First real test drive today, after V8 swap.

Frustrating I feel for ya! I would even consider looking for a low $ stock TBI 350 to swap in while you rebuild the one in the truck.

L31MaxExpress said:

Did you put a set of 350 injectors and a 350 chip in the ECM?

Click to expand...

Ah, so about that.... now I'm second guessing myself about the injectors. 99% sure they are from a 350. I know for SURE they came from a V8. I always assume that the V8's are a 350 and not a 305.

SO, the ECM. Bought it from a guy on Marketplace. It's from a 1990 RCSB, 350, 5-speed. Service # 1227747. I can show the message history if necessary.

So, I guess the next thing to do... is make sure the TPS wiring is correct and bump the timing a tad.

Someone mentioned tuning the ECM. How the Hell would a person even know where to begin with that? Like oh, here's some random aluminum heads. Let's write a PROM to match without knowing anything about them.

Sean Buick 76 said:

I would even consider looking for a low $ stock TBI 350 to swap in while you rebuild the one in the truck.

Click to expand...

I'm sorry, but that statement is too funny. I'm sitting here giggling as I type this. Yeah, let's drop in some one else's problems while I tear apart a fresh rebuild, and rebuild it again. LOL!

DeCaff2007 said:

Ah, so about that.... now I'm second guessing myself about the injectors. 99% sure they are from a 350. I know for SURE they came from a V8. I always assume that the V8's are a 350 and not a 305.

Click to expand...

Hello DeCaff,

Now that you have an engine with a good ring seal, more than enough compression in
all 8 cylinders to support smooth operation, and the valves are adjusted evenly, with
the correct preload, we have a solid base to build upon.

And we'll push this over the finish line step by boring step.

For example, the rest of the fuel system is back to new condition. However, you
are only 99% sure that you have the correct injectors. In order to move the
injectors up to 100% sure you have the correct ones, here's a list of TBI injector
part numbers, arranged from lowest to highest flow:

EDIT: Based on feedback in reply #136, verified data match with reply #137, and
corrected any discrepancies. (Part numbers, flow data, omissions, etc)



If after comparing the numbers on your injectors to this list, if you find that you
have the 5.0 jobs, then you will need to get the 5.7 units. Of course, if you already
have the correct 5.7 injectors, then we'll move them into the 'verified good' column
and continue down the list of items needed to make this a successful 4.3 > 5.7 engine swap.

No magic, just gotta run down a lot of details.

For what it's worth --

Road Trip said:

Hello DeCaff,

Now that you have an engine with a good ring seal, more than enough compression in
all 8 cylinders to support smooth operation, and the valves are adjusted evenly, with
the correct preload, we have a solid base to build upon.

And we'll push this over the finish line step by boring step.

For example, the rest of the fuel system is back to new condition. However, you
are only 99% sure that you have the correct injectors. In order to move the
injectors up to 100% sure you have the correct ones, here's a list of TBI injector
part numbers, arranged from lowest to highest flow:

You must be registered for see images attach

If after comparing the numbers on your injectors to this list, if you find that you
have the 5.0 jobs, then you will need to get the 5.7 units. Of course, if you already
have the correct 5.7 injectors, then we'll move them into the 'verified good' column
and continue down the list of items needed to make this a successful 4.3 > 5.7 engine swap.

No magic, just gotta run down a lot of details.

For what it's worth --

Click to expand...

Alright, thanks for that. Any ideas where the part numbers are located on the injectors? Hey, I noticed that there's a color missing from the 5.7l row.

Road Trip said:

Hello DeCaff,

Now that you have an engine with a good ring seal, more than enough compression in
all 8 cylinders to support smooth operation, and the valves are adjusted evenly, with
the correct preload, we have a solid base to build upon.

And we'll push this over the finish line step by boring step.

For example, the rest of the fuel system is back to new condition. However, you
are only 99% sure that you have the correct injectors. In order to move the
injectors up to 100% sure you have the correct ones, here's a list of TBI injector
part numbers, arranged from lowest to highest flow:

You must be registered for see images attach

If after comparing the numbers on your injectors to this list, if you find that you
have the 5.0 jobs, then you will need to get the 5.7 units. Of course, if you already
have the correct 5.7 injectors, then we'll move them into the 'verified good' column
and continue down the list of items needed to make this a successful 4.3 > 5.7 engine swap.

No magic, just gotta run down a lot of details.

For what it's worth --

Click to expand...

That list is way wrong.

Here is the actual list several of us compiled on gearhead-efi.com with the correct sizes. The only one I will debate is the 305 injector size. The fueling falls in line closer using 55 lb/hr as the flow constant. Using 50# will make the 305 pig rich. A 350 truck is 61 lb/hr and there is no such thing as a 90 lb/hr. The 74 lb/hr big block unit is a high pressure version of the 46# 4.3L injector, running at 30 psi.

The big problem I see is even with a stock cam, good aluminum heads can make a TBI 350 make 300-315 hp at the crank. Depending on whether you use 12 psi (what I have always considered stock pressure the injectors were flow rated at or the 13 psi others claim, the 61s are down to 54-56 lb/hr @ 10 psi. Ignore CC, the math is the same regardless and I used PPH rating for simplicity.

54 x 2 / 0.45 x 0.85 = 204 hp
56 x 2 / 0.45 x 0.85 = 211 hp





To get enough flow to feed a ~300-315 hp engine requires about 20-22 psi. 20 psi is ~ 79 lb/hr and 22 psi is 83 lb/hr. Could also swap to an 80 lb/hr 454 injector but atomization is better with smaller injectors at higher pressure and the idle will be noticeably less rich.

79 x 2 / 0.45 x 0.85 = 298 hp
83 x 2 / 0.45 x 0.85 = 313.5 hp

DeCaff2007 said:

Alright, thanks for that. Any ideas where the part numbers are located on the injectors? Hey, I noticed that there's a color missing from the 5.7l row.

Click to expand...

on the top where the connector plugs in

L31MaxExpress said:

That list is way wrong.

Click to expand...

Thanks for the heads up. I went back and verified all that did match, fixed any discrepancies,
and documented the edits on the right hand side of the list. It's one thing to share 17 year
old data from enthusiasts you don't know, completely another to share more accurate data
from someone who is here *today* with a proven track record in this forum for tuning/pushing
the performance limits of what's possible in a GMT400 engine bay.

The way I see it, precious few people are still interested in TBI part numbers, flow data, and
color codes, so for the good of the GMT400 TBI community we should do whatever we can
to minimize any possible confusion.

DeCaff2007 said:

Alright, thanks for that. Any ideas where the part numbers are located on the injectors? Hey, I noticed that there's a color missing from the 5.7l row.

Click to expand...

With any luck, as described by @tayto in reply #139. Looking around, folks have commented
that the color codes may or may not still be on the injectors, so you may end up having to take
a magnifying glass to them in order to see any remnants: (TBI injector identification)

Let us know what you discover.