calculating peak rpm hp

Anyone know if there is a formula for calculating peak rpm hp with the cam duration included? Didnt see any on wallace.

Too many variables.

When you really wanna know, you dyno it.

Other than that, it’s just a guesstimate.

Yeah, i understand. Just looking for a guess anyway. Not sure where to shift this 511 at once i get to the track. 330cc heads and a 270@50 solid cam. Seems to pull hard to upper 6000 range. Thanks

If you're serious about how it runs on the track, then you should be testing different shift RPM points. Pick a starting point (6500?) and go up & down in 200 RPM increments to see what works better.

Even the "good" engine sim programs I've used have been really hit-or-miss on predicting peak HP and torque RPMs. They were off as much as 300-500 RPM on their predictions compared to actual engine dyno testing (e.g., over-predicted torque peak RPM by 300 and under-predicted HP peak RPM by 500).

I agree. 6500 is a good starting point. The simulators are not accurate from what i have see. My guess would be 6700/6800 peak hp on my combo. Was hoping someone here had something simular and knew what theirs is.

Solid roller or flat tappet ?
For what it is worth , my 505 with a 272@050 solid flat tappet .5400ish converter , 4.1 gear 28"radial .
Chassis dyno always showed peak HP at converter stall(5100 footbrake vert) , but motor pulled to 6500 without any drop off
With CNC source heads , Victor and 4150 prosystems carb I shifted at 6000 . 10.50s . I tried a little more not big gain , but it never seemed to give up under 7000 with either converter .
With TF270 heads , bigger tbrake vert , Super Victor and 1050 dominator . I only ran this a couple times . BUT shifting at 6000 it didn't fall back onto converter , shift light stayed on @6000 - so stall increased .
10.25@130 .
I believe with the bigger heads it wanted a higher shift probably 64-6600 which would have allowed rpm drop back to converter on shift

That is now to be another day , due to block issues .
Why the low shift ? It ran the numbers I wanted and was doing it easily at low stress .

Tex

Sounds simular. I was watching some of my in car videos cruising the back roads and i was shifting at 6000 most of the time on pump gas. Now with a mix of 110/93 sunoco i find im shifting at 6500+ just going by sound and feel. On the street i rarely watch the tach. I have a vid edited that i will try to post. Had too much 110 to 93 and it didnt like it. Real fat but gives an idea .

https://youtu.be/JVHbtN-uVsE
Heres a in car vid running fat on 5 gal of 110 to 2 gal of 93. Tach is in the 6000 to 6700 rpm range. Now with 70/30 mix 110/93 runs way better pulling hard in the upper 6000 range and bouncing off the rev limiter at 7200 in first. I would say the peak power is at least at 6600. Vid no really a good example but it what i have now.

Solid flat tappet. 270/276. 640 lift on a 110.

If you shift at 6500 the actual rpm at the shift may actually BE 200 to 250 rpm higher. I found that out when i put in data logger. I run an airshifter on a rpm switch.

My turbo action valve body takes 600 rpm to complete the 1/2, 400 rpm on the 2/3.
Doug

Not rocket science.
Just try shifting it at different rpm and see what makes it ET best.
Try it at 66, 68 and 7000 and see what it likes best.

I start with 500 RPM increments and the go to 100 after finding the highest and lowest shift points, especially on putting any new parts in the car, converter, cam, jetting and so on

For sure, but thought i might try short shifting at 6000 to start. Then 6500 and go from there.

Any such way like that will ultimately find out what i likes best.
Love ya man, but frankly you make things more involved and harder than anybody that has ever posted on here... lol

Just who i am. I leave no stone unturned if possible. I like the opinion of others as well. Wheres the harm and besides, this site would pretty slow if no one was asking questions simple or not.

Never said there was any harm in it, but in this thread( like some others) you answered your own question. ....... try different rpms till it runs the best...... way early in the thread.
I suspect you already knew that to be the answer. Thats my only reason for saying what i said

Yes, you are correct . i usually have direction before the question, but i like to get others opinions on here because i have had my mine changed more than once on here. Always more than one way to skin a cat and i like to get all the angles. Sorry to irritate anyone with this.

