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STROKER KIT?? 

 

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 Post subject: STROKER KIT??
Posted: Tue Mar 15, 2005 2:38 pm 
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im in the process of redoing my motor to suit a supercharger..
i was talkin to a few motor rebuild places and all recomened forged pistons..rods etc.. one place said you mite be able to find a stroker kit that will include everything i will need to strenghten it up also they said it will proberly go to like a 4.4L... any one know if these kits even exist?? or were can u buy them if so??

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Posted: Tue Mar 15, 2005 5:58 pm 
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If you go off the total valve area it doesnt work out feasable to stroke the 2V 4ltr engines cause it wont breath efficiently. Even the std bores run out of flow efficiency with a ported head after about 5500rpm depending on who mods it for ya and your cam characteristics. This is not to say that you cant rev falcons past 5500rpm nor that you wont get more power out of a stroker but expect it to be an off idle monster rather than a dyno queen. Probably about the best effort in this field is Pyro with his safe 309rwkw

 

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Posted: Tue Mar 15, 2005 6:01 pm 
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I think Brad (waggin) looked into increasing the displacement of the 4.0L I6... I believe the answer from his research is that the engines already have very long strokes and its not actually possible to increase the displacement in this manner.

 

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Posted: Tue Mar 15, 2005 6:02 pm 
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ok so what do u mean by of idle monster?? rather then a dyno queen??
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Posted: Tue Mar 15, 2005 6:04 pm 
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slycruza wrote:
ok so what do u mean by of idle monster?? rather then a dyno queen??


s**t of torque down low as opposed to big kw figures up high.

 

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Posted: Tue Mar 15, 2005 6:15 pm 
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Yup dead right. See when you stroke a V8 you allready start with a shorter stroke than a 6 (about 86mm from memory) and a bigger bore which the accompaning head can and do accomadate larger valves so they still breath fairly well when the appropriate cam is used, but in the I6 4ltr there isnt any option apart from the Tickford head to go bigger valves. This is also another reason why ford turned towards 4V heads before looking at thier turbo options due to the much larger valve area available

 

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Posted: Wed Mar 16, 2005 10:40 pm 
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Jaysen wrote:
Yup dead right. See when you stroke a V8 you allready start with a shorter stroke than a 6 (about 86mm from memory) and a bigger bore which the accompaning head can and do accomadate larger valves so they still breath fairly well when the appropriate cam is used, but in the I6 4ltr there isnt any option apart from the Tickford head to go bigger valves. This is also another reason why ford turned towards 4V heads before looking at thier turbo options due to the much larger valve area available


Thats a lot of a**-UMPTIONS there. IF you have ever looked at a OHC port (either int or exh) there is more than enough port there. There looks to be a lot of dead flow area. If the port flow was staturated putting in larger valves would show no flow increase. AND also if the valves were too small a stroke increase would show no power/torque increase. The only motor I would say thats possible on is the 302 ->347 Windsor.
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Posted: Fri Mar 18, 2005 2:18 am 
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Bert wrote:
Jaysen wrote:
Yup dead right. See when you stroke a V8 you allready start with a shorter stroke than a 6 (about 86mm from memory) and a bigger bore which the accompaning head can and do accomadate larger valves so they still breath fairly well when the appropriate cam is used, but in the I6 4ltr there isnt any option apart from the Tickford head to go bigger valves. This is also another reason why ford turned towards 4V heads before looking at thier turbo options due to the much larger valve area available


Thats a lot of a**-UMPTIONS there. IF you have ever looked at a OHC port (either int or exh) there is more than enough port there. There looks to be a lot of dead flow area. If the port flow was staturated putting in larger valves would show no flow increase. AND also if the valves were too small a stroke increase would show no power/torque increase. The only motor I would say thats possible on is the 302 ->347 Windsor.


This is incorect Bert. For optimum performance you should look at achieving a gas velocity of 280-300ft/sec at your desired HP peak. This is allready happening in the std 47mm valves at a little over 5000rpm. If you are to now increast the volume of the filling cylinders then you will efectively increast the gas velocity through the same open valve. To make the big statement that " big valves will saturate port flow " is a load of BS. Big valves give you the oppotunity to run lower lift cams which not only reduce parastic losses due to lesser valve train loads, It also optimises the dwell over nose characteristics of the cam. In effect this will give you a wider and more useable torque band and the valves and seats will now last longer as a good side effect. The arguement here is not the fact that there is ample room in the port walls for them to be modified, its the fact that once you speed that incoming gas up too much you will in effect lose power, the exact same way a std cam runs out of puff at high RPM.

