AFR Head topic

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Re: AFR Head topic

Post  Lem Evans on November 16th 2016, 4:17 pm

Being that there is some name dropping going on I'll get in the mix.

About 1990ish I was talking to J. Kaase about something to do with an engine and he replied "you'd be surprised what doesn't matter". I did not respond but, I though to myself 'then there has to be the inverse'....a guy will be surprised what does matter.


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Re: AFR Head topic

Post  dfree383 on November 17th 2016, 7:28 am

Scott Foxwell wrote:
Lem Evans wrote:
Straubtech wrote:
dfree383 wrote:
Straubtech wrote:
dfree383 wrote:
Straubtech wrote:The more piston speed you put in an engine the more demand is put on both induction and exhaust.

Can you please explain your comment?

Does it take more energy to walk 5250 feet then it does 4491 ft?  And the reason for this analogy is I'm not that smart so I have had to learn this stuff in terms I can relate too so in by no means am I belittling you with this question.

How much faster is a 6.7 rod the a 6.8 on a 632" ford?

We are not talking rod length sir, we are talking piston speed.  Stroke and rpm determine the fpm a piston will travel in an engine.   The rods just "hanging" out.

I prefer that my rods don't 'hang out'....they may 'go along for the ride' if they wish. Smile
LOL...poor choice of words...
but Rod legnth does effect piston dwell at TDC and BDC and the other ugly factors like side loading and friction.
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Re: AFR Head topic

Post  gt350hr on November 17th 2016, 8:54 am

Lem Evans wrote:Being that there is some name dropping going on I'll get in the mix.

About 1990ish I was talking to J. Kaase about something to do with an engine and he replied "you'd be surprised what doesn't matter". I did not respond but, I though to myself 'then there has to be the inverse'....a guy will be surprised what does matter.


He told me the same thing about the "mountain motors'' with the 5.300 strokes. "Whatever it takes to hook the piston to the crank works".

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Re: AFR Head topic

Post  IDT-572 on November 17th 2016, 8:54 am

At a point the speed is the same regardless of the rod length, but the rate at which the piston gets to that speed will be different.

Long rod will leave TDC slower and will accelerate differently to max speed than a short rod.

This is what changes how air speeds up, starts, and stops in the port.
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Re: AFR Head topic

Post  IDT-572 on November 17th 2016, 8:57 am

gt350hr wrote:
Lem Evans wrote:Being that there is some name dropping going on I'll get in the mix.

About 1990ish I was talking to J. Kaase about something to do with an engine and he replied "you'd be surprised what doesn't matter". I did not respond but, I though to myself 'then there has to be the inverse'....a guy will be surprised what does matter.


    He told me the same thing about the "mountain motors'' with the 5.300 strokes. "Whatever it takes to hook the piston to the crank works".

I guess it matters if your making plenty of power and you don't sweat the small stuff.

But I bet in NHRA Pro Stock their looking for everything that does matter.
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Re: AFR Head topic

Post  gt350hr on November 17th 2016, 9:05 am

Straubtech wrote:
dfree383 wrote:
Straubtech wrote:
dfree383 wrote:
Straubtech wrote:The more piston speed you put in an engine the more demand is put on both induction and exhaust.

Can you please explain your comment?

Does it take more energy to walk 5250 feet then it does 4491 ft?  And the reason for this analogy is I'm not that smart so I have had to learn this stuff in terms I can relate too so in by no means am I belittling you with this question.

How much faster is a 6.7 rod the a 6.8 on a 632" ford?

We are not talking rod length sir, we are talking piston speed.  Stroke and rpm determine the fpm a piston will travel in an engine.   The rods just "hanging" out.


MAX piston speed remains constant for a given stroke and RPM scenario that is 100% correct. Rod length changes affect the piston speed off of and back onto TDC along with dwell at BDC and TDC. Nothing new .

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Re: AFR Head topic

Post  JBR-3 on November 17th 2016, 9:31 am

Maybe this will help:

Stroke and RPM alone will give you a number, that number is the average piston speed
from TDC to BDC. This number can be useful. Rod length makes no difference to this number.

Instantaneous piston speed is read off a graph that is a modified sine wave. Piston speed at TDC
is zero, then gets very large, then back to zero at BDC. The peak piston speed does depend on
rod length.

