So over a year ago I picked up a '93 240sx hatch that was fairly stock. It was a fun car to putz around in and finally the head gasket went on the stock 4 cylinder. I've been eyeing options for the car's new powerhouse and my domestic friends kept pushing for an LS. A close friend of mine with a '96 SS Camaro sat me down and asked for my ideal goal for the car. My response was something that I can street occasionally (when the weather permits) and I can progress with when I decide I want more and more power. As he's a LM7 turbo guy, he slowly convinced me to grab an LM7.

While planning out the overall parts I'd like for the car I started to learn about the LS family. From countless hours reading for a few months and wrenching on some LS's with friends I came down to a final goal for the powerhouse and went out to a pulled engine place and grabbed an LM7 that came out of a 01 Tahoe. Spent the rest of the night stripping off what accessories it came with, most I won't end up using, and got it on a stand. The overall plan is a supercharged LM7 with LS'X' replaced parts where I needed them and all new gaskets, seals, LS heads that are built, a new cam, and intake. Thanks to the Mighty Mouse and Modern Mouse articles I've been following, as well as a lot of user experience I've decided to stay stock internals in the short block, but refresh some worn parts. After speaking to one of my connections I was able to get a Fueled Racing swap kit for a great price and knocked out my search for a front sump oil pan. The heads I ended up grabbing are LS1 heads to which I followed up to order a 225/238 .612"/.585" 113+3 cam, .660" lift platinum springs with steel retainers, and 7.400 chromoly pushrods from Brian Tooley after speaking with him about the build. Next to order are GTO (04-06) accessories since they are nice and tight to the engine, my harness, GTO ECU and finally the YSI.

A few days have gone by and I'm at the point of being able to work on the build since I have more time. That said I've run into a big concern while collecting parts. While speaking to my Camaro friend one night of wrenching on his new swap he mentioned I should grab some bearings and rings since I was planning on sending the block and head to a machine shop to get verified they are in spec, and have matching mating surfaces and everything hot tanked. I went through and ordered King SI rod bearings, King SI main bearing and Mahle piston rings. Obviously more things need to be decided and bought, but the initial power goal is around 650 to the rear. Now I'm on the fence about installing them. I've heard horror stories about LM7's being finicky when opened and parts are touched. The best thing some people are saying is to run a stock bottom end how you receive it. Is this really the case? What concerns should I be aware of by having a local machine shop install the new bearings?

 

People use 5.3's because they are crazy cheap, like $250-400. If you plan to rebuild one, you're in 6.0 spending territory already. Most swaps into small cars only require the truck long block, so the complete dropout is not needed

650hp from a 5.3 will require some form of boost. Id stab a cam kit and oil pump in and rock everything else totally stock

Spend your money on the rest of the swap and upgrading the drivetrain to handle what you throw at it, not rebuilding a budget engine

 

Getting the 5.3 was not only a budget thing. The price was right, yes, but from a combination of what I've been told, seen and read is that the aluminum blocks have a tendency to blow under boost. That said, with the compression readings I was finding stock, LM7 and LQ9's were at the top of my list for NA displacement prior to boosting and were iron blocks.

I do get that the 5.3 is the budget build engine, but overall I'd like to do it right once so I can drive it around without having to swap a block due to a broken rod or some other failure. The thought of refreshing the bearings after having the block cleaned, so I can get dust and junk out of it from sitting, seemed ideal. That said, it would most likely require a set of new main and rod studs/bearings right? Possibly a balance with all the new hardware?

Again, I'm weighing my options from input. I plan on calling some machine shops tomorrow that focus on domestic engines to get their input.

So, that said with the parts I mentioned, should I refresh it or leave it well alone and throw on the parts, heads, and rock stock internals for the duration of the 5.3?

 

I would just refresh the block and boost it. I am actually going the exact same route, but just waiting for funds to send my block to the shop and have it hot tanked and install new hardware.

With that being said, replace the bearings and piston rings but leave everything else stock. If you are bored, you can perform a DIY port and polish on your heads too =).

 

Talked to two local machine shops, my tuner, and some of the sponsors of LS1 tech over the phone. Overall with my goal it seems smarter to take care of the consumables (bearings) and all seals. That said, my tuner asked me why I don't just go through and get aftermarket rods and pistons while I'm at it so I can take advantage of all the machine work since it's a set fee for block assembly and crank polishing/counter balancing. That said from what I've seen it makes sense since the rods come with rod bolts and the pistons will have their own rings. Built block seems to be the right way of going for the 650 whp goal. Plus when I decide to up the boost and swap heads I'll know my block is solid and broken in.

 

So, you're forging it anyways

Buy a bare 6.0 block and a junkyard 4.8/5.3, blown up is fine. You'll be buying all the 6.0 specific stuff already, use the 5.3 core for all the misc covers/sensors/bolts etc that nickle and dime a build to death

You missed the point of a 5.3. A forged 5.3 will run north of $2k in the end, where a JY 5.3 is $250-350 and will hold every bit of your power goal completely stock

 

Pocket -

I totally understand where you're coming from. My concerns came up with the fact the block had been sitting in my garage for almost a year and I'd like to get it cleaned out internally and get the exterior cleaned up for paint. The cost of the rebuild isn't a concern.

The point most people go for is a cheap iron block build for boost. My goal is something reliable, clean, and overall can handle what I throw at it later on without having to pull the block. I've always had the mentality of "do it right the first time" so I'm trying to do just that. The main reason I went for the 5.3 was the availability and the fact I wanted an iron block that could handle boost and give me a piece of mind.