Eric's cam challenge

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RustyRatRod said:
Yall two need to get a room.
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He needs to learn to read and read someone other than DV.

Seat to seat timing is what the engine sees. Especially at overlap.

If you understand two strokes and can apply time/area then you can understand how wrong DV is.

Of course I don’t have 19,000 cam tests on the dyno either. I can make the argument that those same tests didn’t really mean much either.
 
I have NOT read 13 pages, but from a cursory look at his chart..... was it 15-20 hp difference from best to worst?
I can see a concern for a heads-up racer needing every hp he can get, but is 15hp worth this much work for a street/strip car?
Am I supposed to be unhappy when my 540 makes 685, instead of 700?
 
Whew!!!
I’m glad I figured out that I’m happier when I avoid getting involved with on line cam arguments.

Carry on.

On a positive note……..
I approve of RRR’s new avatar:thumbsup:
 
Newbomb Turk said:
He needs to learn to read and read someone other than DV.

Seat to seat timing is what the engine sees. Especially at overlap.

If you understand two strokes and can apply time/area then you can understand how wrong DV is.

Of course I don’t have 19,000 cam tests on the dyno either. I can make the argument that those same tests didn’t really mean much either.
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You're preachin to the choir, but in all honesty, yalls constant bickering is gettin old. I know bad info muddies up the waters, but the same old dick measurin on every single thread turns people away from the discussion. Nobody learns anything like that.
 
33IMP said:
I have NOT read 13 pages, but from a cursory look at his chart..... was it 15-20 hp difference from best to worst?
I can see a concern for a heads-up racer needing every hp he can get, but is 15hp worth this much work for a street/strip car?
Am I supposed to be unhappy when my 540 makes 685, instead of 700?
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Right. A good driver (or bad one) can make that 20HP difference.
 
RustyRatRod said:
You're preachin to the choir, but in all honesty, yalls constant bickering is gettin old. I know bad info muddies up the waters, but the same old dick measurin on every single thread turns people away from the discussion. Nobody learns anything like that.
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That’s not my problem.

Until the errors are fixed this **** continues.

You can’t be that wrong and not get it corrected.

You and I both know **** like this festers.

Holley power valve timing is the perfect example of this, and this is no different.

The dude is wrong.
 
I don't see how lift at 0.006" is meaningful at all not that one number tells you all about the cam. I think Crane had something with the 0.050" lift thing. It seems to be working well as a comparison measure does it not?
 
1MeanA said:
I don't see how lift at 0.006" is meaningful at all not that one number tells you all about the cam. I think Crane had something with the 0.050" lift thing. It seems to be working well as a comparison measure does it not?
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Think in terms of pressure differential between the manifold side of the valve compared to the piston side of the valve.

.006 lift changes the pressure differential above and below the valve.

You calculate that as time/area. IIRC the .006 lift point is for hydraulic lifters.

For solid lifters it should be the lash point.
 
1MeanA said:
I don't see how lift at 0.006" is meaningful at all not that one number tells you all about the cam. I think Crane had something with the 0.050" lift thing. It seems to be working well as a comparison measure does it not?
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It's meaningful and useful everywhere. Comparing advertised to .050 tells you how fast a rate the lobe is.
 
Newbomb Turk said:
Think in terms of pressure differential between the manifold side of the valve compared to the piston side of the valve.

.006 lift changes the pressure differential above and below the valve.

You calculate that as time/area. IIRC the .006 lift point is for hydraulic lifters.

For solid lifters it should be the lash point.
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The annular area is tiny at 0.006". Don't you think that this is the point where you can say that the valve has moved off of the seat and gives the largest duration number? Its the marketing duration point.
 
1MeanA said:
The annular area is tiny at 0.006". Don't you think that this is the point where you can say that the valve has moved off of the seat and gives the largest duration number? Its the marketing duration point.
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I don’t know another way to say it. Did you think about it?

Let’s just look at the exhaust valve.

I’m just pulling a number out of my *** but let’s say there is 500 psi in the chamber 1 degree before the valve opens. Now move the valve .006 off the seat.

What happens to the pressure?

Stop and think about it. When the valve cracks the seat the pressure changes.

So it matters exactly when the valve opens and closes.

These engines run off of pressure differential. So when the valve leaves the seat shut happens.

And the engine knows it.

Slow lobes are easier to control at higher rpm but they kill torque at low rpm.

You need to forget what you think you know and think in terms of pressure differential.

Then it will make sense.

Or don’t bother.
 
33IMP said:
I have NOT read 13 pages, but from a cursory look at his chart..... was it 15-20 hp difference from best to worst?
I can see a concern for a heads-up racer needing every hp he can get, but is 15hp worth this much work for a street/strip car?
Am I supposed to be unhappy when my 540 makes 685, instead of 700?
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There was a 50 hp swing from 620-670 hp in the top ten was like a 25 hp swing..
Torque was a 25 lbs-ft altogether and about 15 lbs-ft in the top ten.
 
