Budget Fuel Injection for a 383...

[Mark B]

Hey guys,
I want to build a 383 for my third gen. I definitly want to go Fuel Injected. At first I was thinking of going TPI because its so easy, but I the TPI setup will choke the 383. What would be a good FI setup that wont choke the motor but wont empty my wallet? Mabey an LT1 setup? Whats involved in putting an LT1 setup on a standard 4-bolt main 350 block?

[redws6]

if you want to put a lt1 intake on your 350 you would have to,

do some modifications to the back of the intake to get the distributor to fit.

get a remote thermostat housing

and i think there are some more odds and ends to it.

i would just go with this setup if you wanna spend the money.

[Injuneer]

You can't put an LT1 PCM/fuel injection on a Gen 1 SBC, unless you find some way to replicate the high and low resolution pulse pattern from the LT1 OptiSpark distributor. You can't put an Opti on a Gen 1 block, so you would have to add the optical module at the front of the engine, or in the distributor, somehow.

The LT1 intake will not bolt directly to the Gen 1 heads. Bolts are in a different location, bolt angles are wrong, and there are no coolant passages in the LT1 intake. They are available, fully converted to fit, at a price.

Painless has a new DFI system - haven't seen it, but it is supposed to be very user friendly. Holley Stealth Ram is a good setup. The Stealth Ram setup is a replica of the LT1 intake, to some extent. A low end FAST or Accel/DFI Gen VII, with injectors added to a well-designed single plane intake. The latest issue of Chevy High Performance has an article on installing the FAST with a 4 bbl throttle body.

[DeWynter]

TPI will not choke the 383 untill after 5500 RPM, dont listen to old wives tales, and propaganda. If your just making a nice street car TPI will be totaly fine. If you want to start getting more flow from the TPI for high RPM racing, then repalce the Base intake first, not the runners, as they out flow the base.
A stock runner will flow - 203.17 CFM
stock runner with base will flow - 198.72 CFM
Stock throtle body will flow - 550+ CFM (depending on year)
now even with a conservitive flow of 175x8 cylinders = 1400 CFM total possible flow with a high velosity(which makes torque) the bottle neck now lies with the throttle body.
Now with calculations I wont get into right now a 383 can only pull in 536 CFM @ 5750 RPM without using a supercharger. With a 52mm throttle body you can flow 850+ CFM. Mathmatics are great. with a 383 you will need at least 24 # injectors, I use 30 # (better duty cycle) TPI is no Dog of a motor. With hand fitting and port matching and a few tweaks and some elbow grease a TPI motor can make alot of power. Dont get me wrong im not saying its a High RPM preformer or that it can compare with a LS1 for potential, but it seems to get the short end of the stick. It all depends on what you want to do with the car. Drag or street, TPI isnt a great drag motor, as it cant make the really high RPM power. But on the street it will feel like a tire shreding monster. Another thing that many people do and really drag down the preformance of the TPI is put heads on with big intake valves. the stock 1.94/1.5 combo is great for torque as it keeps the intake air velocity up as the 2.02 seems to drop the velocity enough to drop the torque numbers. Sorry for the long post but I wanted to help promote the under dog.

[TraceZ]

You can run a LT1 intake on your car. There is a guy that modifies the intakes for a distributor and coolant lines. you might be able to get him to sell you one.

Go to www.lt1intake.com and check it out. He has pictures documenting the installation in a 3rd gen car.

It doesnt use the LT1 PCM. It uses a TPI injection setup on the LT1 intake, so the distributor from the TPI works.

you can go directly to the FAQ, HERE

[Injuneer]

.....
A stock runner will flow - 203.17 CFM
stock runner with base will flow - 198.72 CFM
Stock throtle body will flow - 550+ CFM (depending on year)
now even with a conservitive flow of 175x8 cylinders = 1400 CFM total possible flow with a high velosity(which makes torque) the bottle neck now lies with the throttle body.
Now with calculations I wont get into right now a 383 can only pull in 536 CFM @ 5750 RPM without using a supercharger. With a 52mm throttle body you can flow 850+ CFM. Mathmatics are great. with a 383 you will need at least 24 # injectors, I use 30 # (better duty cycle)

A couple of questions....

Why would you multiply individual cylinder head bench flow by 8 to get some sort of peak demand? Doesn't work that way. All 8 cylinders are not on the intake stroke simultaneously, and even the ones that are are not at the same point in the intake stroke.

