I must start by stating that I never thought I'd install FI in my car because of how little I drive it. I was plenty happy tuning carbs with my LM-1 with reasonable success. I logged on here last Fall to see Vince had taken the plunge with the Holley MPFI. He made it sound very intriguing. A while later I was mucking around Ebay and found a brand new C950 900 cfm TBI kit with 75 pph injectors on Holley's Store. I made an offer and a few days later the big brown truck delivered the complete kit to my doorstep for $900.

I started the install in January on my '66 383SBC Nova. I fabbed some brackets to mount the pump and filter in front of the fuel tank and ran 3/8" hardline along the frame and subframe connectors to about the passenger door. I transitioned to Summit's -6 teflon fuel hose along the trans tunnel and up to the throttle body.

I mounted the ECM under the dash on the passenger side and punched a hole through the firewall, near the wiper motor for the harness. I removed all the split loom from the Holley harness and rearranged the various connectors for my engine bay. I cleaned up the 45 year-old chassis harness while I was at it and put everything in split loom.

I picked up a junkyard distributor from a TBI truck with harnesses and wired it into the Holley harness and my MSD 6A with a new cap, rotor and plug wires.

The closest map on Holley's database was for a 9.5:1 355 with Holley heads and a 235@50 cam that made around 400 hp. My 9.8:1 383 has AFR 195's and a 223@50 cam. I figure it makes 410-420 HP. I set up the timing map based on what my motor liked with a standard distributor and reworked the idle area of the fuel map.

I couldn't sleep this morning and headed out to the shop at 4:00 am to finish things up. I crimped the last wire to interface my LM-1 wideband controller with the Holley O2 connector and realized I was done. I turned the key; the motor rolled over about 10 times and fired up!

It was surging pretty bad at idle. I had the butterflies open too far. The engine would go into the 1750 rpm high vacuum area of the fuel map where it was very lean. This pushed it back to the idle area where it picked up enough fuel to rev back up. Closing the butterflies solved this. I still had to add some fuel to the idle area but it soon settled into a relatively smooth 800 rpm idle.

My Dad came over to drive while I worked the laptop. The fuel map was overall very lean. He could barely let out the clutch without the AFR going to 18:1 and causing all kinds of bucking. I kept adding fuel over an hour drive and got it in pretty good shape. We haven't ventured into the high load/high rpm areas of the fuel map yet, but just driving around under 3,500 rpm we got it running pretty good.

All in, with fuel system, computer controlled distributor, misc wiring, new battery cables, etc., I'm into this EFI around $1,400. I'll be the first to admit the self tuning feature of Holley's new systems would be nice. However, I do enjoy the tinkering and the laptop tuning is a pretty cool learning experience. I look forward to improving the tune over the next few months.

For anyone considering the EFI plunge, I would definitely do it again. The devil is in the details. I had zero experience with EFI. Take your time, do it right, and you'll never adjust a carb again.

I had picked up a use Stealth Ram and set it on a new 383 I was getting built. I had a guy there just to tune that thing and it still took what seemed like forever to tune. Dyno operator did say after some tuning it had great throttle response.

In the car as you are doing it will take many miles and when done you will know it it tuned to the best it can be. I tip my hat to you for doing it in the car on a new endevor such as that. Guys on this site do know how to tune and will give you a hand if you need it.

Yeah, carbs are a PIA ,but I can tune the hell out of a Holley. The Edelbrock system looks nice. For 3 G's, I seriously doubt I'll ever be able to make that upgrade. I wish! Nice grab for $900.

Glad to hear I inspired somebody! But, you have more ba!!s than me as far as tuning an EFI system, dont think I have what it takes. One good thing though is that you will have a better understanding of EFI systems IMO once its all said it done.

Good luck!

Don't underestimate yourself, Vince. You successfully tuned carbs with your LM-1. If you can change fuel and air jets to give an engine what it wants you can punch keys on a laptop too.

The wideband makes it a lot easier. I think what I accomplished in under two hours would take days if not weeks with a narrowband. I still have a ways to go but at least the car is drivable. I might just schedule some dyno time to tune the high load areas of the fuel map.

I do have an observation about carbs vs EFI. I tuned both a 600 and 780 vacuum secondary Holley on my engine before converting to EFI. The 600 gave me about 21.5" Hg manifold vacuum at 60 mph flat cruise, 14.5:1 A/F. The best I could get out of the 780 was 19" after fiddling with air bleeds and emulsion jets. The Holley TBI only provides 18" of vacuum under these same conditions. The engine saw 44° of ignition advance in all examples.

I've had the system installed about three weeks and 250 miles. It's been very reliable. I continue to tune the fuel map and, as expected, it keeps running better and better.

I was fighting a problem where the engine wanted to die when I pushed in the clutch after coasting to a stop. It would slowly recover. I paid more attention and noticed that after pushing in the clutch, it was idling around 16:1 (target is 13.5:1) and the ECM was subtracing fuel from the base fuel map. I realized that the cells of the fuel map of higher RPM and lower MAP were 10-25% rich. As I coasted through these cells, the ECM would start pulling fuel to maintain the target A/F ratio. The closed loop compensation was around 85% when I pushed in the clutch. the ECM would pull 15% fuel from the idle cells for 5-6 seconds until it caught up and the idle would stabilize.

Thanks to idle spark control and IAC PID parameters, it's idling better than I ever achieved with a carb. It pulls steady 15" Hg at 800 rpm.

I ran through the gears one time at WOT from a rolling start to about 100 mph. the WOT A/F ratio started about 12.2 and increased to around 12.7 by 5,000 rpm. It felt really good.

