94 350tbi/700r4 swap

[Smokey burnouts]

I've searched and read till I'm dizzy about 5.3/5.7tbi swaps and even trying to just heads/cam my current motor. A 5.3 costs me the motor and all that is needed. I got the 94 4x4 burb in the driveway just sitting, so can be robbed of any and all parts.

I'm getting bout 8mpg and the k5 struggles to maintain speed at 60 up hills. The MPG ain't huge deal but the fact the it won't get out its own way and struggles on hills is getting old.

Is it worth swapping some or all the drive train out the burb in the K5?
Just looking for performance vs cost advise for getting the K5 lil more streetable...

Thanks
Daniel

[hemi43]

I'm in the process of gathering parts to do the 5.3/4L60E swap. To me it's a no brainer. The old 350/350 combo was great in it's day, but is nowhere near what can be had today. I have an 07 Silverado with he 5.3 and it's been the best truck I've ever owned. It performs great and the 07 weighs 1000 LBS more than my 70 Blazer. Keep in mind that stock gearing will have to be changed. My 70 came with 3.07:1 and that will get swapped out with 4:11's. I'm running 33"s, so that combo will be right in it's sweet spot.
Dan

[Smokey burnouts]

No brainer as in I should do the 5.3 over the 5.7 Tbi or just swap out the 350/350 with something period?

Should my 72 have the 3.07 rear if it hasn't been changed?

[Blazerowner]

I think it depends on how much you drive it. A 5.3 is a great engine for fuel economy and power and can be had for a good price. Under 1k in many cases with everything needed. It can also be adapted to the th350 if you don't want to spend the extra cash for an overdrive. The tbi is a good engine but probably won't do much better for fuel economy.

[Smokey burnouts]

Originally Posted by Blazerowner

I think it depends on how much you drive it. A 5.3 is a great engine for fuel economy and power and can be had for a good price. Under 1k in many cases with everything needed. It can also be adapted to the th350 if you don't want to spend the extra cash for an overdrive. The tbi is a good engine but probably won't do much better for fuel economy.

What would be your GUESS for total 5.3 swap(motor, harness, ect)....$2k?
Would you do the 700r4 with the 5.3 or leave the th350 in there? If I went 5.3 and th350 what gears should I run in axles... 3.73 or 4.11?

I can handle **** mpg with good performance, but crap performance and crap mpg ain't working!

[87Skier]

I'll be interested to see how this turns out. I've been thinking about either building the sb 400 I've got sitting around or upgrading to a newer engine (5.3L).

Anyway, I did what hemi43 said, 350/350. I used the original th350 and swapped in a newer 350 (actually a 97 Suburban engine). The only real difference is that I went for the carb. I've had good luck with Quadrajets, as far as drivability is concerned. Its not great for fuel economy. I think I average around 10. But it starts up better than my 89 and 96 Chevy and runs a little smoother. The overall power band could be better on mine.

I personally wouldn't try to swap in the 94 engine and electronics. I would either go back to what was simple using the 94 as a starting point or go with the new stuff. Early 90's are OBD I systems and I think its harder to deal with.
There is a ton of support for the 5.3 stuff.

[ls1nova71]

Originally Posted by Smokey burnouts

What would be your GUESS for total 5.3 swap(motor, harness, ect)....$2k?
Would you do the 700r4 with the 5.3 or leave the th350 in there? If I went 5.3 and th350 what gears should I run in axles... 3.73 or 4.11?

I can handle **** mpg with good performance, but crap performance and crap mpg ain't working!

I don't know what your truck has in it for gears, but 3.07 was standard in a 4x4 V8 blazer, so if you have bigger than stock tires then you probably need better gears. If your current engine is in good shape, just feels gutless, then I would swap in some 3.73's or 4.11's, that may hurt your mpg's some, but for the cost of an engine swap, it would be the easiest and cheapest way to go. Especially since you say you can handle some mpg loss. But if you are dead set on swapping the engine, I personally wouldn't bother with the TBI. You'll get way better drivability, gas mileage and performance with an LS, but expect to spend a little more than 2k on the project, probably at least double that.

[Smokey burnouts]

Originally Posted by ls1nova71

If your current engine is in good shape, just feels gutless, then I would swap in some 3.73's or 4.11's, that may hurt your mpg's some, but for the cost of an engine swap, it would be the easiest and cheapest way to go. Especially since you say you can handle some mpg loss.

