Maximum RPM?
- Thread starter JJRJR
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JJRJR said:
Stomp it.
Listen for valve float.
Grab the next gear.
:drive: 
Big John
Sit back, relax Don't bitch about the cigar smoke
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Well... it gets complicated, but with a big block Mopar, the heads don't breathe well enough at high RPM to make power.
You're safe keeping your engine RPM under 6000, and honestly you may even run quicker shifting it at lower RPM.
You're safe keeping your engine RPM under 6000, and honestly you may even run quicker shifting it at lower RPM.
JJRJR said:
Okay, a more serious approach...
First question is best discussed with your engine builder. If he's worth his salt he'll be able to give you a fairly accurate assessment based on the internals that he has installed. You're probably fairly safe asking this question on this site as we really don't have any loud mouths that rush to answer theses types of questions but aren't truly qualified, but generally speaking soliciting this type of info on an internet forum will only help you in perforating your freshly machined engine block. Talk to your engine builder.
Second question - Chrysler wedges are excellently designed engines; deep skirts provide a robust home for the reciprocating assembly. 383s have huge bores and short strokes (only marginally longer than a 340 in case you did not know) so they twist up quickly. The hydraulic lifters, stamped steel rockers, soft valve springs, and stock cam profile are the limiting factors here. Probably no need to twist a stone stock 383 above 5,800-6,000. You've already reached the point of diminishing returns by that point.
Third question - Absolutely! Which is why I started my answer to your second question the way that I did. Upgrade the aforementioned components and you're now turning 7,000 if needed. Your cam/intake/carb/head/piston (compression ratio) combination will dictate what the best shift point will be; just because you can twist it to a higher point doesn't mean that there is necessarily any benefit in doing so. It all depends on your engine combo - which brings us back to my first answer: Talk to your engine builder.
Ray
Thanks Ray, great answer. I will speak with him. Now that I've decided to go with 3.91's I was just concerned with highway driving. I guess these motors, built correctly, can do 4,000 all day long on the highway, or do I need to be concerned that I'll be turning about 3,300 at 70 mph on 28 inch tires? I have no plans for this car to see much highway driving, but sure don't want to be concerned with busting up the engine if I want to pump it up to 100 mph or so every now and again.
John
John
JJRJR said:
I think this answer comes down to personal preference; I prefer not to cruise at above 3,000 for extended periods. Short blasts are not a concern. Others will chime in. Let's see what they say...
george68hemirr
I think you guys are full of shit.
when she is all done take her on a dyno.......the guy will see on his laptop when she loses horsepower at a certain rpm.....thats your shifting point 
sixgunrunner68
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I'm with Ray on this.ACME A12 said:
Three grand starts to drone on me after about ten miles or so and I'm only at 60 mph. I enjoy the acceleration factor so keeping to the back roads where I can lace into it then cruise at 45mph all day is cool. It's not a question of reliability just your own sanity.
Just be sure of what you want. Of course you can have the best of both worlds with some form of overdrive but it's another check to cut.
V269
Well-Known Member
I have a basicly stock 383 outside of an after market intake,750 dp holley carb and headers. I also have a 4-speed with 3.91 gears. This set up work's very well and I can drive it at highway speed's with no problem's. Step her up to 80,90, or even 100 mph very quickly with out issue at all. Not that I drive at this speed for long but It is easily done. Dump the clutch off the line hold it to the floor and ram gears all I want. The 383 takes it. Period. You don't need to over rev it to go fast but I have never hurt mine flooring it through the gears. :banana: 
69hemibeep
Sponge Bob Square Wheels
Never mind I was going to be a smart A$$ :leave:
sixgunrunner68
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Please, by all means. Let her rip.69hemibeep said:
mcmopar
Well-Known Member
Not a problem at 3000 rpm for me even with tti headers and 3" Magnaflow mufflers. Sounds downright mean! I cruised up to Columbus, OH from Orlando back in 2005 for the Mopar Nats and had no problems running 3200 rpm for hours at a time. It depends on your exhaust setup how bad or even if there is a droning noise. I had a '71 Charger SE with a 440, auto, 3.55 gears, stock exhaust manifolds, 2-1/4" pipe and Cherry Bomb turbos. The thing would drone so bad at 40 mph it made you want to use earplugs! My runner with the hot 383, tti headers, 3" dia. exhaust pipes and Magnaflow mufflers doesn't drone anywhere near as bad. Is it loud? Not too bad but it is louder than a stock setup. It sounds great at speed (60-75 mph) and I can still hear my stereo.
Roadcuda
Well-Known Member
Yeah, go ahead! What makes this time any different?sixgunrunner68 said:
ot:
69hemibeep
Sponge Bob Square Wheels
OK. Mine makes good power to 7000 and want's to keep going :jester:Roadcuda said:Yeah, go ahead! What makes this time any different?sixgunrunner68 said:
69hemibeep said:
You have a SLIGHTLY different head design than what he has...
moparchris
Well-Known Member
Rev it till the rods fall out then back it off 50 rpm.
