Hello all,

First of all, thanks for your time and for reading this. This is my first big engine build/swap so these questions are going to be very entry level and are more confirmations of my understanding from a lot of the great info I've gathered from everyone on this site. I've been a member of car specific forums in the past and can understand these types of post can be a little frustrating sometimes. If you feel like I'm asking questions that are too simple or whatnot, feel free just to click along to the next post.

I'm in the early phases of an LY6 build for a BMW E46 LS swap. I have my LY6 torn down and at the machine shop. It has a little over 70k miles and was from a salt truck from Maine so there were probably many hours of idle time as well. Unsurprisingly the machine shop found that the cylinders were out of round and recommended overboring to 4.030. Magnaflux and head tests checked out and the crank may need a slight polish. Everything else seems to be within normal working order. As with just about everyone, I'm definitely budget conscious but want to invest the money where it counts to make this build a successful one with a good longevity. Not trying to cut corners and have to pull the engine and start again a year after it's done. I am going to keep everything N/A, looking at texas speed BFD cam with corresponding pushrods, valve springs, long tube headers from sikky and obviously a tune from a local shop. There are two other builds like this I've found online and both resulted in ~450whp. So those are my goals. Now on to my main questions:

In selecting the rods and pistons I've come across a couple combinations and am leaning toward one. I was hoping to check some of my understanding here and see if I can find out where my gaps in knowledge are. My machine shop has been really helpful, but I'm just trying to bring enough understanding to the game to have a good conversation about options with them.

Currently looking at a combination of forged pistons and rods from Mahle and Callies Compstar. Previous posts on LS1tech seem to like these brands. Specifically I'm looking at the 4.030, 4032 alloy dome pistons from Mahle:

ls-6-0-&-6-2-dome-2020-web.pdf (mahle.com)

Combined with the 6.125 rods from Callies:

Callies Performance CSC6125DS2A2AH Callies Compstar Connecting Rods | Summit Racing

My alternative options were a Wiseco dome Pro Tru Street with K1 connecting rods
Wiseco PTS523A3 Wiseco Pro Tru Street Pistons | Summit Racing
K1 TECHNOLOGIES 012AE25610 K1 Technologies H-Beam Billet Connecting Rods | Summit Racing

However, these pistons only accommodate a 6.098 rod and I've been reading that the 6.125 rod length is beneficial due to geometry of the stroke and reduction of piston tilt, which makes sense in my mind. Pushing closer to the bottom of the piston vs. more from the center point. Is this a significant thing in your eyes? The mahle/comstar combo solves this issue for a few extra dollars and the compstar rods seems to be lighter as well.

I also looked in the Wiseco K394X3 Wiseco Professional Series Piston Kits | Summit Racing from Wiseco to get a 6.125 rod option, but in addition to being a decent amount more expensive they appear to all be 2618 alloy. My understanding is the high silicon content of this alloy creates more expansion and contraction with thermal changes as a trade off for ductility making it more forgiving for boosted/nitrous race applications, but poorer lifespan and daily usability (piston slap on warmup).

So long story short, how does my selection of Mahle/Compstar look to you guys? The advertised CR is 10.9:1 at 70cc with the dome which seems reasonably safe from my research? They have a flat top option with lower CR as well. Where are my gaps in knowledge? The wrist pin on the piston is listed as 0.927 and 0.928 on the rod, I image that is the tolerance that accounts for the "floating pin"?

Thank you all very much for helping a noobie out

 

So 450 WHP is your goal, which is about 525 FWHP.
The stock short block will handle that and more. The stock heads will support that and more.
Basically you put a nasty cam in and send it.

 

Thanks for the input. Yeah, from what I hear the foundation of these engines are super robust,
so I know I’m well within the safe parameters power wise.

What are your thoughts on my piston rod selection? The mahle compstar combo I linked should play nice together for the selected overbore size correct?

Thanks again!

 

You don't need aftermarket pistons or Rods for your build

 

Note the engine used for these tests.

 

Thanks everyone for the input. If I replace the pistons with new 4.030 gm pistons and reuse my rods, do I need to have the crank balanced still?

 

I have a L96 in my 1965 Olds Cutlass with the following done to the engine and she is a beast on the street. My hp goal was similar to your goal (anything north of 450whp).

Engine: L96 Gen IV 6.0L (Stock 4" bore, stock rods)
Heads: LS3 heads with trunnion upgrade, BTR dual valve springs
Intake: Truck Intake Manifold
Cam: Custom Spec Cam Motion 224/236 .595/.595 112 +3
Pistons: Mahle Flat Top OEM Replacements (Part # 224-3665). I wanted to up the compression from 9:6:1 to around 10:6:1. I did this my replacing the stock dish pistons with the flat tops mentioned above and using BTR head gaskets with a thickness of .040.
Headers: Hooker 1 3/4 Long Tubes with Pypes X pipe

Trans: 4L80 with a FTI 3200 stall

Rear: Strange Engineering S60 with 3:73s

I was like you in that I wanted to do it right the first time. I did go a little overboard with this build (first build) and for my next build I plan on using a lot of Summit Racing brand products, which I heard are top notch for our LS engines and their is plenty to choose from.

If you have any questions I am here to help in anyway that I can.

 

https://ls1tech.com/forums/generatio...-thoughts.html

Here is a thread I started, some good build ideas from some smart fellas,

 

Thank you very much for this. You’re right, very similar to my plans so I appreciate you insight and experience on this.

 

Thanks for the link! I’ll check it out.