Question for you guys...

I have an '89 Blazer that I'm getting ready to put a little money into and make a little more road-worthy.

The motor is a 350 TBI. My question is, what is the best thing to do to get a little more power out of this motor?

I have been looking into putting some performance type headers on, thinking that may help a little. And I believe that with this motor its not really possible to add a performance cam or anything along those lines.

Does anybody have any suggestions?


TIA

More power is always a matter of money. What's your budget?

Headers and open exhaust is rarely a bad call, but your ceiling is pretty low with the TBI induction and wheezy stock cylinder heads.

A roller cam SBC crate engine would be an easier swap than an LS, though potentially more expensive.

I have no experience/affiliation with this company, but it's a pretty good gauge for what you have to pay for horsepower, unless you can get resourceful on finding parts and do the work yourself.

https://blueprintengines.com/collections/gm-compatible-small-block-crate-engines

The cylinder heads are ***** Start by swapping those to later model truck heads and the edelbrock manifold to fit the different bolt angle.


Edit. Not edelbrock. Its GM

https://www.summitracing.com/parts/nal-12496821

Easiest thing you could do now for seat of pants feel would be swapping to 4.10 or numerically higher gears.

If you start messing with the engine much, you'll run into the tuning issue. The options for TBI tuning were minuscule when I decided to go LS 7 years ago, I'm sure there are even less people doing it now. If you're dead set on keeping the 350, vortec heads, intake manifold, & ditch TBI for a carb. You could do a cam swap if you wanted once carb.

I'd buy a 5.3/4L60e to jam in there, it's not too hard and can definitely be done for less than $4k.

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If you start messing with the engine much, you'll run into the tuning issue. The options for TBI tuning were minuscule when I decided to go LS 7 years ago, I'm sure there are even less people doing it now.

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I don't know how you arrived at this conclusion. There are tons of options.

Thanks for the responses everyone! I'll definitely look into everything that was suggested.

End goal is definitely doing the LS Swap. However, until I gather the funds I'm just trying to get a little more out of my current setup.

On the subject of the LS motor... Is my best bet to hit up a scrap yard and pull one from a wrecked truck/tahoe?

robertf03 said:

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If you start messing with the engine much, you'll run into the tuning issue. The options for TBI tuning were minuscule when I decided to go LS 7 years ago, I'm sure there are even less people doing it now.

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I don't know how you arrived at this conclusion. There are tons of options.

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While retaining the stock throttle body? Best I recall running across involved swapping to a big block TBI unit, but that seemed not worth the effort. Aftermarket TBI is a great option, but you start creeping up into LS swap price territory pretty quick with that approach.

Those TBI trucks don't make for easy modification for significant power gains.

JonesAg13 said:

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Thanks for the responses everyone! I'll definitely look into everything that was suggested.

End goal is definitely doing the LS Swap. However, until I gather the funds I'm just trying to get a little more out of my current setup.

On the subject of the LS motor... Is my best bet to hit up a scrap yard and pull one from a wrecked truck/tahoe?

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If that's the case don't bother with the headers, they won't work with an LS, so that would be money gone less anything you can get resale.

I'd second the gear swap idea. That would serve you well before and after the LS.

No sense in spending money on a 350 just to yank it for the LS later.

Running a fuel rail w/ return and DBC TB is most simple IMO, this is most 99-02 engines. If you find a newer engine, an older fuel rail & DBC TB would fit without an issue. Your wiring harness will need to match the TC, red/blue for DBC & green/blue for DBW. You can strip down an OE harness yourself, send it off to someone to have made into a standalone, or buy a brand new standalone harness for $500. AN fittings & hose to adapt your current fuel lines match up to fuel rails. AC Delco EP381 fuel pump will drop right in, but not a good choice for boost or 6.0 w/ cam. If this is a 4x4 vehicle, GMT800 Pacesetter longtubes will fit if you don't want stock exhaust manifolds.

Junkyards or asking around your carbro friends (presuming people on Texags have friends) are the best ways to source an LS. Use car-part.com to check out pricing from nearby yards. I ordered my LQ9 through LKQ Online, it came from one of their yards in MN and shipping was ~ $200.

Dumb question but are TBIs not bolt on interchangeable with a carb? Possible intake manifold changes?

Not a suggestion as much as I've always wondered that.

You can bolt a GM TB unit onto a carb intake manifold with an adapter if those adapters are still being made. A carb wouldn't bolt onto a TBI manifold.

