Removing Pistons from Rods 383

[miller]

Just for what it's worth...
I 'still' feel like crap, on my piston/rod deal. Trusted a engine shop to mount 'em for me, after one pin didn't drop in. Long story short, piston cracked on the press.

Probably just me, being the old guy I am, but does not make me wonder why...in the manual, shows the 'tool' to use, and how to use it.

 

[Cranky]

It is normal to heat the small end to just past blue (straw), to install the piston pin. I heat to this range, and do not go to cherry red. You will damage the rod at this level. If you do not heat it enough, it will cool and contract too fast, and possibly not get the pin installed properly.

Problem is, I've seen way too many overheat them. That's when I started doing my own.

I do not know of anyone who does this. The pistons are matched to the lightest one, the rod big ends are weight matched, then the overall rod weight is matched by grinding the small end. Piston pins are usually assigned to a piston to get the lightest piston/pin combo. One set of rings, and one set of rod bearings are weighed for bobweight computation, and the last is about 4 grams of oil weight is added. You will NEVER get everything exactly the same weight, so why split hairs over it. A half gram spread is pretty damn good considering stock specs are 2 grams.

Right but I'm thinking that the rods' small end and pistons could be weighed in order to determine if they need to be balanced. If they do indeed need balancing, then they would have to come apart for removing any weight off the top of the rod ends or pistons. Couldn't you place the rods' big end on the balance fixture with the piston and little end on the scale and all of them were the same....then place the big end on the scale with the piston acting as a holding fixture for the small end, wouldn't that work....or at least tell if it's close enough?

 

[condor74]

Problem is, I've seen way too many overheat them. That's when I started doing my own.

Right but I'm thinking that the rods' small end and pistons could be weighed in order to determine if they need to be balanced. If they do indeed need balancing, then they would have to come apart for removing any weight off the top of the rod ends or pistons. Couldn't you place the rods' big end on the balance fixture with the piston and little end on the scale and all of them were the same....then place the big end on the scale with the piston acting as a holding fixture for the small end, wouldn't that work....or at least tell if it's close enough?

I could probably do that if I was doing the balancing job myself but to convince a shop to do it that way may be a challenge.

 

[69Bee]

Problem is, I've seen way too many overheat them. That's when I started doing my own.

Right but I'm thinking that the rods' small end and pistons could be weighed in order to determine if they need to be balanced. If they do indeed need balancing, then they would have to come apart for removing any weight off the top of the rod ends or pistons. Couldn't you place the rods' big end on the balance fixture with the piston and little end on the scale and all of them were the same....then place the big end on the scale with the piston acting as a holding fixture for the small end, wouldn't that work....or at least tell if it's close enough?

I agree, it is a delicate operation. Not enough heat, pin stops too early, and too much heat, pins can fall out. I had a customer do his own, and made them cherry red, and I basically could push the pins out of the NEW Eagle rods with my thumb.

As far as the piston/rod assy balance, they really need to be balanced separate because the rods do both rotating (big end) and reciprocating (small end & piston/pin) If the piston/pin/small end are made the same weight as an assy, the reciprocating aspect could still be screwed up.

As far as getting them apart, I use two old piston pins on the flats of the piston, and press out the pin with another old pin that is smaller than the original pin. You just need to be careful, and if the pin boss gets pinched, it can be honed on a rod hone with a piston mandrel to fix it.

 

[Cranky]

I could probably do that if I was doing the balancing job myself but to convince a shop to do it that way may be a challenge.

Roll him a bone and offer to pay for his time if he can check them like that....

I agree, it is a delicate operation. Not enough heat, pin stops too early, and too much heat, pins can fall out. I had a customer do his own, and made them cherry red, and I basically could push the pins out of the NEW Eagle rods with my thumb.

As far as the piston/rod assy balance, they really need to be balanced separate because the rods do both rotating (big end) and reciprocating (small end & piston/pin) If the piston/pin/small end are made the same weight as an assy, the reciprocating aspect could still be screwed up.

As far as getting them apart, I use two old piston pins on the flats of the piston, and press out the pin with another old pin that is smaller than the original pin. You just need to be careful, and if the pin boss gets pinched, it can be honed on a rod hone with a piston mandrel to fix it.

Yeah, I understand the balance recip vs rot etc but if the pistons and little ends are all pretty much the same weight in relation to each other, then they were probably balanced. That's what I was talking about. If the weights vary, then they probably were not so then you need to take things apart. I was just talking about a way to find out if the rod and pistons had been done and to see if things were equal. After all, the little ends should be the same along with the pistons right? Same thing with the big end.

Years ago I machined a simple fixture to support the piston at the pin boss for pressing the piston pins....in or out.

 

[mopar 3 B]

If they have to come apart why not fix the rods for foating pins and minimize the possibility of piston damage? Removing the piston pin is way simpler than installing them.
Rods are also lots easier to come by.

 

[condor74]

Installation is easy. I have hung many press fit pistons using a rod oven and in a pinch a gas range top stove. Just heat the small end and the pin slides right in. That part has never been a problem.

 

[mopar 3 B]

Anyone ever shrunk the pin using dried ice? We use to do it with close tolerance fuel injectors.

 

[condor74]

I have done that installing hardened valve seats in heads.

Anyone ever shrunk the pin using dried ice? We use to do it with close tolerance fuel injectors.

