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Spun bearing, LSx Motor vs SBC, SM465 or swap

yakmastermax

yakmastermax

1/2 ton status
Joined
Feb 4, 2012
Posts
165
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Location
Albuquerqu NM/ Austin TX
So I really messed up and now my truck has got a spun bearing. Overheated to about 240 deg and ran with a little less than 2 qts oil. Truck won't make more than 25psi oil pressure now, vibes terrible from the front end, and squeals.

Luckily I've got about 1300 in savings and I just picked up a second job.

I know I need a new motor and I'd like to get it before winter really rolls around. My truck currently has the original 305ci with a mechanical fuel pump and a quadrajet, a SM465 with a mechanical clutch linkage and an NP208C. I recently painted the truck and lifted it.

I'm trying to decide which route to go. My coworker and the tow truck guy both are recommending an LS swap. My coworker specifically mentioned the LQ9 6.0 Motor but I'm open to the 5.3

I'm also considering putting in a used 350 under the quadrajet.

The q-jet needs about $500 dollars of work. It needs to be jetted and tuned for the CO altitude and probably needs a rebuild too.

I'd really like to keep the SM465 because that transmission is the sole reason I bought the truck and have kept it so far...

I'd really appreciate any input on the matter.

http://www.advanceadapters.com/products/sy-712577--chevy-v8--v6-engine-to-the--gm-sm465-4-speed/

6 months ago:


Today:
 
My guy down here, builds Qjets for $150....

If you cant find a decent price, you could always ship it to him,or me,
And i could have it back to you in about 5 days.
 
Most likely. I think its 1979jimmy350 or something like that that has done the 465 to ls.
 
I have a guy that rebuilds quadrajets for me and he always feels guilty for taking to long, so he doesn't charge me.

Martin
 
Myself, I would just throw a 350 in there and call it good.

Martin
 
Truthfully, i would too. If this was your toy, i would do the LS. Or even if you had another car. No offense but it sounds like you are limited on knowledge. That being the case, the swap is gonig to take you probably 3 months to do. A motor swap you could get done in a weekend with a competent wrenching buddy.
 
This is indeed my second vehicle and I do believe I'll be able to get some help from a friend with a real shop. His demo-derby season just ended.

My knowledge is quite limited as I've never actually swapped a motor in anything.

I'm just trying to get a feel for the pros and cons between the two options: 5.3 vs 350.

I'm leaning towards the 5.3 for the sole reason of the modern EFI. Even with a used 350 I'm going to have to work with the quadrajet which is currently about 6000ft out of tune and looking old (mounting gasket between carb and manifold is cracking).

I'm also trying to see if I can keep the SM465, which it seems I can with either option.
 
If cost is an obstacle to an LS swap, at the very least have you considered TBI?

As it was available in your body style, and it is still relatively easy to find '87-91 setups, it wouldn't be too ridiculous of a swap. Since you need a "new" motor, finding someone with a running TBI 350 setup that is being parted out could be an option too, if you don't want to build the motor.

Just a thought.
 
A running TBI out of a junkyard would be a good starting point.

I would stick with a Gen 1 350 and either TBI it or rebuild the Q-jet and then play with it to learn a little bit about them before diving into the LS trend. The LS can really cost some money and draw out the time it is down, and that can lead to either giving up, or trying to build a monster and having it down for years, and giving up anyways.

EDIT another good idea and an easier to find motor is a 96-99 Vortec 350. You can buy a running motor, buy a carbed intake for the Vortec heads and be on your way. Plus this route gives you more STOCK HP than any of the other motors listed besides the LS, but is phenomenally cheaper than the LS.
 
I did an ls swap in mine specifically for the efi. I already had a good motor but wanted the reliability and fuel mileage of efi and an ls swap was cheaper than adding fi to my current engine but I did all of the work myself including reworking the harness.

I used a 4.8 in mine cause that's what I found and it was cheap. Perfectly happy but mine is a dd, if I towed with it a lot I would want a bigger engine. That being said Ive towed way over the gvwr for my truck and had no problems:D

I also hooked it up to a sm465 using factory over the counter parts, no adapter parts but I don't know if the 4.8 flywheel works on the other engines:dunno:

With all that said, you should do lots of research on the swap before diving in. Its a pretty in depth swap if you do all the work yourself and expensive if you pay someone or buy lots of prefabed items. Depending on skill level you may be better off to stick with 1st gen or tbi stuff.
 
