need 383 perf. advice

[la.68charger]

I just got a '68 Charger with original, 61K 383 2bbl. engine. Low end performance is lacking. I have a stock 4bbl intake and carb setup available. Would it be worth the time / trouble to install the 4bbl setup? Without changing cam or doing head work, is there anything to be done to add a little more power on the low end?

[Dino]

What's the rear end gear ratio?

[c00nhunterjoe]

The 3.35 stroke will always lack low end torque compared to longer stroke engines, but I love the 383. A good 750 holley and aluminum intake will definatly wake it up. I have posted several articles on stock build up 383s. A 9:1 bone stock long block with only intake, carb, and longtubes will yield 400 hp.

Here is an eye opening read:   http://www.moparmusclemagazine.com/techarticles/mopp_0209_383_engine_restore/viewall.html

[Ghoste]

What he said.  The 383 won't give you the same kick in the ass thump of a 440, it just doens't offer the torque.  On its plus side, it will rev a little more quickly and a little higher than some of the larger displacement engines out there.  They respond well to tweaks like any of the Chrysler big blocks and they are easy to work on.  Think of them like a giant small block (kind of).

[Challenger340]

Change the CAMSHAFT if you are changing the 2 bbl engine to a 4 bbl setup...changing just the intake and carb over has very limited gains if ANY at all(usually none)
because,
the 2 bbl camshaft has insufficient lift or duration to utilize any of the extra air & fuel or rpm the 4 bbl provides.

Think of it as the "program", that tells the Valves how "much" to open, and for how "long". The 2 BBL Cam has no performance capabilities at all !

IMO,
one of the biggest mistakes anyone can make is to add a 4bbl Carb & Intake, to the stock 383 2 bbl engines with the 2 BBL CAM, and then wonder why the thing doesn't even "open" the 4bbls when floored...
The 383's are decent performers in stock trim with the addition of even a CompCams 268H in conjunction with the 4bbl Carb & Intake.

[c00nhunterjoe]

I agree on the cam swap. Something in the .520's or .530 lift range with a 240ish @.050 mixed with headers, intake and a good 4 barrel wil give you well over the 420 hp range, excellent turn key reliability, and enough low end torque to fry tires along with mid-top end power rivaling many larger cube builds.  Then, you pop the hood and "oh, its just a B motor"

The key really is head flow. Even edlebrocks don't flow very well compared to other makes. For instance a aftermarket small block chevy head flows more then th big block mopar heads do. Even with eddy heads on a 440, its choked. Not saying it won't perform, it will, but 300 cfm is not a lot of flow for a 440, let alone a 500 stroker. Then worse then the intake is the exhaust flow.  Unless you can afford to spend big money on mopar heads you don't get the full potential of your build. The expense of heads, then custom headers to match those non-stock design adds up.

The 383 can make better use of the available head flow, both stock and aftermarket (stealth and eddy). Its definatly the best bang for the buck.

Also, when you pick a cam, to aid with the lacking exhaust flow, go with a split lift and duration cam to get even more power from your build.

[Budnicks]

What's your budget ?? = Performance 101 stuff really, 4bbl aluminum Intake probably a dual plane for street use, a decent 700cfm-800cfm Holley style 4bbl Carb, a good set of 1-3/4"min.-1-7/8" headers, 2.25" or bigger, free flowing mandrel bent tubbing exhaust system, with an X-pipe or H-pipe & free flowing mufflers, a better camshaft, w/matched springs & asst. components that are more suited for what ever purpose you intend to use it for, some mild head porting, a good multi-angle performance valve job, a good hotter electronic ignition, some low ohm resistance plug wires & hotter coil, a quality K&N or gauze type air cleaner element, a higher stall speed TQ converter, lower rear gears, better bottom end & 400hp easy....

[heyoldguy]

If all you want to do is switch to a stock 4bbl carb and intake manifold, all you're gonna do is LOOK 4bbl cool. There is a reason that the factory used different exhaust manifolds, valve springs and camshaft on the 4bbl engines.

But I say go for it. Cool counts for something.

[doctor4766]

What's your budget ?? = Performance 101 stuff really, 4bbl aluminum Intake probably a dual plane for street use, a decent 700cfm-800cfm Holley style 4bbl Carb, a good set of 1-3/4"min.-1-7/8" headers, 2.25" or bigger, free flowing mandrel bent tubbing exhaust system, with an X-pipe or H-pipe & free flowing mufflers, a better camshaft, w/matched springs & asst. components that are more suited for what ever purpose you intend to use it for, some mild head porting, a good multi-angle performance valve job, a good hotter electronic ignition, some low ohm resistance plug wires & hotter coil, a quality K&N or gauze type air cleaner element, a higher stall speed TQ converter, lower rear gears, better bottom end & 400hp easy....

Why does the aluminum intake make much difference other than the weight factor?

