128 my take, anybody see it like this ?

[juuhanaa]

I'm going to say that the 10:1 result isn't possible. With an IVC of 51° the DCR will be in excess of 11:1.
Something is off with the calculation. Maybe the intake valve size is causing a problem?
I'm also curious as to why there are commas rather than decimals in the appropriate places in your Torque Master screenshots.



SCR.jpg



Cam.jpg



DCR.jpg

Kevin, seems like you input 352 cid instead of 302. Yea the 2.02 intake doesn't necessarily fit every chamber with a 1.6 exhaust If i use decimals in the program, it crashes. I dont know, i have windows 8.

IMG_20220918_200105.jpg

I still dont understand why retard entire cam using a smaller exhaust When using a larger exhaust valve, i would retard exhaust only, if everything else stay same.

[skinny z]

That's a good catch on that input.
Several times I noticed the stroke jump to 4" when I calculated the DCR.
I'll have to revisit that and try again.

[juuhanaa]

I still dont understand why retard entire cam using a smaller exhaust

Maybe the program tries to tell me there is more benefits to close the intake later combined with a higher cr, or something else... Anyway i like the bigger intake valve and smaller camshaft combo. But i also like big headers!

[skinny z]

Kevin, seems like you input 352 cid instead of 302. Yea the 2.02 intake doesn't necessarily fit every chamber with a 1.6 exhaust If i use decimals in the program, it crashes. I dont know, i have windows 8.


IMG_20220918_200105.jpg


I still dont understand why retard entire cam using a smaller exhaust When using a larger exhaust valve, i would retard exhaust only, if everything else stay same.

I found my input error. DCR settled in at 8.7.

As for retard on the cam, one thing comes to mind and that's that this is a limitation in the program. It's not really offering valve events that can be manipulated but rather a result based on the cam as a whole. The small exhaust valve needs more time to evacuate the cylinder so retarding the cam extends that time. It seems your thinking is the opposite?
Once the LSA is defined (a basic program parameter) and the RPM range specified (a user input can be selected or it can be a result), all the rest falls into place.
Does the exhaust duration change when you change the exhaust valve size?

It'll be a while yet, but I'll get the TM program again and have a go with my pile of parts. Maybe then I can experiment.

[Stan Weiss]

I'm going to say that the 10:1 result isn't possible. With an IVC of 51° the DCR will be in excess of 11:1.
Something is off with the calculation. Maybe the intake valve size is causing a problem?
I'm also curious as to why there are commas rather than decimals in the appropriate places in your Torque Master screenshots.

SCR.jpg



Cam.jpg



DCR.jpg

Because many places around the world use a comma where we use a decimal point. The program checks with Windows for what to use. I believe what the Country Code setting maybe is what Windows uses to decide.

Stan

[RevTheory]

...snipped...

Question though: What were the specs that gave you 49° of overlap?

I used some .903" lifter profiles from Howard's for an AMC. 263* adv. single-pattern on a 107. Full restoration Jeep with exhaust manifolds kept me from pushing it any further.

[skinny z]

I'm going to say that the 10:1 result isn't possible. With an IVC of 51° the DCR will be in excess of 11:1.
Something is off with the calculation. Maybe the intake valve size is causing a problem?
I'm also curious as to why there are commas rather than decimals in the appropriate places in your Torque Master screenshots.

SCR.jpg




Cam.jpg



DCR.jpg

Because many places around the world use a comma where we use a decimal point. The program checks with Windows for what to use. I believe what the Country Code setting maybe is what Windows uses to decide.

Stan

Thanks as always Stan. That clears up that.
Seems to me there's a province in my own country that does the same thing.

[juuhanaa]

Kevin, seems like you input 352 cid instead of 302. Yea the 2.02 intake doesn't necessarily fit every chamber with a 1.6 exhaust If i use decimals in the program, it crashes. I dont know, i have windows 8.


IMG_20220918_200105.jpg


I still dont understand why retard entire cam using a smaller exhaust When using a larger exhaust valve, i would retard exhaust only, if everything else stay same.

I found my input error. DCR settled in at 8.7.

As for retard on the cam, one thing comes to mind and that's that this is a limitation in the program. It's not really offering valve events that can be manipulated but rather a result based on the cam as a whole. The small exhaust valve needs more time to evacuate the cylinder so retarding the cam extends that time. It seems your thinking is the opposite?
Once the LSA is defined (a basic program parameter) and the RPM range specified (a user input can be selected or it can be a result), all the rest falls into place.
Does the exhaust duration change when you change the exhaust valve size?

It'll be a while yet, but I'll get the TM program again and have a go with my pile of parts. Maybe then I can experiment.

