How to R&R pistons and Balance Rods

[BogusSVO]

How to R&R pistons and Balance Rods
1G 6 Bolt 4G63T

The used rods and pistons, the pistons are being replaced due to cracked and broken ring lands.

I start off by marking the front of the rod with a center punch

Next is to find the proper sized press pieces to press out the wrist pins.

Due to the pressures used to press out the wrist pin, care must be used, the piston itself can bust sending pieces of it flying that can and will cause injury.

After the pistons have been pressed off, and the small end inspected for scoring, the rods need to be numbered on both the rod and end cap.

Now the rod and caps can be split and cleaned, I use a glass beader to remove all the grime

Once that is done I spray them down with a good brake cleaner and blow them dry

Chase the rod bolt threads with a nut to remove any dust left from the glass beading.

Now to match the rods back with the caps

Install the rod nuts.

Now the rods are clean and assembled, they can be balanced. Start off by weighing all the small ends

The weight will be matched to the lightest one.

Once the small ends are matched, weigh the overall weight of each rod, and match the overall weight by removing material from the bottom of the rod.

Now that is done, it is time to match the weights of the pistons WITH OUT the wrist pin installed.

Then weight match the wrist pins.

Now that all the weights are with in 1/10 a gram the pistons can be hung back on the connecting rods. The small ends must be heated so the wrist pin can slip through it.

This must be done very quickly so the wrist pin is fully in place before the small end of the rod contracts around the wrist pin holding it in place.

 

[dsm10o0]

How much would you charge to put 2g pistons on 1g rods?

 

[mitsuturbo]

Do you not generally clip the caps and rehone the big end before balancing the rods, or did you skip that in this tutorial for the sake of keeping it short and sweet? Also, do you usually take material off the bottom of the cap, or do you sometimes round off the area around the rod bolts? I've seen both methods used, and they both seem to be effective. However, whenever we did this, we took from the bottom of the cap.

 

[BogusSVO]

Most of the time the rods get checked for spec, but not polished. I just skipped the step on checking the big ends, Guess that's another procedure I should do a write up on.

I tend to balance on the bottom of the rod. I have seen the method where some take it from the rod bolt boss.

 

[GSTwithPSI]

Dale, what's the purpose of indexing the front of the rod?

 

[BogusSVO]

It helps to keep the rod orientated to the front of the engine.

On a 4 cylinder engine, and most V6 engines it really will not matter if the rod is flipped, since they have individual rod throws on the crank, the rods are made with large bevels in the rod so they do not contact the radius on the crank.

Now on a V8 with a shared rod throw, the rods have a large and small bevel, the rods must be hung so the small bevels face each other. If the small bevel faces the crank the small bevel can contact the crank and cause a failure.

 

[biglady112]

For those guys doing this at home or at a friends, you do not have to heat the small end. We were able to press in the new pins and new pistons without any heat. We used the same press and tooling that we used to press the broken pistons off. The heat makes things easier, but it can be done without it.

 

[mitsuturbo]

The rods in our engines do have a small oil exit hole that happens to help lubricate the thrust side of the cylinder wall. If the rods are installed 180 out, things won't work as intended. I've never installed a rod backward, but i'm sure it's probably not good. I expect you may end up with a lot of unwanted scuffing on your piston and cylinder wall, to say the least. Furthermore, stock 4g63 rods also have something cast into them which denotes the "front" facing side. The procedure as illustrated is great for a general audience working with more than just 4g63 stockers. I always stamped the rod bolt bosses on the rod and cap so that they could be easily matched if they were somehow separated and mixed up.

 

[GSTwithPSI]

I'm fairly sure you can't install a stock rod backward (as Dale confirmed), which is why I was asking what he indexed the front of the rods for. They are symmetrical, and the only oil holes I've ever seen in stock rods were centered in both the wrist pin and crankshaft bores. Can you elaborate more on what you are referring to?

 

[BogusSVO]

You are correct about that on the oil jet hole on the stock rods, that did not even dawn on me.

I have been looking at H beams the past couple weeks, and they do not even have the oil jet.


The Dot I stamp goes back to the first weeks of training 20 years ago, it just helps idiot proof it if the rods get set to the side for a few weeks and you forget the orientation.

Stamping the rods and caps should be done when the engine is tore down, here again, training.

 

[mitsuturbo]

Quoting GSTwithPSI:
I'm fairly sure you can't install a stock rod backward (as Dale confirmed), which is why I was asking what he indexed the front of the rods for. They are symmetrical, and the only oil holes I've ever seen in stock rods were centered in both the wrist pin and crankshaft bores. Can you elaborate more on what you are referring to?

See that hole in the top side of the hole on the big end? Look at where it goes...

 

[GSTwithPSI]

I know what hole you are talking about, I had just never seen it written anywhere that it was for lubricating the thrust side of the cylinder wall. That does make sense, but I have always read that the stock rods have the oil hole on the exhaust side to cool the exhaust side of the piston crown. This is the same reason the oil squirters are located on the exhaust side of the motor.

I've always installed my rods this way (hole toward the exhaust side), but I don't necessarily think installing one the other way around would be detrimental, at least not anymore than removing the oil squirters from the block would be. Please, mitsuturbo or Dale, chime in with your thoughts.

 

[mitsuturbo]

Well, considering Eagle rods don't even have that hole in them, and they're still being used successfully, it must be unnecessary. So i guess it would likely make no difference if they were installed "backward".

(this may help explain why my oil pressure is so high now that i have eagle rods as well)