Drop in LS3 pistons and rods

[Rem0v3r]

Well I got my forged pistons and rods in... and I screwed up..
The kit was advertised as ls3 drop in, which is cool, except I have the l99 and forgot that the pistons and crank are different in the l99..

I've learned a lot so far so I'm gunna post the info for anyone who cares..

The l99 piston, rings and pin weighs 661.5 grams (I only weighed 1)
The gen 4 rod and bearing weighed 681.4 grams

The tsp h beam rods weighed from 630.9 (bearing weighed 37.2 grams and not included in the above number) grams to 632.2 grams (1.4 gram variance)

The JE pistons weighed from 522.5 grams to 524.6 grams (2.1 gram variance).. just to note that 6 of the pistons weighed within half a gram of each other..

I'm not sure what an acceptable balance is but I wanted to get them within 0.5 gram of each other. I may contact JE to see about switching out the lightest and heaviest piston so I dont have to cut the shit out of all of these...

With pins and rings, the new assembly weighs around 23 grams more on the piston side than the old pistons which means I'm going to have to either add weight to the old crankshaft, find an ls3 crankshaft used, or buy a forged unit..

Fun fact, chevrolet must have substituted my crankshaft for a different one during engine building as the codes dont match what is actually supposed to be in there.

[eLeSthree]

How did you get those weights for the stock stuff? I was looking for the stock ls3 bob weight for a loong time. Gave up and bought a motor.

CP/Carrillo said they could make me a drop in set if I gave them the weight. Kinda silly though to spend that much on custom stuff just to NOT balance the crank.

Whos kit did you buy? LS1tech seems to think the summit stuff aint bad.

[bayarea408]

For as long as i can remember the Differences between the 2 engines lies in the valve train DOD AFM / cam, less duration and less lift. The Pistons are butterfly cut for valve relief reducing the compression from 10.7:1 to 10.4:1. The two engine short blocks bore and stroke the same. Aside from the valve train and slight compression difference the only other difference is how the PCV system is ran and what trans it hooks up too.

So from how i understand it, you should be able to drop in your LS3 forged internals on the L99 as long as you have a cam job / LS3 conversion for proper valve train spec's and travel.

If i am WRONG, please let us know any specific differentiation in the crank. The rod and crank should be the same.

[gsxrturbo]

the l99 crankshafts are lighter then the ls3.i call tsp about there drop in pistons and rods.they said there kit would not work on a l99.

[Rem0v3r]

I pulled the pistons and rods out, dismantled one and weighed it...
Wish i had caught my mistake before they shipped it out.. now I'm gunna have to pay extra to have weight added to the crank.

[RupertPupkin]

So these drop ins you don’t have to get them balanced, or are they already balanced prior to shipment?

I was told that the block would have to be honed and spec’d for the drop ins to work. At that point, buying anew block would’ve been better

[eLeSthree]

Originally Posted by RupertPupkin

So these drop ins you don’t have to get them balanced, or are they already balanced prior to shipment?

I was told that the block would have to be honed and spec’d for the drop ins to work. At that point, buying anew block would’ve been better

That's why I was asking who's kit this is. To my knowledge, no one makes a drop in piston rod kit for the ls3 that does NOT require balancing of the crank. Summit offers what they call a "drop in" piston rod upgrade, but when you read closely it requires balancing.

Vengeance Racing makes a drop in kit for the LT1 that matches the stock weight and does not require balancing, but not ls3.

If you have a low mile stock bore 4.065 ls3 block, you could probably get away with just balancing and dropping in a 4.065 piston, but any engine builder will advise you to go to a 4.070 piston and hone the cylinders from 4.065 to 4.070. That's the right way to do it, but I have done it the wrong way and that LS1 motor is still running strong today in a 2003 Silverado RCSB.

[UNRIVALED SS]

It doesn’t really matter what you buy. There is no easy way to do what you’re trying to do.
You need to disassemble the thing and have that rotating assembly balanced by a Competent machine shop.
While you’re at it have them check the clearance in those forged pistons and make sure you have the proper rings for the hone on the cylinders.
Better yet , have them do the least little bit of touch up honing to give the right texture for the rings you bought.
There’s no quick drop in way to do this level of engine modification.
Good luck with it .

[racesloth]

Originally Posted by Rem0v3r

I pulled the pistons and rods out, dismantled one and weighed it...
Wish i had caught my mistake before they shipped it out.. now I'm gunna have to pay extra to have weight added to the crank.

Measure out the cost of adding weight and labor to make your crank work - it may be easier to just buy a forged crank and have a stout bottom end...

[Juiced1]

Pretty sure the L99 and LS3 have the same crank.

[Rem0v3r]

The "kit" is sold by texas speed but is for ls3.. I have an l99 and the cranks are different. The weights are different I believe due to the valve reliefs that the l99 has but the ls3 does not..
My crank was balanced.. I'm having some block work done and hopefully I'll be re assembling this weekend. I'll keep you guys posted.

[Rem0v3r]

Originally Posted by racesloth

Measure out the cost of adding weight and labor to make your crank work - it may be easier to just buy a forged crank and have a stout bottom end...

Cost me $245

[Rem0v3r]

Originally Posted by eLeSthree

That's why I was asking who's kit this is. To my knowledge, no one makes a drop in piston rod kit for the ls3 that does NOT require balancing of the crank. Summit offers what they call a "drop in" piston rod upgrade, but when you read closely it requires balancing.

Vengeance Racing makes a drop in kit for the LT1 that matches the stock weight and does not require balancing, but not ls3.

If you have a low mile stock bore 4.065 ls3 block, you could probably get away with just balancing and dropping in a 4.065 piston, but any engine builder will advise you to go to a 4.070 piston and hone the cylinders from 4.065 to 4.070. That's the right way to do it, but I have done it the wrong way and that LS1 motor is still running strong today in a 2003 Silverado RCSB.

Unfortunately I already spent the money.. it's all good now after the balance.. I did nd a cracked sleeve after honing.. it's currently being replaced.. rings are now gapped at 26-28 instead of the 10 that Chevy did lol.. the pistons and rods were in perfect condition surprisingly.. no cracks, no microwelds.. nothing.. really not sure how my sleeve cracked.. I've always ran on the conservative side...

If I hadn't have pulled the pistons the crack would have gone un noticed and I probably would have windowed the block sooner or later.