77 Cordoba with 400 engine are 906 heads an Improvement over OEM?

[monaco66coupe]

I have a good running 77' 400, but I want to up the power without going crazy. I have a 69' Intake and AVS, as well as 906 rebuilt heads on the shelf. The car already has new dual exhaust, and mopar electronic Ignition.The lean burn is gone.The Original TQ four barrel works well, but the Intake looks pretty low plane to me. it is very good 50-90 MPH, as it has the 3:21 9 1/4 limited slip, but low end is a bit groggy.
The 76' mopar book shows 50HP more than the 77'. Was that all lean burn, or cam? I want to maintain driveability. A 69' 383 HP engine Isn't out of the question. I don't care to go to the 440, as the A/C is all new, and the brackets are different, as well as the mileage issue.
Any suggestions would be appreciated!

 

[challenger6pak]

The flow will basically be the same between the two head sets. The main difference is that your 77 heads will have the hardened valve seats. The gas mileage should be better with the 383 due to smaller cubic inches and more efficiency due to higher compression.

 

[Darter6]

The horsepower difference may be that the early lean burn engines didn't have cats. If I remember that was one year only. Chrysler was doing strange things with the catalitic converters, some cars had them some didn't. I worked at the dealership back then in PA and bought a Aspen new with a 318 and it didn't have a cat. By 77 all Chrysler passanger cars had them. My 79 300 California car has 4 of them and a smog pump. Nice score you got with a 400.

 

[monaco66coupe]

The horsepower difference may be that the early lean burn engines didn't have cats. If I remember that was one year only. Chrysler was doing strange things with the catalitic converters, some cars had them some didn't. I worked at the dealership back then in PA and bought a Aspen new with a 318 and it didn't have a cat. By 77 all Chrysler passanger cars had them. My 79 300 California car has 4 of them and a smog pump. Nice score you got with a 400.

Thanks! I bought it off the FBBO, and I was attracted to it because of all the heavy duty options, which are rare on a Cordoba. I am still not satisfied with the TQ and Ethanol, so the vote is still out on the Intake/carb. The eng/trans is in excellent condition, showing 35k miles. By all appearances the mileage is true.

 

[tallhair]

Try just changing the intake to an aftermarket and a eddy carb and pertronix or mopar perf electronic ignition and see how that goes.

 

[slepr1]

I started my upgrades with changing the gears. I switched the rear end to a 8.75 with 3.91 posi gears. Made a big difference. Then I got the 'must go faster bug'.

Btw, Once you start upgrading heads, other engine components should be matched to compliment and work together. This is where it becomes an expensive hobby.

 

[rumblefish360]

The TQ is a more flexable carb. That particular year TQ isn't the best to eek out a lot of power potential. While it can be modified, I'd seek an earlier version.
The cast iron heavy weight intake can go. Finding a TQ aftermarket intake in a dual plane could be airflow hard. The Performer isn't a big leap over the stocker.
You could use a cam upgrade over the factory unit. Just remember that it is a short stroke engine and sensitive to a cam to large.

Being you changed the gear ratio, you cam choice should start with the cams cruise rpm, where your driving in at Hwy. speed. 70 mph? At what rpm? The cam should have a cruise range in that area. (Or lots of torque!)

The biggest problem with the 400 is low compression. It doesn't need much but it started life with ratio in the toilet.

 

[charger360]

is the distributer you put in stock? is it a mopar perf one? the curve of the distributer is going to make or break how that engine feels with a late model low compression engine like yours. more initial advance really helps wake it up but you need to be able to keep the total mechanical advance at a reasonable amount I would shoot for 15 or so at idle with the vacuum advance off and 34-36 total mechanical with at least 50 derees of vacuum advance. the tq will blow away the stock avs if it is set up right as it is much bigger cfm wise than avs. I would hunt down an aftermarket intake as much for the weight as performance. if you really want an avs style carb the eddy thunder is nice I have run most of the carbs out there they all work pretty good if you can tune them. good luck!

 

[rumblefish360]

Dang! I forgot about the distributor some. Those lean burn carbs lack the vacuum port. While it is possible to add one on, it is a good bit of work some may not enjoy taking on.

 

[natas33]

Honestly ringing the hell out of a 383 and waiting for rods to go flying and sort of being in disbelief they still haven't, is even more fun in a way, than burning the tires on a roll in 3rd gear in a 440. both sort of net the same end result in a race from a stop start depending on mods and car setup. 383/400's are really underrated imo. how do so many small blocks make 700+hp with same or less CI's and a much smaller bore size...... engine is basically an air pump.. and is governed by how much air it can pump in and out.. which is governed by cylinder head flow, valve lift, and rpm. a 383 with a good valvetrain is just happy at 8000rpm. sure stuff breaks a lot easier.

- - - Updated - - -

Advancing the timing a good amount helps the low CR 383 and 400's wake up a little. so does removing the factory pistons and fitting them backwards in the bores! I forgot how or why that trick works exactly, and the correct way to go about it, but it did, I swear.