ericjon262

I really love sleeper cars, nothing is more badass to me then a car that hides in plain site. but I also love more "modern" powerplants, like the LTx motors, in fact I have one in my garage, that I planned to put in to my car, and I started thinking, TBI's are typically looked at as dirt slow, LTx's are typically looked at as relatively powerful so I thought up a bad Idea, why not run the lt1 with a TBI, mind you a worked over 454 unit. with a different intake the LT1 looks ALOT like a GEN 1 motor, esp when you paint the heads and intake black to look like an L03. it would probably be a royal pain in the *** to tune, but I could work around that, and at a glance (who really checks out what appears to be a TBI 305) it would look like another POS 305!

Pro sides to doing it:

Sleeper look
Less wiring to deal with
more power

con sides:
fuel economy would probably take a slight hit.
Less room to grow without going to Dual TBI/4bbl TBI.
TBI computers aren't to bright.

pound

iTrader: (7)

Why would anyone talk you out of this? It sounds like a very interesting idea. Post pics if / when you do it.

ericjon262

I'm mainly just wanting to hear the con side of doing this, I thought of another "pro" side to it, less wiring harness modification.

NufNuffZ28

iTrader: (10)

The computer system on a TBI is mouch older and slower. I bet you would also lose performance over a straight LT1 swap as well. Even the 454 TBI unit won't support as much HP as a stock LT1 intake will.

If you want to keep it SBC looking, sell the LT1 intake, put a miniram, HSR, etc on it and run a distributor. Plenty of people do that.

ericjon262

I'm not really looking to make 500 hp either though, I was planning on throwing a hotcam in the LT1, and maybe slight head porting (polishing the exhaust and blending the seats on the intake) and that should be easy enough for a 454 unit. I also wouldn't run the TBI ECM, I would either run an '747 w/EBL or a TBI PCM as outlined in the stickie by fast355.


I'm not really looking to make 500 hp either though, I was planning on throwing a hotcam in the LT1, and maybe slight head porting (polishing the exhaust and blending the seats on the intake) and that should be easy enough for a 454 unit. I also wouldn't run the TBI ECM, I would either run an '747 w/EBL or a TBI PCM as outlined in the stickie by fast355.

UnderCover89TBI

iTrader: (25)

so mainly doing this for aluminum heads? would u still be runing the optispark? the water pump on lt1's are cam driven. that'd be a giveaway. doesnt really sound like that cool of an idea to me. just my opinion though.

ericjon262

well, and because I've got an LT1 sitting in my garage. and even if I go multi port on it, the heads will be painted , no one will know they're aluminum unless I tell them.

No, I would be running a GEN1 FI distributor.

I've got a way to make it less of a giveaway.

and you're entitled to it, I'm mainly trying to find any significant downside to doing it this was as opposed to multiport.

thomas1976

Nothing fenomenal about LT1 engines, they have from 270 to 310 hp stock, just like any mild 350 sb build.

A mild 350 should get in the 350hp range @ around 5000rpm, wich could probably be done with 2" bored and slightly ported TBI intake manifold with a 46mm TB.
Similar to my 360 tbi, not dynoed yet, but it blew the stock transmission in only 3 days (1.5 days to tune it and 1.5 days of fun), the 2000 stall is too high because the tires spin like crazy.

In theory, the 90lb TBI injectors @20-30psi fuel pressure should support 420 to 520 hp.
@20 psi should be no problem with a VRFPR, @24-30psi there may be some wasted fuel at idle and light trottle.

The 100-140lb TBI injectors that are being tested may change TBI performance a bit if they work well.

Not sure, the "ported" 54mm TBI TB, could be in the 700+ cfm range.

400-500hp 350 will probably require a forged crank for safe 6000rpm operation and 50-54mm TBI TB.

Pocket

iTrader: (24)

I think it's silly to drop that much effort and money into a carb look. LT1 is a great platform to build up and very few people have gone above it's limits

That being said, heres some solutions

GMPP LT1 carb intake or singleplane EFI conversion

This uses a conventional injector setup and would require the EFI manifold
http://www.summitracing.com/parts/EDL-3878/

Sneaky setups like these use the carb manifold still and utilize the newer injectors
http://www.summitracing.com/parts/FST-30226-KIT/

Some even mock carbs
http://www.summitracing.com/parts/PFS-70027/

If you must go TBI, heres the TB for you
http://www.summitracing.com/parts/ACC-74202S2/

The hard part of TBI is not the TB, or the injectors as a TGO sponsor has modified injectors to rediculous sizes. Its in the control system. The most advanced TBI setup is on the LO5 trucks and its only marginally better than what came in 3rd gens. Yes there is aftermarket but its very expensive compared to your stock LT1 system

ericjon262

The main money drop would be an intake, which is only about $300 new, I'm sure I could get a used one for $150 somewhere. I hadn't really considered any of the central point injection systems, but they are an option I hadn't thought of.

you brought up one of the few parts of the system I hadn't thought of, the engine management. how would the EBL compare to an LT1 PCM?

Pocket

iTrader: (24)

Pretty lame. Chips vs live feed is pretty hard to overcome

thomas1976

Interesting. You mind explaining the difference between the EBL and the LT1 PCM a little more detailed?

RBob

iTrader: (1)

The early LT1 PCMs used a chip, same as ECMs such as the '7730. The later LT1 PCMs used flash. The downside to the flash based LT1 PCMs is that it is very easy to turn them into door stops. The flashing takes a few minutes and if it is disrupted, such as powering the PCM from the vehicle battery during the flashing, instant door stop.

The EBL is flash based, difficult to turn into a door stop, and takes about 3 seconds to update.

RBob.

thomas1976

What do this therms mean?

RBob

iTrader: (1)

door stops

A door stop is what is placed at the bottom of an open door to prevent it from closing. Say you open the people door to the garage and you are carrying stuff in and/or out. To prevent the wind from blowing the door shut you place an object at the bottom of the open door.

Hence, a 'door stop.'

What happens with the flash based LT1 PCMs when the flashing fails, is that it will not run the engine. To recover the PCM the flash chip needs to be un-soldered from the PCB. Placed into a programmer and flashed. Then soldered back into the PCM.

Note that this is not an easy task to accomplish without damaging the PCB.

RBob.

UnderCover89TBI

iTrader: (25)

damn bob you actually explained what a door stop was not just what you used it for in your description! that's classic!

ericjon262

you're the expert in the field as far as I'm concerned other then the lengthy flashing process, does the Late LT1 PCM have any substantial "1-ups" on your EBL?

RBob

iTrader: (1)

The LT1 PCM is SFI and late model ones will run a 4L60E transmission. Then either a blessing or a curse (your choice), the later ones are ODB-II. I haven't looked into the LT1 PCMs much, mostly because of the flashing issues. But there are several models over the years.

So which one to use will need to be researched.

RBob.

xch3no2

covered,
I was freekin rolling on the floor..

Rob is our genial ambassador also