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Piston Installation

7K views 38 replies 12 participants last post by  PetesPonies 
#1 ·
atitagain has been looking at my build thread and brought to my attention that the pistons may be installed wrong. So let me post a picture as I was under the impression that the arrow is supposed to point towards the front, but it may be that the notch itself is supposed to be towards the front.

Which is correct?

Thanks, Allen
 

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#2 ·
The pistons don't matter ...but the connecting rods do. The piston pins are off set in the piston slightly and it was an old horse power trick to swap them around. It does put a very and I mean very slight more strain on the crankshaft but if you aren't looking for the 300.000 mile motor shouldn't be a problem. Just make sure the numbers on the rods are facing out!
 
#5 ·
Just make sure the numbers on the rods are facing out!
Looking back in my pictuces, I can clearly see that there are no numbers on the rods and caps facing the outside of the engine.

The engine (thank goodness) is still on the stand. Sounds like I need to take the oil pan back off and really check.

Next question is, can I just rotate the rod (and caps of course) and retighten the caps and carry on like nothing ever happened? :shrug:

Thanks,

Allen
 

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#3 ·
Just to explain why the position of the rods matter.

The proper chamfer on the rod has to go against the radius on the crank. It has been two years since I assembled my engine but I am remembering the rods had a big and little chamfer on them and you have to position them properly against that crank radius.
 
#6 ·
The notches face front. The chamfer on the rods face AWAY from the other rod on that crankpin. If the pistons are on the rods backward...ie. the notches face rearward, but the chamfer on the rods is in the right place, it's no big deal. In fact, that's an old trick to relieve the factory offset which side-loads the piston to mitigate piston "slap" before they have time to expand as the engine warms up. The pistons may be a bit noisy but the reduced friction will free up some horsepower. It doesn't put any additional stress on the crankshaft, either.
 
G
#7 ·
Allen, if there are no numbers on your rods/caps, then you better check the chamfers. The notches are supposed to face forward as everyone says. They could be installed backwards on purpose, but no reason in your case. Whenever I disassemble an engine and there are no numbers, or the numbers don't make since, I change them, stamp them right then.
 
#8 ·
I was looking for arrows stamped into the tops of your pistons and couldn't see anything. Then I realized you are calling the > notch an arrow. As others have said your pistons are technically installed backwards but if the manufacturer cut reliefs in both sides of the dome it obviously means that there is no cause for concern on the pistons. The rods are an entirely different story.
 
#10 ·
Sooooo are you saying you just installed them backward?
If so... sure just twist them around and re-tighten, I guess.
My advice...get a book with pictures that show you where the chamfer on the rods go.
Think about it....the chamfer show be up against the crankshaft throws...NOT the ajoining piston, right?!
(Now you got me scratching my head)
Get a book with pictures!!
6sally6
 
#13 ·
The picture shows the #4 and #8 rods/caps. I'm trying to figure out the "chamfers" that is being advised. Help me out a little here.

BTW, the numbers are not towards the cylinders as Tom Monroe's book suggest, so it looks like I will be trying to turn them in place.

I really want to know what I'm looking for on the chamfer thaough in case I do an engine with no markings on the rods.

Thanks again,

Allen
 

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#14 ·
That pic doesn't show the numbers I mean. I'm talking about stamped numbers, #1-#8. The rods will have a chamfer on both sides, but one side will be larger. You should see the difference, but you have to remove the cap and lift the rod off the journal.
 
#15 ·
Here is a picture of the numbers. I can see the chamfer on the sides of the piston rods. One side is basically square, the other side is sloped a bit. I'll try and get a picture of what that is for future references.

Also for future reference, you can forget about turning a piston rod with the engine together. That ain't happening!!

Now to figure out the best way to do this...ugggh

Allen
 

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#18 ·
never mind the numbers

Turn, never mind where the numbers are or are not, it doesn't matter. Why ? because it could have been renumbered at some point in its 50 yrs.........At the shop we have disassembled LOTS of Fords that were numbered as if they were a Chevy........We have sold MANY extra main bearings sets because some idiot hammered the thrust into position #5........

