Piston tongue

[Don S]

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

[Dave in MN]

Originally Posted by Don S

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

Who manufactured your pistons?

[Gary WA]

Doesn't matter with a no slit piston as long as the rods are right .The cap oil slinger opening must face the camshaft.

[Don S]

So having them facing the camshaft is not a problem,oil cups all face the cam.

[Don S]

I just checked a nos set of Arrowhead pistons with the split skirt,they have no tongue.

[Tom Wesenberg]

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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.

[ursus]

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.

[Don S]

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.

[Kohnke Rebabbitting]

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.

[Don S]

So any thoughts on orientation of the tongue?

[TDO]

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.

[Peter J]

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

[Craig Lewis]

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.

[Kohnke Rebabbitting]

If piston clearance is right, the pistion slap will only come from rods being out of alignment.

[Don S]

Lots of ideas but no conclusive right way / wrong way ??

[Don S]

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 !!

[George Miller]

I have worked on engines for 60 years never seen a piston with a tongue.

[ursus]

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.

[MikeK]

[MikeK]

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.

[Don S]

From Mikek's description it appears that I will pull the pistons and 180 deg them so the tongue is on the cam side. No answer from Macs or Snyders ,I e-mailed them both.Thanks

[Tom Wesenberg]

Originally Posted by Don S

From Mikek's description it appears that I will pull the pistons and 180 deg them so the tongue is on the cam side. No answer from Macs or Snyders ,I e-mailed them both.Thanks

On the outside of the piston skirt, is the contact area equal on both sides? I've seen some pistons with less contact area on the non-thrust side, just for the benefit of less drag.

[Don S]

Tom I can't tell now because they will be staying in place. I believe they may have been the Silvolite pistons as mentioned by Ursus. Should have her running this weekend.I will let you all know how it goes.

[George Miller]

Originally Posted by Don S

Tom I can't tell now because they will be staying in place. I believe they may have been the Silvolite pistons as mentioned by Ursus. Should have her running this weekend.I will let you all know how it goes.

You know the dipper has to point to the valve side. You will have to take the wrist pins out and turn the piston 180 on the rod. If they are all in the same way, I would just leave them like they are.

[Don S]

George, there were 2 right and 2 wrong,and yes I did have to remove the pins and 180 the pistons on the rods. The dippers all face the cam as they should. Just finishing up prior to running her. Thanks for all the support !

[George Miller]

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Originally Posted by 1930 coupe

I found a old piston stamped front from the factory and the slot is on the drivers side. On all the pistons I have seen the slot is in the tongue, so judging from this piston it seems the tongue goes on the drivers side. I do not know if it makes a big difference or not.

If the slot is in the piston yes it makes a difference. If no slot probable does not make a difference. If it makes a difference they should be marked front.
With that said I would put the side that the slot use to be in to the driver side.

The piston on newer cars have the wrist pin off set to one side. They have to go in with the mark on top to the front.