Why is a 383 limited to 536cfm @ 5,750 rpm? That would represent a volumetric efficiency of ~84%. It is possible to do way better than that on VE.... Cup motors routinely operate in excess of 100% VE. A well-designed street motor should be able to get into the 90+ range. Why would you even be concerned with 5,750rpm, when its easy to run 6,000-6,500rpm on a 383 and make good torque on the bottom end, and good power on the top end?

It's sort of hard to get used to looking at a head or intake that only flows ~200cfm, when a good set of LT1 heads will easilly flow 270cfm and the LT4's with a correctly ported intake will run 300cfm.

One point that becomes very confusing is the constant reference to a particular part being "able to flow so many CFM"..... that doesn't really mean anything, unless you state a corresponding pressure drop - e.g. 28" H2O on a head flow bench.

I guess I'm missing the point or something

[Mark B]

How does this sound...

There is a company that makes a high flow TPI base that will work with Vortech heads. I was thinking of doing this...

Somewhere around 9-to-1 compression
1.94/1.50 Ported Vortech Heads(Can handle up to .6 lift cam)
Cam ?Help?
High Flow Vortech TPI Base
Accell Superram runners
Accell Superram Plenum
30lb injectors
52-58mm Throttle Body

Would that be a good setup for a 383? Should I ditch the iron Vortech heads for something else?

[DeWynter]

A couple of questions....

Why would you multiply individual cylinder head bench flow by 8 to get some sort of peak demand? Doesn't work that way. All 8 cylinders are not on the intake stroke simultaneously, and even the ones that are are not at the same point in the intake stroke.

Why is a 383 limited to 536cfm @ 5,750 rpm? That would represent a volumetric efficiency of ~84%. It is possible to do way better than that on VE.... Cup motors routinely operate in excess of 100% VE. A well-designed street motor should be able to get into the 90+ range. Why would you even be concerned with 5,750rpm, when its easy to run 6,000-6,500rpm on a 383 and make good torque on the bottom end, and good power on the top end?

It's sort of hard to get used to looking at a head or intake that only flows ~200cfm, when a good set of LT1 heads will easilly flow 270cfm and the LT4's with a correctly ported intake will run 300cfm.

One point that becomes very confusing is the constant reference to a particular part being "able to flow so many CFM"..... that doesn't really mean anything, unless you state a corresponding pressure drop - e.g. 28" H2O on a head flow bench.

I guess I'm missing the point or something

Im sorry to have been misleading with my peak intake I ment it as a number that would be there if every cylinder was pulling at the same time which of course is not possible. The flow number were taken from a site that has compiled number from many different manufactures and I belive the stock numbers were taken from a university. The site I have writen down is not where i got the original Info but does have the same info. http://www.stealthram.com/flowcomparison.html
I believe almost all the flow numbers were done at 28" H2O, but dont quote me. The number for CFM intake at 5750 RPM was derived from Engine analyzer Pro 3.3 with a standard 382.97 cu engine running a stock TPI intake system with a 52mm throttle body, and yes at 5750 volumetric eff is 84% which is the lowest eff at any RPM above 3000 with stock L98 heads. With the TPI Intake it will not matter how well the heads flow as the intake will always be you bottle neck. As you can see from my post I also said with TPI a 383 isnt a drag motor, never said a carbed, Lt1 or LS1 383 cant run up into the 6500+ range. I belive I made it clear that I was talking about TPI which will not run at 6500 RPM due to the flow restictions of the intake. I stated it was a good street motor.

[DeWynter]

How does this sound...

There is a company that makes a high flow TPI base that will work with Vortech heads. I was thinking of doing this...

Somewhere around 9-to-1 compression
1.94/1.50 Ported Vortech Heads(Can handle up to .6 lift cam)
Cam ?Help?
High Flow Vortech TPI Base
Accell Superram runners
Accell Superram Plenum
30lb injectors
52-58mm Throttle Body

Would that be a good setup for a 383? Should I ditch the iron Vortech heads for something else?

There is alot of info in thirdgen.org about the pros and cons of the vortech heads on the modified TPI base, If you want to go High RPM go to an aftermarket intake like a mini ram, or steath ram. BBK is going to be introducing a new intake for the TPI engines soon to and it says on their site it will be $499, which seems cheap to me.