intake and carburator?

[euroZ06]

Hi,

I have a perfectly running 68 with 383. I bought the car already restored, and have been enjoying it for about a year. The car drives well, and starts right up. All seems to work very well! However, I would like for it to be a bit faster/more power.

I have stock gearing in the diff, so I want to find some 3.55 gears with 489 case, but that's a challenge. I found some shop that is selling 741 case with 3.55's with a clutch type sure grip (used) for $750, which seems steep and plus is not the right case... I heard 741's are weak.

I really like the stock look under the hood (stock headers, stock air box), so I was thinking of maybe upgrading the intake and the carburetor. Now, i'm not techy, and finding a shop that does work on these is proven to be very difficult here in NYC. So, here are my main questions. A. Which intake and carb combo should I go for, for some power? Engine is stock. B. do carburetors come pre-set, or would I need to tune the car after installation? might sound easy to some, but to me getting the car to run right, sounds like a nighmare... considering now it runs perfect.

I have thought about headers... but can I just swap in headers with a stock exhaust system to gain power? If header is 3 inch and exhaust is 2.5, wouldn't it be worthless? If I do decide on the header, which one provides the best fitment? I know header fitment is a constant issue...

thank you for all the help and advice.

[Bad B-rad]

741 case  8 3/4 3rd members are not as strong as the 489/742, but they are not made of glass.They will take some abuse, but I think for about $200 more then that shop wants for the used one,you can get a rebuild 8 3/4 3rd member, in 489 or 742 with a new ring and pinion, in any ratio you want.
I would think there should be a few good shops in NYC.
Although NOT NYC, I know of two in Long Island that could do your work.

[Bad B-rad]

As far as carb and intake, would have to know what camshaft you have, and what you are trying to do with the car.
For a street car, I have had GREAT luck with the  Edelbrock Preformer RPM Intake manifold(and use the fel-pro valley tin with heat cross over blocked off)
I like it because it is a high-rise duel plane intake, and gives you the best of both worlds.
I also like edelbrock AVS carbs, because of the EASY quick adjust secondaries. But a good Holley with E-choke will also do, again for a street motor I would use a 750CFM for a 383, thats just me.
I am sure a lot of guys will have a lot of answeres as to what they like and what has worked for them.
But those are my picks, I have had great luck with them, I have also used the Mopar aluminum 4 BBl intake, and it works well, but it is just a copy of the cast iron unit, and the Edelbrock preformer Rpm, beats it everytime.

Now if you have an all out strip motor, then the Preformer Rpm, will not be for you.

Are you running a Magnum/Roadrunner cam?

[XH29N0G]

Some quick thoughts:

My guess is that changing the gears will make the biggest difference in response because the effect is basically torque multiplication 3.55/2.76 = 1.28 and this will behave like you are increasing torque by 28%. 

I think it would help to have an idea of what cam and compression you have (as mentioned above).   

There are a few articles that review intakes.  The one at this link is where I started http://www.hotrod.com/articles/hrdp-0712-mopar-intake-manifold-comparo/

The Performer RPM and some of the taller intakes will most likely not work with the stock air cleaner assembly.  I use one and have to use a significant drop base aircleaner for clearance.  I think there are tricks with the unsilenced 68 air cleaner assemblies (putting in a drop base and using the top, but you will have to do some digging.  For the 1970 air cleaners I had to do considerable modification and found it easier to use an aftermarket one. 

The jetting on the carburetors will need to be optimized.  Even out of the box, some are very lean. 

I have overcarbed an engine and even though it may have made more power up top, it was more sluggish down low.  I would think that could happen pretty easily with a 383.  If it were me, I would probably try a 650 or 750 double pumper, but I think the recommendation will be vac secondary for drivability.  What ignition do you have?  I found the MSD electronic has been very nice.  Carburetor types - I like quick fuel (Holley types), and have heard very good things about preform.  I know many others use edelbrock and like them.  I am not an expert so see what others say once you have size figured out, then figure out brand.

Headers will also require exhaust work.  If you go that route, get nice headers that fit.  I have some that were designed for a 440 and they hang very low, and would scrape.  I had to physically modify them.   