 

[Mike67]

I've read through all of the post and have not seen this question asked....why are you worried about it? Is this a hipo hi rpm motor?
Secondly if you are worried about the piston be damaged why don't you just pony up the $60 just to be safe? Just curious....

 

[condor74]

I've read through all of the post and have not seen this question asked....why are you worried about it? Is this a hipo hi rpm motor?
Secondly if you are worried about the piston be damaged why don't you just pony up the $60 just to be safe? Just curious....

Yes it is a high rpm high performance motor. 11.5 to 1 forged pistons are performance oriented. The reason I have not just ponied up is I am not sure I trust a shop not to make a mistake. If there was a good local shop that was familiar with mopar I would feel better. I picture pistons re mounted backwards on rods. Maybe I am being paranoid. These are the joys of trying to build performance on a budget.

 

[Cranky]

Yes it is a high rpm high performance motor. 11.5 to 1 forged pistons are performance oriented. The reason I have not just ponied up is I am not sure I trust a shop not to make a mistake. If there was a good local shop that was familiar with mopar I would feel better. I picture pistons re mounted backwards on rods. Maybe I am being paranoid. These are the joys of trying to build performance on a budget.

I feel your pain on not trusting the local shops. Not too long ago I drove 80 miles one way to have some work done by a good shop that actually likes Mopar and this is Houston! All the guys that were close by and good with Mopars have either died or retired. Even the best Chevy shop around (or so they say) seems to not care about anything Mopar. I think it's rather sad that they have so much business with GM products that they think they can can do shoddy work on anything not GM. Makes me want to take any GM work I might get to them....NOT!!

 

[condor74]

I feel your pain on not trusting the local shops. Not too long ago I drove 80 miles one way to have some work done by a good shop that actually likes Mopar and this is Houston! All the guys that were close by and good with Mopars have either died or retired. Even the best Chevy shop around (or so they say) seems to not care about anything Mopar. I think it's rather sad that they have so much business with GM products that they think they can can do shoddy work on anything not GM. Makes me want to take any GM work I might get to them....NOT!!

My issue was I once had to explain to a respected chevy machinist that mopar rods have an oil squirt hole that sprays on the opposite bank and it does matter which way the pistons are oriented on the rod. I wonder how many are running around with this incorrect assembled by so called experts .

 

[69Bee]

My issue was I once had to explain to a respected chevy machinist that mopar rods have an oil squirt hole that sprays on the opposite bank and it does matter which way the pistons are oriented on the rod. I wonder how many are running around with this incorrect assembled by so called experts .

Ummm, while the rods do have an oil squirt channel, todays bearings do NOT have the "V" notch for the hole. The real and actual reason rods go on the piston in a certain way is that the rod has a larger chamfer that is oriented towards the journal radius for clearance. If you install two rods on a journal with the tangs in, you will lock it up tighter than Dicks hatband due to running the rod (or rod bearing) into the crank radius. On Mopars, the bearing tangs go to the outside of the motor. Also, pistons have an offset (usually 0.060") to counteract the effects of the thrust angle due to the rotation of the crankshaft. That is why pistons have a front, in addition to valve notches or domes that need to be taken into account for clearance.

 

[condor74]

Ummm, while the rods do have an oil squirt channel, todays bearings do NOT have the "V" notch for the hole. The real and actual reason rods go on the piston in a certain way is that the rod has a larger chamfer that is oriented towards the journal radius for clearance. If you install two rods on a journal with the tangs in, you will lock it up tighter than Dicks hatband due to running the rod (or rod bearing) into the crank radius. On Mopars, the bearing tangs go to the outside of the motor. Also, pistons have an offset (usually 0.060") to counteract the effects of the thrust angle due to the rotation of the crankshaft. That is why pistons have a front, in addition to valve notches or domes that need to be taken into account for clearance.

I agree and the squirt hole is how I have always oriented them. Pistons on this engine do not have a front and the orientation of the pistons is set due to the shape of the wedge shaped dome. with the relief in the middle for the spark plug. On flat tops you are corrct.

 

[condor74]

I finally got around to removing the crankshaft, rods, and pistons so I can send them in to have them broke down and balanced. I have had a lot of other things going on from my Daughters 4H, the holidays, and campaigning my Dodge Dart bracket car. I originally started this build back in 2011. I hope to have it going soon though.

 

[mopar 3 B]

My issue was I once had to explain to a respected chevy machinist that mopar rods have an oil squirt hole that sprays on the opposite bank and it does matter which way the pistons are oriented on the rod. I wonder how many are running around with this incorrect assembled by so called experts .

Piston makes no difference but the rod sure does. Putting the piston on the rod right just helps prevent the rod from being installed wrong.

 

[condor74]

So I called down to the machine shop today to see how the balance is going. He explains that he needs a flex plate as he doesn't have a Chrysler one laying around. I told him I dropped of my Moroso SFI approved flex plate off with the pistons rods and crank. He puts me on hold and comes back a few minutes later saying he found it. and it was blending in with the cart it was sitting on. Bright gold colored flex plate blending? I know it may have confused him because it doesn't look like the standard Chrysler 4 ear flex plate. Hope this is not indicative of things to come.

 

[fratzog lover]

Would love to know how this story ended.

 

[moper]

With the proper fixture they can be pressed off safely. But bad things can still happen and if they get damaged that's it. If it was me I'd have them take them off and if they damage one it's free. Then just buy a new set of something modern and have that balanced... The rods can be honed to install as full floating if the pistons have the grooves for the retaining clips.