Hey there! Long time reader, and did some searching, but wanted some people's opinions on a motor combo I've been brewing up.


I want a 383 TBI setup for my 91 RS. Its got the 305, 700R4, and 2.73 gear 10 bolt.

I want a 350 block, 400 crank, vortec heads, GMPP vortec intake manifold (probly will port match the two to the gasket in my garage) and I wanted to run 1.5 full roller rockers with the GMPP HOT cam. Now, if I do this right I should have a great torquey runner, right? I can get an 500rpm stall converter to help with launches...

Now, my question is about the TBI. I want to keep all the wiring stock (easier on me) and use the factory computer. I can get a buddy to burn a custom chip for me, but the actual TBI is where I"m having problems. I've seen the holley unit, its 670CFM, but I don't think thats enough to feed this motor. This motor will probly top out at 5500RPM, should I invest in a TBI from turbo city? They seem to do great work.

Also, my rear gears..I love them for the highway. I have a 45 minute commute from my house to work, is this motor going to destroy my rear? Am I gonna bog it down? Should I invest in rebuilding the rear with 3.42 gears?

Finally, I want the ability to add a blower to it. I know that procharger makes good truck blowers for TBI, does anyone have any experience with the blower for Camaros?

Thanks so much for your help!

 

I have a TBI 383 (crossfire, but essentially the same)..
I would recommend a 2" TBI from a BB truck and also the BB 90 pph injectors.
You said 500rpm stall converter, but i think you probably meant 2500, i think this would be a good choice.
It will need quite a bit of time spent on chip tuning, but if your friend is competent, it won't be a problem.
I can't help with the blower question sorry.

 

I'm pretty sure the factory rating on these things were 1500RPM or so (flash stall) I'm probly going to go with a 2000RPM unit. I meant to say 500RPM over stock. :P
I don't think it will be too low due to the extremely broad torque curve I'm hoping to produce with this thing. I really hope the curve is broad and flat from 2000RPM all the way to 5500RPM. It'll make for a good street motor that can make people pull a double take.

The TBI I was referring to from turbo city is
http://www.turbocity.com/product_inf...roducts_id=143

Which is a BB unit...but flows 730CFM.

Is that enough? Too much? Am I better off going with the holley unit thats 670CFM?

 

You will run out of fuel way before you run out of air. Go with the BB TB and don't worry about it. Do a search about max HP for TBI and do some reading. There are some tricks to pushing 400 hp. Mainly gettng fuel figured out. I hope your friend is competent, this won't be a combo for the unexperienced.

 

Fuel problems? I figured the 70# injectors (and AFPR) would be able to feed this beast.

My buddy's pretty good. He was able to custom burn a chip for his fiero. His fiero is running a 3.2 (bored stroked 2.8) with a pretty hot cam, upgraded injectors, hand ported intake, plenum, heads...etc.

We can always use a 350 police caprice chip as a benchmark, right? Plug in those numbers, and tune as necessary, right?

 

For a bit of a guide as to how much fuel it will want, mine is running just over 110mph in the 1/4 and i am running 90pph injectors at 20psi to achieve about 92% DC at 5800rpm, showing mid 12's on the WBo2....
With a smaller cam, 16psi was sufficent, just.. oh ok, the DC was too high then too ;-)

 

Im looking at doing the exact same thing that you are doing, and Ive found that a 2 bbl tbi just isnt going to do the job for over 400hp. Your motor n/a will have that, and if you want to go with a blower you will need a serious tbi. On a 2 bbl , two injectors just cant spray enough fuel. The Holley Commander 950 looks perfect, which is what Im saving for. It is setup for boost, but I think you have to buy a map sensor separate. $50. They arent cheap by no means, but its better than tpi I feel because of the ease of tuning. Holley rates the 900cfm model for between 375-600hp IIRC depending on injector size. The older projection models used crap injectors and arent really worth the money of upgrading the pod and injectors. Anyways like I said its not cheap, but I think a 4 bbl stand alone system is a must if your going to run a blower and want an easy reliable system. So for now im going to run carb until I find a good deal or I save the money. What I dont understand is why a 650 carb is good for 400-450hp, but a 650 tbi 4 bbl is not? Hope this helps.

 

QUOTE: What I dont understand is why a 650 carb is good for 400-450hp, but a 650 tbi 4 bbl is not?

i wondered that too. thinking of the 670 cfm GM/Holley vs even a 625 CFM carb. #1 we have an inj and pod restricting the air flow. 670 may be rated without thepod/inj. also TBI is rated at diff vacuum than carb. i believe a 670 TBI may flow as a 600 carb due to way it is measured. dont know why measured diff.. #2 also a carb is MAF(air past a jet) and is somewhat self metering vs our speed density TBI. possibly the fuel flow is proportionate to rpms as far as getting fuel into engine. with rpms comes the fuel with a carb. idle circuits seperate so large main jetting. it was said our deficiency is not so much the air flow but more so the fuel flow. that may be our limiting factor for higher HP/RPM combos.. granted we up FP well beyond the stock 12-13 lbs and this helps. large TBI injectors at high pressures create other issues such as idle. add to it a large cam and it gets dicey.

GM went to MPFI for a good reason.

 

If you are going by Holleys Recomendations, that is where the injectors in the 650 CFM unit become too small for the power being produced. If you actually talk to the techs they will tell you to size your system in the middle of its band. For example, lets say you have a stock 250 HP 350. The 670 2 bbl is rated at 275 and is a good choice. The 670 TBI has plenty of air flow left, just runs out of injector. Raising the holley injectors at higher pressures is not a good idea as it drastically cuts the life expectancy.

 

I ended up buying the Holley 670 unit and also was not happy with the injector and injector pod. I found after I shut the car off the injectors would drip into the bores On top of that I was only running 15psi. No matter what i tried i couldn't keep them from leaking!! I eventually scrapped the Holley pod and retro fit the GM pod (with 90# injectors) on the Holley body.

 

Holley injectors from my experience are crap.

 

Interesting, Bones232 and Gunny, are you talking about the older injectors, or the newer Delphi injectors? I know the older ones had issues. My understanding was that the Delphi's were a decent injector.

RBob.

 

My experience is with the older ones. So I guess this is a word to the wise out there. . .if you plan on getting a used Holley 670 off of Ebay, be careful.

 

I would hope they are the "old" injectors... I bought the TB brand new about 3 yrs ago. I can't imagine a company like Holley continuing to market such a weak product.

 

Gunny, OK, good to know it is the old ones. Thanks.

Bones232, the old injectors can be identified by a black cap over each injector. Where the new ones (Delphi) have an open top with the connector exposed. The connector coming off the injector at a 90° angle to it.

RBob.

 

yeah it also has a zinc plated (it could be brass) bracket holding the injectors in place. It appears that I may have the newer version. I could never get them to stop leaking. I lowered fuel pressure, increased hold down bracket pressure on the injectors... nothing... I didn't bother trying to change the o-rings, i just swapped in the gm pod... I also wasn't overly thrilled that the injectors were held in by a cheap looking bracket with a single mounting point... Didn't seem like it would hold too much fuel pressure...

Since I switched to the gm pod all has been well... I wouldn't sweat running 20psi or more...