Already sitting at 7.5-8 MPG didn't think it could get much worse hahaha!!! Was told motor was freshly rebuilt no long ago and seems like it's in good shape. Maybe some Vortec heads and a cam might help.
Truck has 35's on it so maybe the 3.07 gear is just too much strain for the motor at 50+mph. I gotta put pedal through the floor to maintain speed

[hemi43]

Just try a gear change and see what happens. 35's with a 3.08 gear is just too stiff IMO. If you were to put something like a 3.73 in your truck and not do anything else, I bet your performance and fuel economy would improve because the engine will be in a happier RPM range. If it was me, I would put 4:11's in it, this way if I ever wanted to upgrade to an overdrive transmission I would already have the proper gear ratio.
My 2 cents.
Dan

[hemi43]

Speaking of gears, look what just showed up a few minutes ago.
Sweet!!!

[hemi43]

OOPS !! Wrong picture and can't figure out how to delete it. Here's was the intended picture.

[Smokey burnouts]

Originally Posted by hemi43

Just try a gear change and see what happens. 35's with a 3.08 gear is just too stiff IMO. If you were to put something like a 3.73 in your truck and not do anything else, I bet your performance and fuel economy would improve because the engine will be in a happier RPM range. If it was me, I would put 4:11's in it, this way if I ever wanted to upgrade to an overdrive transmission I would already have the proper gear ratio.
My 2 cents.
Dan

Thanks man👍
Would 4.10's be terrible with the th350 if I never went to a OD trans? Cause if the gear swap helps I foresee me just doing power adders to current motor or just saving up and doin a 5.3 swap and keep the th350

[hemi43]

Originally Posted by Smokey burnouts

Thanks man👍
Would 4.10's be terrible with the th350 if I never went to a OD trans? Cause if the gear swap helps I foresee me just doing power adders to current motor or just saving up and doin a 5.3 swap and keep the th350

Terrible? absolutely not !!
With your 35" tires and a non-overdrive transmission like your T350, you would be reving around 2430 RPM at 60 MPH. IMO that's not a bad RPM for an older engine.
If you decided to put an overdrive in with the 4.11 gears, you would be reving about 1650 RPM at 60MPH.
I like to see an engine at around 1800RPM @ 60 MPH, so realistically you could go up to a 4.56 gear.

I only have 33" tires and that's why I opted for the 4.11's
Dan

[Smokey burnouts]

Hemi.... So if I were set on keeping the T350 and 35's would you go 3.73 then?

[Smokey burnouts]

Since I'm thinking change the gearing in the rear is way to go(well yall informed me this was way to go). Regear stock axles or are there junk yard axles I could find with 3.73 or 4.11 gears that would bolt up under these trucks without having to move spring perches?

[hemi43]

Originally Posted by Smokey burnouts

Hemi.... So if I were set on keeping the T350 and 35's would you go 3.73 then?

Either will work. If you plan on doing mostly city driving, then the 4.11's would be good. If you plan on doing quite a bit of high speed driving then the 3.73 would be better. It's really just a matter of preference.
As far as swapping out complete axles, I would prefer to just change the ring and pinion. It will be cheaper in the long run.

[Blazerowner]

I think you can easily find a 5.3 with the harness for around 1-1500. I see them on Craigslist often. If I didn't have a ton of money tied up in my 383 I would be throwing one in. With a few mods I have heard you can easily get 400 hp out of them and still habve great driveabilty. I am putting an ls3 in my Chevelle because of this. Just can't beat In my opinion and parts are predominant in the aftermarket. I have 3.07 gearing in my blazer and with the th350 it actually had good manners on the street and highway. I would think the 5.3 would be that much better.

[robs71k5]

Originally Posted by Blazerowner

I think you can easily find a 5.3 with the harness for around 1-1500. I see them on Craigslist often. If I didn't have a ton of money tied up in my 383 I would be throwing one in. With a few mods I have heard you can easily get 400 hp out of them and still habve great driveabilty. I am putting an ls3 in my Chevelle because of this. Just can't beat In my opinion and parts are predominant in the aftermarket. I have 3.07 gearing in my blazer and with the th350 it actually had good manners on the street and highway. I would think the 5.3 would be that much better.

I have a fresh 383 in my blazer also and 3.08. I find it a little hard on the juice but on the hyway it performs pretty well . I had my tack hooked up but it seems to have an issue with the tack when starting when it's hot I disconnected the tack and it starts right up no problem so I can't remember were the rpm were sitting . but I was also wondering about 3.73 and I'm running 33 inchers.
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[Smokey burnouts]

Guess I'm at point where I have to decide on 5.3 or just heads and cam my current engine.... Checked the rear and I think I got 3.73, was really hoping I was gonna get added performance with a gear swap!

[fourspeedwagon]

Keep us posted Smokey--- Ive been going around the same circle trying to decide the best/most economical route.