Don Terrill’s Speed-Talk

Posted: **Wed Oct 02, 2019 9:02 pm**

Let's say that the cubic inch and all other engine parameters stay the same and the lobe profile is the same, how much RPM will the peak power of an engine increase withh more duration? And how much increase from moving valve vents.

Here is an example just on the intake lobe:
273@0.050 at 110icl. Events would be open at 26.5 and close at 66.5 and let's say it makes peak power at 7000rpm

What if the intake duration went up 279@0.050, still at 110icl. Events would be 29.5 open and 69.5 close. How much higher would peak power be?

Now let's say that this 279@0.020 is at 114icl. Events would be 25.5 open and 73.5 close. How to much higher would this be over the previous ones?

Just trying to understand camshaft events a little better.

Posted: **Wed Oct 02, 2019 10:25 pm**

Sounds like you should play with a good engine simulation program. With that you can make lot's of changes and see what effects they have. They can be very good learning tools.

Posted: **Thu Oct 03, 2019 10:10 am**

lekid wrote: ↑Wed Oct 02, 2019 9:02 pm Here is an example just on the intake lobe:
273@0.050 at 110icl. Events would be open at 26.5 and close at 66.5 and let's say it makes peak power at 7000rpm

What if the intake duration went up 279@0.050, still at 110icl. Events would be 29.5 open and 69.5 close. How much higher would peak power be?

Now let's say that this 279@0.020 is at 114icl. Events would be 25.5 open and 73.5 close. How to much higher would this be over the previous ones?

Too many unknowns to give you an answer.
You didn't give the bore and stroke. A 6 degree increase in duration, will give you a bigger increase in peak HP RPM on a 350ci engine, then it will with a 420ci engine.
Is the port/carb/manifold on the small side, or the large side of being correct for the peak HP RPM ? This will effect the increase in peak HP RPM.
Are the ports sufficient to move the power up in RPM, with the duration increase, without increasing lift too ? If you don't have enough valve lift for the port and RPM, adding duration will not increase peak HP RPM.

Posted: **Thu Oct 03, 2019 12:44 pm**

Let's say 406sbc (4.155x3.750).
Lets say that the intake is proper for the rpm and head is porper for the added rpm.
Lift stays the same.

Posted: **Thu Oct 03, 2019 1:38 pm**

lekid wrote: ↑Thu Oct 03, 2019 12:44 pm Let's say 406sbc (4.155x3.750).
Lets say that the intake is proper for the rpm and head is porper for the added rpm.
Lift stays the same.

Let's not.
If you have a 273@.050" cam, in a 406ci, and it's only peaking at 7,000rpm. Something is bad wrong.

Posted: **Fri Oct 04, 2019 4:49 pm**

The cam change suggested in the first post is as likely to loose power as to gain on the typical 23 deg. headed 406.

Randy

Posted: **Fri Oct 04, 2019 5:44 pm**

What if you saw the worst valve train deflection ever and a loss of net valve lift how would you treat the situation?

-wph-

Posted: **Fri Oct 04, 2019 7:01 pm**

WPH wrote: ↑Fri Oct 04, 2019 5:44 pm What if you saw the worst valve train deflection ever and a loss of net valve lift how would you treat the situation?

-wph-

HMMMMMM Fix the problem before you ask how an unavailable answer would help.?

Posted: **Sat Oct 05, 2019 10:47 am**

Okay, let's add that this engine sees 400hp (around 1,600pph) of nitrous and it is never ran N/A.

Posted: **Sun Oct 06, 2019 2:19 pm**

lekid wrote: ↑Sat Oct 05, 2019 10:47 am Okay, let's add that this engine sees 400hp (around 1,600pph) of nitrous and it is never ran N/A.

OK, now neither intake lobe will be anywhere close to correct. Your so far off on cam duration for a NO2 engine that peaks at 7,000, that there's no reason to look at what change you would see from taking out the wrong cam, and putting in another wrong cam.

Posted: **Sun Oct 06, 2019 8:29 pm**

lekid wrote: ↑Wed Oct 02, 2019 9:02 pm Let's say that the cubic inch and all other engine parameters stay the same and the lobe profile is the same, how much RPM will the peak power of an engine increase withh more duration? And how much increase from moving valve vents.

Here is an example just on the intake lobe:
273@0.050 at 110icl. Events would be open at 26.5 and close at 66.5 and let's say it makes peak power at 7000rpm

What if the intake duration went up 279@0.050, still at 110icl. Events would be 29.5 open and 69.5 close. How much higher would peak power be?

Now let's say that this 279@0.020 is at 114icl. Events would be 25.5 open and 73.5 close. How to much higher would this be over the previous ones?

Just trying to understand camshaft events a little better.

In general your first probably would not be enough difference to justify the change, your third one may be a cpl hundred rpm higher depending on where it's installed and may hurt tq, adding nitrous all will peak 2 to 300 lower at the hit of the button.

Posted: **Sun Oct 06, 2019 9:28 pm**

WPH wrote: ↑Fri Oct 04, 2019 5:44 pm What if you saw the worst valve train deflection ever and a loss of net valve lift how would you treat the situation?

-wph-

Call Tom at 3V PERFORMANCE!

Posted: **Mon Oct 07, 2019 8:25 am**

CamKing wrote: ↑Sun Oct 06, 2019 2:19 pm
lekid wrote: ↑Sat Oct 05, 2019 10:47 am Okay, let's add that this engine sees 400hp (around 1,600pph) of nitrous and it is never ran N/A.
OK, now neither intake lobe will be anywhere close to correct. Your so far off on cam duration for a NO2 engine that peaks at 7,000, that there's no reason to look at what change you would see from taking out the wrong cam, and putting in another wrong cam.

Maybe I did not explain myself correctly. I auspect that the peak HP is around 7000rpm but engine makes power up to 7600rpm.

My original cam might be "completely wrong", but it sure works pretty damn good right now. Engine made just a touch over 700hp on the engine dyno and according to weight/mph calculator, it makes 1,100hp on the 350 jet. It seems to gain around 65-70hp per 50ho jet increase but got around 1/2 of that on the 400jet which leads us to believe it needs more camshaft since it is nowhere close to maxing out the nitrous kit

I guess we will find out how the other "completely wrong" will do.

Posted: **Mon Oct 07, 2019 9:40 am**

What is your weight, et and mph?

► 1100 - 700 = 400 - if greater than 700 this will be less than 400

► 350 / 50 = 7

► 65 * 7 = 455 HP

► 70 * 7 = 490 HP

► (400 / 350) * 50 = 57.14 HP per 50 shoot

Need to work on your math, Has your nitrous system been flowed?

Stan

Posted: **Mon Oct 07, 2019 10:00 am**

Im not sure on the cam but my friend ran into a problem where car stopped gaining with larger nitrous jets. A different cam helped, bit more exhaust duration and earlier opening to help get rid of exhaust. Car ran better on all shots really but allowed more to be sprayed

Don Terrill’s Speed-Talk

Camshaft duration vs valve events vs RPM

Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM

Re: Camshaft duration vs valve events vs RPM