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AMC 258 w/4.0 head & EFI

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cjthenoisemaker View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cjthenoisemaker Quote  Post ReplyReply Direct Link To This Post Topic: AMC 258 w/4.0 head & EFI
    Posted: Jul/15/2011 at 4:15am
I wanted to take my 258 and rebuild it in the near future. While this happened, I wanted to use the 4.0 head and its fuel injection system for more power and supposedly better fuel economy over using the Carter 2BBL or MC2100. I've gone and read writeups on swapping a 4.0 head onto a 258, but most people use the 258 intake manifold and MC2100 which was my original idea until I had to change the plan.

So has anyone used the MPFI system from a 4.0 with the head?
Setsuna - 1985 AMC Grand Wagoneer (R.I.P.)

Failure - WAS a 1984 Ford F150

Nodoka - 1987 AMC Grand Wagoneer: 360/727/NP208/Dana 44s
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Post Options Post Options   Thanks (0) Thanks(0)   Quote poormansMACHINE Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 6:40am
Fuel mileage and horsepower between the injection and a well tuned stock carb is negligible.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 7Xpacemaker Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 6:59am
I am working on a project that is a little bit like this. I am putting a supercharged 4.0 in my '77 Hornet and am currently working on a megasquirt system for it. My Megasqirt system is using the hall effect sensor in the distributor from a '87 Ford 300 six cylinder. This will create the pulses to fuel injection. Also, I am using a fuel pump from an '87 Ford 300 six also. This requires a regulator, which I am unsure as which avenue I am going to pursue. Some Jeeps have a fuel filter with a built in regulator. Using this would prevent me from having two individual pieces in the system. My megasquirt requires an IAT sensor (already on jeep manifold), temp sensor (on 4.0 thermostat housing-ms uses a GM sensor), an injector harness, the IAC plug off of the throttle body, a high idle plug (optional), a MAP sensor, and a few other things. I am running an MSD system through the (fairly) stock 96 distributor. I mounted the Megasquirt controller inside the car and made a two piece harness with an aircraft (cannon) plug that can be disconnected at the firewall. This way I could disconnect the engine compartment harness after I am done building it, as the car is basically stock now. When I do the installation, I don't want a lot of down time when I make the switch. My time is limited in the garage because of my kids right now.Unhappy
C.J.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 9:13pm
Well, I agree with PMM... mostly. The deal is the EFI system keeps the engine in tune for conditions pretty darned good, whereas the carb is tuned for ideal conditions and is just fair in all others. Tune it in the summer for warm weather and it runs, but not the best, in winter. As far as all out power there is really no difference -- for the conditions the carb was tuned in. So on a dyno there is no difference, day to day the EFI engine should average better power, if only 1-5 hp depending on how different conditions are from when the carb engine was tuned. That's the main reason there is a 2-3 mpg advantage to EFI -- tuning better matches conditions. The smarter the computer (some learn driving habits) the better the mileage difference.

So overall an EFI engine runs better longer, but doesn't really produce a noticeable power increase. Where you gain power when switching a carb engine to EFI is that the tuning is more efficient, closer to the most you can get from the engine. There isn't much to gain from simple, inexpensive bolt-ons on modern engines because they are already pretty finely tuned. You might be able to get 10-15 more hp from a 4.0L with bolt-ons (no cam change or going into the engine proper), but that's it. Not much more to gain from even a cam change and keep it EFI friendly. You can take a 74 360 that produces around 200 hp and make a carb/intake/exhaust change and gain a good deal of power... 20-30, and another 20 from a cam change (not a "lopey" cam, but still street/power brake friendly) -- easy to get 50 hp, not real hard to get 100. Of course part of it is size, but you get the idea. Even an old six can easily gain 20-25 hp without too much work. This is why super chargers and turbos are becoming the norm for hopping up a modern engine. It's expensive though -- $5K+ for a kit to add 50+ hp ("how fast can you afford to go" takes on more significant meaning today!).

