Hello,

I have a 1974 corvette that I would like to convert to fuel injection. I was originally going to go with a FAST Ez efi setup, but upon my recent trip to the junkyard, found that for about 100 dollars I can get all of the primary components of the Gm TBI system. I would like to convert to efi for the many reasons it is better (power, fuel economy, ease of starting...)

Here are my questions about it:

1. Would it be able to handle my engines horsepower? It is a '74 L-82 with edelbrock performer intake, holley carb, hedman headers, and it has been cammed. What horsepower can the system handle? I'm making about 300 hp (I also dont want to lose horsepower!)

2. Would it work with the stock hood and my jegs drop base 14 x 3 aircleaner?

3. Could I retain my stock tach drive mechanical tach and use my same points distributor by making mods to the system or a tach drive tbi distributor?

4. Does anyone have a complete list of steps and parts that are needed to setup the system? What ecu and tbi unit should I use?

5. If the other questions are N/A, should I just save up and get the fast system? Should I convert to a tpi system instead?

Let me know!


Edit: I think I'm going to covnert to TPI instead, from what others have suggested and from what I have researched, let me know what you think about this!

Thanks,
Will

 

I am actually thinking of this myself and had bookmarked the following page. Not sure if it answers any of your questions but I found it interesting. http://www.automedia.com/TBI_Fuel_In...ht20001001fi/1

You are going to have to get an HEI unit. You can find them with tach drive. This may effect your air cleaner too

 

Thanks for the information, I too have checked out that article, quite informative. I have seen the tach drive hei distributors, but dont they have to be a "computer controlled" distributor, with the 2 plug connectors and no mechanical or vacuum advance?

Thanks,
Will

 

Anyone have any ideas? The two things i'm most worried about are the tach/distributor and the air cleaner.

Will

 

Probably the easiest thing to do is change your mechanical tach for a 75 up electronic one. This will allow you to use the correct 7 pin GM dizzy. This was mentioned in a recent thread - do a search.

As to aircleaner, even with a manifold adaptor, the throttle body will not be appreciably taller than your current carb - certainly something that could be handled with an aftermarket unit.

 

Ok, I was thinking that, what is involved in that process? Also, would tbi be restricting to my engine? It proably makes 300 hp. Should I go tpi instead, as if I'm going to change the tach, I might as well go with the "best" system. I was only thinking tbi as I know it very well from working on a 91 firebird and 91 sonoma, and it works amazingly (We went to the nj beach from pennington,filling up the tank only once before with some other driving that day, and the gas gauge didnt even move from full! The 5.0 tbi firebird gets more mpg then my moms toyota highlander v6!) . I think if I am going to change the tach, Im just going to do tpi instead but let me know. For tpi, ive read you can use a 3.1 cavalier harness and then just get the ecu and intake setup is that correct?

Thanks,
Will

 

Will,

1) TBI - A stock TBI unit does not have great flow numbers. This can be corrected by getting a larger TBI. but you're starting to get into money. Even the Holley 2 barrel unit (quite a size upgrade from the stock 350 TBI) is claimed to flow only 600 cfm and not recommended for 300HP.
2) TPI - Anything is possible, but I would not try to start with a 3.1 V6 harness. There are a lot of old Camaro TPI harnesses out there if you look, and these will make a far better starting point. Look at the Jags That Run website. The owner/author has a complete manual giving instructions on installing a Tuned Port into a non-TPI car inexpensively. Also talk with forum member MRVETTE, who has substantial experience with TPI wire harnesses.

 

Use the 454 TB. It is larger than the 350 unit. I believe it is rated at 670 CFM, has larger injectors and a spacer under the injector tower (that can be installed on the 350 unit). The GM 502 retro fit kit for the 454 equipped truck used a stock 454 TB for 330 horsepower. Some are getting in the vicinity of 450 horsepower with a vacuum referenced fuel pressure regulator and some custom tuning to compensate for other modifications. There was an individual on the 454SS Forum that bored the 454 units to flow an estimated 900 CFM, but he has quit doing them due to the expense vs what people were willing to pay.