I know you mention you want to find a shop, I do not have any suggestions or know any in NYC, but I know you want to find someone you can work with.  There is nothing worse than getting someone who promises things and cannot deliver.  I had that issue once and now am much more careful about where I take my car.  I also decided to use the car as a learning experience.  Replacing the intake and carburetor are not difficult and there is satisfaction when you succeed.  It also can be a slippery slope.  I went carburetor, then intake.  Pretty soon, I was looking for heads, and then a cam, after that it was steering, etc....  I am not a mechanic, but have found it therapeutic when I work on it for hours and accomplish something.  When something breaks, well that is not therapeutic.

Good luck, and have fun.

[Bad B-rad]

Yes the Performer RPM is a bit tall.
The Mopar Aluminum 4BBl may be an option if you must keep stock air cleaner.
The other thing with headers, is some headers have issues with the trans throttle valve linkage(most convert to cable), so just make sure the shop you pick knows there Mopar stuff  or the project may run into a few unexpected bumps, and most of the time that means time, and money.
Also just based on it sounding like your 383, may be stock, or mildly built, I would do a vac 2nd, as XH29NOG said it is SO EASY to over carb a 383 street engine, and I just think you may be better off with vac 2nds.

[c00nhunterjoe]

If the engine is a bone stock restoration rebuild, it probably has 8:1 pistons in it. Unless you are planning on a total overhaul, almost all of your bolt ons will have negligent gains. I would almost bet it is a 250 hp 383. Doing a dp4b intake, 1 3/4 long tube headers, 650 holley, might get you to 275. A carefully selected cam could get it near 300. Not trying to bust your bubble, just saving the heartache after spending a grand (if you do the work)  and the car still only runs 14.10s at 95 mph.

[Challenger340]

Gears will help,
BUT forget the Headers, Intake & Carb, all the "bolt-ons" you want won't amount to squat extra power unless you change the Camshaft.

The Cam determines how much, and for how long the Valves are opened allowing Air/Fuel into the Cylinder. The more Air/Fuel you get in... the bigger the boom and more power. 
Highly doubtful any rebuilder stock type Camshaft supplies either enough Valve Lift or Duration to utilize the extra Fuel any newer/better 4 BBL Intake & Carb can provide.... let be even a 2 BBL !  if that's what's on there now ?

Think of the Camshaft as the "program" ?
You can Bolt on anything you want.... but unless the "program" itself changes.... it ain't going to do anything different ?

[Bad B-rad]

If the engine is a bone stock restoration rebuild, it probably has 8:1 pistons in it. Unless you are planning on a total overhaul, almost all of your bolt ons will have negligent gains. I would almost bet it is a 250 hp 383. Doing a dp4b intake, 1 3/4 long tube headers, 650 holley, might get you to 275. A carefully selected cam could get it near 300. Not trying to bust your bubble, just saving the heartache after spending a grand (if you do the work)  and the car still only runs 14.10s at 95 mph.

Correct!
I have noticed for years, that all the rebuild "KITS" have like 8.2:1 compresssion ratio, even thought they say STOCK rebuild kits.
I would think if you order a kit for a 67 383 2Bbl, that is should have 9.2:1 compression, and a camshaft that is a copy of the original.(that is stock for that year, that engine)
And a  rebuild kit for a 68 383 Roadrunner, should be  10:1 compression, and a RR/magnum camshaft,(again stock for that year, that motor) but it seams that no matter what year you ask for, they send you 1974 smog 8:1 compression ratio pistons?
Why do they do this?
It sucks cause SO MANY 383/440's have been rebuilt using these style kits, and then when they suck, you have a lot of people VERY disapointed, and it also starts to give the engines a bad reputation, as people think that thats how they should run.
WHY are the kits like that?


So without knowing the cam shaft and compression ratio, it is tough to give advice about going single plane, or duel plane, and what CFM carb, and so on.
So with out opening the engine, up you could take the car to the track, and if you can run it a few times, knowing the gear ratio, and weight of car, size of the engine the 1/4 mile time can tell you a few things about the engine, and with that info, some guys here could tell you about what the aprox hp is.

