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?

[Challenger340]

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

I think what Ron is getting at is the closed chamber heads will provide higher compression....... for more "useable" areas under the curves in both Horsepower & Torque......
I agree, the higher compression will help noticeably.

[heyoldguy]

A noticeable bunch eh?

[Challenger340]

A noticeable bunch eh?

[firefighter3931]

A noticeable bunch eh?

Well, the difference from 8:1 to 9.2-9.5:1 would be quite noticable....more noticable than from say 10:1 to 11.2-11.5  

Of course the cam, induction, stall speed and gearing come into play but i'd say it's a worthwhile upgrade. He needs to get some measurements and do the math to come up with a suitable combustion chamber volume to dial in the static compression.  


Ron

[Ghoste]

Actually the quote is "help a bunch", not "gain a bunch".  (semantics I know, but still)

[Budnicks]

Actually the quote is "help a bunch", not "gain a bunch".  (semantics I know, but still)

HeyOldGuy is a really good guy, he's a great head porter, he's a great professional engine builder too, he's just messing with you guys & has a somewhat dry sense of humor sometimes, some of you guys don't seem to get "maybe"... I'm just saying....

[Bithand]

If you study the 383 build in mopar action you will see a 450 HP dyno proven combo with good TQ curves.

Add a set of 84cc. Eddy Heads and you will be nudging the 500 HP mark in a very streetable combination

[heyoldguy]

Actually the quote is "help a bunch", not "gain a bunch".  (semantics I know, but still)

HeyOldGuy is a really good guy, he's a great head porter, he's a great professional engine builder too, he's just messing with you guys & has a somewhat dry sense of humor sometimes, some of you guys don't seem to get "maybe"... I'm just saying....

Thanks Budnicks,

Oh, I'm messing alright.

I'm back from MATS 2012. Went there to see the grandson run his mom's '71 Scamp, the daughter-in-law run her '09 Challenger and my cousin run in the "warRock" Warlock pickup.

Just moments ago I finished cc-ing some 906 and 915 heads, specifically to see what compression ratio differences I might find in swaping head for head. 

The 906 heads cc'd 90cc and the 915 came in at 83 cc.

What kind of compression ratio difference will that make on a 8:1 compression ratio +.030" 383 ci engine? About .450 ratio difference! If your ratio with the 906 heads was 8.011:1 and you switched to the 915, you would go all the way to 8.469:1 compression and gain about 2% in power. So if the heads flowed exactly the same, the engine that was making 300 HP would now be making 306 HP. You feelin' the power surge? I know I'm heading out to snatch up all the 915 heads I can find!

Send your 452, 906, 915, 346 heads to a qualified head porter, and for about $900 plus shipping, he can give you 10% more power. That $900 should include new valves, seals and bronze guides.

Better yet. Buy the aluminum head if you can afford it. Get the compression ratio increase with the better combustion chamber shape and even more airflow from the redesigned ports.

[silvercloud]

So, if you have an assortment of castings to choose from-516s, 906s, 346s, 452s-in similar condition as far as guides, valves, and assuming the 516s have been cut for the 1.74 exhaust valves to make them even with the rest, can the 516s flow with the newer castings? With a rookie (ie MP template) port job? I have seen so many different opinions on this subject-wondering what the experienced builders over here have to say. This is my scenario-car is getting reassembled on a budget, the motor that is being installed now is a placeholder basically while funds come together to assemble a low deck stroker. Having said that, the "placeholder" may be holding its place for longer than anticipated  , so I want to make it as good as I can on limited funds. I have a 400 out of a truck that was supposedly rebuilt not long before the tranny went south, so there it sat. I plan to reuse the short block assuming compression test and visual inspection confirm its suitability, add a cam, intake and headers and go. Was thinking about installing the 516s I have kicking around to up the CR-thinking with a stock 400 every little bit helps?-but not if I'll be going backwards flow-wise.

