Wrist pin slid out

[OldnSlow]

So while I was replacing my blower fan bearing, I was inspecting some internals. I see that my wrist pin has slid out and gouged the cylinder wall. I am not an internal engine guy (yet) . What do I need to replace? Can it be just that cylinder and piston? Or do I need to consider more? The engine runs good, I don’t want to dig any deeper than I need to. It is a 63 102hp. Thanks for any advice.

[OldnSlow]

Also, any clue what causes this?

[Vairone]

If the wrist pin is the correct size, the con-rod will need to be replaced as the wrist pin bore is too large.

Pull the head, remove the con-rod from the crank, remove the piston / rod / cylinder assembly and replace the parts as needed.

[Brizo]

Also, any clue what causes this?

If the pin end of the rod was heated with a torch, it may have been too hot and was stretched as they pushed the pin in place. Or if it was pressed together cold and not correctly aligned, the bore may be galled or stretched. I would look for damage to the piston pin bores also. It would be very rare but the pin diameter may have been too small.

[vairmech]

I personally would not take the chance and just replace everything for that cylinder. For the cost of a rod it is not worth worrying over if it is good or not.
You need a piston w/pin, cylinder and a rod. Maybe a single set of rings. Your piston and rod need to be taken apart and then weigh the piston without rings and also weigh the rod with nuts, then you need to match weights of the two new items to the old.

[Dennis66]

I agree with Ken. As long as you have the head off that side, it would be a good idea to check the other two cylinders. This could be from a shoddy rebuild job. We can give details of compressing rings, etc. When you are ready to assemble. Dennis

[66vairguy]

I personally would not take the chance and just replace everything for that cylinder. For the cost of a rod it is not worth worrying over if it is good or not.
You need a piston w/pin, cylinder and a rod. Maybe a single set of rings. Your piston and rod need to be taken apart and then weigh the piston without rings and also weigh the rod with nuts, then you need to match weights of the two new items to the old.

When a rod fails, often the block is damaged beyond repair. Replacing the rod makes sense.

You really don't know what was installed in your engine or if the piston or rod weight is correct/balanced. Trying to match it might not work.

The factory balanced ONLY opposing pistons and rods. I'm not aware of any special attention to factory rod balance, BUT the factory pistons were numbered in weight groups and the same number value had to be used on opposing pistons. Since it seems your pistons were replaced, please post a picture and we can tell if it is a stock replacement or an aftermarket piston. In the old days the TRW pistons were amazingly close in weight if you bought a set. Rarely did you need to balance them. If it is a stock piston you have no way of knowing if the builder made sure they were balanced!!! One option is to pull the opposing piston and rod and "balance" weigh them and try to get your new piston and rod equal (rarely done).

While balancing rods and pistons is preferred, it is difficult to do precisely. The factory rods varied and trying to grind off material can sometimes lead to a weak rod. I did mine to tight tolerances, but like many of the guys who build race engines, I had a number of rods and "cherry picked" them from a batch to get the weights close. Most do not have that luxury. If your engine is a "daily driver" then a good used rod will be fine, but note some of the EM engines used lighter rods vs. the turbo engines and later EM engines. So the replacement rod should be the same style.

While I'm not endorsing this. Many don't bother to "balance" rods and pistons for "daily drivers" and never have an issue.

[Wittsend]

To 66vairguy's point "While I'm not endorsing this. Many don't bother to "balance" rods and pistons for "daily drivers" and never have an issue." I did not balance the rods and pistons separately (which is proper) but I did compare them as opposing sets. Initially there was a .7 gram discrepancy on two sets and 1.3 gram discrepancy on the third set.

That being said the weights (rod & piston combined) varied between a low of 941.9 to a high of 945.1 grams (a 3.2 gram range). I also had a spare set of two but they each weighed a bit over 950 grams and I excluded using them. Wise or not I juggled two rods/pistons (by TOTAL weight) and got the discrepancy down to two sets at .3 grams and the third set at .7 grams. From what I have read under 1 gram discrepancy is desirable and for a low revving daily drive 2 grams is tolerable.

I say all that to illustrate what you might find. And as best you can have a target weight to strive for. You can:

1. Assume the opposing rod/piston were matched to the bad one. Removed the rod and piston and weigh each separately and seek similar new. Note that ideally the rod is weighed on each end and matched in that regard as well. If you doubt the original paired set were accurate you would have to remove the opposing side (and weigh) which doubles the work.

2. Seek a (used) relatively matching total weight rod & piston and hope for the best.

3. Acquire any available rod & piston and have an even greater hope for the best.

[66vairguy]

Good advice from Wittsend.

Your are at the point of doing an O.K. repair on an older engine, or going for a full proper overhaul that would be expensive.

While many of us like to do the best job, frankly less than best is fine for a daily driver hobby car that is not going to be abused or raced.