Two engines running with the same stroke and RPM will have the same average piston speed,
but the piston in the shorter rod engine will momentarily reach a higher peak speed than the
piston in the longer rod engine. This is always true, but the difference is very small between
the two peak speeds.

Incidentally, the peak piston speed always occurs when the rod and crank are at a right angle
to each other. This obviously happens at a different position of crank rotation. But, here too
the difference in crank degrees is pretty small (but not the same).

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Re: AFR Head topic

Post  Scott Foxwell on November 17th 2016, 12:40 pm

gt350hr wrote:
Straubtech wrote:
dfree383 wrote:
Straubtech wrote:
dfree383 wrote:
Straubtech wrote:The more piston speed you put in an engine the more demand is put on both induction and exhaust.

Can you please explain your comment?

Does it take more energy to walk 5250 feet then it does 4491 ft?  And the reason for this analogy is I'm not that smart so I have had to learn this stuff in terms I can relate too so in by no means am I belittling you with this question.

How much faster is a 6.7 rod the a 6.8 on a 632" ford?

We are not talking rod length sir, we are talking piston speed.  Stroke and rpm determine the fpm a piston will travel in an engine.   The rods just "hanging" out.


   MAX piston speed remains constant for a given stroke and RPM scenario that is 100% correct. Rod length changes affect the piston speed off of and back onto TDC along with dwell at BDC and TDC. Nothing new .
Peak piston speed and piston acceleration will change with rod ratio. For the same bore/stroke, same rpm, a shorter rod will put more demand on the induction.

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Re: AFR Head topic

Post  Scott Foxwell on November 17th 2016, 12:41 pm

JBR-3 wrote:Maybe this will help:

Stroke and RPM alone will give you a number, that number is the average piston speed
from TDC to BDC. This number can be useful. Rod length makes no difference to this number.

Instantaneous piston speed is read off a graph that is a modified sine wave. Piston speed at TDC
is zero, then gets very large, then back to zero at BDC. The peak piston speed does depend on
rod length.

Two engines running with the same stroke and RPM will have the same average piston speed,
but the piston in the shorter rod engine will momentarily reach a higher peak speed than the
piston in the longer rod engine. This is always true, but the difference is very small between
the two peak speeds.

Incidentally, the peak piston speed always occurs when the rod and crank are at a right angle
to each other. This obviously happens at a different position of crank rotation. But, here too
the difference in crank degrees is pretty small (but not the same).
Usually around 76*. Excellent post.

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Re: AFR Head topic

Post  Gary Blair on December 14th 2016, 5:14 am

Lem Evans wrote:Being that there is some name dropping going on I'll get in the mix.

About 1990ish I was talking to J. Kaase about something to do with an engine and he replied "you'd be surprised what doesn't matter". I did not respond but, I though to myself 'then there has to be the inverse'....a guy will be surprised what does matter.


470 CI with a 4.50 stroke mattered. Got the score up at Engine Masters. Bunch of speed off TDC.


Last edited by Gary Blair on December 14th 2016, 9:52 am; edited 1 time in total
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Re: AFR Head topic

Post  Scott Foxwell on December 14th 2016, 6:04 am

gt350hr wrote:
Lem Evans wrote:Being that there is some name dropping going on I'll get in the mix.

About 1990ish I was talking to J. Kaase about something to do with an engine and he replied "you'd be surprised what doesn't matter". I did not respond but, I though to myself 'then there has to be the inverse'....a guy will be surprised what does matter.


    He told me the same thing about the "mountain motors'' with the 5.300 strokes. "Whatever it takes to hook the piston to the crank works".
How many years did it take them to keep those 5.3 stroke engines from coming apart at the rpm they wanted to run them? Wink

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Re: AFR Head topic

Post  rmcomprandy on December 14th 2016, 7:55 am

IDT-572 wrote:At a point the speed is the same regardless of the rod length, but the rate at which the piston gets to that speed will be different.

Long rod will leave TDC slower and will accelerate differently to max speed than a short rod.

This is what changes how air speeds up, starts, and stops in the port.

