Unsure of how to move forward with 81 EFI Imperial

[commando1]

You have to get out of the keep it original. If your going to donate it to a museum and not drive it, sure leave it as a static display. Why f#$& around with some engineers pipe dream EFI. The system is a controlled fuel leak, probably worse than a carburetor. Then throw the uneducated ignition control in the mix you will be lucky to get 13 mpg out of a mellow 318, that is unacceptable especially with the very highway favorable rear gear. Put it back to a carburetor and a distributor that will let it eat.

Brilliant way of describing it. Bravo.

 

[fury fan]

You have to get out of the keep it original. If your going to donate it to a museum and not drive it, sure leave it as a static display. Why f#$& around with some engineers pipe dream EFI. The system is a controlled fuel leak, probably worse than a carburetor. Then throw the uneducated ignition control in the mix you will be lucky to get 13 mpg out of a mellow 318, that is unacceptable especially with the very highway favorable rear gear. Put it back to a carburetor and a distributor that will let it eat.

If you had a better type of EFI setup (like Ford's EEC-IV or GM TBI) the results would be worth the effort to fix it. But not this version. No parts, no knowledge base.

I agree with @70bigblockdodge - swap it to a carb and some type of electronic ignition.
Swapping to -302 heads (used on 318s during the Dodge truck TBI era), although quite a bit more to find a good set, would make a good improvement over 1981 heads.

 

[King Hooter]

All I know is I'm so happy that my 81 was converted back in the early 90's. And just how much better it runs now than it did when I bought it, in '06.

 

[70bigblockdodge]

If you had a better type of EFI setup (like Ford's EEC-IV or GM TBI) the results would be worth the effort to fix it. But not this version. No parts, no knowledge base.

I agree with @70bigblockdodge - swap it to a carb and some type of electronic ignition.
Swapping to -302 heads (used on 318s during the Dodge truck TBI era), although quite a bit more to find a good set, would make a good improvement over 1981 heads.

Maybe on the GM system but even those are a PITA to work on (OBD2 is going to be 30 years old in 2 model years.
Best I can tell in FSM is the Imperial uses 360 head of the day, as per valve specs, calls for 1.88/1.60, I have not looked at the casting numbers on head in my car. I did get a rusty/locked up truck 318 with factory 4 bbl it also has 360 heads. So basically Chrysler did the hot rod trick and put 360 top end on a 318 I have not been able to get any pistons out of the 4 bbl 318 to measure the compression height. So the 302 castings on a Imperial may be a downgrade, not sure the combustion chamber shape will make up the loss in flow especially if you throttle it with a 2 bbl and intake.

 

[fury fan]

Maybe on the GM system but even those are a PITA to work on (OBD2 is going to be 30 years old in 2 model years.
Best I can tell in FSM is the Imperial uses 360 head of the day, as per valve specs, calls for 1.88/1.60, I have not looked at the casting numbers on head in my car. I did get a rusty/locked up truck 318 with factory 4 bbl it also has 360 heads. So basically Chrysler did the hot rod trick and put 360 top end on a 318 I have not been able to get any pistons out of the 4 bbl 318 to measure the compression height. So the 302 castings on a Imperial may be a downgrade, not sure the combustion chamber shape will make up the loss in flow especially if you throttle it with a 2 bbl and intake.

I was thinking of OBD1 TBIs, for whatever that's worth.

IMO putting 360 heads on 318s was one of the sillier things Chrysler did.
They took an engine that had low compression, put better-flowing heads on it that reduced compression even further, and kept hte 318 cam that couldn't take advantage of the heads. Yes, hp increased, but it wasn't the performer it could've been if they had maintained CR and/or used the 360 2-barrel cam.

There's a guy on FBBO that did a bunch of dyno tests on low-CR mid-late 70s bigblocks, and dispelled the myth that CR is required to make hp.
BUT - everyone agreed they made less hp/torque than if they had higher CR (duh), AND his dyno data didn't show below 3000 rpm (where we spend 99% of our time).

In an 81-83 Imperial I would want throttle response and a little more torque if possible, and I think hte -302 heads would do that. (or Magnum heads would be best)
Ultimately the rear gearing would dictate how the engine should be configured, though?
And thank heavens it should have a WR trans with deeper 1 & 2 gearsets.

 

[70bigblockdodge]

I was thinking of OBD1 TBIs, for whatever that's worth.

IMO putting 360 heads on 318s was one of the sillier things Chrysler did.
They took an engine that had low compression, put better-flowing heads on it that reduced compression even further, and kept hte 318 cam that couldn't take advantage of the heads. Yes, hp increased, but it wasn't the performer it could've been if they had maintained CR and/or used the 360 2-barrel cam.

There's a guy on FBBO that did a bunch of dyno tests on low-CR mid-late 70s bigblocks, and dispelled the myth that CR is required to make hp.
BUT - everyone agreed they made less hp/torque than if they had higher CR (duh), AND his dyno data didn't show below 3000 rpm (where we spend 99% of our time).

In an 81-83 Imperial I would want throttle response and a little more torque if possible, and I think hte -302 heads would do that. (or Magnum heads would be best)
Ultimately the rear gearing would dictate how the engine should be configured, though?
And thank heavens it should have a WR trans with deeper 1 & 2 gearsets.

OBD 1 is all so non supported now because OBD 2 has been around almost 30 years. It's also random categories. OBD 2 at least grouped systems and has room to add. A computer format that is enduring 30 years is impressive.
All those dead low compression engines are a emissions joke. It was supposed to suppress detonation and high temps to reduce NOx levels. Actually has so much dead spot it promotes detonation because nothing moves, it's like air on a hot and humid day the air just hangs there.
I don't buy those Dyno numbers on a low compression engine. You can tweak the inputs to get a result with a controlled Dyno load.
When in fact the engine runs like crap in a car. I have this combo in my Challenger, low 8.42:1 compression, big cam, it literally has nothing below 3500 rpm, needs like 40° Btdc ignition timing and will not even run on 89 gas without complaining. A unless you want to have 4.10 rear gear and a 4k plus converter, miserable combo.
Same as a vacuum secondary and a double pumper. On a Dyno they can run almost equal, at a stop light there is a huge difference.
I'll take the bigger heads on it any day. Wack .040-.050 off the 360 heads and you will lose nothing. The trans fixes the tall rear gear without having to develop a OD. I think it is compared earlier in this thread. It's like a 6+ :1 compared to a 7+:1 first gear. That combustion chamber on the 302 castings was a step in the right direction, but I think it is remediated by the piston height.
I guess we will see. I'll have a look under the valve covers but have no intention of pulling it apart yet. I'm using the 4 bbl intake and deleting the computer ignition. Hopefully it will have some snap and live on a diet of crap gas. All while delivering 20+ mpg at 75 mph cruise, that will beat my wife's Jeep GC for a trip.