EFI increases driveability (just crank and go no matter what the weather, no warm-up really necessary) and a little fuel mileage, but driveability is the most noticeable benefit. The 4.0L head breathes better than the old 258 head. It won't add a noticeable power increase by itself (may 5-7 hp, but only in the higher rpm range, nothing noticeable from a standing start). Adding a better exhaust, intake, and bigger carb (or EFI) wakes the 4.0L head up -- now you're doing something to take advantage of the higher flow. The increase in efficiency can also increase fuel mileage -- as long as you take it easy. Most tend to take advantage of the extra power potential so end up with about the same mileage as before or a couple mpg drop. But about the same mpg with more power is a win-win to me!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote poormansMACHINE Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 10:49pm
Best example of how well both the antique and new tech systems compare.
Some of you may remember John E from Arizona. He has the carbed 258. drove from Az to Cordova and raced it. Next year he had the Chrysler EFI system and did the same. All data (fuel mileage and 1/4 times) were so close, you'd be really hard pressed to make an honest call.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Wrambler Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 11:56pm
I agree and remember well his disappointment with his efi result.
The true key is if you are a John E. You have to tune to perfection.
Everyone has a thing and if tuning a carb is yours then leave efi off your budget and tune.

My 69 Rambler, 4.0L, 82 AMC T5 gets 22-24 city and 28+ highway with 91 Wrangler efi.
I like the no tune ,  hit the key and go

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65 Ambassador Ragtop rustbucket

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Post Options Post Options   Thanks (0) Thanks(0)   Quote nali Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2011 at 1:48am
Originally posted by 7Xpacemaker 7Xpacemaker wrote:

I am working on a project that is a little bit like this. I am putting a supercharged 4.0 in my '77 Hornet and am currently working on a megasquirt system for it. My Megasqirt system is using the hall effect sensor in the distributor from a '87 Ford 300 six cylinder. This will create the pulses to fuel injection. Also, I am using a fuel pump from an '87 Ford 300 six also. This requires a regulator, which I am unsure as which avenue I am going to pursue. Some Jeeps have a fuel filter with a built in regulator. Using this would prevent me from having two individual pieces in the system. My megasquirt requires an IAT sensor (already on jeep manifold), temp sensor (on 4.0 thermostat housing-ms uses a GM sensor), an injector harness, the IAC plug off of the throttle body, a high idle plug (optional), a MAP sensor, and a few other things. I am running an MSD system through the (fairly) stock 96 distributor. I mounted the Megasquirt controller inside the car and made a two piece harness with an aircraft (cannon) plug that can be disconnected at the firewall. This way I could disconnect the engine compartment harness after I am done building it, as the car is basically stock now. When I do the installation, I don't want a lot of down time when I make the switch. My time is limited in the garage because of my kids right now.Unhappy


I m slowly (kids , money , etc ... )  building the same for a 232 :) Supercharger ( I have a M62 Eaton ), 4.0 head , dual exhaust and Megasquirt . Do you have pictures ?
66 Ambassador 258 Supercharged in project
Olds Delta 88 1979
Buick 38 Coupé .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 7Xpacemaker Quote  Post ReplyReply Direct Link To This Post Posted: Jul/18/2011 at 6:52am
I will post a few so far. I am getting ready to start on the 4.0 in the next month or two...
C.J.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thikstik Quote  Post ReplyReply Direct Link To This Post Posted: Jul/19/2011 at 5:00am
EFI is better at raising volumetric effeiciency because a dry manifold that isnt full of gas droplets charges the cylinder with more air.  IIRC ,7% more. That's like a pound of boost. Of course, the I6 intake, by design is pretty bad for fuel puddling and uneven mixture, so efi wins there too.  Also, a computer is always getting feed back of engines parameters and building tables (block learn/integrater) to give the perfect mixture/timing to the engine under all conditions/demands.  I do agree with others that a well tuned carb/dizzy can nearly match efi. At WOT, the advantage of EFI IS negligable.  As far as hiway cruising... I would say OD would easily trump efi for ultimate mpg.  The I6's really can tolerate being clamped down with a deep OD ..whereas in the city they shine well with only 3 speeds. I sure hope you do this project nevertheless.
75 gremlin x, jeep 4L headed 258,Clifford cam, intake,header. 390 holley. I want a 282 VAM motor!

AC/PS/PDB.

72 AMX , 304 2bbl, 3speed, now disks...probably will sell, want an automatic /AC.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote nali Quote  Post ReplyReply Direct Link To This Post Posted: Jul/19/2011 at 5:29am
Whatever the efficiency, I thing it s funny to convert an old engine to EFI and Megasquirt .
Will the millage better ? Not sure .
Will this be reliable ? Not sure

Will anyone learn while swirtching to EFI  ? Yes for sure .

Our 40 years cars are toys . :P
66 Ambassador 258 Supercharged in project
Olds Delta 88 1979
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