best bang for the buck in modifying existing heads
Posted: Wed Jan 23, 2002 12:52 am
Bill Robinson has come down to earth from ULTIMATE Formula One heads to something less costly than insane.
We still really need to know the objectives because they make a diff in what to do and what to spend.
I think maybe WRX heads are at the top of the food chain for starters, but would require some other changes too.
However, whatever you start with, I think the choices are going to be very similar about what to do...for the street.
My first choice is a good knowledgeable, skillful porting job.
The rough casting leaves a lot to be desired in the areas of port contour for optimum flow.
The polishing is just an extension of porting, which is no biggie, but the experience to know what to do, and what not to do, in reshaping the ports is valuable and uncommon. There's more than just porting that can be done to the heads. Metal in the area of valve seats and guides can be removed and combustion chambers can be reshaped. Properly done, head porting will provide an increase in torque and power throughout the entire engine operating range.
The legendary 22B uses the same block as the EJ22T. It makes the same horsepower and torque as the other hot Japan Domestic Market Subaru engines, but it leaps away from three times more expensive Porches and whatnot. Because the torque and horsepower peak at about three rpm and stay there all the way up to about 8500. It has what is described as a LOT of area under the power curve.
Cost to rework heads - $1200 to $2500 - power increase: 15% - 25%
Notice it costs about twice as much to realize 2/3 or 67% more gain
Working with the valve train to reduce reciprocating mass and friction, while at the same time increasing size, will enable even better volumetric efficiency to aid in the above gains and also permit higher rpm's for an increase at the top end of the power band. You could also just do a competition valve and valve seat regrind with the fancy valvetrain components, and not the heads for an economical increase.
Cost for new valvetrain components mild to wild - greatly dependent on how exotic you go with materials and components is like doing heads
You can go crazy not only with valve size changes, but also with lifters, springs, keepers, nuts, and associated hardware.
So valvetrain mods can go from almost nothing to right up there with the fairly expensive headwork
Mild to wild valve train mods - $200 to $2500 for an increase of 5% to 10%
Why spend at the top end of that range for only a 5% to 10% increase? Because the 5% to 10% increase would result from the lower mass, friction, and larger valve openings with no other modifications. But usually somebody spending the bucks here is doing it because of the desire to take advantage of some wild cam grind to realize an overall increase much greater than the 10%.
Careful selection of a cam profile can be accomplished to provide more torque down low in the operating range for greater acceleration at lower engine speeds, or more high end power, for greater top speed, or sometimes even, a little of both. And the thing is, the fancy valve shit, and the cams, are kind of married to each other. Other than increasing the size of the valves, the rest of that fancy valvetrain money is not too well spent performancewise without a cam to take advantage of the lower valvetrain mass. So better breathing goes with bigger valve holes, but also lifting the valve higher (lift), keeping it open longer (duration), and ramp rate (acceleration and speed of opening and closing), all contribute to greater volumetric efficiency.
Given a choice, most people go with a different cam before a valvetrain mod, because it's usually less expensive, yields about the same amount of power increase, and can be tailored to increase the power where desired on the rpm band. Also valve size increase with modern 4 valve heads often limited by the neighboring valves, so you really have to spend the bucks to get the bang out of a valvetrain mod only.
Cost for cams is pretty standard per stick depending where you shop -
$500 - $1000 for custom stuff, half that for comp bump sticks off the shelf.
Increase in power: 10% - 15% with stock valves, 15% - 20% with a top of the line valvetrain
So you can get some appreciable increases for a few hundred, or drop somewhere in the hood of 3 to 4 large, depending on where you shop, and pick up a 35 to 40 percent (it's not usually linearly additive) increase in peak power just by optimizing volumetric efficiency, without increasing compression or boost. This assumes your induction system does not choke off your gains upstream or your exhaust does not smother it downstream. Once you get started, it can be hard to stop. That's why they ask how fast do you want to go? They're really asking how much do you want to spend? For me, aside from increasing boost, which eventually leads to temperature associated problems, somewhere in the range of $2000 to $2500 in getting the cylinder head ported with a more aggressive cam profile that enhances low end torque even further is probably my limit. Limits are like armpits, most everybody has one. What's your limit Bill?
Larry Witherspoon
4260 W 182nd St.
Torrance (Los Angeles), CA 90504
day/office phone 562-982-7720
larry.d.witherspoon@boeing.com
ssspoon@aol.com
<http://rd.yahoo.com/M=153641.1824646.33 ... k=22800125> []
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We still really need to know the objectives because they make a diff in what to do and what to spend.
