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1950 mercury Flathead Engines

13K views 21 replies 4 participants last post by  alittle1 
#1 ·
I cant seem to find any thing on the Mercury pistons that have the expansion slot in them. I need to know when you install them in the engine does the slot face the Thrust side of the cylinder wall or towards the intake. The engine I took apart was 50/50 2 one way 2 the other way. Those 4 pistons were burnt with a hole on the thrust side of the pistons. I would think the piston slots would need to be all one way not random. I need a Flat head expert to answer this. I have rebuilt lots of Ford engines but never a Mercury with these pistons ,
 
#2 · (Edited)
rsfyj said:
I cant seem to find any thing on the Mercury pistons that have the expansion slot in them. I need to know when you install them in the engine does the slot face the Thrust side of the cylinder wall or towards the intake. The engine I took apart was 50/50 2 one way 2 the other way. Those 4 pistons were burnt with a hole on the thrust side of the pistons. I would think the piston slots would need to be all one way not random. I need a Flat head expert to answer this. I have rebuilt lots of Ford engines but never a Mercury with these pistons ,
A picture or two would be nice. By slot, would you be referring to the chip taken out of the piston face that is on the thrust side to clear the head?

Or, try this: http://www.hotrod.com/techarticles/engine/hdrp_0511_ford_flathead_engine/photo_15.html
 
#12 ·
krooser said:
As you know the oil squirt holes should face inward... I have never seen expansion slots like that... must be an aftermarket piston?
>>true about the oil hole but you can pin these pistons either way my engine had 2 going one way and 2 going the other way. i think a shade tree mechanic did the engine at one time. After Ford sold it
 
#13 · (Edited)
Many pistons have a mark, notch, arrow, etc. to show "front" of the piston.

In your case, the photo shows how the pistons are installed:



EDIT- The photo above shows a basically stock piston, if you look closely you can see the front orientation on the crown, pointing to the left. The last photo (I removed it and replaced w/this one) I'm unsure of the way the slot was slanting- but it should have been correct anyway.

Unless there are "left bank" and "right bank" pistons, one bank will have the slot on the major thrust side, the other bank will have the slot on the minor thrust side.

So unless there is a pin offset or a relief in the piston crown facing the valves, it really doesn't matter how they're installed, IMO.
 
#15 ·
The reason

I was concerned about the orientation of each piston and the slot. 2 pistons on each side had a burn hole through to the top ring. The only other odd thing I found was in the chambers of the head, on each head I found a square bump in the chamber casting right in front of the spark plug hole on the thrust side in all 4 pistons. Is it possible the bump impeded the flame travel and over the miles it burned a hole through all the pistons where the chamber had these bumps. The other 4 chambers did not have these bumps.
 
#16 ·
cobalt327 said:
Many pistons have a mark, notch, arrow, etc. to show "front" of the piston.

In your case, the photo shows how the pistons are installed:



EDIT- The photo above shows a basically stock piston, if you look closely you can see the front orientation on the crown, pointing to the left. The last photo (I removed it and replaced w/this one) I'm unsure of the way the slot was slanting- but it should have been correct anyway.

Unless there are "left bank" and "right bank" pistons, one bank will have the slot on the major thrust side, the other bank will have the slot on the minor thrust side.

So unless there is a pin offset or a relief in the piston crown facing the valves, it really doesn't matter how they're installed, IMO.
C327,
I don't think that is the same piston that he is talking about. The 'slot' is an after-thought that someone is using to relieve the expansion of the piston.

rsfyj,
Have you got a picture of the 'NEW' pistons for your Merc that shows this slot?
 
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