I have searched and found a few threads, but all for performance upgrades, I�m doing a near stock rebuild and it�s my first time. Looking for some specific advice on my situation.

Engine: 5.3 LM7 from 2001-2002 Tahoe
Upgrades: Low end truck cam, LS7 springs (don�t believe those matter for what I�m asking but figured I�d mention)

Due to several internet and book sources I was under the impression that replacing my pistons was pretty much a necessity for a quality rebuild. I�ve since learned that may not be the case but, alas, I�ve already pressed off the stock pistons and everything is back from the machine shop.

So the machine shop has quoted me $380 to weight match my old piston assembly to my new piston assembly and press the new pins in. The pistons only cost me $190 (stock replacements) and I�ve already spent $1600 with them for block and head work. I�m really not wanting to spend that much for this job. My project has a long way to go still.

I have every rod and cap labeled to their cylinder. I still have all of my old pistons, rings, wrist pins and bearings. Can I just buy a precise scale for less than $380 and do this myself?

I could talk forever and I like to read and learn. let me know if you need more information.

 

For a stock rebuild with stock replacement pistons I would press them on the rods and run them the way they are. If you wanted to buy a scale and weight match them there is no harm in that. Most stock rebuilt engines are not balanced and have no issues with their balance. Just my opinion.

 

To balance they usually just add metal to the crank to ensure smooth rotation. Having a rotating assembly that is not balanced could cause some issues for reliability. I don't think they usually just weight match pistons....they could be off a few grams here or there but that's why they add Mallory to the crank, to offset weight from one end to the other.

 

Thanks for the reply!

If that cost was for balancing the entire rotating assembly and adding heavy metal to the crank I could understand it better. But they didn�t even ask that I bring the crank back in.

Just �bring us your old pistons, rings, pins and rods and we�ll match them and press the new ones in.�

Is heat pressing the pistons onto the rods really a $300+ job? Genuine question

 

Yep 👍

 

Thanks for the advice!

 

While you want a balanced crank at all times when it comes to it balancing of pistons cranks and rods(in weight matching and such) is usually something done to high performance builds. Why? Because you're gonna Rev the living daylights out of it and you want the least amount of vibration coming off these parts. Now why would you want the least amount of any type of vibration coming off these parts? Because it means wear and tear to include power loss in the long run.
Look at it in terms.of a drive shaft. The more vibration the less hp gets to your rear tires and will ultimately break. Now when it's nice and smooth majority of the hp is getting to the rear tires and you don't have to worry about breakage.
Will this benefit every engine of course but a stock rebuild has all the balancing it needs to get the job done. 🤘🏼

 

Vibration + harmonics = lost power, Good balance usually will equal longer engine life as well...

 

One method to "match" piston/pin weight is to fit lower weight pins, M-350.
This could save the high cost of Mallory "slugs" in the counter weights.

 

Based on the input I�ve gotten, for this stock rebuild I think I�ll just weigh my old pistons/pins/rings for each cylinder and weigh my new pistons/pins/rings for each cylinder. If there is no more than a few gram difference between old and new I�ll just run with it.

If it�s drastically different then I�ll get the shop involved.

 

A lower weight is fine, just overbalanced which is great.