I think maybe WRX heads are at the top of the food chain for starters, but would require some other changes too.
However, whatever you start with, I think the choices are going to be very similar about what to do...for the street.
My first choice is a good knowledgeable, skillful porting job.
The rough casting leaves a lot to be desired in the areas of port contour for optimum flow.
The polishing is just an extension of porting, which is no biggie, but the experience to know what to do, and what not to do, in reshaping the ports is valuable and uncommon. There's more than just porting that can be done to the heads. Metal in the area of valve seats and guides can be removed and combustion chambers can be reshaped. Properly done, head porting will provide an increase in torque and power throughout the entire engine operating range.
The legendary 22B uses the same block as the EJ22T. It makes the same horsepower and torque as the other hot Japan Domestic Market Subaru engines, but it leaps away from three times more expensive Porches and whatnot. Because the torque and horsepower peak at about three rpm and stay there all the way up to about 8500. It has what is described as a LOT of area under the power curve.
Cost to rework heads - $1200 to $2500 - power increase: 15% - 25%
Notice it costs about twice as much to realize 2/3 or 67% more gain
Working with the valve train to reduce reciprocating mass and friction, while at the same time increasing size, will enable even better volumetric efficiency to aid in the above gains and also permit higher rpm's for an increase at the top end of the power band. You could also just do a competition valve and valve seat regrind with the fancy valvetrain components, and not the heads for an economical increase.
Cost for new valvetrain components mild to wild - greatly dependent on how exotic you go with materials and components is like doing heads
You can go crazy not only with valve size changes, but also with lifters, springs, keepers, nuts, and associated hardware.
So valvetrain mods can go from almost nothing to right up there with the fairly expensive headwork
Mild to wild valve train mods - $200 to $2500 for an increase of 5% to 10%
Why spend at the top end of that range for only a 5% to 10% increase? Because the 5% to 10% increase would result from the lower mass, friction, and larger valve openings with no other modifications. But usually somebody spending the bucks here is doing it because of the desire to take advantage of some wild cam grind to realize an overall increase much greater than the 10%.
Careful selection of a cam profile can be accomplished to provide more torque down low in the operating range for greater acceleration at lower engine speeds, or more high end power, for greater top speed, or sometimes even, a little of both. And the thing is, the fancy valve shit, and the cams, are kind of married to each other. Other than increasing the size of the valves, the rest of that fancy valvetrain money is not too well spent performancewise without a cam to take advantage of the lower valvetrain mass. So better breathing goes with bigger valve holes, but also lifting the valve higher (lift), keeping it open longer (duration), and ramp rate (acceleration and speed of opening and closing), all contribute to greater volumetric efficiency.
Given a choice, most people go with a different cam before a valvetrain mod, because it's usually less expensive, yields about the same amount of power increase, and can be tailored to increase the power where desired on the rpm band. Also valve size increase with modern 4 valve heads often limited by the neighboring valves, so you really have to spend the bucks to get the bang out of a valvetrain mod only.
Cost for cams is pretty standard per stick depending where you shop -
$500 - $1000 for custom stuff, half that for comp bump sticks off the shelf.
Increase in power: 10% - 15% with stock valves, 15% - 20% with a top of the line valvetrain
So you can get some appreciable increases for a few hundred, or drop somewhere in the hood of 3 to 4 large, depending on where you shop, and pick up a 35 to 40 percent (it's not usually linearly additive) increase in peak power just by optimizing volumetric efficiency, without increasing compression or boost. This assumes your induction system does not choke off your gains upstream or your exhaust does not smother it downstream. Once you get started, it can be hard to stop. That's why they ask how fast do you want to go? They're really asking how much do you want to spend? For me, aside from increasing boost, which eventually leads to temperature associated problems, somewhere in the range of $2000 to $2500 in getting the cylinder head ported with a more aggressive cam profile that enhances low end torque even further is probably my limit. Limits are like armpits, most everybody has one. What's your limit Bill?
Larry Witherspoon
4260 W 182nd St.
Torrance (Los Angeles), CA 90504
day/office phone 562-982-7720
larry.d.witherspoon@boeing.com
ssspoon@aol.com
<http://rd.yahoo.com/M=153641.1824646.33 ... k=22800125> []
_____
<http://us.adserver.yahoo.com/l?M=153641 ... =289868129>
To unsubscribe from this group, please send an email to:
BC-BFLegacyWorks-unsubscribe@egroups.com
zZz <http://docs.yahoo.com/info/terms/> .