Piston tongue

D

Don S

Senior Member
I have just installed the pistons back in the block,head on etc,realised that I may have the piston tongue facing the wrong way. I have them all facing the camshaft. Is this a problem or not. I could still remove them and change them to face the other side,some input from our engine builders please. These are the solid skirt type piston. Thanks
 
Don S said:
I have just installed the pistons back in the block,head on etc,realised that I may have the piston tongue facing the wrong way. I have them all facing the camshaft. Is this a problem or not. I could still remove them and change them to face the other side,some input from our engine builders please. These are the solid skirt type piston. Thanks
Click to expand...

Who manufactured your pistons?
 
Doesn't matter with a no slit piston as long as the rods are right .The cap oil slinger opening must face the camshaft.
 
I never heard the expression "piston tongue". What is it?

If one side of the skirt has more wear surface than the other side, then that side should be the thrust side, which is the cam side.
 
Arrowhead pistons? Wow, have they made any of those since the 1960's?
I believe the gentleman here has the solid skirt pistons of the type that were available back in the 1980's and early 1990's sold by Snyders or Brattons. The catalog at the time stated that the pistons were to be installed so that the "popsicle stick shaped" thickened portion was facing a certain way, because this made them slightly heavier on one side in order to counter the slight imbalance due to rotational thrust forces.

Maybe somebody here can recall, has an old catalog, or informed opinion regarding the proper orientation. I do remember that the catalog was emphatic about this matter.
 
Ursus,you are right,these pistons are from the 90's. The tongue is a 3/4" wide piece the shape of a tongue cast into the piston on one side only. Heard somewhere that the tongue should face one way or the other. Hope someone knows if it makes a difference and why.
 
The reinforcing that you see in side of the piston is where they used to put the expansion slot before they cheapened them up, and quit the slot.
 
You can go to synder's on line and you can e-mail them , I'me sure they can answer your question. I've asked them a few questions and they have been very helpful.
 
I'm getting set to do the exact same thing with a set from Mac's. New pistons with a casting on one side that looks like a tongue depressor. I remember hearing that it faced the "thrust" side of the engine. The pistons also have a red dot on the wrist pin boss.
Thanks
Pete
 
Pistons are generally bored with the wrist pin hole slightly offset.
This is why pistons have orientation marks such as arrows,dots and possibly in your case the tongue.
As I understand it the offset sets your thrust side & discourages piston slap.
If you have documented advice on the piston orientation then they must be installed accordingly or you'll end up with a very noisy engine and probably a "high wear" situation.
 
I see in Macs catalogue that the thick section of the piston should face the passenger side. Now does that mean that the thick section is on the passenger side or on the driver side facing the passenger side. Shouldn't be this confusing !!
 
Don, I admire your dogged persistence in this pursuit! I have seen folks post photos of their engines here on the Barn and noticed the pistons placed with the thickened portion on either side of the block. I emailed one such fellow to ask about this once but he never responded. I do know that this feature was common on Silvolite 28-34 Ford pistons for many years. I am sure many are unaware of it.

Mr. Kohnke notes that some pistons had the thickened area on the slit side, which is usually the driver's side. He also referred to it as reinforcement, which makes sense because the slit tended to be a site of crack formation on the old pistons with only a slit on that side. The slotted pistons havent been made for quite a while perhaps because aluminum alloys have improved to where this feature is no longer useful.

My understanding is that the major thrust occurs on the expansion stroke as the piston is driven downward by combustion. The thrust force falls more on the driver's side of the piston as the force is transmitted through an angled connecting rod. To compensate for this imbalance, pistons may be designed with a slight offset in the pin location or a slight addition of weight to the non-thrust side. The non-thrust side in the Model-A is on the passenger side of the cylinder and that is where Mac's says to place the thickened or weighted side of the piston.
 
Pistontongue.jpg
 
The thrust side of a model A engine is the valve chamber side.
The Left hand driver's side is the non-thrust side.

Ford has partially compensated for this by moving the bore centerline 0.125 away from the thrust side. This results in decreased angularity and thrust pressure.

All model A pistons I have encountered have centered (not offset) pin centers.
Engines with zero bore offset often have offset pins.

Having both would definitely affect engine breathing (like a cam profile change)
and asymmetrical rod angularity also affects the torque/HP curve.

mmfp_0711_05_z+ford_small_block_stroker_engine_build+rod_angularity_and_piston_side_thrust.jpg
 
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