RPM for a stock 1973 318 with a 430 inch cam?

General Mopar Tech Discussions

  1. mopar73dge

    mopar73dge Well-Known Member

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    no longer available
     
    Last edited: Aug 16, 2019 at 1:08 PM
  2. yella71

    yella71 Well-Known Member

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    ok here goes.....maximum RPM is just before it kicks a rod out the side of the block. Is that what you were looking for?
     
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    • Ron H

      Ron H FBBO Gold Member FBBO Gold Member

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      So all the motor had 'done' was the cam? Shoulda been some other mods/machining done to accept the cam; but no clue as to the cam over stock..
       
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      • BeatersRus

        BeatersRus Well-Known Member

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        ty to the mod.

        to the op,we would need more info,cam size compression ratio etc etc.
        are they factory rockers,or aftermarket,etc etc.
        id say safe limits are 52-5500 rpm.
        screaming at 5k at around 70 in 2cnd sounds about right.
        make sure your kickdown is adjusted properly.
         
        Last edited: Aug 16, 2019 at 2:18 PM
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        • mopar73dge

          mopar73dge Well-Known Member

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          Bored 30 over all stock valve springs etc. FBO IGNITION SYSTEM. thanks
           
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          • Cranky

            Cranky Moderator Staff Member FBBO Gold Member

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            Here's a combo with a 72 teen with 115k miles on it. .480 lift cam, MP springs rated for them but don't remember the number, heavy MP rockers, headers and associated parts to help it go 13.50 @ 102 mph shifting at 6200. It hasn't come apart....yet. Bottom end is stock and probably has 116k miles on it by now. But like BR said, 'safe' limits are probably no more than 5500 if you want it to live for awhile.
             
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            • 69a100

              69a100 Well-Known Member

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              I'm sooooooooooooooooooo confused here? I take cranky is quoting something you said at one time here? How can a stock motor be bored .30 over? You may have stock type parts in your motor now, but it sounds like it's a rebuilt motor to me, therefore it's not stock from what I'm reading, even with the FBO ignition! I forgot my question. REV it until it explodes, then you'll have your answer! Good Luck!
               
            • 68Moparmaniac

              68Moparmaniac Well-Known Member

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              :rofl:
              Seriously, I think Cranky is pretty close to the RPM range of a stock motor w/aftermarket cam without knowing exactly what you have spinning around inside, induction/ exhaust/ ignition etc. all plays a roll. Engines that are able to live up in the higher RPM ranges have had extensive precision balancing work done, way above the basic balancing done at the factory.. some engines from the factory were better than others. Yella71 has a profound opinion that rings true, just sayin.
               
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              • Darter6

                Darter6 FBBO Gold Member FBBO Gold Member

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                Cranky is right, One thing is rpm is judged by the quality of your valve springs. If the valve springs are factory stock, that 4800 rpm is just about where the stock springs will float the valves.
                 
                Last edited: Aug 16, 2019 at 2:18 PM
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                • mopar73dge

                  mopar73dge Well-Known Member

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                  I meant 030 over and I am learning a lot about people good luck
                   
                • Cranky

                  Cranky Moderator Staff Member FBBO Gold Member

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                  No, wasn't quoting anything he said at one time. Was just saying what a buddy and I did with a teen with better springs, HD rockers etc. And many write .30 over for .030 over. Not everyone is a machinist or knows decimals all that well or just don't think of adding a '0'. And things can be stock or nearly stock even if it's bored over and have an aftermarket ignition. It may not be pure stock but nearly stock. Does everyone have to be so literal....and nitpicky?
                   
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                  • BeatersRus

                    BeatersRus Well-Known Member

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                    im wondering why you have stock valvespings with the new cam?
                    am i the only one?
                    also,with a stock valvetrain,
                    you are likely going to run into valve float before you reach max rpm.
                     
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                    • Cranky

                      Cranky Moderator Staff Member FBBO Gold Member

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                      ???
                       
