Engine Swap Everything about swapping an engine into your Third Gen.....be it V6, V8, LTX/LSX, crate engine, etc. Pictures, questions, answers, and work logs.

questions regarding engine swap

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Old Aug 11, 2025 | 10:21 AM
  #1  
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questions regarding engine swap

Hello Everyone,

I currently have a 1986 IROC (Bought in 1990), my engine is the standard 305 4bbl. It currently has 210,000 km on the engine (car). Last year a had the transmission and rear end rebuilt as they where both having some issues. My questions which I have a lot (I apologize in advance) are

1) I have done some research and it seems most information I have found are in favor of replacing the engine with a 350 rather then rebuilding the 305, is this correct?
2) If I go down this path, I live in Canada has anyone put the turn key gm crate 350 engine in their car. I am looking at the lowest HP which I believe is 333hp and 381 torque (GM code is19433031). My goal is for a reliable car that I can take out for drives, rather then go to the dragstrip. In Canada we do not have as many options for getting crate engines, also the gm motor is under warranty for two years.
3) there are 3 choices for this engine, each getting more expensive. Is the turn key the best value?
4) is 333hp horsepower too much for the frame on a 1986, really don't want to have to put extra bracing on the car. Hoping that someone has put this engine in their car and can give me advice as I am trying to figure out total cost (as close as possible) to this upgrade.
5) lastly, one of the reasons I am leaning toward the turn key is all of the front end accessory are included in the kit (New alternator, power steering pump, air conditioning compressor,)

Looking forward advice

Glenn
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Old Aug 11, 2025 | 10:44 AM
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Car: 91 WS6 GTA
Engine: 5.3
Transmission: 4l60e
Re: questions regarding engine swap

Originally Posted by Rookie20
Looking forward advice

Glenn
glenn if you buy a sbc long block, yoiu can transfer all your old parts onto the new engine.
300-350 hp is perfect, lots of fun, reliable and good fuel mileage.
a turn key set up nice, but, there no real reason for it, unless you want everything brand new.
Everyone alwyas goes for the 350 becuase it is bigger, and makes more power for free.
Same as those who want a 400ci engine. Same physical size, but more cubic inches.
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Old Aug 11, 2025 | 12:09 PM
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Re: questions regarding engine swap

most information I have found are in favor of replacing the engine with a 350 rather then rebuilding the 305, is this correct?
Of course. All the internal parts cost the same, or if they differ, the 350 ones are less. It's essentially 45 FREE cubic inches.

the lowest HP which I believe is 333hp and 381 torque (GM code is19433031)
The lowest NEW GM 350 HP is the 260 POS which is for all practical purposes a replica of the 165 HP wonders of the mid 70s. Makes anywhere from 160 to 200 depending on how it's installed (headers vs manifolds, 2bbl vs 4bbl carb, etc.) One that's "rated" at 333 HP would have Vortec heads, which will require a different intake, unless that comes with it in whatever option you choose; and if it comes with one, your carb probably won't fit on it although I'm not going to do all that research for you. Should make 260 - 275 HP in your car, with headers, a good cat-back, and appropriate other supporting goodies. That's around 230 HP or so at the wheels, maybe 250 at best. Which is still between 2 and 3 times what your 305 puts out so it'd still be a nice little bump. It would even have a chance at keeping up with new minivans.

is 333hp horsepower too much for the frame
A 2.8 6-cyl is arguably "too much for the frame" in some uses. These cars need subframe connectors and a few other chassis improvements to really take advantage of higher power, or to provide a more "modern" driving experience overall. For example, TIRES, brake upgrades, LCA lowering brackets. Your car specifically almost certainly has 2.73 gears which is yet another handicap it faces. Gears that pin the engine into a range of RPMs where it hardly ever gets off idle aren't real good for exciting driving no matter what HP number it can claim.

​​​​​​​really don't want to have to put extra bracing on the car
You don't "have to" do anything, even including the things I just mentioned, if you set your standards low enough on the finished product.

​​​​​​​all of the front end accessory are included in the kit
Sounds great, until you realize that those accessories won't fit under your hood, and the alt & AC compressor are on the wrong sides. Not sure whether the PS arrangement used on it will fit; some of those, the pump hits the steering gear in our cars, which seems likely for that setup, given that that looks like truck accessories. It's also likely that the oil pan on that won't fit our cars. Probably not a good idea.

​​​​​​​Is the turn key the best value?
Almost certainly not.
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Old Aug 11, 2025 | 01:13 PM
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Car: 82 TA
Engine: Zz430 clone w a torquestorm blower
Transmission: Magnum f
Axle/Gears: Ford 9 w 4.11
Re: questions regarding engine swap

I'd recommend the SBC 350 of your choice, and use your stock accessories. Any of the lower- mid hp crate engines will work, just pay attention to the rear main seal/crank style. Use some headers and a 3 in exhaust. Use a modern efi like edelbrock or Holley unit. They're an easy install and get going easily. I used a pro Flo xt on my car it's been awesome. A friend of mine just did an iroc w a Holley system and he is super happy w it. A turn key zz6 would be fun but likely not the best financial decision.

if your ps pump/alt are good re use them. If not replace them but either way, use your current belt/pulley setup. It all fits and will decrease variables.
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Old Aug 12, 2025 | 04:44 AM
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Re: questions regarding engine swap

Thanks for the advice, I appreciate it.
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Old Aug 21, 2025 | 08:58 AM
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Re: questions regarding engine swap

So after listen to everyone advice I have ordered the 350 deluxe crate engine from gm (:SKU 19433038) this engine comes with the intake, carburetor and distributer installed. (Scheduled to be installed mid Sept) This does not come with the alternator, power steering pump and air conditioner compressor, since they where on the wrong side of the engine. Question. Since I am installing a new engine, would it make sense too install all brand new components (alternator, power steering pump and air conditioner compressor, including hoses)? (I am a little worried that these are all original, almost 40 years old). Can the original components still be purchased from GM, if not is there a reputable aftermarket manufacture?
The shop who is doing the engine swap asked if I wanted to change the torque converter? Just curious has anyone installed this engine in their car, just looking for input on new torque convertor, and would be it beneficial. (The new motor is 333hp and 381lb-ft.
Lastly I am currently running the original stock exhaust system, one pipe two exhaust tips. Should I replace, and if so any recommended exhausts (headers)

Thank you for your time
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Old Aug 21, 2025 | 09:36 AM
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From: CT
Car: 82 TA
Engine: Zz430 clone w a torquestorm blower
Transmission: Magnum f
Axle/Gears: Ford 9 w 4.11
Re: questions regarding engine swap

That should be pretty cool. The intake/carb/air filter combo may be a little tight under the hood but that should be easy to figure out. Totally use headers/3 in exhaust. And while you're at it, replace your ps pump and alternator/starter. Then it's all good and you don't need to worry. Your radiator will cool it well as will the stock fan. It should be fun.
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