So I live at about 7000' but most any traveling I do involves dropping down to 3000 to 0 ft. I don't want to have to re-tune whenever I go out out town. Has anyone done this how did it work out?

 

A lot of folks have done it. While I can’t speak to their experiences with XYZ system I’ve done about 1/2 a dozen LS swaps over the years in various vehicles (all factory PCMs) so I feel somewhat qualified to hand out the info I am about to, but obviously can’t comment on specific systems. There are things to consider universally.

1. Fuel lines: Are your current lines up to the task? Most likely not given that most EFI systems operate in that 50 psi range and nothing ever in a C3 had those types of pressures.
2. Pump and tank situation: What are you gonna do about the fuel pump? Replace the existing tank with an in tank setup or run an external pump? Pros and cons to either.
3. Multi port vs TBI setup. Depending on your goals and appearance preferences there are systems that bolt onto a single plane carb’d intake or units that require true multi port intake setups. The TBI setups actually make decent power and have all the adjustability you desire but they are a compromise and you have to use the absolutely correct intake manifold. The carb plus signaling characteristics of dual planes can actually mess with a TBI style fuel injection.
4. Ignition timing: What are you gonna do about your ignition? Leave as is or convert it at the same time? A huge benefit to adding fuel injection is the infinite adjustability your timing curves will have via the ECU timing curves. IMO if you don’t convert your ignition your leaving 1/2 the gains on the table.

The big player right now in that game is Holley and I would take a good hard look at their lineup. There are also other players in the game as well. Edelbrock makes a decent multi port setup called Pro-flow. There is also FItech.

I’m sure others will chime in with additional info.

 

A bit over a year ago I put the Summit Max system on my 77. basically a budget system. helped out a friend here in Australia install the same system. were both extremely happy with the results. your 75 is much like my 77. I ran a thread awhile back, "77 EFI Conversion". you may wish to check it out. used the factory tank. added a homemade baffle and fuel pump setup. new line to the front. Filter/Regulator in the right rear quarter panel. Car runs fantastic. Lots of ways to do this nowadays. if you Google search Corvette EFI Conversion, pretty sure you should find my old thread.

 

I have a Edelbrock Pro Flo 4 on my 71 LS5. I am totally happy with the system. It comes with a port injected manifold, a distributor, and the ECU and sensors required for install. Additional things you will need for install is a fuel system capable of providing 43 or 58 psi depending on the map you run. That is determined by the cubic inch displacement and vacuum your engine normally runs at idle or camshaft. The other thing that will be required is the install of one O2 sensor bung on your exhaust for O2 sensor install. The system is relatively easy to install if you have changed an intake manifold and have basic wiring ability. It does require a power and ground wire connected to the battery which turned out to be the most challenging part of the install. I just followed the positive battery lead to the starter route through the tunnel. The system gives you fully adjustable mechanical and vacuum advance. It has E-tuner 4 software available for download on your Android device or the optional tablet. I would not buy a unit with the optional tablet. There are plenty of android tablet available for less than $100. In my case, I always have my phone, which means I always have monitoring and modification ability or you can use a tablet. Below is a picture of the digital display. You can play around with the software available in Play Store by running it in the demo mode and see what setup is like for the system. Whatever system you decide on, it should solve the problem you are trying to fix. Good luck.

PF4 digital display

 

I was actually considering this set up. Anyone have experience with this?

 

Oops, lol.
FAST 30227-06KIT EZ Fuel Self-Tuning Throttle Body Injection Kit...

 

I've been running a FAST EZ-EFI 2.0 to control my RamJet 350. I like it just fine. Not the throttle body that you're looking at, but I already had the RamJet 350 and the GM TPI-to-FAST conversion kit seemed the way to go.

 

Remember, a lot of aftermarket EFI is SD (Speed Density) and does not use a MAF (Mass Air Flow) meter like the stock LS motors. That means the EFI calculates mass of air based on MAP (Manifold Air Pressure).

For example, my FAST XFI system uses the MAP it reads before engine start as baseline and then uses dynamic MAP readings to calculate air flow. It has the capability to add a second MAP sensor to continually measure ambient pressure but I don't have that capability installed. So, my system only uses one baseline MAP setting and does not adjust real-time for changes in elevation. Not an issue since I live in FL.

If you are truly driving from 7000 feet to 0 feet in one drive, I would look into either a system that uses a MAF sensor or one that supports two MAP sensors for realtime barometric corrections.

This is from the FAST XFI 2.05 update documentation:
[*] With dedicated remote Baro sensor, supports live corrections of engine load and table indexing in load indexed speed density mode for changing barometric pressure (altitude changes).

