87RockTPI

So was thinking of doing a LS1 swap at first but after doing some research and talking to great sources it seems an LS3 would better suit my application. I have an 87 IROC Z with 54K original miles.

Currently I have the stock 305 running but am wanting to take my time and get the necessary components ( and budget) in order to avoid delays and downtime. Car sat awhile due to other priorities. Moved into a new house and have adequate room to work on and do things right.
Besides the obvious components of the motor, accessories, and transmission are there any differences in application and clearances, fitment etc compared to LS1?

Also considering the substantial power increase the chasis I know will need upgrades. I had kenny brown subframe connectors put in years ago. Kenny brown doesnt look like they have made suspension components for the car now for awhile. I remember some knock off components copying the design which seized production for quite some time but thats all i remember.

Rear end I know will need replaced. Im thinking a strange rear end.

I am wanting an automatic, what modifications should I be prepared for in this arena?

Thanks in advance

Abubaca

iTrader: (3)

How are you going to be driving this car? Race? Street? Both?

What's that LS3 putting out, 500hp? ....so you'll need a rear end that can handle that power. How you drive will determine how soon you need it! I street drive my 400hp 383, and so far, the stocker is holding up, BUT.....I'm aware it isn't forever. Look at all your options, but don't forget that Hawk's 8.8. Not cheap, but cheaper than other options. I'm a fan. Some aren't.

....fuel pump and the pump wiring. Look at the Hotwire kit from Racetronix for the wiring. Talk to them about what pump is best. Of course, that's just one option. it's working well for me.

What engine management system are you going to use? make sure it can control an automatic transmission. ....and I'm pretty sure a 4L60e/4L80e will fit just fine, but you'll want to look into power levels and upgrades. Just old fashioned research. New, used, rebuilt, aftermarket...all kinds of options. Even if you don't buy, don't be afraid to call up vendors and talk about options. They know you're going to call around, and ultimately (hopefully) you're just gonna buy one. You'll learn TONS! About the trans, and about customer service. For that kind of money, it's IMPORTANT.

Subframe connectors are important, but sounds like that's covered.

There's SO MUCH involved, it can be overwhelming, and certainly more than you/we can touch on in one thread. You'll find things as you go too, which sometimes can hurt, but putting one foot in front of the other is often the only way to learn if you're doing most of it yourself.

I'd google LS3 swap, and read EVERYTHING. Good luck. Search is your friend, then ask lots of questions!!!!!

87RockTPI

Right fuel pump as well. Tank is original to car wonder if I should replace it?

Car will be street mainly. Not a daily driver. I will go to the track mainly for test and tune. Want to do as much power as I can without having to install a cage or anything.

five7kid

iTrader: (14)

LS3 crate engines come in 430-525 horse configurations. If you're talking about a used Vette or Camaro engine, that's the lower end of those power ratings.

The "Connect & Cruise" kit from GM (https://www.summitracing.com/parts/nal-s0005) will give you all the stuff for the engine & transmission, including the control system. You'll have to get the stuff to bolt it into the car, and hook up exhaust. And whatever rear end you get, you'll have to get a driveshaft to mate to both (I prefer getting a new one made, personally).

That HP will probably keep you above 11.50 at the track. Barely.

Unless the interior of the fuel tank has gotten nasty, an upgraded fuel pump should be all you need (Walbro 255 or similar). Replace that while you have the rear end dropped out for upgrading.

87RockTPI

Thats my other concern. I dont want to butcher the car up by putting in a cage and other requirements.
Basically my goal is when done look like it left the factory that way. I also dont know if a 6 speed auto would even fit?

I have a guy (same guy my brother used) in Rolla Mo that builds really good 4L60E's.

Also, whats with the LS3 with VVT? First ive come across it since Ive shifted focus to LS3 just last week.

five7kid

iTrader: (14)

Sorry, bad link in my response (too many copy & paste jobs today...).

I guess we should know what your intentions are. Crate engine, or junk yard salvage?

As I understand it, LS3 is not VVT. The automatic 5th gen Camaros had 6.2l with VVT called the L99. Slightly less horsepower, but better mileage.

The 4L65E is an internally-upgraded 4L60E. Up to you what direction you want to go, a new factory unit with warranty, or a privateer build job.

6L80E won't fit without modifications. 4L80E will. And, obviously, the 4L65E and 4L70E will (same basic dimensions as TH700).

Blackdog36

iTrader: (3)

87RockTPI, any progress?

I'll soon be swapping in an LS3 & TR6060 manual into my Camaro. Bought a Strange S60 with their helical gear differential few years back. Was at a good price but some people like the aftermarket rears with Ford 8.8. It would be best to get new rear end but it's at least $2,500. I bought a used set of LS1 brakes and sent rear backing plates to Strange for them to install. Had front spindles cut to run LS1 front brakes. So think about your brake situation cause that can add $$ too. I second the Racetronix fuel pump. With cam only LS3, you really need this kit over regular Walbro 255 to be on safe side.

You don't have to cage the car. Reason most people do is due to race track rules that once you go so fast, one is needed.

You can turn a LS3 into L99 (with VVT) and vice versa. Easier and cheaper for you to find a L99 & 4L80E pullout combo. VVT will give you more torque through low-mid rpm's but a lot of people delete it to run bigger cams.