What MS parts req'd for 300 EFI build

Kobane

New member
Right now I have a 300 with a crane 260H cam, efi headers, Offy C intake and a 500cfm Edelbrock 4BBL. I'm wanting to convert over to Megasquirt. There are so many options and setups that choosing is impossible. What parts are required to get me started? What would work best for EFI? I have a 93' 300 EFI intake manifold and can find throttle body, or do I use my Offy C and find a TBI and tune with that? I would like to control the dizzy and electric fan as well. Thanks in advance guys.
 
Why not go with the stock EFI Parts to start with? Manifolds, throttle body, Idle Air Control valve, fuel rails, injectors and Fuel Pressure Regulator, TFI distributor, coolant sensor, manifold air temperature sensor and in tank fuel pump. DIY Autotune offers a PNP kit so you can plug right in to the 64 pin EEC-IV harness. If you use the stock down pipes from the EFI exhaust manifold you have a bung in the cross over tube for a Wide Band O2 sensor. Doesn't get much easier than that.
 
To be honest this is going to be a bit of a how truck with some "go". I hate what the sloppy wiring harness, intake, etc on the EFI trucks look like. I have contacted a very keen machinist and have talked about installing MPFI injector bungs in each intake runner in my Offy C intake. I would like to use a GM TBI for TPS, IAC, etc and use the MPFI for the fueling as I have a GM TBI off a 305 in my garage, and I can steal some sensors from work lol. Anyways would this idea work?
 
I'm assuming you mean "show" truck.

Fine. You can build your own wiring harness to whatever you want it to look like. If you prefer to ditch the stock intake for something else you will most likely lose some driveability. If form is more important than function that's OK, but it's tough to have the best of both worlds. Almost any combination can be made to work. Just how well it works is another matter.
 
If the stock intake would work better for the application then that is certainly something I would entertain, but putting a used wiring harness on an otherwise brand new engine in a chassis with a brand new wiring harness is in my opinion taking a step back. I am a Caterpillar mechanic and have access to some pre made 2 wire, 3 wire, and 4 wire wrapped and loomed lengths of harness as well as full access for Deutsche connectors from 2 pin to 32 pin, also have some pretty sweet terminating resistor splicers that internally splice connections and you just make the appropriate plug and go from there.

I just thought the Offy C intake with MPFI would be pretty cool, but if the OEM manifold will work better in all for it.
 
learning curve is kinda steep with megasquirt. its pretty common, even doing a stock retrofit, to end up with an engine that just cranks and cranks with no fire, or something that runs really crappy.

adding custom throttle body or a manifold that might not atomize fuel very well adds more variables to the equation, hence the caution.

maybe one of holley carb-style TBI retrofit things would be a better solution for you to do a clean install. Megasquirt can run a chevy style TBI unit, which has the added advantage of hiding lots of sensors inside it, but the road isn't mapped out as well... MPI is going off into virgin territory.

either way, go for it! post your results!
 
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