[Ghoste]

Run a little cooler but also, the aftermarket ones are all cast from aluminum.  Its sort of like another way of saying to open your options.  (at least I'm unaware of any aftermarket intakes cast from anything but aluminum)

[doctor4766]

Ok, just asking since I have the factory cast dual plain intake running a 750 Holley with phenolic spacer and was wondering if there'd be much, if any, advantage in swapping it out.

[Ghoste]

To just swap from the factory to an aftermarket with no other changes, probably little difference.  Depends somewhat on the intake selected of course but as mentioned above, all of these things are part of a system and to unlock the full potential of each you kind of need the whole system to interlock and work in unison.

[doctor4766]

I have had the engine rebuilt,new pistons, 30 over, Crane H272-2 camshaft, windage tray, headers, 750 carb,stock conv, no 'real' head work, other than machining and new valves etc
Can't wake this thing up though. Goes ok, but certainly won't rev to anywhere near 6 grand on the tach, no matter how mean it sounds.
I'm sure I'm missing something basic.
Perhaps I need to get it on a dyno.....?

[Ghoste]

Stock converter can be a bottleneck.  Final drive ratio can too.  With the other mods you can certainly benefit from another intake but it may not be the magic bullet either.  Dyno time always helps.  A 383 should hit 6 grand easily enough, I don't know that you should need to and I don't know that I would in mine but it should do it.

[doctor4766]

Got a 3.23 rear end, so it's no monster and like I said, it goes alright, but is lacking somewhere along the line.
Perhaps I do need to look at the TC at some stage but I'm sure it won't make the engine rev higher.
Thanks mate 

[Cooter]

No low end in 383? Wanna step it up? Well, Lemme see......

Swap for 440, or stroke the 383. Shorter stroke than small block Chebby.

[SRT-440]

More compression and 3.91's would help also. 

[terrible one]

383s can be plenty impressive and can be made to produce good torque, can't argue against the stroke and cubes of a 440 but it's all about the right combination

http://www.youtube.com/watch?v=BAWpWcgqX6w

[greenpigs]

I have had the engine rebuilt,new pistons, 30 over, Crane H272-2 camshaft, windage tray, headers, 750 carb,stock conv, no 'real' head work, other than machining and new valves etc
Can't wake this thing up though. Goes ok, but certainly won't rev to anywhere near 6 grand on the tach, no matter how mean it sounds.
I'm sure I'm missing something basic.
Perhaps I need to get it on a dyno.....?

What is the actual CR on the motor?

Depending on what was used your replacement pistons may be sitting DEEP in the bore & you got 8:5 or less CR.

If you access to a chassis dyno I would use it.

[doctor4766]

I have had the engine rebuilt,new pistons, 30 over, Crane H272-2 camshaft, windage tray, headers, 750 carb,stock conv, no 'real' head work, other than machining and new valves etc
Can't wake this thing up though. Goes ok, but certainly won't rev to anywhere near 6 grand on the tach, no matter how mean it sounds.
I'm sure I'm missing something basic.
Perhaps I need to get it on a dyno.....?

What is the actual CR on the motor?

Depending on what was used your replacement pistons may be sitting DEEP in the bore & you got 8:5 or less CR.

If you access to a chassis dyno I would use it.

I don't remember the exact compression ratio but I DO remember it was calculated at under 9
Something to do with the head cc's. The heads were just reconditioned without any tricking up and the pistons were these

[firefighter3931]

I have had the engine rebuilt,new pistons, 30 over, Crane H272-2 camshaft, windage tray, headers, 750 carb,stock conv, no 'real' head work, other than machining and new valves etc
Can't wake this thing up though. Goes ok, but certainly won't rev to anywhere near 6 grand on the tach, no matter how mean it sounds.
I'm sure I'm missing something basic.
Perhaps I need to get it on a dyno.....?

What is the actual CR on the motor?

Depending on what was used your replacement pistons may be sitting DEEP in the bore & you got 8:5 or less CR.

If you access to a chassis dyno I would use it.

I don't remember the exact compression ratio but I DO remember it was calculated at under 9
Something to do with the head cc's. The heads were just reconditioned without any tricking up and the pistons were these

Those are replacement low compression cast pistons so your static compression is anemic...especially with an open chamber iron head.  If you could locate a set of closed chamber 516/915 heads it would help a bunch. The engine is overcammed as well 


Ron

[doctor4766]

So the 906s aren't much chop Ron?

[Ghoste]

Not in your case.

[doctor4766]

We had originally ordered a MP magnum cam for the engine but to cut a long story short, Mancini supplied a 509 lift camshaft instead (that's another freakin story) and we sourced the Crane locally.
So to sum it up Ron, what can I work with that I already have if I want to wake her up? And what would you change? Remembering I'm not looking for dragstrip performance, but would like to light 'er up at the drop of a hat.

I've even considered a 440 but from what I read, the 383 should be able to perform somewhat better than it does now.

[heyoldguy]

If we change from 906 to 915 or 516 heads we gain a bunch of power? What quantity would a "bunch" be?