The only way that you will get a stroker kit to work in a 2V 4ltr head is to run a monsterous amount of lift to optimise dwell over nose and to then match the duration to the rev characteristics of the new setup.

 

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Posted: Fri Mar 18, 2005 3:36 am 
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Just another s**t opinion... :roll: :lol:

 

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Posted: Fri Mar 18, 2005 7:01 pm 
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Jaysen wrote:
This is incorect Bert. For optimum performance you should look at achieving a gas velocity of 280-300ft/sec at your desired HP peak. This is allready happening in the std 47mm valves at a little over 5000rpm. If you are to now increast the volume of the filling cylinders then you will efectively increast the gas velocity through the same open valve. To make the big statement that " big valves will saturate port flow " is a load of BS. Big valves give you the oppotunity to run lower lift cams which not only reduce parastic losses due to lesser valve train loads, It also optimises the dwell over nose characteristics of the cam. In effect this will give you a wider and more useable torque band and the valves and seats will now last longer as a good side effect. The arguement here is not the fact that there is ample room in the port walls for them to be modified, its the fact that once you speed that incoming gas up too much you will in effect lose power, the exact same way a std cam runs out of puff at high RPM.

The only way that you will get a stroker kit to work in a 2V 4ltr head is to run a monsterous amount of lift to optimise dwell over nose and to then match the duration to the rev characteristics of the new setup.


How did you work out the gas velocity value??

How can you say you will lose power when gas velocity is too high??

If that is the case why did Nascar use the Robert Yates High port Heads instead of Clevland 4V heads. Yates heads flow more than CHI 3V and have ports smaller than 2V Clevland heads. Look at this site about the porting techniques http://mototuneusa.com/thanx.htm I am not a big fan of his but it is a good example of port velocity and porting.

The std cam runs out of puff because it is generally so small there is a "saturation" of flow as you would call it.

What I am getting at if the head could not flow as well as you are trying to infer it would not make the power that many people are getting out of it, std, XR6, ported, whatever.
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Posted: Fri Mar 18, 2005 8:44 pm 
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What about kraiger heads?
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Posted: Sat Mar 19, 2005 3:05 am 
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Bert wrote:
How did you work out the gas velocity value??

How can you say you will lose power when gas velocity is too high??

If that is the case why did Nascar use the Robert Yates High port Heads instead of Clevland 4V heads. Yates heads flow more than CHI 3V and have ports smaller than 2V Clevland heads. Look at this site about the porting techniques http://mototuneusa.com/thanx.htm I am not a big fan of his but it is a good example of port velocity and porting.

The std cam runs out of puff because it is generally so small there is a "saturation" of flow as you would call it.

What I am getting at if the head could not flow as well as you are trying to infer it would not make the power that many people are getting out of it, std, XR6, ported, whatever.


port gas velocity is calculated by
flow rate=piston speed*(cylinder cross sectional area/port cross sectional area)

or in a 4ltr falcon motor

(rpm*2*stroke in mm/25.4/12)/60*{[ (92.25/2)sq*pi]/[40/2]sq*pi]}=288.83ft/sec@5000rpm

The reason behind the head choice on the nascars as bigger isnt always better and the 4V heads have huge ports.

Saturation of flow is hardly what I would call a std cam. Restrictive flow is more the description and this being said it relates back to my original statement about gas velocity. Once the velocity exceeds 300ft/sec, turblence ( which is very hard to measure ) is a major problem around the port and valve acting like a venturi. This is THE REASON why small cams run out of puff and why bigger cams have bigger lift to allow more flow at higher engine RPM and longer duration so that you can achieve maximum cylinder filling due to the enertia of the moving gas. Cam profiles are what allow you to control your VE and choose when you would prefer max VE to occur. Std cams are designed to give a good VE at lower engine RPM at the expense of HP because this is where most of the every day drivers who buy falcons drive them. By having good cylinder filling at lower RPM you can produce max torque down low too (about 3000rpm off the top of my head in a std falcon)

Maybe some of the Fluid Dynamics Physicists on FM can give a better insight to the fundamentals of gas flow, and the differences between lamina and turbulent flow. A fantastic book regarding performance is Four Stroke Performance Tuning by A. Graham Bell. This outlines in far more detail what I have allready stated, and is backed up by many other texts and real life examples that I have seen.

 

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