Bench build: A TBI 350 for autocross?

My Turd Gen Camaro needs love. Lots of love. The TBI 305 that's in it was weak when new, and plus it's started to smoke.

I'm thinking with my wallet, and here's what I've come up with: A mild 350, maybe 355 with stock Vortec heads, mild cam and a TBI on top. The easy button would be a TBI to Vortec intake manifold, but that is far out of budget, summit says $398.97.

Now, they make adapter plates that adapt the three bolt TBI to a square bore, 4160 flange type of manifold Summit says that one is $39.97.

Now, the reason for TBI is for simplicity and reuse of what I already have. Maybe swap to a larger TBI, or bigger injectors in what I have now, re use my existing accessories, brackets, etc. Off the shelf headers fit, and possibly even the kickdown cable that's already on my car. Burn a new PROM chip, or maybe convert to Megasquirt, who knows.

Not looking for huge power numbers, chances are this will never see a dyno for me to know what it's making anyway. I just need a torquey engine to get me around the cones without making so much power that I'm struggling to keep the rear end in check. Also, I need enough power that I'm not grenading the stock ten bolt.

LS swaps are out of the question, at least for now. The amount of swapping and parts scrounging needed just isn't in my comfort level/budget right now.

Thoughts? Praises? Curses? Miata?

Vortec heads, mild cam (short-ish duration, but a good bit of lift and fairly fast lift rates), headers if you can, plus a bigger TBI should do the trick.

I'd definitely do the TBI to 4150 square bore adapter setup, and I'd probably toss it on top of a RPM airgap or similar manifold (there's some cheap Chinese knockoffs of them that are almost as good). The bigger TBI will definitely help with the dual plane manifold (dual plane manifold needs a bigger carb / TB than a single plane, as each cylinder can only pull from one side, rather than the whole carb / TB).

I dunno what stock Vortecs will take for lift (and whether you might need to swap valve springs), so I'm not gonna recommend a cam at the moment. But if you get the right cam in there, it should pull like a tractor right from idle and still be able to rev a bit (should pull to around 5500 or a little higher). If it comes out anything like the similar build I did on a Mopar 360, it ends up being really hard to be in the wrong gear for a lot of things.

Use a carb?

In reply to BrokenYugo:

My car is fuel injected, and to run a carb without changing the fuel sender is to run an adjustable fuel pressure regulator. $200.97 on Summit.

So I'm trying to make the best of what I already have.

Yeah, when it's already got EFI that has aftermarket tuning support, I see no reason to convert to a carb when that existing EFI can definitely do what's needed with cheap / available parts.

Skip the tbi vortec intake. Cheapest ebay single plane you can source for the heads and tbi adapter. I'd also run a stone stock vortec longblock, with long tube headers and ultimate tbi mods and a baffled oil pan. It'll be very torquay over a broad range, and very streetable. And simple.

I autocross an 89 chevy truck 350 with a bazillion miles on it. Edelbrock tbi intake, 305ho heads, stock 65 chevelle exhaust manifold and 2 inch true duals. Blows the tires right off.

You'll have plenty of fun on a stock vortec converted to tbi.

Oh, and there's some guys over on geafheadefi with tunes already for this.

I'd run Vortec heads and a mild cam, with a carb manifold on top and a square bore to TBI adaptor. Ultimate TBI mod, 155lph fuel pump (stock one is only good for 250 HP or so), Harris Performance spring and chip, wires and coil, and a full 2.5" exhaust with long-tube headers. That baby is gonna be pretty damn quick.

In reply to BoostedBrandon:

You'll need to factor in the $3,750 fine you'll get from the EPA.

Nick (LUCAS) Comstock wrote: In reply to BoostedBrandon: You'll need to factor in the $3,750 fine you'll get from the EPA.

You could go with a newer TPI setup from a junkyard/craigslist for cheap. Also, an old LT1 engine from a 90s Camaro or Caprice/Impala SS should be cheap to buy, too.

In reply to Mr_Clutch42:

I did entertain that route, but haven't ruled it out.

What's this "ultimate TBI mod" I'm seeing?

BoostedBrandon wrote: In reply to Mr_Clutch42: I did entertain that route, but haven't ruled it out. What's this "ultimate TBI mod" I'm seeing?

Cut down the air horns on top, Dremel out the bores a bit. Basically the most little works you can do to a tbi to make it flow as well as it can without swapping to something else. Google untimate tbi mods and you'll have a better idea what

Sounds like a lot of effort when Miata is the answer.......

But! If you want to stick with your antique Camaro I can get behind that. Would picking up the cheapest wrecked late '90 pickup/Tahoe/suburban and yanking out the Vortec 350 and installing it with some free flowing headers be the easiest and cheapest route to a reliable 300 hp?

I mean, you'll still get spanked by dudes driving hairdresser barbiemobiles but you knew that already.

KyAllroad wrote: Sounds like a lot of effort when Miata is the answer.......

He's aware. Heck, he's autocrossed my S2000 a couple of times so he knows what he's getting into. There's a lot of emotional attachment to this car, and that trumps overall competitiveness. Not to mention it satisfies his inner redneck.

Spoolpigeon wrote:

KyAllroad wrote: Sounds like a lot of effort when Miata is the answer.......

He's aware. Heck, he's autocrossed my S2000 a couple of times so he knows what he's getting into. There's a lot of emotional attachment to this car, and that trumps overall competitiveness. Not to mention it satisfies his inner redneck.

BoostedBrandon wrote:

I think this goes right along with the joke requirement that you can't own a Camaro unless you can simultaneously smoke a cigarette, drink a beer and shift

I know guys, just poking fun.

We had a "turd" gen camaro here in CKR for years do very well. Of course CP with lots of roundy track parts and trailered to the events helped him out......

Sort of like the F-4 Phantom, it may not be elegant but throw enough horsepower at the problem and it will perform.

I did a similar engine build on a third gen I owned in college. 355 roller block, vortec heads (modified for higher lift), LT4 hotcam, short headers to a 3" single exhaust. I found a good deal on a marine version of the TBI to vortec intake, so I ran that. I modified the ECM using Moates.net hardware and tunerpro software.

The biggest hurdles:

Hood clearance if going the square bore + adapter route (single plane will likely not fit)

The stock 305 TB is pretty restrictive. 454 throttle bodies are bigger and have larger injectors but are hard to find. I ran a Holley replacement thottle body but modified to use the GM injector pod (the early Holley injectors were not dependable). I ran ~30psi of fuel pressure and used a vacuum referenced regulator to get the idle fuel pressure lower for better low pulse width fuel control but still have enough flow to make ~360 flywheel hp.

Ultimate TBI Mod

I've got a 454 TBI body, that I'd let go for cheap.

JMcD wrote: The biggest hurdles: Hood clearance if going the square bore + adapter route (single plane will likely not fit)

Here's a way around that.

In reply to RealMiniParker:

How cheap is cheap? Because I am CHEAP.

In reply to BoostedBrandon:

PM sent

In reply to BoostedBrandon:

It looks like patgaz has the engine you want for $400. Look over in the $2015 classifieds.....