Yes i think its opposite, because i look at the TDC as a reference point. Retarding the cam/later EVO reduces time to evacuate the cylinder. When i change to a smaller size exhaust valve, the program recommend less advance and an equally larger intake centerline while keeping the exhaust duration same.

Can i ask what program you used to calculate the DCR?

Thanks,

[skinny z]

Kevin, seems like you input 352 cid instead of 302. Yea the 2.02 intake doesn't necessarily fit every chamber with a 1.6 exhaust If i use decimals in the program, it crashes. I dont know, i have windows 8.


IMG_20220918_200105.jpg


I still dont understand why retard entire cam using a smaller exhaust When using a larger exhaust valve, i would retard exhaust only, if everything else stay same.

I found my input error. DCR settled in at 8.7.

As for retard on the cam, one thing comes to mind and that's that this is a limitation in the program. It's not really offering valve events that can be manipulated but rather a result based on the cam as a whole. The small exhaust valve needs more time to evacuate the cylinder so retarding the cam extends that time. It seems your thinking is the opposite?
Once the LSA is defined (a basic program parameter) and the RPM range specified (a user input can be selected or it can be a result), all the rest falls into place.
Does the exhaust duration change when you change the exhaust valve size?

It'll be a while yet, but I'll get the TM program again and have a go with my pile of parts. Maybe then I can experiment.

Yes i think its opposite, because i look at the TDC as a reference point. Retarding the cam/later EVO reduces time to evacuate the cylinder. When i change to a smaller size exhaust valve, the program recommend less advance and an equally larger intake centerline while keeping the exhaust duration same.

Can i ask what program you used to calculate the DCR?

Thanks,

I look at from the standpoint of EVC.

There is a link to the calculator I use at the end of this tech paper on Dynamic Compression.

http://members.uia.net/pkelley2/DynamicCR.html

[juuhanaa]

I found my input error. DCR settled in at 8.7.

As for retard on the cam, one thing comes to mind and that's that this is a limitation in the program. It's not really offering valve events that can be manipulated but rather a result based on the cam as a whole. The small exhaust valve needs more time to evacuate the cylinder so retarding the cam extends that time. It seems your thinking is the opposite?
Once the LSA is defined (a basic program parameter) and the RPM range specified (a user input can be selected or it can be a result), all the rest falls into place.
Does the exhaust duration change when you change the exhaust valve size?

It'll be a while yet, but I'll get the TM program again and have a go with my pile of parts. Maybe then I can experiment.

Yes i think its opposite, because i look at the TDC as a reference point. Retarding the cam/later EVO reduces time to evacuate the cylinder. When i change to a smaller size exhaust valve, the program recommend less advance and an equally larger intake centerline while keeping the exhaust duration same.

Can i ask what program you used to calculate the DCR?

Thanks,

I look at from the standpoint of EVC.

There is a link to the calculator I use at the end of this tech paper on Dynamic Compression.

http://members.uia.net/pkelley2/DynamicCR.html

Thank you for link and reply. Actually now when you say it, 2.02 intake for the 302 rhymes better

[CamKing]

If it 's accurate for a Chevy, but not a Ford, it's not a formula, it's a rule of thumb.
If it's accurate for a Small Block, but not a Big Block, it's not a formula, it's a rule of thumb.
If it's accurate for a 350cid SB, but not for a 406cid SB, it's not a formula, it's a rule of thumb.

[EDC]

If it 's accurate for a Chevy, but not a Ford, it's not a formula, it's a rule of thumb.
If it's accurate for a Small Block, but not a Big Block, it's not a formula, it's a rule of thumb.
If it's accurate for a 350cid SB, but not for a 406cid SB, it's not a formula, it's a rule of thumb.

I always get in trouble when I say this but...

"There are absolutely no absolutes."

[CamKing]

"There are absolutely no absolutes."

Sorry, but a2 + b2 = c2, for every right triangle there is.

[skinny z]

"There are absolutely no absolutes."

Sorry, but a2 + b2 = c2, for every right triangle there is.

How about the 128 rule in it's most directed application?
That would be a 10.5:1 SBC with a 2.02" intake valve (so looking at an average CoD) and 350 CID. The objective is maximum torque as observed on an engine dyno.
No area under the curve etc. Just maximum output.

EDIT: That question is probably unfair to ask and it isn't meant to put anyone on the spot.
I am curious as to any answer though.
FTR: The only spec to come out of that "formula" is the LSA. And in the case above, it falls in at 108.

[juuhanaa]

Im just remembering a colonoscopy and the shape what i saw on the screen.. It was not a perfect triangle and i listened when doctor literally explained about it is an interesting shape I was thinking cylinder heads at that point and nodded yes it is