Well guys, today was the day that I was hoping to start my build thread on LS1 Tech, however due to sad circumstances I am unable to do so.

This morning I started ripping apart the motor I was planning on using in my build: a 1973 240z with a 5.3 LS Turbo and a 6 speed Magnum.

The 5.3 I bought off of Kijiji (Canadian version of Craigslist) was supposedly pulled from a low mileage running truck about 6 months ago. I bought this along with a set of 243 cylinder heads and another 5.3 aluminium motor. Since then I had the heads rebuilt and had started gathering various parts for my build. Today was the day to start assembly on the motor. My plan was to put the rebuilt 243 cylinder heads onto the stock 5.3 bottom end and run at minimal PSI until the rest of the conversion was complete and then put the proper internals in the bottom end and turn up the boost. However, when I removed the cylinder heads on the running truck motor, turns out it looks like there has been a massive coolant leak and other issues in the motor. One of the pistons has a hole in it and all of the cylinders have rust and deposits. So much for the good Kijiji deal eh lol.

Well at this point I am deflated as the guy will not get back to me and as the other motor I bought is pretty much a blank block, I have some decisions to make.

SO.. before my questions here are my build specs along with items purchased already:

-5.3 LS (have both aluminium and cast blocks)
-243 ported heads, stock mill, upgrade comp dual springs, and pushrods
-02-04 Z06 Cam
-Truck Intake
-LSA exhaust manifolds
- Magnum Performance Turbo (Not sure specs as have not purchased yet)
-T56 Magnum (against to be purchased)
-Holley HP EFI engine management
-4.11 Rear gears
-Stock GM 3 layer MLS 5.3 head gaskets

Goal is about 500 RWHP and will be used mostly for street, but will see the strip as well.

Questions:

1. The first and most obvious question is now that I am looking at doing the bottom end for the 5.3 is which motor to use? I know the cast iron ones handle boost a bit better, but I am not sure I will ever be putting enough boost through to worry about it. Thoughts?

2. As I am doing the bottom end, which internals should I use? Again, the plan is to keep this on a budget as I wasn't planning on spending very much on this, but at the same time I want to be happy with the end product.

3. Any additional items I should ask / add when I go to the machine shop? LS stuff is foreign to most engine builders up here in Alberta, especially in small towns, but I just want to make sure it is done right. Also anybody know a rough price to get the machining done on the bottom end done and cylinders honed. I would like to do assembly myself as never done it before.

4. I also have read that some people just bore out the 5.3 to a 5.7 to use a stock rotating assembly for an LS1. Again, will this handle the boost?

Thanks guys!

 

If you're looking for 500 horse, just go with the iron block and stock internals. I normally don't recommend using stock internals but on such a low power goal, you won't have any problems, if tuned properly. You'll probably end up making that power on 10 pounds of boost or so. Just a fresh set of piston rings, ARP studs and bolts throughout, and you'll have a solid setup.

 

With that low of goal I would use the aluminum block for sure. Save you 100lbs. The aluminum block 5.3 is one of the strongest aluminum blocks because of the thick cylinders walls. It can handle a lot of power. I have a forged aluminum 5.3 I'm planning on 800-900hp

 

Lol two conflicting views. So here is my thought:

1. To save money I will use my 5.3 ls crank, have it balanced, and then bore out the 5.3 bored out to stock ls1 bore, then use ls1 connecting rods and pistons. Probably forged.

Feedback?

 

For a turbo deal it's probably not worth the expense to bore the block out. I would just rebuild the aluminum block with the stock rotating assembly and open up the bearing clearances and ring gaps a little.

 

One more vote for rebuilding the aluminum block. What is the condition of the rods and crank out of the iron motor ?

 

I vote aluminum as well. The weight savings will be well worth it. With boost, you don't need to bore it, leave those thicker cylinder walls and your power goals are relatively low for a turbo 5.3L so no worries on maximum block strength anyway.

The stock crank and forged rods/pistons with get you where you are talking about with plenty of room to spare as far as power handling goes.

 

End of discussion!

 

Aluminum block and grab some Gen IV 04+ rods and pistons for the 5.3L. They are stronger. Also, just reuse your stock crank. Get it ground down .010" and use the proper bearings. That combo will handle 600HP all day.

And you will want more once you get used to 500.

 

Heck just ship it to Thompson motorsports and have them put forged Pistons and rods in it and be done with it.