SIDE NOTE:I have used Keith Black pistons(kb237) for my last few builds, but I used reconditioned stock 452 heads from Indy(areohead).
And I have read the Speed pro 440 6pack pistons are a good choice for a stock build, that they are the same weight, and compression ratio as stock.
Basicly they are what any piston in a stock rebuild kit should be, new pistons that restore your engine to stock specs.

[justcruisin]

The KB237 have a compression height of 2.067, if you are talking about a stock rebuild, most factory pistons fell well short of that, even the 440 magnum had a piston with a height of only 1.990" that was something like .090" in the hole, giving it somewhere around 8.8:1, (not the 9.75 advertised) although the 6 pack was around the 2.065 mark.
If you want to kill an engine from the get go, just use a rebuilder kit.

If you want some more power, best way is to pull a head and see what you have and go from there, anything without compression is going to be a compromise - NA anyway.

[Bad B-rad]

The KB237 have a compression height of 2.067, if you are talking about a stock rebuild, most factory pistons fell well short of that, even the 440 magnum had a piston with a height of only 1.990" that was something like .090" in the hole, giving it somewhere around 8.8:1, (not the 9.75 advertised) although the 6 pack was around the 2.065 mark.
If you want to kill an engine from the get go, just use a rebuilder kit.

If you want some more power, best way is to pull a head and see what you have and go from there, anything without compression is going to be a compromise - NA anyway.

I was just saying that I use the KB237 to get to a true 9.5 to 10 to one (depending on head CC size, head gasket and so on ) Vs the rebuilder 8.2 kits.
I found the KB piston a good value, and gets you good compression for todays gas.


At age 17 I got my FIRST running 440 engine, I was so stoked, I slapped it into a 1974 Charger, and couldn't wait to thrash it.(in 1997)
Well lets just say, I was very disappointed.
I ran very well, but it wasn't all that fast.
I had a 68 Coronet with the #'s 318(factory estimated 230HP 9.2 to 1 compression) that felt just as fast.
The 74 Charger with my new 440 came off the line slow, but around 35-40MPH the power would start to come on.
Well come to find out my first 440 was a 1974 truck motor. Factory estimated 235HP and 8.2:1 compression.

So at 17 years of age, I learned that on paper the 318's 230HP vs the 440's 235HP was because of compression, but also what the two engines felt like in real life, with the lower compression of the 440.
So I clearly understood what lowering the comprssion ratio would do to an engine, and I knew to go with at least a 9.5 to one CR in any engine I was to build,LOL!



So your saying that REAL 100% stock 68-70 440 Magnums,advertised 10.1 to 1(68-69) and 9.7:1(70) is not what they really were?(compression ratio wise?)How off were the factory engines vs what they claimed to be, and why would they claim a 10.1:1 CR and have a true 9.6:1???
I can understand the HP estimate being off, but why would they fib the CR number?

[c00nhunterjoe]

No, the real oe engines were advertised correct. But remember, they used a steel shim gasket, not the typical .041 thick felpro gasket that comes in the rebuilder kits. And those kits and most generic pistons use the nhra drag race correction numbers that account for head and block milling to achieve the numbers. The aftermarket stock replacements are not the same piston as the oe.

[BSB67]

If the engine is a bone stock restoration rebuild, it probably has 8:1 pistons in it. Unless you are planning on a total overhaul, almost all of your bolt ons will have negligent gains. I would almost bet it is a 250 hp 383. Doing a dp4b intake, 1 3/4 long tube headers, 650 holley, might get you to 275. A carefully selected cam could get it near 300. Not trying to bust your bubble, just saving the heartache after spending a grand (if you do the work)  and the car still only runs 14.10s at 95 mph.

This is spot on.

But if you want to play around and have some fun, I would go std Performer or DP4B and a 750 AVS style Eddy, or a 750 Holley style DP

[BSB67]

.....the real oe engines were advertised correct.

Usually not, but there are exceptions.

[BSB67]

Don't really understand  the 440 piston discussion.

[Bad B-rad]

No, the real oe engines were advertised correct. But remember, they used a steel shim gasket, not the typical .041 thick felpro gasket that comes in the rebuilder kits. And those kits and most generic pistons use the nhra drag race correction numbers that account for head and block milling to achieve the numbers. The aftermarket stock replacements are not the same piston as the oe.

