TBI 350 vs. gen III 5.3l LM7

[jsudar]

So, my Blazer has a perfectly good TBI 350 with a brand new 700R4 behind it. The plan was to put on some Vortec heads, a cam, bigger throttle body and a chip and hope I get somewhere close to 300 HP.

However, I'm picking up a 2000 chevy with a 5.3l and 4l60e this weekend.

Would you yank out a factory TBI in good running condition to go through the hassle of installing the 5.3l, wiring, building new engine mounts and all the other problems associated with engine swaps? Is there a big advantage to swapping in the 5.3 and 4l60e?

What do you think?

 

[Grim]

why fix something that is not broke ?

 

[Erik d_lux]

I wouldnt even think twice about installing that 5.3. Installing a Gen III motor was the best thing I ever did. Throttle response from a TBI to that 5.3 is insane.

Also, rarely do I ever see a modified motor on the trail that runs really well.

 

[Tacoma]

You know how much I like TBI stuff.. but I would do that in a heartbeat. There is a world of difference in response between those two engines. You shouldn't have to do much w/the mounts, either. I ran around the oilfields for a while w/a 5.3, I got everywhere really fast.

 

[larrybenny]

I have the 5.3 conversion with 4L60E trans in my 91 wrangler. I took it to Moab for the 1st time 2 weeks ago. The horsepower is awesome, and applied throttle is smooth and steady, unlike a modified motor that comes on the cam with unexpected power that get's you into trouble on the rocks. Total trouble free trip. Gas mileage is double what I got with the old 4.2 carbed engine. 17-20 mpg. around town.

 

[jsudar]

I've got three yesses and one no for the 5.3 swap. I guess I'll be tearing the blazer apart this winter again.

I think advance adapters makes something so you can use old style motor mounts on a gen III block. I remember something about that when Petersen's put a 6.0l in a blazer.

 

[Greg]

IMO, a healthy TBI 350 is a torque motor, all bottom end and nothing else. Want to rev past 4,000 RPM? Good luck with that!

The LM7 5.3 is just the opposite... not to say that it doesn't have the torque, but it LOVES high RPM's. They are revving engines and make most of their power at the top end of the RPM range.

Depending on what you do with the Blazer and how you have it built will really depend on which engine will fit your needs. The LM7 is light-years ahead as far as engineering and you will see the benefits that come along with the added complexity.

If I ever swap a Gen III V8 into another 4x4, you can bet your ass it will be a 6.0 versus the 5.3. I liked my 5.3 but it didn't have the power or brute force that the 6.0's seem to have.

 

[jsudar]

That's why I'm torn. If it was a 6.0l, I would do the swap, no questions asked. But the TBI makes lots of torque and is so simple--all you need to do is carry a spare fuel pump--which I can change in twenty minutes.

The Blazer is set up for rock crawling, but also some desert running (rock racing?) It still has solid axles, but I am running triple bypass shocks and Deaver springs.

 

[Anchor_Mtn]

I would do the swap. I was planning on swapping my 6.0L in place of a tried and true TBI 350...until my wife gave me the green light on a full chassis build. Now the motor is sittin in the corner of the shop waiting for a bunch of tube to get wrapped around it.

 

[Tacoma]

I see you are selling your motor mount adapters, just in time to beat me to the punch.. I was about to say that making a plate to adapt the mounts is super easy. Very commonly done on M715s to allow easy mounting of GM engines to the stock Jeep mounts. They look almost identical.

 

[Shawn]

If you decide to sell the 5.3 & 4l60E I would entertain the price.

 

[Hunt]

The LM7 is junk. Pure crap. Whatever you spent on it, you got robbed.

















No, wait. I lied. I like mine so much I went and supercharged it!

 

[jsudar]

If you decide to sell the 5.3 & 4l60E I would entertain the price.

Maybe. Either way I go, I'm gonna be selling a fuel injected powertrain.

 

[Bart]

I loved my 5.3 in the buggy. If you decide to part with the 700r4, please let me know.

 

[eatrocks]

I would go for the 5.3 over the 350 any time.

 

[mesha]

John we already discussed this when you were picking up the trailer. The 5.3 goes in my buggy and you keep your 350. It just makes sense.



the only part that really didn't make sense was the part about me "paying for it" that is just crazy talk.

 

[jsudar]

Yeah, well the weight of your heavy *ss trailer blew the #3 spark plug right out of the head on my Ford. Now who needs an engine?

 

[mesha]

You should have borrowed my truck too I guess.

 

[waynehartwig]

After seeing how the new GENII/IV motors are designed, I woudl never run an older 350 again. A 5.3 stock is rated for 300 horse, whats the 350? 250HP?

 

[jsudar]

TBI 350 is 210 HP @4000 RPM and 300 ft/lbs @ 2800 RPM on 8500 and under GVW trucks.

Torque monster? Yes. Fun to drive? Not so much.