350 TBI upgrades

[Mike83]

Ok, i dont know why i started a new thread.....im wondering if anyone has had good luck with any of the aftermarket tbi intake upgrades and what cams are good, wouldnt have been a problem if the computer would handle what i had planned. What were your hp/tq gains from upgrades and a decent gear ratio? 89 blazer, 4in lift, 350 tbi, 700r4 shift kit, 35x14.50x15 ss boggers. kind of on a budget (or so the wife says) but want to be able to play with the boggers without powering out and being stuck...any info be great, found out origional build will cost too muchso it be done on other 350 over time.

 

[Doc Feel Good]

I have a super chip in my ECM, and I put in the Edelbrock Performer for the TBI.

I dont know of the actual HP/FtLbs improvement, but looks good and havent had any issues with it.

(its been 6 months)

-Doc

 

[1BEATK5]

first, get an adjustable fuel pressure regulator. turn the pressure up to 13.5psi. that will make a noticable change. you can also adjust the fuel pressure up later when you make some more serious mods. flip the air cleaner lid over, have the tb unit bored out. short headers, and keep the factory single exhaust. just make sure it's 3". some only had 2 1/2".
the block is already bored and tapped for a roller cam, and the gm roller lifter install kit is only $235 from summit. that includes the lifters. pick a small roller cam. like under .450 lift. vortec heads, and either the edelbrock tbi intake, or adapt the tbi unit to a performer rpm or equivalant.
start with the regulator,bored out tbi, and exhaust
you can get the adj. regulator and a bored out tbi for about $325 with shipping
once you get past 270hp you will need a tpi fuel pump to keep up. and a custom prom made.
there is alot of info out there still on modding these.
dont expect huge power gains. just smooth reliable power.
i vote for 4.56s with the 700r4

 

[zombiyjay76]

Had my engine rebuilt 2 months ago. Got the edelbrock intake and cam for the tbi, with headers. still haven't got around to doing that much to the tbi it's self, just a pod spacer and the bowl from hyper-tec. Not sure of my numbers either, but so far so good.

 

[Mike83]

I think im going with a carb swap, 600 edelbrock, performer air gap, .480 cam, and getting heads ground out for flow. for what i do it will work but i hate loosing fuel injection but it will cost me a mint in computer stuff to gain the hp/tq that i want. but if i get my other 2 blazers i will def keep this info in mind because i would like to have a really nice 88-90 sittin on 32s for my daily driver someday!!

 

[Thunder]

How much HP and torque are you after? 280 HP 350+ TQ out of a TBI Does not cost that much to get to. The stock chip and cam with 1.6 to one rockers will support that.
Swapping to a carb will cost you about the same ammount to buy the parts. As a mild TBI build. Unless you alredy have all the parts needed laying around.
As for computer stuff. Having a chip burned chip for a popular aftermarket performance cam and other performance upgrades is only around $250

 

[Hogback Fabrication]

Gears are your best bet, getting more power out of a TBI setup is going to cost you a lot of $$ per hp (or in the case of gears, $$ per how well your truck performs).

The TBI setup is great for what it is but basically everything on it needs to go if you're looking for lots of power. And simply replacing the TBI with a carb is not going to fix that.

The TBI heads really would be the first thing to go and really no matter what you do that's pushing $1K (aftermarket old style heads or vortec with a new intake manifold), then what? Cam? Go too aggresive and the TBI won't like it and/or it will suck as a motor for a truck.

Also, I see people mention bumping up the fuel pressure to "trick" the TBI into feeding more fuel I guess, how does that not destroy fuel economy?

 

[Thunder]

Also, I see people mention bumping up the fuel pressure to "trick" the TBI into feeding more fuel I guess, how does that not destroy fuel economy?

Upping the fuel pressure by its self will take a couple of MPG away. It does on my TBI 350.
But you can find the right combination of base timing advance and fuel pressure. to get the best of both worlds.

 

[Mike83]

Thanks for the input. this site is pretty informative and not just alot of jaw flapping!! Im gonna get my ss boggers under it soon and see how it does and go from there. as it sits right now with 35x12.5 MTs it is not under powered by any means, she will spin them nice in the goey stuff and still do a burnout on highway is i find myself inclined to waste expensive tires haha. i dont have any good trails to crawl around on all afternoon around here anywhere but that would be nice!!

 

[Mike83]

HP wise i was aiming 400-450 and about equal tq, it will take some time but i will have something figured out eventually, just need patience (and the cash!)

 

[1BEATK5]

the adjustable fuel pressure regulator is a must have. not an option if you want more than stock power from a gm tbi and when adjusted properly will have no effect on fuel mileage under normal driving.
the pcm uses the oxygen sensor to adjust the air/fuel ratio up to 3/4 throttle. after that it uses a predetermined fuel map. so if you do ANY mods to the engine, it will run very lean after 3/4 throttle.
so what does that mean?
turn the fuel pressure up so it flows more fuel above 3/4 throttle, but not so high that the computer cant adjust the mixture using the oxygen sensor under 3/4.
if you really want 400+ hp. spend the $ and get aftermarket F.I.
you will also need aftermarket aluminium heads, descent roller cam, and a big ignition to fire some real compression.
also consider hp is made at higher rpms, maybe consider big torque instead
my brothers 2.02 valved, ported head 383 w/9:1 comp. only made 340hp on the dyno. but did make 440ft.lbs of torque.
for some big power. maybe a 383 with vortec heads, modded tbi unit and a custom prom (which as somebody else mentioned aren't too expensive)
and exhaust would satisfy the power hunger. not tons of hp, but a crap load of torque down low where it's needed.

 

[Mike83]

I looked up the idea of after market FI and ya its spendy. but prob worth it. if i stop doing mud drags with this blazer i would just swap in a 454 and have fun. im just gonna build the other 350 tbi i have over the next year and see what happens i think.