Some people don't think well until they are irritaded or upset, no sense in letting them go through life without thinking
AKA, if you don't test and change things how are you going to learn

I agree cab and if i would have never asked any of my silly questions i wouldnt have learned much. Been learning good stuff off this site for a long time now.

WOW 😮. That wasn’t a very cool thing to post. LOL.

nothing wrong with checking others opinion/experience , if only to confirm you are heading in the right direction .

Tex

I thought that was MY claim to fame?

Could be, seems you two only answer my threads when you have something non contributing to say. Its real easy, you dont like my questions, then dont answer them. Plain and simple. Plenty of other guys here very helpful. I have have learned plenty from the others on here.

I will second that.

Ask any questions you like. That's how we all learn. There are never stupid questions, only stupid people. Lol! Some people on here make comments about the repetition of questions. Sometimes we forget that people come and go off of this site all of the time. What people need answers to aren't in the first couple of pages listed and we all know too well how wonderful the SEARCH function works on here.
My old combo with a 262/266 lift on my 440 liked a 6,800 rpm shift point. Car would slow down with a 6,500 or 7,000 shift. You'll find the sweet spot real quick.

FWIW once you establish your shift speed, you may want to try changing RPM for just one gear. For example, you may be able to run the 2-3 shift out a bit more than the 1-2 shift. Or it could be the opposite. It's not always that the engine wants to be shifted at the same RPM at every shift change.

Well i could have just asked who on here has a engine combo simmular to mine that knows their max hp rpm, but i thought maybe their might be a calculator for this i didnt know about. I know the track will tell exactly what its gonna want, but just driving it sounds and feels like its about the 6600-6800 area. Will see. Thanks

I may just give that a try. Watching the vid the tach is not moving much on the 1 2 shift, but the tires were spinning pretty good and spin even more now that i have the fuel mix better sorted out. Looks like 600rpm drop on the 2 3 shift which is same character of the vert when it was behind my 408sb.

i do this often to be sure my old mind hasn't forgotten what i used to know. what's this thread about ?

you may want to try changing RPM for just one gear. For example, you may be able to run the 2-3 shift out a bit more than the 1-2 shift. Or it could be the opposite. It's not always that the engine wants to be shifted at the same RPM at every shift change.

This^^^
All modern transmission have "ratio progression" in which the RPM % drop on shift is widest on the 1-2, and closes up as you reach final drive.

A couple of Stock Eliminator people I know shift their 1-2 200-300 RPM lower than their 2-3. Never tried it on my junk, simply cuz I position the tach "straight up" at the RPM where I shift for easy reference.

Also, I don't use a shift light any more; I was always late on the shift when waiting for the light at the specified RPM. I'm more consistent w/ the approach above.

Regardless, I was never aware of any major shift lag time that caused my actual shifts' RPMs to be so much higher like some of you said. I'd like some type of data logger or playback tach to see what's happening across the whole pass, though.

A powerglide kinda simplifies this option

Yeah i agree. Ill have to get back in the habit of watching the tach. The shift light gave me the opportunity to watch another gauge or two(oil and fuel pressure) going down the track. I barely remember, but it seems like i tried this way back with my small block not seeing much if any difference.

Guess i could launch in 2nd gear.

You may also see different converter slippage on different shifts: the 1-2 has more torque, but the 3-4 is against higher load.
Once you find what works for you, the reason sort of matters less...

Ok thanks. Didnt know that. Looking at the vid again on the big screen i see the 2 3 shift rpm drops 400rpm. Looks like it stays right in the power band all the way thru. I guess this would be a good thing?

At the pure stock drags, where you weren't allowd to add a tach, they use to say "when the fender starts to lay down, SHIFT"

There is a feel to it for sure. I grew up with 4 speed cars. I have a good feel when to shift. Nosing over might be a bit to late, but im definitely no professional .