400 EFI

Tech Question


Ty Edagr, Wichita, KS, 90 dodge d150 318

Longtime reader, First time writer.

I have a 1990 D150 pickup with a 318 w O/D and EFI (computer is located bythe battery, looks like the old Lean Burn boxes.)

The 318 is on its last legs and I don’t have another right now, however, Ido have a totally Rebuilt low compression 400 and trans .

My Question; Richard, is: could I use that EFI on the 400 or should I justget me another small block – maybe a 360?.

Thank you

P.S I am writing you this letter because you seem to have a wealth ofknowledge When it comes to mopars.



You have a bazillion choices here. Since this could fill a book, I’llcondense it down and give you some things to think about.

The stock single-point throttle-body injection was a low-flow, low-po deal.But if you were happy with it, I’d say to just get a rebuilt 318 long blockand be done with it. Iinstalling that small throttle body on a 400 wouldreally choke it off. Plus, you’d be quite lean – you’d need to either find alarger injector (more flow) or jack up the fuel pressure. (remember, unlikea carb, EFI is not a “demand” device – if you increase the airflow, vbiadisplacement increase, cam, whatever – you need to widen the pulse width ormake other fuel-delivery changes.) You’d need to monitor O2 to know when itwas tuned correctly. This is similar to what the rice boys do with theHondas, etc. However, for my money, if you’re gonna go with the 400, I’djust bolt a spread-bore 4-Bbl on it.

The cool-guy way to upgrade would be a 92-up 318 or 93-up 360 (SMPI “Magnum”engine) installation. This is a fairly easy swap in your truck since you canuse the wiring from a ’92-93 SMPI pickup pretty much unmodified. This swap(either displacement) is a huge improvement in both torque and fuel economy.


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