Thanks in advance for the opinions
Jason

[Challenger340]

So, if you have an assortment of castings to choose from-516s, 906s, 346s, 452s-in similar condition as far as guides, valves, and assuming the 516s have been cut for the 1.74 exhaust valves to make them even with the rest, can the 516s flow with the newer castings? With a rookie (ie MP template) port job? I have seen so many different opinions on this subject-wondering what the experienced builders over here have to say. This is my scenario-car is getting reassembled on a budget, the motor that is being installed now is a placeholder basically while funds come together to assemble a low deck stroker. Having said that, the "placeholder" may be holding its place for longer than anticipated  , so I want to make it as good as I can on limited funds. I have a 400 out of a truck that was supposedly rebuilt not long before the tranny went south, so there it sat. I plan to reuse the short block assuming compression test and visual inspection confirm its suitability, add a cam, intake and headers and go. Was thinking about installing the 516s I have kicking around to up the CR-thinking with a stock 400 every little bit helps?-but not if I'll be going backwards flow-wise.

Thanks in advance for the opinions
Jason

IMO,
At the low CR levels you will encounter on the 400 engine...ANY compression increase at all is going to help...even .45 or whatever...
because,
there is far more going on with engine dynamics than needs covered here....on what is obviously NOT a Technical Engine building Site...

Incipient heat to combustion.....flamefront propagation...cam scavenging...chamber shape with a quench flat...etc., etc. all small..but they add up to far more than the simple Compression increase for useable area under the power curve.

All things being equal...if you have the 1.74 valves in the 516's kicking around ready to go, IMO, pretty much a no-brainer to go for them.
Flow-wise...for what you are doing below 500hp , you have PLENTY with even minor bowl cleanup.
I own a Flow-Bench..do NOT go tripping over flow where you are !

Having been a Performance Machine-Shop Owner for the past 30 years, and we port/flow Heads daily....I simply cannot understand the rationale to spending good money.... PAYING someone to port Cast Iron Heads these days.....
because of,
the literal PROLIFERATION of well priced aftermarket Aluminum Heads available ??
IMO,
For what would be spent rebuilding & porting the Irons....done properly......NEW Aluminum Heads can be obtained with even better Flow.

This is NOT to say I discourage the DIY'ers from accessing the gains of the Porting templates etc., I think they are a GREAT IDEA with good gains on limited funds....
just saying....I don't think "these days", it is good money spent PAYING someone else to Port iron heads, unless, due to class rules etc., they MUST be run...and the MOST Flow is req'd.

[silvercloud]

I agree-I would never pay to have iron heads ported with all the aluminum head choices there are out there now. This is a beer-budget build to get the car mobile again after a 25 year holiday from the road. I have the castings, I have an ancient Sioux valve face and seat grinding setup so fresh seats are only a little bit of effort away. Cam choice is going to require a spring change anyway, so I figure it's just as easy to pull the heads to install them. I'll use some steel shim head gaskets to jack the compression a little more at the same time.

Only reason I asked about flow is I read an article a while back on 516s vs 906s where it stated using the MP templates on the 516s actually hurt flow on the exhaust-it was recommended not to touch the short side at all?

Thanks
Jason

[Budnicks]

Actually the quote is "help a bunch", not "gain a bunch".  (semantics I know, but still)

HeyOldGuy is a really good guy, he's a great head porter, he's a great professional engine builder too, he's just messing with you guys & has a somewhat dry sense of humor sometimes, some of you guys don't seem to get "maybe"... I'm just saying....

Thanks Budnicks,

Oh, I'm messing alright.

I'm back from MATS 2012. Went there to see the grandson run his mom's '71 Scamp, the daughter-in-law run her '09 Challenger and my cousin run in the "warRock" Warlock pickup.

Just moments ago I finished cc-ing some 906 and 915 heads, specifically to see what compression ratio differences I might find in swaping head for head. 

The 906 heads cc'd 90cc and the 915 came in at 83 cc.

What kind of compression ratio difference will that make on a 8:1 compression ratio +.030" 383 ci engine? About .450 ratio difference! If your ratio with the 906 heads was 8.011:1 and you switched to the 915, you would go all the way to 8.469:1 compression and gain about 2% in power. So if the heads flowed exactly the same, the engine that was making 300 HP would now be making 306 HP. You feelin' the power surge? I know I'm heading out to snatch up all the 915 heads I can find!

