I have come here in search of help. I have been doing LOTS of searching and reading on this and other forums. But I think I have a unique situation that I am hoping the TBI experienced here can help me with.

The Project:
1987 Chevy V10 Pickup (350 TBI, 700-R4, 4x4)
The Swap:
Cadillac 507ci + 4L80E
The Dilema:
What fuel system to run so I can use a factory GM harness/PCM out of a 93 Suburban that came with a 4L80E?

For obvious reasons, the 2 bbl TBI currently on my SBC just isn't going to be ideal for a motor half again as big. So two options have presented themselves, involving a similar rough estimation of cost.

Option #1:
Run a Holley 900cfm 4 bbl TBI unit with Dynamicefi modification to PCM.
Holley Marine 900cfm 4bbl replacement TBI - $753
Dynamicefi PCM mod to run 4 injectors - $75
Total= $828

Option #2:
Build an Accel Throttle body using 4x port injectors that does not require a hardware modification to PCM.
Accel 750cfm TBI w/ no elec. or injectors - $380
4x 60lb/hr Edel injectors - $244
Edel high press. fuel pump for dual tanks - $203
Total= $827

Now, building the Accel TBI has some minor costs like wiring adapters and new fuel lines. Do I need a fuel pressure regulator? If so that will increase Option #2 by 50-100 dollars. Also, I have access to a PROM burner and tuning software for the '93 PCM (do not know the model yet).

Personally I like the Accel idea because that throttle body introduces fuel below the blades, and uses new style injectors. However one thing I cannot seem to find is if the blades on the accel are progressively linked. If they are not, it wont work in my application. I need low end torque and throttle response. The Cad will very very rarely see over 4000 rpms. I did my fuel estimation based on a max of 400hp and used the forumula on Dynamicefi. My flow rate came out to 58lb/hr per injector(4). Also the accel would look better

What do the TBI experts think?


Parts:
Accel 74135B http://www.summitracing.com/parts/ACC-74135B
Edelbrock Injector http://www.jegs.com/i/Edelbrock/350/3687/10002/-1
Holley TBI http://www.jegs.com/i/Holley/510/500-19/10002/-1

 

Just to clarify. Are you trying to get it done as cheaply as possible?

 

Another option that I have seen a couple of times is to use 2 350 Throttle bodies with 61# standard injectors, Use a dual 4 barrel carb intake with adapters, that should handle all that you are throwing at it and look really cool.

 

Yes I am trying to keep cost down.

Also this is a mild Cadillac motor. And due to being a Cadillac, intakes are very limited. I will be using the Edelbrock 2115 dual-plane intake. There are no 2x4 intakes available without custom fab or lots of cash.

 

I like the title of this thread.
I think there was someone who took a 2bbl. tbi & machined out the the center to make it a mono blade.
A guy on here named Street Lethal did it.

 

Ah I see. Caus I was goign to say this is going to be a pain to tune. You can buy a separate controller for the transmission. And buy one of holley's or fast Easy EFI self tuning setups to run the engine. But you going to be in it for 3k if you do that.

 

I'd get a big block chevy tbi unit, they flow about 670cfm. Port the ridges, get a pod spacer, & a power charger (salad bowl) w/ an open element air cleaner. I'd get it running w/ that & do a vacuum test at wot under load. If the gauge shows vacuum at wot then you'd benefit from a larger throttle body. If it goes to zero at wot then you might not benefit.

 

I'd agree with using a Big Block TBI unit as it will probably be enough fuel and flow to begin with. If not you can always increase fuel presure and/or get some aftermarket injectors for it.

This would be very easy and the cheapest route to go while still useing a factory ECM capable of controling the 4L80e.

There are also write ups here how to repin a 1227747 and others to a 1619747 so now you can use the harness in the truck as well.

 

And a powercharger looks like this.



my friend just put this on a tbi truck. along with kn filter, and flow thru lid. and he felt a ton of performance difference. said it even changed the exhaust tone.

 

There's another way that increases flow if need be, it's a spacer from CFM. Most spacers just add an inch under the TBI unit. They are supposed to increase volumetric efficiency but most tests I've read don't show much if any improvement. But the one from CFM has a tapered cut out so flow to engine can come from both throttle blades and the tests were positive results.

 

Ok, a Cadillac guy has a 670cfm on his car and he has detonation issues when cruising. I don't want that.

Not to mention the 670cfm was designed for a low output 454 and max hp is about 300hp. Yes you can juice it up a little but not a lot. And we are talking about 53 more cubic inches as well.

Like I said, I have already done LOTS of reading on cadillacs and TBI's. If I want a system that has potential for more than 300hp, and I know won't starve the engine, then it's going to have to be one of my two options to keep the investment ~$1000.

 

Detonation is not caused by 670 CFM. 670 CFM is what they came with on the carb version. Detonation is to much spark advance and or low octane fuel.

What is the compresion ratio of the engine?

Do you have HP and tourqe specs? You'll find them to be very low RPM.

I think your underestimating the BB TBI and overestimating the Cadillac engines needs. It's a low RPM torque monster.