Aftermarket TBI units would have a 4 barrel square bore flange and could go right onto the standard carb intake.

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While retaining the stock throttle body? Best I recall running across involved swapping to a big block TBI unit, but that seemed not worth the effort. Aftermarket TBI is a great option, but you start creeping up into LS swap price territory pretty quick with that approach.

Those TBI trucks don't make for easy modification for significant power gains.

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had a long reply typed but the board ate it

cliffs notes: I use tunerpro RT to tune them. Its the same as tuning any gasoline engine. Does it have the right fuel and spark?

you're limited to around 5500 RPM so you won't have stupid dick measuring horsepower numbers with a TBI ECU, but you can build a torque monster without too much trouble. You're limited to 80pph injectors so focust on improving BSFC

silverado_lover said:

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I don't know how we've gotten this far into this thread without a suggestion to flip the lid. You'll really be able to hear the horsetorques then.

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Had a 90 GMC back in the day and it ran pretty good for a stock motor in a 3900lb truck.

To get the most out of it you will have to run 93 octane and purchase a chip.
You have to manually adjust the timing, mine ran best at 6 degrees advanced, any more and it pinged. Stock was 0 degrees



Things I did that made a measurable difference


Dual 2 1/2 inch flow master exhaust #42501

https://www.amazon.com/Flowmaster-42541-40-Muffler-Aggressive/dp/B000182DMO

Accel super coil

https://www.summitracing.com/parts/acc-140011

Underdrive pulleys

https://www.summitracing.com/parts/asp-841051

K&N 14 inch open 4 inch tall element in an edelbrock housing

https://www.summitracing.com/parts/edl-1221


https://www.summitracing.com/parts/knn-e-3750


Hyper tech chip

https://www.summitracing.com/parts/hyp-12012

160 degree thermostat

Ditched fan clutch for a flex fan


https://www.summitracing.com/parts/flx-1319

Those hypertech chips are junk. Ive personally read and compared a tpi chip that only had the base timing increased. You could do that with a wrench for free.

robertf03 said:

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While retaining the stock throttle body? Best I recall running across involved swapping to a big block TBI unit, but that seemed not worth the effort. Aftermarket TBI is a great option, but you start creeping up into LS swap price territory pretty quick with that approach.

Those TBI trucks don't make for easy modification for significant power gains.

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had a long reply typed but the board ate it

cliffs notes: I use tunerpro RT to tune them. Its the same as tuning any gasoline engine. Does it have the right fuel and spark?

you're limited to around 5500 RPM so you won't have stupid dick measuring horsepower numbers with a TBI ECU, but you can build a torque monster without too much trouble. You're limited to 80pph injectors so focust on improving BSFC

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Stupid dick measuring horsepower numbers are all part of the fun, and besides, I'm spending OP's money here, not mine. I always had the impression that a non-vortec TBI SBC would be limited to well short of what a mild 5.3 would give you, but maybe I'm wrong there.

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I always had the impression that a non-vortec TBI SBC would be limited to well short of what a mild 5.3 would give you, but maybe I'm wrong there.

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You are absolutely correct, but its not the fueling system that is the immediate limitation. The cylinder heads, exhaust manifolds, and camshaft that are junk, followed closely by the piston dome shape, compression ratio, and intake setup. a TBI 350 is just as junky as any mid 70s to mid 90's 350. They all need all of the parts replaced to feel like a real v8.

I'm confident you could get pretty close to the factory 96-98 truck torque hp figures with that intake manifold and heads I linked to and some tuning time. Higher if you're willing to swap pistons and cam. What you can't do is mold your own thermally isolated resonance tuned intake manifold or change the valve train angle, so the 5.3 still has the advantage.


here's a decent apples to apples comparison with realistic non inflated numbers

Right, I didn't really mean to isolate the issue to TBI itself as it seems suited to the max potential of the rest of the package, which is low, so I start spending imaginary money making someone else's Blazer more powerful.

The vortec SBC heads are underrated, and cheap.

silverado_lover said:

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I don't know how we've gotten this far into this thread without a suggestion to flip the lid. You'll really be able to hear the horsetorques then.

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First thing that popped into my head when I saw TBI.

I asked this question once in 2011.
Most popular recommendation I got was to advertise it as boat anchor.

That TBI is still sitting in a field in Alvin, Texas to this day.