Somethings to think about ...
The intake valve is more wide open when the piston is approaching BOTTOM dead center; the best rod leverage with a shorter rod happens slightly sooner and will be at a more advantageous position with a higher cylinder pressure being present.

However, overlap crossover flow, detonation resistance, ignition timing requirement and intake runner back-flow is mostly affected near Top Dead Center.

It is all a trade-off and your decision will dictate the importance of the different functions.

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Re: AFR Head topic

Post  IDT-572 on December 14th 2016, 8:00 am

rmcomprandy wrote:
IDT-572 wrote:At a point the speed is the same regardless of the rod length, but the rate at which the piston gets to that speed will be different.

Long rod will leave TDC slower and will accelerate differently to max speed than a short rod.

This is what changes how air speeds up, starts, and stops in the port.

Some things to think about ...
The intake valve is more wide open when the piston is approaching BOTTOM dead center;  the best rod leverage with a shorter rod happens slightly sooner and will be at a more advantageous position with a higher cylinder pressure being present.

However, overlap crossover flow, detonation resistance, ignition timing requirement and intake runner back-flow is mostly affected near Top Dead Center.

It is all a trade-off and your decision will dictate the importance of the different functions.

Good info.............. Thanks bud Wink
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Re: AFR Head topic

Post  Straubtech on December 14th 2016, 8:17 am

Our first build with the AFR head on pump gas (11.7) is 1.50HP per cube. We average around 1.4HP per cube with the GM stuff. This head is going to be a huge success for the BB Ford guys.

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Re: AFR Head topic

Post  rmcomprandy on December 14th 2016, 8:34 am

Straubtech wrote:Our first build with the AFR head on pump gas (11.7) is 1.50HP per cube.  We average around 1.4HP per cube with the GM stuff.  This head is going to be a huge success for the BB Ford guys.

For at least the last 5 years, it has been almost impossible to convince any cylinder producing companies that a Big Block Ford cylinder head like this, would become a success.

If it is not a Chevrolet they just didn't want to hear about it; even if all the prototyping and actual design was done for them at NO cost what-so-ever.
They say there is no market and are looking for a "sure thing" but, don't realize it is staring them in the face. Rolling Eyes

I remember about 10 years ago that all the crankshaft companies said the same things and cold not be convinced about offering big block FORD forged crankshafts. Now they all can't keep them stocked on the shelves.

Each one of those crankshafts is connected to TWO cylinder heads.  Exclamation

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Re: AFR Head topic

Post  Lem Evans on December 14th 2016, 8:38 am

A guy can't sell out of an empty wagon :-}.

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Re: AFR Head topic

Post  Gary Blair on December 14th 2016, 9:53 am

Lem Evans wrote:A guy can't sell out of an empty wagon :-}.

Laughing
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Re: AFR Head topic

Post  Gary Blair on December 14th 2016, 9:57 am

rmcomprandy wrote:
Straubtech wrote:Our first build with the AFR head on pump gas (11.7) is 1.50HP per cube.  We average around 1.4HP per cube with the GM stuff.  This head is going to be a huge success for the BB Ford guys.

For at least the last 5 years, it has been almost impossible to convince any cylinder producing companies that a Big Block Ford cylinder head like this, would become a success.

If it is not a Chevrolet they just didn't want to hear about it; even if all the prototyping and actual design was done for them at NO cost what-so-ever.
They say there is no market and are looking for a "sure thing" but, don't realize it is staring them in the face. Rolling Eyes

I remember about 10 years ago that all the crankshaft companies said the same things and cold not be convinced about offering big block FORD forged crankshafts. Now they all can't keep them stocked on the shelves.

Each one of those crankshafts is connected to TWO cylinder heads.  Exclamation

Same story on intake manifolds. Herr Doctor at Edelbrock knows this full well. The BBF Victor III manifold based on the Chevy BB Victor III price should be north of $1500. Good thing some privateers are willing to invest their time and money for the BBF.
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Re: AFR Head topic

Post  Carl on December 14th 2016, 3:25 pm

Straubtech wrote:Our first build with the AFR head on pump gas (11.7) is 1.50HP per cube.  We average around 1.4HP per cube with the GM stuff.  This head is going to be a huge success for the BB Ford guys.

Agreed. The words; "game changer", and "obsolete", also come to mind.

Smile

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