Mild 400 TBI in a 94 GMC K1500.

[Supercharged111]

Erik, honestly before I wasted my time porting TBI heads I would just get some vortecs or small port aluminum heads but like I said this would be a pure torque/towing engine that I hope gets good MPG. Unmodified tbi heads fit my needs very good I think. I don't care if this engine makes power above 3500 RPM because other then accelerating onto the highway it will never see any more RPM then that.

My Vortec 350, tuned, will absolutely stomp a mudhole on my old 88 TBI truck even though it's 1400# heavier. And that's before the blower. From an idle to redline.

 

[L31MaxExpress]

My Vortec 350, tuned, will absolutely stomp a mudhole on my old 88 TBI truck even though it's 1400# heavier. And that's before the blower. From an idle to redline.

Did a 406 with TBI heads and a Comp high energy 260 cam for a 95 1-ton dually G30 van based motorhome. Had an edelbrock 3704 bored to 46mm and a 46mm TBI unit with 454 injectors. Stomped a mud hole in what any stock 350 Vortec would have made below 4,500 rpm.

 

[Supercharged111]

Did a 406 with TBI heads and a Comp high energy 260 cam for a 95 1-ton dually G30 van based motorhome. Had an edelbrock 3704 bored to 46mm and a 46mm TBI unit with 454 injectors. Stomped a mud hole in what any stock 350 Vortec would have made below 4,500 rpm.

Dude stock the 350 Vortec BLOWS. It's like comparing an LS to an SBC. Sure the top end is better but the damn thing would barely chirp an old dry rotted right rear tire when I bought it.

 

[L31MaxExpress]

Dude stock the 350 Vortec BLOWS. It's like comparing an LS to an SBC. Sure the top end is better but the damn thing would barely chirp an old dry rotted right rear tire when I bought it.

When I still had the 60E, I could practically spin the rear tires off it stock. I remember one of my parents easily spinning the tires on the first test drive back in 98 when they got the thing. Had way more power than the smogger 305 in the old 83 G20. My uncle who already had a 94 C1500 5.7 drove the 97 and went out and bought my aunt and him a 98 Tahoe. The Hecho en Mexico L31 crate engine that replaced the stock engine was a DOG by comparison.

 

[b454rat]

The 350 in my Tahoe runs great. Uses a lil oil, but has 206k on it I think. It won't lite the 295s up, but has good power for being what it is. My old 99 CCSB had the same miles, and was a dog. Granted talking prolly couple thousand pounds weight difference, but it would struggle on the littlest hills. But then again, I had some good running TBI's that felt like they could take on a Vortec, so hard to say what's going on. But either way can't go wrong with a 400...

 

[Erik the Awful]

Erik, honestly before I wasted my time porting TBI heads I would just get some vortecs or small port aluminum heads but like I said this would be a pure torque/towing engine that I hope gets good MPG. Unmodified tbi heads fit my needs very good I think. I don't care if this engine makes power above 3500 RPM because other then accelerating onto the highway it will never see any more RPM then that.

Fair enough. I think my biggest problem with the TBI heads is that they have a 1.94" intake valve, but right above the valve the runner necks down to a 1.7x" diameter. I opened mine up. Engine's still on the stand right now - waiting on parts I ordered three months ago. Stupid Covid.

 

[stephen p luce]

I put a 98 vortec 5.7 in my 89 stepside and am running the TBI injection. Had to go with a 46mm throttle body and the higher pressure f/p and reprogramed the chip to get any driveability out of it. I used harris TBI to do the chip.

 

[Rayar66]

Looks like everyone has different results. Guess I will just need to try it to find out.

 

[PlayingWithTBI]

Had to go with a 46mm throttle body and the higher pressure f/p and reprogramed the chip to get any driveability out of it. I used harris TBI to do the chip.

That's a start but, data logging and tuning is a much better way to go. Modify your ECM with a 28 pin ZIF (Zero Insertion Force) socket and use SST 27SF512 flash chips.
Or, better yet get an EBL Flash-II

Personally, I didn't get very good results with Harris (TBIchips.com). FWIU he's retired due to poor health and someone else took over.