What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Summit Max-efi 500 results/experiences/opinions

J

JohnNoble

Registered Member
 Premium
Joined
Oct 22, 2024
Posts
53
Reaction score
17
Location
Montana
I've been reading through a lot of the posts here regarding available throttle-body fuel injection systems. I haven't seen a lot on the Summit Max-efi 500. If you have used this system I'd love to hear about it. Also, if you are using it/have used it, do you feel that the absence of timing control is really missed?
For background, I'm going to switch from and Edelbrock 750 carb to FI on a old-school 400 sbc with Vortec heads in my 76 K5.
Thanks!
 
Just so you know, its made by FiTech, but its a different design made exclusively for Summit. I have been running one on my 350 since 2020 and its worked great. I did add an 1"open spacer to work with my Edelbrock dual plane manifold, and replaced the handheld controller since the screen cracked. A bonus is the computer is separate, and you can mount it wherever, unlike other manufactures versions of these.
I left my HEI alone, and no issues whatsoever, set at the normal 16/36.
You definitely need a good fuel pump capable of delivering the required 58 psi, although my truck still limped around on half of that when I was having fuel pump issues.
It sure seems like peoples results vary with these type of units, as proper install is important, and you still have to tune it for cold start-ups.
Here's an installed pic for reference, I think I posted this one before.
IMG_20200621_160642_247.jpg
 
@cheavyk10 , thanks for the feedback and the pics. I have the engine out and am going through it this winter. I have a Performer RPM intake as well so thanks for the tip on the spacer. I plan to update the fuel system based upon a lot of other threads here as that seems to be a common theme. What's involved in tuning for cold-starts? I am in Montana and the truck will definitely see 'cold' starts.
 
I basically just had to add more fuel than what the computer is set up with, for starts around 35 degrees or colder. There is a good amount of tuning options you can manipulate with the handheld. Otherwise, the self learning works well.
 
Kind of an open ended question, but for those of you that don't have timing control, do you see where that would or could be helpful?

Just wondering if you feel that things like starting and idle would be improved vs standard hei, given the 0* base timing, and ~20* idle timing of (generically) GM OBD1 timing strategies.

Also, about reliability given lack of vacuum/mechanical parts. Clearly coils, pickups, and modules fail on both, but would eliminating the mechanical timing components from the equation be a win?

I always felt it was a huge waste not to let the ECM control timing (that you had programmed of course), but having never really heard anyone say they regret not going to it, I question my original feelings on the topic. I have a hodge-podge of engine parts between the TPI injection and L31 lower so controlling timing through a keyboard felt very beneficial, but perhaps not all engines require that amount of fidgeting to get the timing dialed in.
 
I have been running one on my 85 k20 since 2021. It is a daily driver with one-way commutes of 53 miles.
I live in the Eastern Sierras; my house is at 5200 feet and drive up to 7100 feet. My engine is an L31 (350), th400, np208. Just regeared to 3:73 from 4:10.
I struggled with setting the carb/timing up before the conversion, especially with the 2k gain/drop in elevation.
It even improved my mpg's from 12 now getting close to 15.
I run an inline walboro pump in line and adjust the fuel pressure regulator down to 60psi.
When I get home ill snap some pics and part numbers.
Dam near everything is programable as far as tuning, but out of the box cant really beat it. if you have a weekend to convert, it's not all that complicated/
 
A distributor is a maintenance item filled with moving parts that eventually stick and things that wear out. Going through a carbon button and jumping a gap aren't very efficient, either. Having only 1 coil limits the high-RPM performance. Nowadays finding good replacement parts (module, pick-up, coil) is a bit of a gamble. It's also never really getting the timing right under all conditions. The advantage is that it's already there and supposedly working, so the swap is easier by changing fewer things at the same time.

What's the drawback to a waste spark system? Less energy delivered compared to COP, I suppose. More time to set up and tune.
What's the drawback to a COP system? Clutters up the valve covers. Additional cost of 8 coils is offset by grabbing a whole set of OEM ones for $50. Some of these things go 100,000 miles without being touched and the coils go many x more.

When I ditched the Q-Jet many years ago with Megasquirt/TPI, the biggest headaches were related to the HEI. I was melting buttons, over-running the cap terminals and losing coils. Converted to 4-coil EDIS and everything got easier to tune. Multiple sparks gave it the best idle it ever had. Granted, keeping the spark control stock would have eliminated some of those headaches.
 
So after reading this I might be interested is using this system on my Dodge when I do the magnum swap. I see there is a fuel pump wire in the harness...if you already have an EFI capable in tank pump can you just let it do the work?
 
Chickntrk said:
So after reading this I might be interested is using this system on my Dodge when I do the magnum swap. I see there is a fuel pump wire in the harness...if you already have an EFI capable in tank pump can you just let it do the work?
Click to expand...
Yup, it has a relay and a wire ready to power your fuel pump.
 
Chickntrk said:
Could I not use that and just let the ECM handle ignition and fuel pump duties?
Click to expand...
You mean the ECM for the magnum engine? I suppose if you could fool the ECM into thinking it has all the parameters met to run those systems, sure, but its voodoo to me.
I don't think the Summit unit would care.
 
Correct…I guess I’m confused about what ignition you run with these systems…Summit says use your stock distributor….so I’m wondering if I’d have to swap back to an old style carb ignition system or if I could use the already TBI ignition system?
 
You must log in or register to reply here.

Latest Posts

Top Bottom