I think I did my 5.3 swap about as cheap as possible and it ran me right about $1800. I also havea ddecent bit of knowledge and with working on it whenever possible, it took me 2 months to get it on the road. Pinsco63 on here just did a 6.0 swap and ended up around $2800. And again, he has about as much know how as I do and it took him 2 months as well.

That said, I don't know if I could ever bring myself to rebuild a 350 ever again. I would have as near as makes no difference the same amount of money into a rebuilt 350 as I would an ls swap. And they just run so good! And in general, they are uber reliable, last longer than a 350, and have more power/mpg. I'm only one truck away from having an all ls powered fleet and when the time comes that it needs a new motor, it's getting an ls also.
 
Thanks guys for the input. I talked more with my coworker today and he seems quite gung-ho to help. He's got a lot of experience and a large shop space to use.

I have been getting other opinions on TBI and to me it seems like a similar amount of labor, about 2/3 the cost of 5.3, and a whole lot less power and drivability.

I called advance adapters today and their take on the matter is that I use their adapter flywheel and throw-out bearing. They sell a complete kit with a clutch set but they also said I could reuse my essentially brand new clutch set bolted to my 305. The flywheel and bearing plus hardware seems to run a little under $500 plus shipping. So far this seems like the easiest way to get the 465 behind a 5.3. The factory bellhousing obviously bolts right up and I can make use of my factory clutch fork and linkage.

I've been looking around and it seems that in the Denver CO area 5.3 motors with exhaust manifolds, harnesses, and ECUs plus accs run $500-700.

My coworker does believe we may be able pull a 5.3 ourselves and save some coin, maybe $400 out the pick a part yard.

Mounts seem to be around $100
Fuel hookup seems to be around $150 in the form of an inline pump and filter/regulator. On that note does anyone off hand know what size the sending hose is on my '83 factory q-jet? 3/8th vs 5/16th?
Accessories and misc seems to be around another $200.

I'm thinking that I'll cut up my own harness and have my coworker or a friend of his flash the ECU.

As many have reported this seems to be around $1500-2000 depending.

http://www.advanceadapters.com/prod...-and-clutch-kit-for-ls-series--gen-3-engines/
 
Honestly, I think that's the best route to go. For roughly 2k, you get a motor thats night and day difference from your current small block. I've been researching this swap myself, and in the future I am planning on doing this to my K5.
 
Didn't have the $$$ to build the motor I wanted when I needed one for my k20 this summer. Did a cheap build on a 350 I got from my buddy for peanuts. Gasket matched a set of 305ho heads and intake. Small comp 4x cam. Swapped everything else off my old motor. Think I came in under 600 bucks for everything. It's no hot rod, but it seems just as healthy as the built 350 I blew up in it.

If I had more coin i would have done the l31 vortec swap, as you need a diff
Intake and flywheel.

Id find a decent short block than go from there IMO.
 
Stock 6.0 truck flexplate, LS2 pilot bearing, and your current clutch will work for the SM465/LSX motor. It worked flawlessly in my truck before I exploded it.

I vote LS, but I'm also extremely biased.

For the harness, read read and re-read the section on LT1Swap.com under 6.0 harness information. It's quite literally a step by step guide to making your own harness.

Again this was what I did my first time around, this time when I went automatic a local guy did mine. Whom I HIGHLY recommend if you'd rather spend 350$ than a weekend reading schematics.

Once you get past the harness, a LS swap isn't any different than a SBC.
 
I was going to ask why the 6.0 option wasn't mentioned. If you're going to go through the hassle of converting to the newer fuel injection, I'd go with the bigger.

We have a 5.3 in the Avalanche, and granted it's most likely geared in the rear for highway driving, but when towing things with some weight, I really wished I was able to replace the 5.3 with a 6.0 when the camshaft and lifter took a crap last last year. Don't get me wrong, it tows decently, but also has that feel like there should be a bit more and it just doesn't give it.
 
I think the 5.3 is perfect for a cruiser that lightly tows. The 6.0 is basically needed for a bigger vehicle or one that tows regularly.
 
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