Tbi 218

[celticsam]

I'm looking at the prospect of using a Petronix electronic ignition and a Holley stand alone TBI with an adapter plate (or a custom intake) on my 48 Plymouth (already converted to 12 volt negative ground). While it won't be a tire smoker, it will always start, regardless of outside temp, never wash the cylinder walls with fuel, and have a little more power than stock. End result? more performance and increased longevity.

Any thoughts or advice?

[Young Ed]

A guy on the 39-47 dodge truck yahoo group made a fuel injected flathead for his truck. He used an early GM setup off a similar sized engine. I believe he made an adaptor plate for the throttle body and adapted the dist to his flathead. Had to put a bung in the exhaust system too.

[41/53dodges]

well, I had been thinking of building a direct injected flathead, but could not think of how to build a proper head for it! The way i figure it, if you are going that far, i myself would go the rest of the way and add a blower, dual exhaust, the whole works!

[celticsam]

I had sat down and figured this pretty much through. Direct port injection would be very difficult with the siamesed intakes runners on a flathead. However, using a MPFI setup, as in the GM 2.8 would work very well. 6 injectors in the intake manifold, set up as batch fire (1,3,and 5 inject on one crank revolution, then 2,4,and 6 inject on the next). Since the displacements are similiar, the computer would read the O2 sensor, adjust the injector pulse width, and have the engine running close to correctly. The problem that I see with this setup (and the reason that I decided on TBI) is the fabrication of a proper fuel rail, Poor injector placement (fairly far from the valve and angled poorly), along with the GM computer's known lack of flexibility and difficulty with tuning. With TBI, all that you need is a MAP sensor, an O2 sensor, a temperature sensor, a throttle podition sensor, a 1 BBL to 2 BBL adapter, a 2 BBL to TBI adapter, an inline fuel pump, the Holley TBI unit, and a computer with harness (Holley or, say, a 88-93 Chevy truck harness) Electronics, I can do. Metal fabrication....not so much.

[Alshere59]

You may want to contact Moose one of the forum members. He can set you up with a manifold that fits your needs.

Here is a link to his web page. http://www.manifoldsbymoose.com/manifoldsbymoose/D-P_Combos.html

[greg g]

When we attended the Plymouth Owners Club meet in Detroit a few years back we talked with a couple of MOPAR engineers that were working on a P15. We spent some time chatting about throttle body FI. specifically using the injectors from a 2.5 mid 80's 4 cylinder set up, as it was pretty simple electronically and pretty reliable.

If you have already converted to 12 V you might want to look into getting the electronic ig set up from a late slant 6, as it is fairly easy to adapt the /6 dist to fit the flathead, a little reshaping of where it meets the block and seitching the drive tang.

The fi uses a do or don't feedback loop, however there probably aren;t many of the old omni/horizon, platform cars left in junkyards, but replacement parts are probably still available.

The other discussion was using gm stuff but using 6 cylinder injector in the intake for a near the port style using 3 nozzels but firing them twice per cycle at the siamesed ports

Half a jeep fuel rail might work, and I have read that ford 5.0 injectors were an upgrade for mounting into the jeeps. Jeep 4.0 stuff could also be a source for distributor.

[celticsam]

The Omni/Horizon has a rather complicated injection system...overly so. rugged, reliable, but complicated. The 218 is roughly 3.5 liters...the 230 is 3.8. With the 3.8 lies the answer. The 3.8 was available in a TBI form in a few platforms...most notable G-bodies. The system only relies on a MAP sensor, an O2 sensor, and a temp (coolant) sensor, an AC circuit sensor if needed, an HEI type distributor, and, depending on year, a throttle position sensor, a speed sensor, or both. For our engines, a MAP sensor at the base of the TBI, a coolant sensor which can also send to a gauge, a Stovebolt Engines HEI distributor, and a Holley 2 BBL style TBI unit would do the trick nicely. The missing piece was supplied earlier...Manifolds by Moose! I e-mailed him, but if he can do a TBI flanged single exhaust manifold, a O2 bung placed at the convergence of the 6 pipes, and away we go! Shoot, I could even put an aftermarket cat converter on it to make it fuel effecient and clean.

[Alshere59]

Make sure you post the build I may do the same if it works out well.

Al

[celticsam]

It appears that this project will be on an indefinite pause. The flathead 218, while basically solid, will need quite a bit to rebuild. At least for now, I am opting for a small block Mopar drivetrain (mostly due to much lower initial and maintenance costs), and am going to keep the flathead for a (as yet unknown) future project. At some point, I'll rebuild it and TBI it...it will just be low on the list. To bad, as this would have been a fun project.