                    • 1967coronet

                      1967coronet FBBO Gold Member FBBO Gold Member

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                      I may be the only one here that thinks stock Mopar springs in good shape should be ok on a .430 lift cam.
                      Im no expert at all but that cant be to much more lift than a stock 340 spec /style mopar cam.

                      Rpms I would say 5000/5500 also , its prob just making noise instead of power at that point anyway.
                       
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                      • yella71

                        yella71 Well-Known Member

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                        stock 318 springs are not the same as stock 340 springs. 340 springs are higher rate springs. your thoughts are not far off the mark tho as a 430 lift cam if its just a mild hydro is not very aggressive. but if the best performance is what your after the springs need to match the cam specs. why any one hotrods a 318 is beyond me, especialy with 318 heads. the small port will cut off air flow at a low RPM . I guess I just think things out first then get the right stuff to have the results im after. if your after power you need parts that will make power. seems like a waste of time messing with stuff that will only make limited power beyond their capability
                         
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                        • Cranky

                          Cranky Moderator Staff Member FBBO Gold Member

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                          In our case we were just messing around with junk that we both had laying around our garages. The teen was still in good shape and pulled down even numbers after a compression check so we started throwing stuff at it. We weren't planning on doing a pocket job to the 360 heads...which only lowers CR on a teen. The combination of parts were way off and the converter was still stock but the engine responded well. Everyone that came by our pit area asked if it was a 340 or a 360 and none of them believe it was a teen but no one wanted to lay any money on the fender to see. Thing is, it's easy to look at the numbers on the block lol. The car was pretty dead off the line cutting a 2.2 60 foot but it started pulling really hard at 3000 on up. Surprised both of us! People always say that there's no replacement for displacement but you can make a little engine think it's bigger just by flowing more air through it. There are still a lot of racers in Comp Eliminator running crazy sounding numbers with even crazier little engines. My first introduction into the itty bitty engine committee was from a guy at work that was running a 56 all steel shoebox Chevy with a 265 launching at 9k and shifting at 9500! The car was running low 11's back in the mid 80's in SS/O. IIRC, he and his buddy were trying to not run faster than 11.50's or 60's so they didn't CIC'ed in competition. They were also running a 5 speed but could only use 3 gears according to the rules at the time.
                           
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                          • yella71

                            yella71 Well-Known Member

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                            Ok Ill go with that If its free its for me. Im not saying you cant make power with small cubes just you need to move air through it. like you said fool it into thinking its bigger. If you put heads with bigger ports that helps but compression is key. its nice to see you know that just putting 360 heads on will drop compression. what is needed is big ports small chamber and as said LOTS of RPM. Oh and lots of money. get some gears in the rear and some tighter valve springs so you can rev that teen to 6500 or better then run it some more
                             
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                            • 69a100

                              69a100 Well-Known Member

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                              You want to play semantics? We can play semantics all day long! In the end there's a BIG difference between factory stock and rebuilt, or even "rebuilt" stock for that matter, they're not the same!!!! Never have and never will!
                               
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                              • Cranky

                                Cranky Moderator Staff Member FBBO Gold Member

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                                Got it going 13.80 with 4.10's on ET streets but it was spinning them when it hit 2nd. Couldn't heat them up since the car didn't have ANY low end lol....so, I had a pair of 29" slicks but that would kill the 4.10's so in went a 4.88 and that's when the 13.50 popped up. The car was crossing around 5200 with the 4.10's anyways. Yeah, we knew the 360 heads would lower the CR but that's all we hand and he didn't want to spend time on a 318 head and the 360 heads would eventually find their way onto a 340.
                                 
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                                • Cranky

                                  Cranky Moderator Staff Member FBBO Gold Member

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                                  If you think I'm playing....that's fine, but I'm no purist either. Rebuilt to stock specs even with an overbore.......rebuilt stock to me. Now rebuilt with highly modified stock heads isn't stock to me anymore.
                                   
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