What is your IAC opening % do you know? Should be less than 10% when the motor is up to temp. Anymore than that, you need to open the throttle blades more and do a tps reset.

That what happened to me initially - pushed the clutch in and she just about stalled, and slowly came back. IAC all along. Hey, I was a newbie (still am)!

I haven't touched the idle speed screw since day 1. IAC currently float around 17 counts at idle. I believe the scale with the C950 is 0-255 counts so 17 would be less than 10 percent.

I don't think the C950 ECM makes O2 corrections near as quickly as the HP series. Although I really enjoy learning about tuning fuel injection, I also admire the work Holley did to provide self-tuning fuel tables that work as well as I understand they do.

Vince - have you found it necessary to manually tune anything in addition to the spark map (acceleration enrichment, cold start enrichment, etc.)?

Actually, I havent done anything other than add some timing to the timing table. Cold start, A/E, have been spot-on as is really. I *may* need to tweak the A/E just a bit cause I think at times theres a VERY slight hesitation/sag when taking off...so I'll probably mess with that a bit at some point. But overall its really just amazing.

Right now I'm reworking the entire fuel system, so once that's taking care of I'll mess with the tuning a bit more.

Well, it just keeps getting better and better. I'm just making very minor changes to the fuel tables now and it runs really good. I can lug it down to 600 rpm in third or fourth gear and ease into the throttle, it accellerates nicely with no bucking or hesitation. I also played some with the acceleration enrichment. I reduced the part throttle by about half and more than doubled the WOT enrichment. The heavy acceleration bog is pretty well gone.

I finally took a nice 88-mile round-trip mostly 2-lane highway drive running 50-65 mph. AFR is in the 14.5-15.0 range at cruise. Checked economy for the first time since the FI install. Got about 13 mpg. It's a bit disappointing, actually, because it got over 15 mpg with the 600 Holley, smaller tires and lower gears. Oh well, it runs so good and I drive it so little that I can deal with the mileage. Does anyone else have similar experience with economy with their FI conversion?

pretty sure the exhaust system is tight? no air leaks affecting the WBO2?

try leaning the cruise till it acts up, surges or something. IOW, try to get some kind of external confirmation that the WB is telling the truth.

I don't think your mileage should have dropped moving from carb to EFI.

Interestingly, my 850DP delivering 12.8:1 gave about 15.1mpg. My new EFI system running 15:1 gave aboyt 15.7 mpg. As far as I was concerned, that's within the margin of error. I didnt lose, but didnt really gain either.

Vince, do you know how your timing compares now vs. then? really doesn't seem right that you went to 15 from 12.8 and only gained a half MPG? You should be able to use a lot more timing at the 15:1 mix, it will help mileage. Are you cruising at like 50°?

Vince, do you know how your timing compares now vs. then? really doesn't seem right that you went to 15 from 12.8 and only gained a half MPG? You should be able to use a lot more timing at the 15:1 mix, it will help mileage. Are you cruising at like 50°?

Tom, the timing was about the same between the carb and EFI. I then added more timing at cruise, then the MPG got close to 17 on the one run I did. The carb likely would of done the same if I had the vac advance hooked-up. Basically in my case, vac advance had more of an impact than EFI did on MPG's.

I think b/c the OD trans has the rpms running so low (2000), AFR isnt as big a deal as opposed to someone cruising at 3500 rpms. What an eye-opener that was for me after going through all that BS to lean the carb out, when really, it had no effect on MPG - on the highway anyway.

That's another thing, low RPM cruise with OD. So, if you spend time getting a good curve in the distributor, all in by 2800 or 3000, what does that mean if you're cruising at 2000? 0r 1800? I think maybe there's more to had here but it's going to have to wait till I've got my EFI running.

I have all my timing in by 2000. I typically cruise at 2100-2200. Running 48* total. I tried 15:1-16:1...was getting a slight missfire with both. I added/reduced timing, but it didnt get rid of the missfire, so I just left the entire table at 14:1, except for 12:1 WOT. Motor just seems to operate MUCH smoother this way, and I dont want to have to mess with it anymore than I have to if you know what I mean. I have a pretty high DCR, maybe that has something to do with it.

I think the 02 sensor is good. I get misfire in the 15.5-16.0 range. It idles well at 13.5. These are pretty typical numbers. I'm also running 44° timing at cruise; same as with the carb.

I think the reduction in economy is due to the fuel injectors not preparing the air/fuel mix as well as a carb. The TBI fuel injectors simply meter liquid fuel which flows around the butterflies into the intake manifold. Vaporization occurs within the manifold only.

In contrast, the booster venturi of a carb mixes air (main air bleeds and emulsion system) with the liquiid fuel prior to entering the intake manifold. Together with vaporization inside the intake manifold, a more ideal mixture is prepared for combustion. I'm not referring to the A/F ratio here. I'm referring to the size of fuel droplets, and the amount of oxygen surrounding each fuel droplet.

I posted earlier that my engine only pulls about 18" Hg manifold vacuum at cruise with the fuel injection. It pulled over 21" with the 600 Holley. In terms of air consumption (manifold pressure), the engine requires about 33 percent more air to maintain highway cruise with the fuel injection compared to the carb. With A/F ratio the same, if the engine is consuming more air, it is also consuming more fuel to maintain steady state cruise.

So where is the extra fuel going? I believe the answer is straight out the exhaust. The fuel droplet size entering the combustion chambers is much larger with the fuel injection compared to the carb. Thus, during combusion, the fuel near the center of the droplet is not exposed to enough oxygen and does not burn efficiently. With burn efficiency reduced, the engine needs more fuel to produce the same amount of power.

That's my theory anyway.