SO the factory rating is correct?
Either way I have also been using the steel shim head gasket, Mopar has them CHEAPER then the felpro ones!!!!
I actually bought two extra sets when I put rebuilt heads on my stock 383.

No doubt the "rebuilder" pistons are low compression but why?

[BSB67]

I just plugged in several factory combos and they range from about 9.5 to 9.7:1,  66bl was about 9.8:1.  That is assuming a factory original head volume of 86cc, but most believe that were never that low, but instead 88.

I don't know why they either never made them, or stopped making long, long ago.  Although arguably, you can get to where ever you want with your CR with a little planning.  But I agree, it would not cost any more to make pistons for 383s, 400s, and 440s with decent CR with the available heads in put them in those kits.

[justcruisin]

70/71 magnums came it at around 8.8:1  -  6.768 + 1.875 + 1.991, 88cc chambers .020" gasket. Almost a full point off the 9.7 claimed.

[Challenger340]

The KB237 have a compression height of 2.067, if you are talking about a stock rebuild, most factory pistons fell well short of that, even the 440 magnum had a piston with a height of only 1.990" that was something like .090" in the hole, giving it somewhere around 8.8:1, (not the 9.75 advertised) although the 6 pack was around the 2.065 mark.

The '68 / '69 factory 440 Magnum Piston had a Compression Distance of 2.035" (not 1.99"), about .050" - .060" down hole @ TDC depending upon final Block Deck Height, with most blocks usually above 10.72"
and,
that's typically what accounted for much of the confusion around real world Compression Ratios ?
because we've seen factory original Blocks as high as 10.735", right down to 10.715", but typically the majority fall .005"+ above 10.72".

The actual factory correct 1968/69 2.035" Cast Flat Top Piston has never been offered in the aftermarket, anywhere, at any time, that I have seen.

And while most BB open chamber heads CC right around 88 CC's, these are usually after being run for many years and with some V/Seat recession as they pound themselves UP into the chamber over time ?
If you can find original low mile castings with nice high seats, and the V/Tips are also maintained on the low end at 1.935".... meaning the Valves are nice and high in the chamber with a thick margin, it was NOT uncommon back in the 70's to see 84-85 CC's even as low as 83 CC's on 906's with NO milling.
Every .010" height you sink a 2.08" Intake valve is .56 CC
Every .010" height you sink a 1.74" Exhaust valve is .39 CC

At 2.4 CC's per .010"
If using an actual 10.72" Block:
* the 2.035" Piston would be .050" down at TDC, or 5 X 2.4 = 12 CC's
* the .020" steel shim Head Gasket would yield 2 X 2.4 = ~5 CC's (easier math)
* the factory 906 Heads(un-run new condition) at 84 CC's (High Factory Seats)
_____________________________________________________________
             Clrc Volume is right around 101 CC's or right about 10:1

Now think about rebuilding/pulling the the Heads, and replacing the ~.020" Steel Shim Head Gasket, with a Composition style Head Gasket which many do at .040", add another ~5 CC's ? an immediate drop to 9.6:1 C.R.
and,
adding rebuilt Heads at 86 ? 87 ? 88 ?

I have NO IDEA why the factory 68/69 2.035" Compression Distance Piston has never been offered in any of the rebuilder offerings, especially since MOST who are rebuilding also seem to use a Composition Head Gasket supplied in the "Kits" which adds ~5 CC's  and lowers the Compression ratio anyways ?
When I've had this conversation with manufacturers ? and done the "math" with them on the phone/email....
Their answer has invariably always been "because the 1.91" and 1.99" offerings still sell, so why change" ?
Once upon a time....
I've even looked at getting a batch of factory correct '68/'69 2.035" pistons made ? But who the heck wants to warehouse/stock and try and resell 60 sets of Cast Stock Pistons these days ?

[Challenger340]

I just plugged in several factory combos and they range from about 9.5 to 9.7:1,  66bl was about 9.8:1.  That is assuming a factory original head volume of 86cc, but most believe that were never that low, but instead 88.

I don't know why they either never made them, or stopped making long, long ago.  Although arguably, you can get to where ever you want with your CR with a little planning.  But I agree, it would not cost any more to make pistons for 383s, 400s, and 440s with decent CR with the available heads in put them in those kits.

