My little 383 project - expert opinions please

[Born_Fast]

Hi guys,

My car came stock with the 318 but now has a 383 with triple-Y-headers, dual exhaust, Edelbrock 4bbl carb and electronic ignition. ...that's about all the dealer could tell me. Now i'm planning to upgrade it a little bit in terms of looks and performance. Nothing spectacular, because if i'm ever going to pull that engine out, it will be to replace it with a 440.

For now i'm considering to replace the carb and intake manifold. Then the valve covers and air cleaner (for looks) and last but not least the dual exhaust, but that's another story.

First of all i have some questions and i hope the technical experts of you can help me out:

Can someone tell me what carb that is? The number on the bottom left seems to say 1411 0731. On the right side it has an embossed WEBER logo. If you know what type it is, then how is the performance of this one, compared to the best street carb you can suggest for a 383?

The intake manifold is from Edelbrock too, but again i have no clue what type or how it performs compared to others.

In short - i would replace both, the intake and carb if i knew it would really increase the performance. However if the difference would only be marginal, i'd rather spend the money on other things.

By the way - the mileage i currently get is between 14 mpg at best and goes down to 10mpg, when driven at higher rpms. This also seems pretty bad to me. Could it be that my carb needs adjustments?

I have not been to a dyno yet, but i guess the power output should be between 280-300 rear wheel hp. Correct?

[Born_Fast]

For valve covers and air cleaner, i'd like to get these:

 

[MEK-Dangerfield]

I really can't answer your questions, but I'll ask one. What gears do you have in the rear end? Taller gears may be fun, but kill your gas mileage. In all honesty, your gas mileage is about what I get with my 440 with a 3:23 rear end. My case is different in that it's on the hiway where I get the best mileage.


  Mike

[Born_Fast]

Mike,

i would assume my gears are as tall as they get. My Challenger runs 70 miles at around 4k rpm in 3rd gear.

That also explains the bad mileage.

[72bluNblu]

The carb is an Edelbrock performer 750 cfm, which is right on for a mild 383. The intake manifold appears to be at least a performer, if not a performer rpm model. If its a performer (basically stock replacement) you might see some gains by going to a performer rpm. The intake manifold also has a number cast into it, usually at the front, that you could look up to figure out which it is. If the 383 is stock otherwise, you may be jetted a little rich on the 750, but as mentioned the gearing could be hurting your mileage as well.

So since the carb and intake are already upgraded versions, you won't gain much by upgrading these further (except for maybe the RPM intake) if the rest of the engine is stock. If it is stock, you can swap in a mild cam to help things out.

[Born_Fast]

Thanks man, these infos really helped!

Since the preowner changed the manifold, carb, headers, valve covers and aircleaner, it would only make sense that he also upgraded the cam.

However i guess there's no way to check this, without removing the engine. Right?

Let's assume the 383 is otherwise stock, then am i correct with my bet on 280-300 horses?

[72bluNblu]

Well, the cam may or may not be changed, depends on if the PO rebuilt the engine. If they didn't, they might not have upgraded the cam, just bolted the other stuff on (hey its what you were going to do right?) The cam probably has a part # stamped on it, you'd be able to see that if you pull the timing cover and timing gear/chain.

In 1970, Ma mopar rated the 4 bbl 383 at 330 hp from the factory. This was with 9.5:1 compression. In '71 it was down to 8.5:1 compression and rated at 300 hp. For the run from 66-71, the 383 in 2 bbl form was rated no less than 270, and in 4 bbl from no higher than 335, but the compression ratio varied from package to package. Even assuming that you've got a stock compression 383 that originally had a 2 bbl (and the lower compression), with an intake and carb you'd be right on figuring 280-300hp. Now, if your 383 had a 4 bbl and the higher standard compression, maybe as much as 330 hp.

The next question is, what kind of fuel does your 383 run on? If it runs on plain old 87 without any problems, you've likely got a low compression model. If you can't run it on anything less than premium, you may have one of those 10:1 compression factory cars. Take a look at the casting numbers on your block, they should tell you the year your 383 was built. If I'm not mistaken some of the hi-po 383's also had markings to indicate what they were. Of course, if the PO rebuilt the engine, who knows.

[73Chally]

Just a quick thought - In your first post you mention the possibility of replacing with a 440.  How much of a possibility is that?  If it has a high likelihood, I would leave the engine as is and save up your money for the 440.  A lot of stuff will interchange, but your 383 looks pretty good as is.  If you think you will be keeping the 383 for a while, then I would find out for sure what you have, and go from there.  A 383 is no slouch, especially since you already have it in the car, so I would probably go with building it up to be more stout.

[Chryco Psycho]

the carb is the AFB 750 Eddy , one of the least adjustable carbs ever made , ti will definatly drop 25+ HP over better carb designs , the intake is decent , it is a eddy RPM
 I agree with above , if you are serious about the 440 save your cash ,the intake will nto fit a 440 & I would not change that anyway , the carb for a 440 needs to be bigger than that for the 383 so spend your cash once unless you can get a good carb at a swap meet or on Ebay for cheap
 what vacuum are you making at idle & in gear if auto

[Born_Fast]

Seems like i really asked the right guys. 

Blu: We don't have plain old 87 fuel here in central Europe. You can only get 95, 98 and in some places 100 octane fuel. I use 95 with additional lead replacement.
Where on the block is that casting number located? Would be great to know it's year and compression ratio. You also mentioned other markings indicating hi-po 383s. Anyone care to elaborate?

Chally: I might swap my engine if (a) i stumble across a good 440 for a reasonable price here in Europe or (b) my 383 would need expensive and time consuming repairs. Honestly i've never driven anything with a Mopar 440, so i don't know what it's like compared to the 383 and if a change is really worth it. I might as well keep my 383 for as long as it's running.

Chryco: So my intake is ok, but by changing the carb i could get 25+ HP? Then what carb can you suggest me? I'd want good overall performance throughout the whole rpm-range and (if possible) low maintenance. I don't own a vacuum gauge, but will check the next time i'm at my local workshop.

[Chryco Psycho]

I guess it depends what you want but I would look at a Holley Avenger , or double pump if you prefere or the Holley HP 750 , or the Proform 750
 stamped into the block in front of the right cylinder head is where you will find the HP designation if it is there 

[Born_Fast]

I guess it depends what you want but I would look at a Holley Avenger , or double pump if you prefere or the Holley HP 750 , or the Proform 750
 stamped into the block in front of the right cylinder head is where you will find the HP designation if it is there 

Thanks Chryco, i'll go see if i find that number on my block.

As for the carbs, i'd really appreciate if someone could point out the pros and cons of the different models mentioned.
I'm not an expert tuner, but want to educate myself before buying the wrong things.

My car has the 3-gear torqueflite automatic and (i've double checked today) runs 70mph at exactly 3500 rpms in 3rd gear - whatever gear ratio that is. 

[Robb]

FYI

cant tell you the gear ratio from that data until you provide the rear tire height.




what part of Central EU ?

[Chryco Psycho]

the Avenger is a basic street carb with choke , easily tuned , the HP series & Proforms are more race carbs with no choke & even more tunability which is especialy good for enignes with low vacuum a bigger cams

[Born_Fast]

FYI

cant tell you the gear ratio from that data until you provide the rear tire height.




what part of Central EU ?

My rear tires are 255/60R15. Would be awesome if you can calculate my gear ratio from that!


I'm living partially in Germany, Switzerland and Austria.