Cam intake closing importance

Small Block Mopar Engine

  1. boilermaker

    boilermaker Well-Known Member

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    Hello all.
    Running 318,30 over, KB 167 0 deck, stock length rods, stock crank (3500 miles on short block). Edelbrock 60779 heads ( not ported). 1.6 rocker arms compression ratio at 9.8:1. I was running a Mopar p#p4120653 “528” solid flat tappet cam ( it was on the shelf).
    Pumping hot averages 135 to 140 psi. Intake valve closes at 72 deg.
    Engine has put the car at 13.0sec with 3.91,28” tire at 105mph. 60 ft average 1.88. Running a 3200 stall.
    The dynamic compression works out to 6.41 ( 528 cam). I need to run engine to 7200 rpm shift points to get the job done in the 1/4 mile.
    I’m going to use a hydraulic roller . The cam from Hughes is looking to close intake at 39 degrees. What effect does the early valve close have on cylinder filling vs the 72 degrees from the old “528” cam.
    I want to select the best of my options. Most calculators online suggests 8.5 dynamic. Is this not going to limit max cylinder filling ( roller)? Last thing I need is to go backwards with a new cam selection.
    Any help is very much appreciated.
    Thanks,
    John
     
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    • Phreakish

      Phreakish Well-Known Member

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      The 72 and 39 degree figures are not comparable. Hughes only lists @.050 figures. The 72 degrees on your MP cam card is likely at a much lower lift figure.
       
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      • yellow rose

        yellow rose Doctor of Thinkology.

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        Did you degree the cam? If not, you have no idea what you have and changing the cam probably won't do a thing.



        Edit: I would never use a hydraulic lifter. If you want to run a solid roller on a HR lobe that's ok. But hydraulic lifters are just not worth the effort.
         
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        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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          And I would never stick a roller in there,lol
          But you really need to bring the compression up to match whatever cam you put in there so you don't need to rev so high. I mean 7200 is crazy, so they tell me.lol, especially with that 528cam
          In your teener it probably power peaks at around 5600, maybe a lil earlier. So that calls for a shift rpm of maybe 6000 with the Eddies, unless yur like me

          I would put another faster solid-lifter flatie in there , but I would first take a buncha ccs outta the heads, or outta something. Those Eddies will take 185 and more psi all day long.
          But by this time , wait for it,
          it might be cheaper to have more cubes.
          In defense of the 318, 105 is pretty doggone good

          Also that 528 cam looks real fine; it just needs a heckuva lot more compression.
          That's advertised to be 284/284/112/60 overlap/241@.050/ lash of 28/32
           
          Last edited: Dec 4, 2019
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          • TripleL

            TripleL Active Member

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            Do you have any links on how these different cams function. I have looked around and cant find anything that explains the difference
             
          • forphorty

            forphorty Well-Known Member

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            At 105 mph, you should be running mid 12s. 3200 is not much stall for a 318 with a .528. As YR asked, did you degree the cam? If'n'itwereme, I would keep the cam, port the heads and add a 4500 converter. I'm assuming you have sticky tires. If so, I bet converter change, bowl blend and possibly ICL change would get you low 12s.
             
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            • boilermaker

              boilermaker Well-Known Member

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              60 ft is soggy. 1.88-1.90 .
              If I can create more pumping compression at a lower rpm then the 105 would be my 12.50 ( more torque).
              I know small engines don’t make big torque but I do like the challenge of small displacement .
              The car is street driven , I’m not sure on the higher stall. Leaving at 3000 rpm with ET streets.
               
            • Wyrmrider

              Wyrmrider Well-Known Member

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              318 with those heads should work fine without new pistons- the flow will fill the cylinder but let's do consider milling them (and maybe some pocket port clean up and opening up around the valves
              How did you get 1.6 rockers? If roller tip go to the http://www.b3racingengines.com/techcorner.asp website and read all 4 tech articles if you want stability and long life from your valvetrain at that rpm
              forget Hughes or any brand for the moment
              do you own this 528 cam? (which by itself means little)
              Figure on solid flat tappet for now if you need to change
              can you get the duration .004 or .006 on the 528 cam
              let's get your current cam working best before spending dollars
              what gas do you want to run?
              what's your quench clearance
              what head gaskets?
              you want to see how advancing current cam by 4 degrees makes in any difference
              and retarded (would like putting in a longer cam) If it dies you know you went the wrong way without spending any money
               
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              • AJ/FormS

                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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                It's really hard to build compression with a 318; there's just not enough swept volume. You said you were at 9.8 right? Well at stock bore/stroke that makes a total chamber volume of 74cc. The heads are 63, and the pistons are 5 and the decks are zero, leaving 6 in the gasket and there's no place to go.
                That 284 cam is wanting 11.8 Scr to come in at 182psi at your stated Ica of 72*. To get there the Total chamber volume has to be reduced to 60.4cc. Where-O-where are you find 13.6cc? You'd have to cut your 60779s to 49.4cc, and then cut the intake side, and then new pushrods.
                EDIT; Or get some domed pistons, or some combination of cutting and dome-ing;credit to yellow rose and Rumble for catching that.
                The problem is the ~652cc swept volume.
                If you take that same 74cc total chamber volume and slide it over a 360 (737 swept), you get a 10.96 Scr, and instantly yur getting somewhere.
                If you slid a 3.58 stroke crank into a standard bore 318 you'd get a swept of 704cc and again sliding the 74 over that will get you 10.5scr
                If you stuck a 4.00 crank in her, you'd get 786.6 swept and 11.63Scr.
                Of course each crank will need zero-deck pistons.
                So the deal is that yur about topped out for Scr in your current combo. The 6cc gasket is about as thin as you can go for piston to head clearance. So you have about two choices, mill your heads or get you a faster ramp cam, and make it the fastest you can find, and follow the cam-grinders instructions to the T, as to springs lifters and redline.

                BUt I'm assuming that you when you said the Ica was 72*, that you actually measured it. Book math don't cut it when yur pressure is as low as yours, and you have a big mechanical cam.

                Lets back up the bus and work with the 9.8. At this Scr that engine wants an Ica of no more than 52* to make a predicted 176 psi. That's pretty small. That Ica comes actually on the factory 360 2bbl stick; that's how small it is. But hang on I got an Idea. What yur after is to keep the 241@.050 and the lift, but a shorter Ica. Well is that is doable? I don't think so but, let's see how close I can get..
                Here's the 284 cam
                284/284/112+2/60 overlap/108 comp(72*Ica)/84power/SFT/28/32
                Here is what I created on paper
                268/276/102+4/68 overlap/128 comp(52*ICA/116 power This cam is about the most screwed up cam you will ever see, but lets see what's wrong with it
                Well firstly, this is a hydraulic, so I haven't converted it to Solid yet, but ignoring that;
                Secondly the LSA is down to 102 which IMO, probably most opinions would say is too tight for an automatic, but hang on; What gear are you trapping in with those 3.91s to hit 7200? The math says it ain't third gear nor second. The math says you got 3.73s or a bum convertor, or a bum tach.
                The math says; 105 with 3.91s and 28s and a 2.45-1.45-1.00 trans, and 5% TC slip, comes to 7500/5200 in direct. But with 3.73s it would be 7160/4930
                So in either case, something is up.
                Here's the thing; if you are trapping in second then yur engine won't care about the 102LSA and in the mean time that 102LSA is creating a heckuva 64* Effective overlap, that I'm hoping will make a power difference, to close the gap between this lil 268 and the previous 284 which had an Effective overlap of 56*, by the spec, but after lashing less..
                So what else is wrong with it? Well about the fastest hydraulic ramps I have seen is 38* from advertised to .050 making the best possible scenario here of 230/238 @.050, about a size and half a size smaller than your earlier 241@.050 and these numbers speak to the power production. So that is gonna bring the power down 250 rpm, which might drop the power 17 hp. Now the increase in effective overlap may blow that out of the water. so we might have an absolute hp number that is extremely close between these cams.
                However, the 284 on it's 112 Lsa will make more power on either side of the power peak compared to the 268. However the 268 will make a boatload more power leading thru the midrange.I mean there is no comparison between 175psi that this 268 cam is predicted to make, and the feeble 135/140 you are measuring now.
                So with that in mind, this cam needs to be converted to an even faster ramped Solid, which would increase the .050s, and then I could spread the LSA, and, and.....and sometimes less is more.......
                If you are trapping in third gear well the rpm drop is to 69%, so if you shift that cam at 6000, the Rs will drop to 3540, which is 2460 rpm, which is a lot. I have no idea what that 268/102LSA /175psi cam would do with that, But I bet it's more than the 284/112LSA/137.5psi cam ever could.
                This is an exercise; I made the camspecs up.
                BTW if you noticed, the power stroke duration of this 268 cam is 116*, compared to 84* on the 284. furthermore the compression is 128* vs just 108* for the 284 cam.
                These two together, conspire to put this 268 cam into excellent fuel economy in steady state cruising, range.... compared to;lousy with the 284 cam.
                The totals tell the tale; 244 for the 268, which is excellent; vs 192 for the 284, which is lousy. Street cams are usually in the 230/234 range.

                Edit: it seems upon reviewing this post,I caught a calculator-error. The power duration of the 284 cam in at 110 (2* advanced) is not 84 degrees but rather 104*. This makes the Compression plus power total to be 212* not 192*, if anybody cares. But the more important conclusion is that this picks up the fuel economy out of the "lousy" zone, and into the "terrible" zone,lol. Otherwise this error affects nothing else.
                 
                Last edited: Dec 5, 2019
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                • yellow rose

                  yellow rose Doctor of Thinkology.

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                  Icon has a really cool domed 318 piston on the shelf for really cheap money. And it's a nice piston.

                  Can't remember if you can get it for the 3.313 stroke and the 4 inch stroke or just the 4 incher.
                   
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                  • rumblefish360

                    rumblefish360 So close, yet so far away

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                    KB has/had, IDK, a small dome slug for the 3.31 stroke.
                     
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                    • boilermaker

                      boilermaker Well-Known Member

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                      Thank you thank you!

                      This is exactly what I was looking for. Man I thought psychometric’s were fun. I have a lot of measuring to do .
                      Thank god it’s winter time.
                      Is there a “go to”online for a bit more depth on your math?

                      Thanks AJ
                       
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                      • rumblefish360

                        rumblefish360 So close, yet so far away

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                        • AJ/FormS

                          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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                          That 284/528 solid-lifter cam is about as big as anybody would ever want to run on the street and works great with matching compression and a manual trans. But on the street, with a 2.45 low gear and 28"tires, and 3.91s, Ima thinking that cam is not gonna like just 3200TC, but I guess we'll see, it kindof depends on your driving style and final Dcr.
                          I said your aluminum heads could run all day on 185psi, and that's true; But you don't have to run 185. You can run less, even down to iron compatible numbers. BUT it is my opinion that since they will run up there, and you spent a good bit of cash to get them,why settle for also-rans at 160psi, you can run iron on that. So you might as well get the most bang for your buck, and crank it up. The thing is; yur gonna need new pistons no matter what, so again, shoot for the 11.8Scr with your 72* ICA. But if your Ica is not 72*, then you gotta recalculate the Scr. Those two are practically married.or if you advance/retard that cam, you have to think about the consequences.

                          If you didn't already have the aluminum heads, there is no way you could run 185psi, and so then there is no way you could target 11.8 Scr. Yeah, it seems you can run more, there are a couple to several guys here on Fabo claiming 200psi, and i have no problem believing that, because my 367 has run on 87E10gas at up to 185psi, and full timing, at full load; indicating that I have at least two grades better gas ahead of me and that suggests 195 right away, with headroom.
                          Everything is all tied together.
                          If down the road you don't like that 284 cam and want to go smaller, well if you decrease the Ica to get there, the intake will close earlier, traping more mixture and the Cylinder pressure will rise and if you're not careful ,then you could get into detonation, So again,on this edgy combo, once all your parameters are chosen, they are more or less written in stone. You can go to a bigger cam with a later Ica, that will work... but you'll give up pressure. And if you think about it pressure is power. We pressurize the mixture, lite it off, and that multiplies the pressure. Then that pressure is applied to the crank and finally to the tires.
                          Everything is all tied together, and in this case, once you have made it into a race engine,like we're doing, there is never such a thing as just putting a smaller cam in it for street......unless you re-engineer the combo.
                           
                          Last edited: Dec 5, 2019
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                          • rumblefish360

                            rumblefish360 So close, yet so far away

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                            Thick head gaskets for the street with the smaller cam.
                            Comet if’s @ .100 should do it.
                             
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                            • Wyrmrider

                              Wyrmrider Well-Known Member

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                              great analysis AJ what lift are you using on the Advertized
                              is that 284 a MP/DC cam if so you need to convert the 284 @.008 to usual .006 or .004 or whatever the sim wants
                              I'd get the Controlled Induction software and play with it or contact you know who for cam timing suggestions
                              OP needs to pick the CR or CR choices first as cam will change big time
                              advancing the 284 cam as tradeoffs
                               
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                              • AJ/FormS

                                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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                                Thanks WR
                                I didn't even get into lift, on the study-cam, cuz it was just an exercise.

                                I was thinking you might pop in
                                The 284/284 cam, I'm guessing has two same pattern lobes on it, and moving it from straight up 0* advance only serves two purposes;
                                1) it trades compression duration for power duration,or vice-versa, which in this case is only 212* total, so there is not a lotta wiggle-room,maybe 6*,right; but
                                2) When you move it from straight up, the effective overlap instantly shrinks, which in my thinking is very bad.
                                 
                                Last edited: Dec 5, 2019
                              • roccodart440

                                roccodart440 Well-Known Member

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                                In contrast, I'd never run a flat tappet again. I agree with YR to run a solid as well.

                                However, AJ is probably right about peak power RPM. I'd have it dyno'd to find out the real numbers an where it's making those numbers. I've run that cam in a big block several times and they make peak HP between 5600-5800RPM.

                                I'd be looking at a roller cam with a much tighter LSA. Yes Yellow Rose, I just said that. YOu don't have the compression or cubes to get away with that size cam on a 112LSA.
                                 
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                                • RustyRatRod

                                  RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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                                  Did you degree the cam? DID YOU DEGREE THE CAM? I never saw that question answered. This help stuff is a two way street. If you stabbed that cam in straight up with a timing set that cost less than 100 bucks, therein could be your WHOLE problem.
                                   
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                                  • Wyrmrider

                                    Wyrmrider Well-Known Member

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                                    So valve closing point is important
                                    the back around to opening intake point
                                    then put in the biggest lobe that you can fit
                                    but too big takes too big springs and frequent spring changes
                                    so do not buy from the bottom of the catalog
                                     
                                  • moper

                                    moper FABO Gold Member FABO Gold Member

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                                    I think the pressure is low for that cam and static compression ratio. The mph says it's making power once the airflow catches up. My first check would be cam accuracy. MP cams flat out suck as far as their actual grinding. They've neem POS for decades now because of it. Pull the front off it and stick a degree wheel on it if you haven't.
                                     
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                                    • K.O. SWINGER

                                      K.O. SWINGER Well-Known Member

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                                      As Nice of a stick as that solid MP is it seems all wrong for your combo reasons already mentioned. That cam was designed to work with 10preferably 11 to 1 compression ratio. there's things you can do such as Milling the head thinner gaskets but in my opinion that's just the wrong camshaft for your setup. Dome Pistons would be your other option
                                       
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                                      • K.O. SWINGER

                                        K.O. SWINGER Well-Known Member

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                                        something in this area I would think would perk your motor up substantially by getting your intake valve close sooner you would be able to develop more compression

                                        Screenshot_2019-12-07-14-43-24.png
                                         
                                      • boilermaker

                                        boilermaker Well-Known Member

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                                        Sorry for the lack of participation in my own post (HVAC service is killing me). First off, id like to say that there is not one bad idea or piece of advice. This form is so full of amazing people that want to help.

                                        I say thank you.

                                        The front of the engine is coming apart over the holidays. I'll let you guy know how much more pressure that cam will make before my next step. I'll dust off my degree wheel and give it a go.
                                        Merry Christmas!
                                        John
                                         
                                      • boilermaker

                                        boilermaker Well-Known Member

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                                        I have Crane 1.6 roller rockers
                                        .038" 1008 felpro
                                        If its cold enough i can run 89 , Hot days 91 octane
                                         
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