More cubes equal less rpm?

Usually that would be what i would expect, but would like some input. Going from 528 to 560 cubes, same fully ported 440-1 heads, same cam of 285/296/114, same 15/1 compression, same 3X intake , alky, same headers. I figure maybe 200 to 300 rpm lower shift points?
I have just bought 4.30 gears to replace the 4.56 i have now. The motor was spinning 7300 in the traps the last run at 150.5 mph. I hope to pick up a couple of mph from the change to 560 cubes.

If nothing with the heads, induction, valvetrain, headers changes....... then yes, I’d expect the peaks to happen a little earlier.

My 572 doesn't care if its shifted 6700-7300. Runs exactly the same. It was actually a little better mph with a 4.10 than a 4.30. Though its quicker with the 4.30. 10.5wx31
Doug

Have you tested the shift points in all three gears to make it run the quickest and fastest MPH before?
If not you should on the new motor before changing anything
My current bracket motor(14.82 to 15.03 comp ratio, 518 C.I. low deck 400 block with 440-1 heads and Jesel 1.55 ratio rocker set up)) ran the exact same ET(within.004), 8.862 at 148.3 MPH and then 8.866) shifting at 7000 on the first pass and the it ran 150.6 MPH 40 minutes later after I changed the shift point on the glide from 7000 RPM to 7300 RPM I'm planning on finding out exactly where this motor wants to be shifted and maybe even experiment with the stall on the throttle before letting go of the button instead of flooring it and letting the box release the tranny brake .965 seconds later
4.56 gears with a set of Hoosiers 13.5x32.0x15W stiffwalls, measuring 104.0 circumference at race pressures, I would have put 4.10 in the rear end but this Dana 60 rear end has 40 spline Mark Williams axle and spool and I couldn't buy a 3 series 40 spline spool from anyone

The 528 liked 7300 the best. I plan on starting with 7000 shifts and move up to see what it wants.

A rare exception: where the new A:F curve with stronger demand is closer to what the engine wants. Most likely: too much HSAB.
Remember that more cubes from stroke frequently means new rod ratio as well, and a vacuum change (higher right @ TDC) during the entire intake stroke.

I know this isn't completely on topic, but here goes anyway.

In every instance I've increased the volume under every mopar head I've tried (primary limiting factor) I've gone faster. From -1s to predator, stock hemi head to millennium. The heads have been over faced with job in almost every attempt, yet inches alway resulted in speed. Even when the efficiency was apparently less.

Let PS have 501 CI , or 600 withe the same induction, and they'll go faster too.

Poli and DT plus everybody else -thanks for the input. Hopefully the changes will help. Going from a steel 910 gram stock bearing size rod to a GRP 6.8 long aluminum 2.100 bearing should lower the bob eeight some, and piston coatings should help? Skirts for sure and i may have the domes done as well. The only other mod will be a better piston pin which i understand helps in a couple of ways.

This is right on, you never ever will see a NASCAR run 300 CID because it makes "more pulses per minute" and all the other theoretically sound technical explanations, you will never see a formula 1 run smaller than the MAX, never see a 400 CID pro stock when 500 is the max (assuming both engines can use the same induction and no rules to favor the smaller CID like weight breaks) you just plain go faster with more cubes, the 73 340 is slower than the 74 360 with same heads, cam, carb, exhaust...

Displacement = vacuum, more is better

As far as how big, there has to be a saturation point? How about when the "choke" point is reached early enough that induction or exhaust tuning is too low to produce enough energy for power gains? The reason i ask is i often wondered if i was close with 906 heads on a 535? The motor was far from optimized so it would be hard to gauge from the power it made.

Isn't the "choke" point found when adding more cam simply does not make any more power ? At any additional RPM ?
No more air can get into the motor.

From what i read, at some velocity flow increase stalls. With a ported 906 on a 535 i would think that will happen somewhere around 6000 rpm? I also read that higher rpm creates more energy for filling the cylinders, so at some point that would come into play. Less rpm equals less increase from exhaust and intake tuning.

Once the velocity goes supersonic the flow stalls.

Kevin

From what I understand, the RPM at which inertia and wave tuning start really taking effect is about 6,000. Under that RPM, not much effect, the higher above that RPM, the more sensitive the engine combo becomes.
I have little experience with low RPM combos, though. Every high RPM combo I've built has responded to more displacement, even when the cylinder heads where the choke.

Shift my hemi at 8500 because I didn't go faster when I reved it higher... 5.0 inch bore space 99 hemi

My logic may not be sound on this, but this is how I see it.

Even at max flow, whatever that is, if the head flows that amount for a longer duration, there's more fuel in the cylinder to burn. Same bore, just more stroke, there's more fuel in that chamber. We get away with stupidly high compression ratios with normal mope heads, because we can't fill the cylinder. A PS head would detonate to death if you ran a static of 16+:1 compression. Whereas some of the highest NA numbers I've made with a mope have been close to 17:1. I think a static 14:1 in a 99 head would have higher dynamic, than a 17:1 best available normal mope head.

At some point these minor increases would get over run by parasitic loss, but I haven't hit that using the standard junk most of us use even at 5.125 stroke.

Assuming you have a somewhat decently optimized combo, a given cyl head will support "x" power, displacement will dictate where that power occurs. On these large engines, friction is a huge factor. between 5000-6000 on a recent 4.75" bore Chebby I ran, friction increased 25%. If you are restricted, manifold depression will also increase with RPM.

I think one factor you may be overlooking is block material. If you are running an aluminum block, which most do with aftermemarket large Mopars you are. It the ability for that aluminum block to take heat away from the combustion process. I think this is a large factor in why you can "get away" with more compression .The heads up car we find the same issue and it has basically an Aussie Pro Stock head on it, but on an aluminum block which we use to try and make weight. It is a very efficient very good working head but the aluminum block is causing some issues. We are getting ready to take it to diesel territpryt on the compression side for that reason, after talking to CP and Total Seal guys..

could be, and the narrow bore space, and the flipity flopity cylinder wall too lol. I'm having a billet bock made to see how that goes with water only in the head. I;ve done filled iron blocks, but all the al blocks I've had have been cast. Might even try CFE if they'll do a hemi


Really the perfect world for me would be a solid cast al block with about an inch or less of water cast into the deck. I don't make the power that requires a billet, but too much for a water casting to stay put.

Now you guys have me wondering if i should run a higher compression ratio? At 528 cubes i believe i was at 15.1 to 1. If i reuse the pistons as is with the same deck hieght I would be about 16 to 1. I would need to upgrade to cometic gaskets so not cutting the domes would make it about a wash. Thoughts? Mega block by the way. 440-1 professionaly ported heads with 400 cfm at .800 intake lift. Net intake lift about .840 to 8.50 (gross .870) Alky injected
Edit; i just s t arted a new thread on this.

I wonder how a softened chamber goes with methanol?

Probably would kill power NA I would think.