Now, I'll ask, are both banks like that ? CAN you turn the assembly over with a wrench ? Usually, if you have even ONE of the chamfers wrong, it won't turn over. The chamfers go towards the crank, unchamfored goes in towards the other rod of the journal's pair. I'm thinking you should take them off and check. LSG
 
#19 ·
Now, I'll ask, are both banks like that ? CAN you turn the assembly over with a wrench ? Usually, if you have even ONE of the chamfers wrong, it won't turn over. The chamfers go towards the crank, unchamfored goes in towards the other rod of the journal's pair. I'm thinking you should take them off and check. LSG
I could turn the assembly with a wrench. However, all of the chamfers were facing in (towards the other rod). I have rectified that situation. I will go ahead and tell that I did take the crank out instead of taking off the heads. I know, I know, what about the timing. Let's just say I payed close attention to what I was doing...

All I need to do is put the timing cover back on now and all is back to the point where I started.

Big shout out to atitagain for catching this in the photos!!

Allen
 
#20 ·
Absolutely hate to bring this thread back up. I installed the engine and transmission today (ALL went smooth as silk). The transmission mated to the engine with no troubles. Didn't have to force anything, it really just fell into place. Put the assembly in, no problems (the fan made a scratch on the radiator support). With the assembly in, I decide to put the nuts on the torque converter. Put the first one in, tighten it down and grab a 1/2" ratchet and socket to turn the engine and put the next nut on. Engine won't budge. I get a cheater and the engine still won't budge. Well, I finally left the office/warehouse because I couldn't get it to budge (even after removing 5 of the 8 spark plugs).

Question is, where to start looking for the problem? Engine has been sitting since September '16 but was pre-lubed. Also was no problem turning it over to re-install the pistons.

Allen
 
#22 ·
I actually can't say that with certainty. In other words, that's the only thing that has changed recently, however, I'm not sure if it would turn after everything was together before the transmission was attached. I honestly don't think the issue is with the trans, but I see where you're going...

Allen
 
G
#23 ·
When you install pistons, you rotate the crankshaft after each install. If something is bent, it will show up as you are turning by severely increased effort needed. So if you were checking things as you installed . . . . . .
 
#25 ·
I think you did not get the torque converter correctly seated before you tightened it down. It's a little tricky, you have to slide it on ( prefilled with fluid) and gently rotate it while seating it to feel basically engage 3 places. A lot of times it gets seated correctly and jarred out of place during the mating up. If you got it tight as you described, you most likely have destroyed the hub and it must be removed and replaced. Ask me how I learned all of this.... I'm really sorry... I know how maddening it can all be!
 
#26 ·
I will add a tip that I was given--- after it's seated and lined up with the flexplate holes tighten the first nut down and then LOOSEN it up. Rotate, tighten an loosen and repeat that until you have done all 4. Then tighten them back down. This will ensure it is properly and evenly seated....
 
#30 ·
The hub is on the torque converter where it engages the input shafts on the transmission. It is soft steel and will be easily damaged if tightened against the transmission out of alignment. That situation will also make it impossible to turn the crank. If you start it up that way, you will strip the gears in the pump housing as well.
 
#32 ·
I've got to be honest (although I could be wrong and you correct), this transmission really mated up easily to the engine. I had the engine on a pallet and had one of my guys and me place the transmission up to the engine and wiggle it in place. We had to turn the torque converter just a little for the bolt holes to line up and then all went smooth. Again, this may very well be what it is so I will loosen the bolt I have tightened and see what happens. If that doesn't get it, I will loosen the trans to block bolts and see.

Thanks to both of you,

Allen
 
#31 ·
Be mindful that the misalignment can also damage the splines on the input shaft and if that happened, you will have to pull it out and file them into shape again. I'd check that anyway because you will ruin the new converter too because you'll think it is seated but it won't be because the spline damage.
 
#36 ·
Well this takes us way back in the original post. Are you sure you have the rods in the correct way with the big chamfer on the throw side.

Did you plastigauge the rod/mains when you assembled the block?
 
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