No seriously, rev it till the limiter says no.
okay seriously, rev it.....oh nevermind.
All kidding aside. Your motor will let you know when its time to shift. You will fel it nose over when its done. If you put good parts in the bottom end then you will not exceed the liits of those parts, the motor will quit making power and you will know. One thing that is very serious. I built a 440 CI motor for a friend and it made 500hp 500lb/ft peak hp was in the 6000s and it ran great. The problem is that guys will run them hard on the freeway and pump precious oil up into the motor with a high volume pump and near stock capacity oil pan. The results are catastrophic. So keep that in mind when you grab some guys Lambo by the short hairs.
Okay 3.91s. I love when people say 3.91s aren't liveable. First off they came stock in Mopars. Dont you think that the drive train engineers ran those things for as fast as they would go for hours on end at the proving grounds to make sure that their piece wouldn't break prematurely? Read that as warranty protection. Secondly the difference between 3.23s and 3.91 is 15% or 450 rpm. At 3000 do you really think the motor cares about 450 rpm. The short answer is no. Thats why I laugh at guys who have to have od. Five grand for overdrive is ridiculous, it should run and drive be currently registered for 5 grand. So my opinion, for what its worth, is the 3.91s are a totally great gear and make a great contribution to a short stroke motor like the 383.
No seriously, rev it till the limiter says no.
okay seriously, rev it.....oh nevermind.
All kidding aside. Your motor will let you know when its time to shift. You will fel it nose over when its done. If you put good parts in the bottom end then you will not exceed the liits of those parts, the motor will quit making power and you will know. One thing that is very serious. I built a 440 CI motor for a friend and it made 500hp 500lb/ft peak hp was in the 6000s and it ran great. The problem is that guys will run them hard on the freeway and pump precious oil up into the motor with a high volume pump and near stock capacity oil pan. The results are catastrophic. So keep that in mind when you grab some guys Lambo by the short hairs.
Okay 3.91s. I love when people say 3.91s aren't liveable. First off they came stock in Mopars. Dont you think that the drive train engineers ran those things for as fast as they would go for hours on end at the proving grounds to make sure that their piece wouldn't break prematurely? Read that as warranty protection. Secondly the difference between 3.23s and 3.91 is 15% or 450 rpm. At 3000 do you really think the motor cares about 450 rpm. The short answer is no. Thats why I laugh at guys who have to have od. Five grand for overdrive is ridiculous, it should run and drive be currently registered for 5 grand.
So my opinion, for what its worth, is the 3.91s are a totally great gear and make a great contribution to a short stroke motor like the 383.
69hemibeep
Sponge Bob Square Wheels
You punctuated nicely :basketcase:moparchris said:Rev it till the rods fall out then back it off 50 rpm.
No seriously, rev it till the limiter says no.
okay seriously, rev it.....oh nevermind.
All kidding aside. Your motor will let you know when its time to shift. You will fel it nose over when its done. If you put good parts in the bottom end then you will not exceed the liits of those parts, the motor will quit making power and you will know. One thing that is very serious. I built a 440 CI motor for a friend and it made 500hp 500lb/ft peak hp was in the 6000s and it ran great. The problem is that guys will run them hard on the freeway and pump precious oil up into the motor with a high volume pump and near stock capacity oil pan. The results are catastrophic. So keep that in mind when you grab some guys Lambo by the short hairs.
Okay 3.91s. I love when people say 3.91s aren't liveable. First off they came stock in Mopars. Dont you think that the drive train engineers ran those things for as fast as they would go for hours on end at the proving grounds to make sure that their piece wouldn't break prematurely? Read that as warranty protection. Secondly the difference between 3.23s and 3.91 is 15% or 450 rpm. At 3000 do you really think the motor cares about 450 rpm. The short answer is no. Thats why I laugh at guys who have to have od. Five grand for overdrive is ridiculous, it should run and drive be currently registered for 5 grand.
BBillyC
Well-Known Member
I'm running 4.10's with a 28.5" tire which the 383 really likes. Prior to that with the stock tire it ran 3500 rpm on the highway and the drone was unbearable. Now it sings at around 3 grand. This year I will either be putting a hemi in the bird or at minimum going to aluminum heads and solid lifters due to the 12.5 to 1 comp ratio. I've cranked it to 6K with no issues but the stock heads and valve train get overworked with the comp cam XE 285. The engine winds up really quick and breaks the tires loose with no problem. I can't wait for spring to arrive in 3 months.
george68hemirr
I think you guys are full of shit.
HEMI"S RULE.....BILLY MAKE SURE YOU GET THE BIG VALVE HEADS....2.40 INTAKE AND 1.94EXHAUST......GET THEM COMP PORT AND POLISHED AND FLOWED.....FORHEMISONLY DOES EXCELLENT WORK.......RACE GAS....I CAN SMELL THE MONEY NOWBBillyC said: