Haxby,

I am planning on doing the Holley HP EFI system on my 540 and will be calling you to purchase one when I get a little further along with the build. I am retaining the MPI intake and throttlebody setup though (mine are highly modified and I have too much into them to throw away). My intake is setup for the Keihin injectors and they will be too small. I was already working them overtime before this years' modifications. What injectors would be the best/easiest to swap in there? I understand that there is no direct replacement for those darn Keihins. What have you been changing over to with success? I was eyeballing the tall Bosch style. I am currently finishing up my intake mods while I am waiting for my block to get out of the shop and would like to get this figured out.

I also would like to ditch my MSD ignition setup and run GM LS1 coil on plug ignition which I understand the HP system does well. Have you done this yet? It is looking like I will basically use the Holley LS1 harnesses and setup adding a crank trigger and using my MPI distributor for the cam sync signal. Does this sound correct? How much work does it take to integrate the factory Merc round harness plug into the system (Main harness that connects to boat rigging?)

Im just trying to get my plan nailed down and appreciate your help. I should be able to get it up to right around 700 hp with Bob Madera's help.

I've been checking out the new Fast 2.0 throttle body system as it's rated to 900hp. Their web site states that you need 9" of vacuum at idle in order for this style system to work regardless of manufacturer. My first question is, how many motors pushing 900hp are pulling 9" at idle? Does anyone have any experience with this style system in motors with 700hp or more?

I bought a Holley commander 950 MPI setup complete with manifold and the whole works. how does this setup compare to the newer holley setups? I have done some work on the old chevy TPI units but never got too involved with the actual tuning of them but I think I understand enough to start playing with the software for my boat. I am building a n/a 489 stroker motor somewhere in the 550hp range and am really considering using this setup. I was going to add the wideband kit to it and have a spacer made to add to my gil exhaust for the O2 sensor. WIll the commander 950 do what I need it to do or should I be looking to buy the newer version? this was a great thread to get started, I don't read too many 27 page threads lol

Alex,
I made it on the water this weekend for the first time and my engine runs incredibly well! Thank you for the First-Class help in my 4500 Carb to Holley EFI / DIS conversion. I’ve joined the 21st century and will never be interested in a carb or distributor again… The Base map you setup for me starts and idles great. It truly is incredible. The RPM doesn’t even fluctuate 50rpm when going in and out of gear, hot or cold. I ran up to my local lake for a quick water test and then headed 2.5hrs away to a 6000’ lake and the EFI didn’t hesitate once. The AFR numbers were spot on the entire weekend.

This software / hardware package is the real deal. I couldn’t be happier!

My engine is a healthy AFR335 / solid roller / 6500rpm engine. Bob Madara supplied a fantastic induction package, that now idles as well as my stock 496mag used to but runs 29mph faster.

Thank you both for the very professional help you have offered!
Jon Beck

Look into Holley's DIS coil system, it consists of 4 dual post coils that operate on a waste fire ignition system. It will setup very nice with the 8" Crank trigger wheel. You can run it with or with out a cam sync, but a cam sync with give you the option to run sequential fuel injection. You will see rock solid timing with a crank trigger!

I am planning on the crank trigger. I will look into those DIS coils. I want to be full sequential so I will be running the stock distributor as oil pump drive and cam sync only. Life got in the way this summer and I am finally getting back onto this project.

I have a 502 mpi with a vortech supercharger that was a kit from Graffig at one time called "extreme supercharger". I like the setup and not real motivated to dramatically modify by tossing the intake and running the holley intake with TBI. Is there an ECU replacement that could be installed and replace the GM ecu without modifying anything else accept the cable harness? I would like to increase my rpm beyond 5200
Thx
larry

Ant updates? I am thinking on a twin turbo 496 Gen VII. Motor running A Holley unit
Any ideas.

550-604. Will work on your mpi ...

http://www.holley.com/550-604.asp

I got a bit too busy this year and have been behind in keeping up to date with this thread. I'll try and get caught up, and answer all the questions I can. Twin turbo's are no problem, do you want to run boost control as well? I think the Gen VII platform will add some cost to the build though.