Is 300 hp possible from a tbi

[westsoundred]

Of course

lol, can I see it?

 

[L31MaxExpress]

I was able to get to 200 rwhp and 300 rwtq with a low compression 1-ton TBI that started out at 180 hp. Internally stock engine save for 1.6 rockers.

I swapped the flat tappet cam for a factory 96 LT4 roller cam and got to 255 rwhp.

Both setups had the same external components. Edelbrock performer rpm intake with the 4 center bolts slotted and tappered wedges to correct the bolt angle (weiand made them for their superchargers), marine square bore to TBI adapter, marine 2" bore TBI unit, thorley tri-y headers into a dual 2.5" catless exhaust with a X-pipe and magnaflow magnapack mufflers. Custom prom chip tuned by me with a Moates Autoprom.

I ran a weiand 177 on the stock engine with just the rockers and headers for about a year too. It made 309 rwhp and over 400 rwtq at 10 psi. It is possible to make over 300 rwhp with TBI heads and stock TBI cam but you need forced induction to get there. The weiand 177 on a TBI engine is a 700r4/4L60E destroyer though. Will break the best built example of those transmissions from the instant torque spike off-idle.

 

[thinger2]

It can be done. Its not gonna be cheap and it just aint gonna work for long with a 4l60e or a 700r4.
By the time you get done .
Though I hate to say it.
LS swap it.
300 hp easy and reliable.

 

[PlayingWithTBI]

Though I hate to say it.
LS swap it.
300 hp easy and reliable.

But what's the fun in that? It's more fun in taking the challenge in seeing what you can do with the cards you're dealt, right? Anyone can swap a Vortec or an LS but, can you build a TBI and tune it to get the torque and HP you want? Yes you can, enjoy!!!

 

[Redneckgeriatric]

i guess we need to redefine "stock" longblock?

 

[westsoundred]

an LS would be fun, but I dont want to get into the wire hardness jumble. I don't mind going with a vortec longblock and a performance intake manifold, that pretty easy to deal with. And with that, I'm scratching at my desired hp range.

the TBI modifications are interesting...I'm not sure if I understand them all. If you replace the 350 injectors with 454 injectors, do you need to upgrade the regulator spring? what else needs to be updated?

 

[westsoundred]

i guess we need to redefine "stock" longblock?

Its like defining the American Dream, it is what you make it.

 

[Gramps]

Well, You don’t necessarily need 454 injectors, it depends on fuel demands. In my case, the 350 injectors couldn’t do the job, we had the pressure cranked to 26 psi - it worked but that’s not sustainable for road use. So 454 injectors went in, pressure came down and was eventually settled at 14psi.
It’s a smidge rich at idle, but perfect through the rest of the rpm range.

If you look up “ultimate tbi mods” you can see what all needs to be done.

Fortunately the dyno guy here is a very thorough dude. Bench flowed my tbi unit, then again with the pod spacer. We also ran with and without the tbi spacer. It actually did improve the Hp and tq numbers.

In your case if you just went with a stock vortec long block with appropriate intake, you likely would be fine with the 350 injectors and a bump in the pressure.

 

[westsoundred]

Well, You don’t necessarily need 454 injectors, it depends on fuel demands. In my case, the 350 injectors couldn’t do the job, we had the pressure cranked to 26 psi - it worked but that’s not sustainable for road use. So 454 injectors went in, pressure came down and was eventually settled at 14psi.
It’s a smidge rich at idle, but perfect through the rest of the rpm range.

If you look up “ultimate tbi mods” you can see what all needs to be done.

Fortunately the dyno guy here is a very thorough dude. Bench flowed my tbi unit, then again with the pod spacer. We also ran with and without the tbi spacer. It actually did improve the Hp and tq numbers.

In your case if you just went with a stock vortec long block with appropriate intake, you likely would be fine with the 350 injectors and a bump in the pressure.

as far as the injectors, I used this website to do a simple xcel sheet
https://www.dynamicefi.com/TBI_Fueling.php

the excel file is uploaded. Does that look right to you? in other words, a stock 350 injector is easily good for 300 hp with a stock 12 psi setting?

 

[PlayingWithTBI]

Well, You don’t necessarily need 454 injectors, it depends on fuel demands. In my case, the 350 injectors couldn’t do the job, we had the pressure cranked to 26 psi - it worked but that’s not sustainable for road use. So 454 injectors went in, pressure came down and was eventually settled at 14psi.
It’s a smidge rich at idle, but perfect through the rest of the rpm range.

I did similar stuff with mine - the 61#/Hr injectors @ 18PSI were running a DC of 99% - 106% (meaning they were open all the time) at WOT in 2nd gear @5200RPM. Here's a screenshot from my EBL Flash2. I jacked it up to 28PSI and got my DC down to ~85% but they started dripping and caused a stumble @ idle.

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I switched to the 7.4 (81LB/HR) injectors running at 15PSI and got a DC of ~80% - 82% but when I ran the "VE Learn" utility it actually shut off the injectors completely (and killed the engine) trying to get the AFR down to 14.7 with my WBO2. So, I put the 61#/HRs back on and set the pressure to 20PSI and now they're running ~90% to 94% but, at least it idles now, LOL. If you look at the cAFR 12.0 and WB 11.3 I'm thinking I can adjust my PE a little and not suffer too much in power. HTH