The BB TBI may need, I did say may need a little more fuel pressure and you can turn up the pressure or buy bigger injectors from a vendor on this forum. You can also use a vacuum type adjustable fuel pressure regulator for more pressure at high rpm/low vacuum situations.

 

I will try to take some pics tomorrow of the dual tbi adapter that I am putting on my 425hp 383. I could make another one for you for the cost of machining and material, probably around $50, I will have to talk to my machinist for the cost of the CNC work. Then you just have Rbob do the 4-injector upgrade to a '7427 PCM and you should be into it for under $500. And it will also control your 4L80E. That is what I am doing. I was going to do a write up on it when done.

 

I'd like to see that as well. Where you at in Idaho?

 

I would personally do a 16197427 PCM with a BBC TBI , surpassing the 300hp level is a no brainer with a BBC TBI , it will work fine and be dead nuts reliable for what you are going to do with it.

Personally I would ditch the dual plane and see if you could scrounge up a single plane manifold , don't know what is avalible for the Cadilliac though.

Just my .02

TOM

 

Hmm, well, maybe I'd give it ago with the 2bbl tbi first and see how that goes before moving up to 4bbl. My engine will be 8-8.5:1 compression. I know the Caddy is a slow turning torque monster. But I am getting conflicting views on wether or not a 2bbl is sufficient. But one guy IS using one, so it's worth a shot. and would be a good intro to tuning an ecm.

 

I think that 4bbl TB has progressive linkage, I've considered it myself.

Don't buy anything from cfmtech you don't have to, nothing is more offensive than useless hype & outright ignorant BS posted on any website, they are FULL OF IT.

A modded, high-pressure GM 50mm TBI will support very close to and possibly more than 500hp.

Lotta bad advice out there, listen to ppl that actually build successfully.

 

Actually I would probably agree with putting s BBC TBI on your Caddy. I only went this route because it was relatively inexpensive and not something you see everywhere. And because my 383 is somewhat close to the limits of two factory injectors even at elevated fuel pressure(from what I have read). With this setup I should be running stock fuel pressure and pretty close to stock pulsewidth on the injectors. I am still a ways from putting it on the engine but I have most of the details sorted out. I had my machinist CNC the progressive radius around the inside of the TB and Plenum holes for a more straight shot from the TBI to the manifold. I also made my own AN adapters by turning the original adapters down on a lathe and tig welding a drilled AN plug to the other end. I have lots of time to do this stuff but as with most people little money so I try to make as much of this stuff as I can.

 

EagleMark, I am up by Spirit Lake

 

Well gregs78cam, that is some fancy work. So that fits over a standard spread/square bore? intake manifold? I definitely want to know how this turns out on your motor.

My motor wont be 400hp, but I'm hoping for over 300. Upon advice of more experienced caddy owner/operators, I am going to break in the motor with a carb. More time to figure out a good TBI plan. I am going to try to get a more accurate potential HP estimate for my engine setup, and then that will help with planning the eventual injection setup.

 

Yup should fit on any spread/sqaurebore manifold. That sounds like a good plan. Airflow is not a problem with a BB TBI, the issue becomes fuel flow. There were injector pods made with larger cavities for fuel to flow through, so one of those with, say 81# injectors should work for your Caddy. Good luck.

 

Does anyone happen to know the #/hr rating of the Holley 670cfm injectors?

 

I think they come with different injectors...I know thier is an official Holley 670 tbi thread on here somehwere a should find it.

 

That is very cool! I don't care what anyone will say about it, that is a very cool piece. I hope it works as good as planned, if not it still has the wow factor!

That's not far from me here in Coeur d'Alene. If you'd like to touch base sometime feel free to contact me. I would like to see that in person.

I also have a freind who's a retired machinist, he still has all his equiptment but the old CNC died. He enjoys working on unique projects so if you need a machinist help with that I will introduce you to him. He is in Post Falls.

 

[QUOTEDoes anyone happen to know the #/hr rating of the Holley 670cfm injectors? ][/QUOTE]

My understanding is that Holley rates their injectors at a higher FP than GM. I think it is 20. so you cannot compare Holley to GM by #s.

I too would go with GM 7.4L TB. I am not sure if you can bore it later on but I suspect so. I am sure Holley offers larger butterflies in Dominator sizes(>2.00).

 

Thanks. I will definitely let everyone know how it turns out.

 

Ok, so consulting more Cadillac resources I have a reasonable expectation of a max HP of about 330 with the mild build I am doing. Mild cam, intake, exhaust, tad stiffer springs.

So I think, the 2bbl can work with tweaking it as described here and on Dynamicefi. And hopefully with a fabbed electronic controlled distributor to work with the ECM, it would all work smoothly.

 

I am fairly certain the 81 368 DFI cars used an HEI EST distributor controlled by the ECM.

 

There you have the distributor as well. So with the BB TBI it should be a low dollar EFI conversion.

If by chance that distrubote does not work and there is not a EFI type distributor available, the large cap HEI distributor is a very easy conversion to EFI.

 

Yes, it looks like I should be able to do this build. Once I get the motor broken in and aquire all the pieces I will update this thread. Thanks you all for your input.