I don't have much experience with EM engines, but as I mentioned, knowledge posted over the years indicates the early EM cars rods were lighter/smaller. The first turbo cars got a more "robust" connecting rod that supposedly was used on all the 63 EM cars. Of course in 64 the EM cars got the long stroke engine. Hopefully someone with more knowledge than myself will confirm or correct this.

[Vairone]

I don't have much experience with EM engines, but as I mentioned, knowledge posted over the years indicates the early EM cars rods were lighter/smaller. The first turbo cars got a more "robust" connecting rod that supposedly was used on all the 63 EM cars. Of course in 64 the EM cars got the long stroke engine. Hopefully someone with more knowledge than myself will confirm or correct this.

Early connecting rods are lighter because they have a thinner cross section on the beam. 1962-63 turbo engines had an increased cross section for additional strength. All 1964-69 connecting rods followed with the same, larger, cross section.

[vairmech]

You guys are getting way to technical for this repair! I stand with what I said about matching weights! BTW, a 102 used the big rods and 1.25" dia valve springs!

If this is a repair that is what should be done. Remember, he said it was running good with no issues.
All I can say is send the parts to me and I will match weights and I might even be able to find the same rod number. If you have anything other than a stock piston, that may be an issue.

[RexJohnson]

Pins can move on factory piston just like ones that were not properly done. I have seen 102's with the light rods so they probably used the rods that the factory had on hand. Like Ken said keep it a simple repair.

[OldnSlow]

You guys are awesome! This is great advice and knowledge. I ordered a new cylinder, piston, rod, rings, and gaskets with the pin pressed in from Clark's. This is an occasional driver that is driven easy and will be stored during the hard winters up here in the Rockies, so I am going to go for a reasonable repair. On y'alls advice, I pulled the other head as well to inspect the pistons and cylinders. To my inexperienced eye, it all looks ok. My brother is a high-end bike and OHV engine builder, so he is going to come and take a peek as well. I do have a few questions, where I pulled the head on the other side, do I need to replace the head gaskets and the cylinder to block gaskets? If I have to do that, is it worth honing and re-ringing it at the same time? Again, it ran well and had good compression, that one cylinder was low, but not as bad as you would think looking at it. I will attach pictures so that you folks can tell me what you think.
Again, many thanks!

[jimbrandberg]

I would've probably just replaced the one rod/piston/cylinder assembly with the engine still in the chassis. I may have still used the same piston since it's especially the rod that holds the pin. Maybe not since the groove in the cylinder probably didn't do the piston skirt and rings much good.
Now you're in the predicament of where to draw the line "as long as you're in there".
I like to knock the pistons into the top of the cylinders with a ring compressor but you can't do that when there's a carbon ridge. I suppose Early is easier to install from the bottom since they don't have the clearance slot. I like to present the rod/piston/cylinder to the crankcase as an assembly.
I've seen big or little connecting rods in 102s so hopefully the one you got matches okay. The big 63 rod cap is different than a 64 and later, it has more clearance for the wide cam lobes. It's not an issue if someone has put a Late Model cam in there.

I would leave cylinder base gaskets if I'm not removing the cylinders but would probably change them if they're disassembled.
I would replace the head gaskets. I think the stock steel crushing kind are more forgiving if the head gasket surface has not been flycut again.
Don't forget the cylinder baffles and put the inner o-ring on the pushrod tube after you put it through the hole in the head. I go in stages with a criss-cross pattern for torquing the heads with a final of 30#s. I generally use new head nuts.

It will be interesting to read how much stuff you did and how it all comes out. I tend to take a lot more chances with my own engine.

I wonder if your predicament is because someone didn't heat the rod when installing the pin.

[Dennis66]

Essentially, you have this cylinder apart. Carefully remove the rings from the piston and measure the end gap in the cylinder. If gap is okay, I wouldn't bother with the other cylinders. If gap is excessive, I would then check all cylinders. As Jim said, base gaskets are optional, but quite a bit of work - either pulling rod caps, or fitting jugs back over pistons and rings. I've done it both ways. Head gaskets, definitely. Jim seems like steel, I prefer copper. Not very expensive. Dennis

[66vairguy]

Just my OPINION, but based on your input -- I'd just repair the one cylinder and not touch the others. As for the other cylinders, my experience is I rarely find a Corvair cylinder with a lot of upper chamber wear, just a ridge of carbon that when removed shows no wear that needs to be reamed. Point is - don't do new rings and hone the other cylinders. If the wear is that bad, and it DOES NOT appear to be the case, then a full rebuild would be the best.

If you don't "disturb" the other cylinders (and let crud in the gap) then cylinder to block gaskets do NOT need to be changed.

Unless I need a thicker head gasket, I use the compressible steel gaskets. The are more forgiving of gasket surface imperfections and any minor variations due to minor head warping. The problems with steel or copper seem to be about the same and I suspect come down to installation problems. A fellow in our club had a leaking head gasket issue that was found to be a gasket that "dropped" out of position when the head was installed and was "smashed"!!!

You need to clean the gasket surfaces and carefully look for any damage.

Good luck.