When "new" with nice thick Valve Margins, and very low-mile V/Seats "high" in the Chamber.....
I've seen them as low as 83-84 CC's "back in the day" (70's) at the dealership, which I took home(with permission) because the warranty engines cam complete with no core exchange when rods went through the side of the Blocks.
But,
I believe for the majority you're correct around 85-86 CC's or even higher from factory depending upon final V/Seat depth.

I think the NHRA minimum legal spec back then for a 906 Head was 79.5 CC's, and for the 915 it was 73.5 CC's ? so we bought a Burette and were always checking, so we could MILL them down to that...... then do the Intakes... one thing led to another... more & more equipment to do what we needed, pretty soon a guys gotta PAY for all that stuff he's acquiring and your hobby becomes a JOB.

[Bad B-rad]

Challenger340 just dropped some knowledge on me!!

I get what your saying about who would want to stock all those cast pistons today(if someone were to make a cast replacement piston that would give correct factory compression ratio, and correct weight.
But THEY WOULD SELL!!!!
As long as people KNEW the difference.
Who in there right mind would want to take a 440CI/375 HP 480Ftlbs tq motor and rebuild it to 230HP, 300FT lbs tq?
No one.
And if so, order a 1974 440 kit, then bam you got your 230HP Motor.
I am sure there is a bunch of pepole who dont know any better, and want to save some cash, and rebuild the engine themselves.
I also bet 95% of those people would spend the extra money on a piston if they were told they would lose 100-150HP by using pistons that are not factory correct.


Or maybe go a step higher, and go with forged replacement pistons to give correct, CR, and close to correct Weight, so a guy wont have to have the engine ballenced.


I also never under stood the use of composite Fel-Pro head gasket, unless to lower CR.
Would you use that maybe if the deck, and head were not in ideal shape?
I could see maybe the added material helping conform to irregular surface, maybe a touch more them Mopar steel shim. 

[Bad B-rad]

I know its off topic, but the crappy "rebuilder" pistons are why I have gone with just a re-ring/ re-bearing job on a few 383's.
I didnt have a ton of cash to spend on them and I didnt want to de-tune the motor with a 2 point CR drop.
So I just gave them the farmers special.

[Challenger340]

That's why the L2355F Piston is so popular, because at 2.067" CD and the 7 CC Flycuts, if a guy just "squares" the Block anywhere around 10.71" height, it yields right around low/mid 9's C.R. with a composition gasket.

Everyone likes to talk "Horsepower", as is the most prevalent mindset to speed ? With Horsepower being related to Air Flow @ RPM.

But it's not the "horsepower" you are killing with the low pop rebuilder Pistons, so much as the Ft/Lbs Torque, which really is what you "feel" seat of the pants and moves the Car.
It was the 480 Ft/Lbs Torque from factory originally that made these things respectable, in conjunction with the "advertised" 375 hp @ 4,800 rpm.

We've seen 535 Ft/Lbs and 479 HP @ 5,000 rpm using the L2355's and a XE284H Cam using UN-touched OOTB Stealth Heads... and I mean UN-touched other than check the guides/springs, mill correct to 80 CC's for 10.3:1 C.R. and re-assemble, installed on a .005" down decked Block.
Stock LY Rods W/ARP Bolts
Stock Stamped Steel Rockers & Pushrods
The last guy on a budget we did one of those for LOVES IT ! He just leaves it in "D" and let's it shift all by itself at 4,800-5,000, and you would be surprised at just how "quick" the dam thing is with 3.55's and an 11" Converter !

[heyoldguy]

"I have a perfectly running 68 with 383."

Hmmm. If it ain't broke, don't fix it.

[heyoldguy]

Double post, go figure. Then maybe I really want to make this point. Dunno.

[BSB67]

Still don't understand the 440 piston discussion.  The OP has a 383.

But if we must.  The 68/69 piston has little to nothing to offer worthwhile to the knowledgeable performance enthusiast.  Cant get to zero deck for use with closed chamber heads, and will still detonate with open chamber heads unless you put a big cam in.  No valve notches.  I have a set of +0.030"NHRA approved 68/69 pistons (1.033 - 1.034" CH) in excellent shape.  Tried to sell them.  No one was interested.