’t a bad bit of machining. He’s going to look into the B&S engines he has to see if he finds any more that may match mine (most of his business apparently is Kohler).

After thinking about it a couple of days I asked him to return the rod to me. I located that sheet of copper I had and it miked at .022”. I was hoping it was .032” but that’s enough to leave only .010” of piston sticking up too far. I’m hoping that will work out. So, I used my jeweler’s saw today to create a copper head gasket. Now awaiting the rod to arrive back..

A couple of questions just to cover the possibililies since I am going to have to stack something together (right now that’s copper and a regular head gasket).
-Should I look for a thicker sheet of copper to completely counter the .032”of piston protrusion?
-What about a “sandwich” of copper-standard gasket-copper?
Not looking to create more problems. Just curious as to your thoughts.

Thanks,
ron
 

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It's not really good to sandwich a gasket together, they are better off as one piece, but it might work.
Next would be to have the piston checked for height and piston pin location to make sure that is correct.
The only other thing I could think of is if the top of the cylinder block, the 'Deck' was ever 'Milled' down at one time due to warping which is possible but rare.
That would make the piston too high and would also set the valves down lower because the seats would have to be lowered if that was done. Then the valve stems can be ground to shorten them to get the clearance needed.
Another odd thing would be the crankshaft having more stroke than it should causing the excess piston height.
You would have to measure your stroke from BDC to TDC and see what you get an if it is within specs.
 

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I am not for 'stacking' gaskets as I think it is a short term solution. If you can get some thicker copper sheet, you can make a lifetime gasket out of it, and be sure from the get-go there will be no problem. That is the way I would go if there was no other source for a rod that is comparable to the one you want to replace.
tom
 

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Discussion Starter · #20 · (Edited)
ST1100A & tomw0-
I understand about the potential problems with stacking. The only sheet of metal I have thick enough for a one-piece gasket is .064” aluminum. No one has mentioned it as a possible but that’s what the head is of course. What are your feelings on using aluminum? Or maybe brass? I might be able to find it.

edit:
ST1000A- I used the wrist pin to align both pistons and top surfaces line up nicely, so not a mis-machined piston. The valves are on loose side of clearance so either they’ve already been shortened or ?? I’m at a loss. I’m just going to deal with it as below. The nice thing is a flatly is easy to change out head gaskets.

I found a packaged piece of .090” aluminum at the hardware store. That’ll take care of the .032” of piston sticking above the cylinder deck plus the thickness of a normal compressed head gasket. Got some aluminum spray paint to help seal both surfaces. We’ll see how it works. If it doesn’t at least no major disassembly is required to remedy situation.

Thanks,
Ron
 
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