Send your 452, 906, 915, 346 heads to a qualified head porter, and for about $900 plus shipping, he can give you 10% more power. That $900 should include new valves, seals and bronze guides.

Better yet. Buy the aluminum head if you can afford it. Get the compression ratio increase with the better combustion chamber shape and even more airflow from the redesigned ports.

HeyOldGUy I think I saw the cars & Warlock on the live webcast from the tower, at LVMS MATS Mopar event, that "warRock" black step side truck sounded pretty damn good, even the tower race announcer said something about it, being a powerfull 451 combo from Idaho, or something like that...

[c00nhunterjoe]

I have a buddy with a 72 duster running a bone stock 400 bottom end. The usual bolt ons, cam, intake, carb, and crazy fenderwell exit headers. The car runs mid to high 12's on slicks consistantly.  More compression is never a bad thing, but budget motorscan still be fun. Granted that duster is probably 1000 pounds lighter then a 2nd gen charger, it is still a strong engine. That car was a blast to drive.

If you already have the 516's then I say run them. Gaskt match the ports and leave it at that. Run the thin head gasket and hope for just under 9:1 and enjoy filling up on 87 octane. Don't over cam it and she'll run just fine.

[chargerbr549]

I think the new edelbrock e street heads with a 75cc chamber might be the best bang for the buck on your 383 for under a $1000.

http://www.summitracing.com/parts/EDL-5090/

[Budnicks]

I think the new edelbrock e street heads with a 75cc chamber might be the best bang for the buck on your 383 for under a $1000.

http://www.summitracing.com/parts/EDL-5090/

for a low compression bottom end street beater or occasional strip car, that's a great idea 

[ACUDANUT]

If your on a buget and want great results, change cams.  Adding a Torquer intake and holley 750 will wake that engine up....Don't forget to get a pair of HP exhaust manifolds too. 

[ACUDANUT]

Also 906 heads are not junk !!

[c00nhunterjoe]

If your on a buget and want great results, change cams.  Adding a Torquer intake and holley 750 will wake that engine up....Don't forget to get a pair of HP exhaust manifolds too. 

Dump the manifolds for headers. Tons of articles swapping manifolds for headers with big increases. The rest I agree!

Also 906 heads are not junk !!

Yup, definatly not junk. But if you have to rebuild. Set from scratch its not economical. By the time you buy 2.14\1.81's, pay for machining to install them, buy valve springs, new valve guides and seats, you might as well have just bought a brand new set of aluminum heads...

[BSB67]

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?

A lot of Blah, Blah, Blah on this thread.  Didn't read them all so I don't know if anyone attempted to answer your questions.

"is there anything to be done to add a little more power on the low end?" - If everything else is right, i.e. the tune, not really too much can be done to help the bottom end power.  Switching to the right 4bbl (small primaries) and intake, it might make it a litter crisper down low.  Someone mentioned a gear change.  This will not add power, but will allow the motor to get to its higher power levels sooner resulting in noticeably better low speed acceleration.

"I have a stock 4bbl intake and carb setup available. Would it be worth the time / trouble to install the 4bbl setup?" - Only you can decide if it is worth the time and trouble.  Adding a 4bbl will add power, but if it is a single exhaust system, not much.  However, adding the 4bbl, and a good dual exhaust system is worth it in my opinion, but you would only see the benefit above 3000 rpm.  Everyone did this back in the day, and it was worth a decent amount of power, but it will still be slightly less than a factory 383 hp due to the camshaft difference.

If it is a 383 2bbl with single exhaust, and you want to do something, I would suggest installing a dual exhaust with either factory hp manifolds, or 1 5/8 tube headers.  Often times, old exhaust systems will suck performance out of a car and simply replacing them, even like-in-kind, will restore some power.

[MagnumForce]

I say go for it, the 4 barrel setup with 4:10's in the rear will give the car plenty of low end muscle!