 

Ran a sniper system all summer and like everything there is a learning curve but I was very happy 99% of the time. Might go to a Fitech in the future

 

Like the idea of GM factory fuel injection, bet its the most reliable.

 

You are correct in that it is the most reliable from the standpoint there are 1000’s of hours invested in the PCM platforms for vibration resistance, weather resilience, and the like. Hands down no aftermarket PCM goes through even 1/10th of the development for harsh environments the factory stuff does.

It also has 100’s of features which are absolutely unneeded IE cat converter monitoring, EGR control, EVAP system control, fuel tank pressure sensors, and so on and so forth. Not to mention the fun and games involved with tuning out the security system. I did my LS swaps about 10+ years ago when aftermarket PCMs really weren’t a thing.

The concept of being able to tune a motor with a handheld controller just wasn’t a thing back then like it is now. Not to mention how flexible the aftermarket PCMs are now to aftermarket setups vs the OE type units. Things have improved IMO to the point that if I were to do a swap today the only reason I would use a factory style PCM is.
1. I got the PCM and wiring for little to no cost
2. I needed the factory PCM because I was integrating it with a factory gauge cluster or something along those lines.

 

When I look up FAST I find lots of long running threads about avoiding noise on the system and goofy home brew ways to avoid it that should not be necessary. I wouldn't buy one just because that.

 

After some of the recommendations I've gotten on this thread, I'm leaning towards the edlebrock proflo 4. I like being able to correct the timing also.

Which AFR heads would you recommend for the system? The 185s are affordable, but will they work with this setup?

 

That may be but I installed mine taking care to just follow directions and don't have any noise issues. My ECM is in the passenger cab, the leads from the MSD go straight back to the bulkhead for about a total of about 6" to 8" of ignition control leads in the engine compartment. I wrapped that with heavy duty foil (just because it was easy) and haven't had any problems with noise.

 

I was running my engine with GM 730 ECM and playing around with an autoprom doing programming and whatnot. Wonderful fun stuff, and I learnd a bit of stuff, and you can monitor & tweak all kinds of parameters on your laptop.....but really--- as soon as I got the FAST EZ-EFI 2.0 hooked up properly--- the engine ran better (even before I tweaked things in) than after years of me playing around with the GM 730 ECM. I now "believe" that these self-learning ECMs actually work ok. Of course, if I was really knowledgeable and had a dyno I could have made that GM 730 ECM do anything I wanted...... but FOR ME, the self learning ECM worked out quite well.

 

I really do like the idea of self learning, I don't have a dyno, nor do I have time to spend constantly messing with it. I'm in my 50s and want to drive it more than I work on it. One of the main reasons I'm considering a conversion. I really hadn't thought about a factory set up, id have to look more into that. I'd love it to be like my truck and never have to consider timing or fuel when i travel.

 

Look around. Read the reviews and pick the system that has the best reviews overall. For me it was easy because FAST made th conversion kit to mate the EZ-EFI 2.0 with the TPI system, which was really similar to my Ramjet system, which I had already learned from going to ramjet MEFI to the 730 ECM. I also already had my old MSD tach drive distributor which i locked out with a MSD kit and removed the vacuum advance mechanism. It was just the most economical way to replace that POS MEFI system.

You do NOT have those limitations.

 

A Quick Question; The highest horsepower Edelbrock Pro-Flo 4 EFI Systems advertises is 550 hp (1,000 with larger injectors), Does anyone actually have experience with higher horsepower? I really like this system as well.

 

I see you recently became a forum member, Welcome, and I have to ask, how many carbureted vehicles have you owned?
Your 75 Corvette was designed to run fine within the elevation ranges you plan to operate in.
I grew up in Corona, CA which is close to sea level and drove up to my parents cabin at Big Bear Lake at over 7,000 feet for decades and never had to tune any of my vehicles at the different elevations.
At that time none of my vehicles were equipped with factory efi and were all carbureted.
For the past 20+ years I drive from near sea level to the Lake Tahoe area, over 8,000 feet elevation, and have had no problems with my vehicles that have been carbureted, even any of my hi performance vehicles.
If you are seeing issues driving between the elevation ranges during your daily drives, the main problem may be as simple as a carburetor rebuild, timing correction and a good tune up.
You should not need to make corrections at the different elevations and your issues could be elsewhere.
New efi systems are amazing though, so no arguments here.
Good luck!

 

I have been considering this also. I purchased an FI tech TBI but have not installed it yet. My question is can you elaborate more on the intake manifold choice. I have a dual plane but am not adverse to a swap to single plane if it will produce better results. Curious minds want to know.