 

I thought that was true about the flow of a stock tbi, i have researched many FI systems, the holley one included and yes they say it cant support over 275 hp (I think that was it), that being said, I think I'm going to go tpi or FAST instead. I think I could get the TPI stuff for cheap, and I'll find a electronic tach from a 74 or later to put in. One thing I was wondering is how to set up the throttle cable on it, how it that done, can I use the stock cable?

Thanks,
Will

 

Also for a EFI swap, would my alternator need to be changed, I currently have a new 63 amp alternator in it, and it handles everything on (all lights, highbeams, radio, and both blowers) with no discharge (On the ammeter) at 500 rpm idle no problem.

Will

 

how do you tune the car?, or generaly get to run correctly? can you plug a laptop into the ecu?? and change stuff?

 

OBD I requires that you burn new chips for changes or install an emulator so you can use a laptop to tune.

 

You can run the TPI with FAST using this kit:

http://www.compperformancegroupstore...Category_Code=

You can still use the mechanical tach, as this system doesn't control timing.
I am running this system, and am very happy with it so far....

 

Now there is an idea! I forgot about that, but i have seen it before. So if I were to get all of the tpi stuff and just not use the gm ecu or wiring, i would use FAST's and then i could keep my distributor and it would be tunable from their computer handheld thing? That sounds great. Since you say you're running it, could you give me any tips or info on the system, as you say you're happy with it. Does not having timing control affect the performance or system in any way?

Thanks,
Will

 

I've been adjusting the timing the same way I did while running a carb, for the type of driving I do (cruising) this is good enough. No loss of performance that I've noticed. If I was racing I think I would go with a different system where you'd have more control

Tale a look at the instructions here:

http://www.fuelairspark.com/Instruct...-%20EZ-EFI.pdf

Yeah, I know they're for the TBI unit, but it uses the same computer and hand-held programmer, and it's wired up the same way.

Check out the F.A.S.T. home page and see what else they offer. They even have they're own forum, with some member's names you might recognize

 

Will, here's a pic of the F.A.S.T. harness on my LT1 conversion, using the MSD tach drive distributor. I had to swap out a couple of connectors, shorten a few of the wires, but otherwise it plugs in the same as on a TPI.
I originally was going to run TPI, but since I have raised port heads(Brodix IK200's), the manifold base would not cover the port on the head, and it seems no one makes a manifold that does(ended up selling the TPI unit)

[IMG][/IMG]

 

Thank you very much for all of the great information! Your setup looks great. That is probably going to be the route I go, I'll either stick with my original points distributor or go with another tach drive unit. I have done much research on the FAST EZ EFI tbi unit and its installation, because that was what I was going to do originally. My car is going to be my daily driver, no super performance stuff, although I'm going to rebuild the engine eventually, for now, I'm looking for the better fuel economy, power, and ease of starting of an EFI system. My understanding with the FAST TPI harness is that I would need to run speed density (MAP), not MAF correct? And for the early TPI units, I would need to block off the cold start injector, and for all, the EGR?

I'll probably do this project during next summer, as I have other work on the vette to do during winter, and plus, working on the cold is not fun!

Thanks,
Will

 

The F.A.S.T. harness for the TPI/LT1 is set up for MAP, so when TPI shopping try to find one that originally used the MAP sensor(88-92 if I recall, could be wrong though)
Let me know when you plan to do this swap and I'll PM you my phone# if you have any questions & I'll try to help

 

Alright, thanks again! I'll probably do it in the summer, but gather parts over time until then. I'll let you know when I'm going to do it. Since I need a MAP TPI, one other consideration is the intake bolt holes, as didnt they change to be more vertical, and since I have older style heads, I would need to drill it out, correct? Do you know what the optimal year TPI would be for me?

Thanks,
Will

 

Will, the TPI unit for an 88-91 Corvette uses the MAP sensor and has the standard intake pattern, so that's the one you'll want to look for. The unit I was going to use was from a 90 Vette and it bolted up fine, with the exception of the little problem I mentioned before