I would guess all the specs are pretty important, I do get what Newbomb Turk is saying as soon as the valve seal is broken obviously **** is happening, but it seems like @ 50 seems to describe a little more if you were gonna go by only one @ spec how it's gonna react in your car eg.. A 220° can be all over the map in advertised duration. I prefer when cam companies give both and wish they also gave .200 specs also.
 
33IMP said:
I have NOT read 13 pages, but from a cursory look at his chart..... was it 15-20 hp difference from best to worst?
I can see a concern for a heads-up racer needing every hp he can get, but is 15hp worth this much work for a street/strip car?
Am I supposed to be unhappy when my 540 makes 685, instead of 700?
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Agreed.

I only looked briefly myself. But I think that the biggest gap was between 1 and 2, and the gap between 2 and 15 was very small. This might suggest something as well.
 
BSB67 said:
Agreed.

I only looked briefly myself. But I think that the biggest gap was between 1 and 2, and the gap between 2 and 15 was very small. This might suggest something as well.
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There's a 50 hp gap between 1st and 23rd. And 1st is a 238° and 23rd is a 244° obviously the other cam specs are pretty different.
 
Newbomb Turk said:
I don’t know another way to say it. Did you think about it?

Let’s just look at the exhaust valve.

I’m just pulling a number out of my *** but let’s say there is 500 psi in the chamber 1 degree before the valve opens. Now move the valve .006 off the seat.

What happens to the pressure?

Stop and think about it. When the valve cracks the seat the pressure changes.

So it matters exactly when the valve opens and closes.

These engines run off of pressure differential. So when the valve leaves the seat shut happens.

And the engine knows it.

Slow lobes are easier to control at higher rpm but they kill torque at low rpm.

You need to forget what you think you know and think in terms of pressure differential.

Then it will make sense.

Or don’t bother.
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I'm a retired engineering tech (not specializing in engines) so I think I understand although I'm not sure what your level of understanding of physics is when you talk about the engine knowing things and running off of pressure differential. Delta P is just a means to an end. As we know camshaft theory is complex although doesn't need to be for most people. There are as with everything drawbacks from maximizing aspects of design such as duration, life, area under the curve, etc. A lot more experienced people than you or I came up with the 0.050" number but it is only one measure for helping builders. Rate of lift might be another good number to look at or perhaps a curve. The problem is a squarish lobe would give the best looking curve. Looking at something and knowing what to do with it are 2 different things.
 
1MeanA said:
I'm a retired engineering tech (not specializing in engines) so I think I understand although I'm not sure what your level of understanding of physics is when you talk about the engine knowing things and running off of pressure differential. Delta P is just a means to an end. As we know camshaft theory is complex although doesn't need to be for most people. There are as with everything drawbacks from maximizing aspects of design such as duration, life, area under the curve, etc. A lot more experienced people than you or I came up with the 0.050" number but it is only one measure for helping builders. Rate of lift might be another good number to look at or perhaps a curve. The problem is a squarish lobe would give the best looking curve. Looking at something and knowing what to do with it are 2 different things.
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When you mention a "squarish " lobe, I think of the stock eliminator "cheater" cams. Radical rates, confined within fixed lift and duration numbers..... and cams that are incredibly hard on valvetrains and short lived..
But definitely part of how a stock eliminator car can be a couple seconds faster than a real stock car..
(And really an advantage for Chevrolet, because their "advertised" durations were so huge, it made grinding a cheater cam MUCH easier.)
 
1MeanA said:
I'm a retired engineering tech (not specializing in engines) so I think I understand although I'm not sure what your level of understanding of physics is when you talk about the engine knowing things and running off of pressure differential. Delta P is just a means to an end. As we know camshaft theory is complex although doesn't need to be for most people. There are as with everything drawbacks from maximizing aspects of design such as duration, life, area under the curve, etc. A lot more experienced people than you or I came up with the 0.050" number but it is only one measure for helping builders. Rate of lift might be another good number to look at or perhaps a curve. The problem is a squarish lobe would give the best looking curve. Looking at something and knowing what to do with it are 2 different things.
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Got it.
 
273 said:
There's a 50 hp gap between 1st and 23rd. And 1st is a 238° and 23rd is a 244° obviously the other cam specs are pretty different.
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For average hp:
The difference between #1 and #2 is 7.9 hp
The difference between #2 and #14 is 6.8 hp.
 
BSB67 said:
For average hp:
The difference between #1 and #2 is 7.9 hp
The difference between #2 and #14 is 6.8 hp.
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Yes average there's less of a difference, from 1st to 23rd these a 25 hp difference.
 
Hurray!!! A few smart people get it [ what the 050 number can tell you ] but Newbomb Turk is not one of them.
Post #299 by NBT is typical of somebody who loses the argument, unable to use reason & logic, & so resorts to crude vulgarity as we see in post #299.
And I NEVER said seat/adv timing doesn't matter, as NBT keeps saying that I did. [ you will find that confirmation by me in an earlier post on this thread ].

Many will probably be unaware that NBT posts on speed talk, under the moniker of 'A Class Act'.....a contradiction in terms if ever there was one.......

Go & have a look......

He doesn't dare post the bullshit on ST that he serves up to us on this site because there are some veeeery smart people on ST, much smarter than him, & he would be run out of town posting his BS there....
 
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