Shinerunner

Hello everyone. I am just starting an 5.3 ls swap into my 53 olds 88 holiday coupe. Original engine locked up couldn't get it free. Has anyone done a swap in a 53. Looking for any advice or suggestions. I am a newbie. But have a neighbor mechanic helping me. I was really torn about keeping original rocket 303. Cost for total re build including trans was too expensive. But I like the idea of having modern engine.reliabilty. and more horsepower. Locked up engine kinda made up my mind for me. I was able to get a ls3 5.4 and all acc. For free so that also helped my decision.

Olds64

Welcome. Sounds like a cool swap. There may have been somebody that swapped an LS engine into an early Oldsmobile. But you aren't going to find motor mounts, brackets, etc. for doing the install. Make sure you keep us posted and show us some pics, STAT!😳

harner

Hey, welcome to the LS family. Your terminology has me a little confused with "ls3" - 5.3's came in a few different flavors, but the LS3 is an aluminum 6.2L. Arguably the most common 5.3 was the LM7, which is an iron block. There was also an L33 - aluminum block 5.3. Many others, feel free to read up on them here: https://en.wikipedia.org/wiki/Genera...l-block_engine

The first thing I would do is make sure you have a 5.3 and not a 4.8. The blocks are identical, but pistons are different. Also, determine whether you have a Gen 3 or Gen 4 engine, which generally you can tell by looking at the timing cover.

Some obstacles you need to worry about:
- Motor mounts, as Olds64 mentioned. Olds to LS swap are slim pickens. I think the gbody ls swap mounts may be the closest thing to it. However, there are load of swap adapter plates out there. If you or your body is fluent with a welder, you can make anything work.
- Transmission/converter, I don't know what came in a 53, but you'll probably want to look into a Chevy TH400 adapting a 4L80E trans. You can either get a converter spec'd or go the manual route.
- PCM/Wiring Harness, Holley Terminator X is a popular option, but you can go the cheap route and find a standalone harness that uses a truck ECU. Look into tuners in your area. Alternatively, you can go the carb route but you're going through all the swap work, might as well go Fuel Injection the right way.
- Fuel system, Tanks Inc makes tanks and accessories to allow you to modify your stock tank for an in-tank fuel pump assembly. Alternatively you can run a fuel cell and either internal or external tank. If you decide to do a cam or other mods (forced induction, etc), you'll need to look for larger fuel injectors. Regarding a fuel pressure regulator, the stock C5 returnless regulator is popular. I use Hot Rod Fuel Hose for their fuel line PTFE kits and they make a fuel system kit as well for LS swaps. I run it on my 5.3 swapped '94 Trans Am.

They are the major components off the top of my head. All of which are hurdles that I am facing as part of my build - a turbo LS in my '75 98 sedan. Feel free to check the build thread in my signature for details.

Olds64

Don't forget that the OP might want to change the differential too. This would be a daunting task in my mind. There's no way an LS engine and 4l80e would play happy with the 2.76:1 rear gears in my 71 98. Probably a concern for a 53 too.

harner

You are correct. I mean, I don't even know if an 80e would fit without clearancing. Gears, posi/spool, custom driveshaft, etc. Every drivetrain and engine component/system would need addressed in some manner. It's not quite as easy as the days of dropping a SBC into everything for $50 and driving down the road the same day.

Don't let it stop you. The Internet has limitless resources on how to properly swap an LS into everything and anything. It depends on your budget and how far you're willing to go.

Olds64

The OP should start by determining what kind of differential is in his 53 and what kind of gears it has. My dad; Oldsguy, swapped a mild 455 and TH400 combo into a 47 66 he had. He got a custom driveshaft built and it was a tire smoking machine. I think the rear gears were steeper than 4.11:1.

Bfg

You might as well change the interior while your at it, some high back bucket seats would be fitting

OLDSter Ralph

I suggest selling the 53 Olds as it sits right now and buying something else. I can see this becoming a mess and no one else wanting it......when you run out of money. If you want "modern engine reliability and more horsepower", just buy something newer. "People" do know how to "unlock" and engine and may be the ones to get it.
Keep in mind you'll need a different transmission, driveshaft, suspension upgrades, exhaust system, brakes and differential. Don't under estimate the costs and fabrication. I may sound harsh, but its being realistic about your capabilities and cost.

Tedd Thompson

I'm with Ralph, unsticking that engine maybe doable, have you pulled the engine out yet for a look see? You will have to take the trans out with the engine if you can't rotate the flywheel to get to the bolts, then remove the pan. If you are lucky the stuck piston, or pistons will be where you can get to the rod bolts nuts. Then drive out the offending stuck pistons from the bottom to the top. There will be at least two that you can't get a wrench on, hopefully they aren't the problem pistons.

Either rebuild the 303 or look for a used 324 or another 303, there is still a lot of old stuff still out there.... Tedd