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That actually clarifies a lot. Thanks!
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The point is that a ported 530 will not give up the area under the curve that a 531 will.
Stock for stock the 531 makes a little more power. Nobody's arguing that.
But, if you want to build something that is say, sub 400whp (Jon could comment better on what the actual output might be, I'm just guessing), and doesn't necessitate a gnarly cam, a worked 530 will not be a restriction, and will provide better midrange torque than a 531 will. All you are doing going with a 531 is costing yourself midrange. The 531 is only truly a better choice on a wild enough build where the power band and cam choice reflect the stage at which a worked 531 will have ideal port velocities, etc.
The 531 head was only fitted to the 740 and as far as I'm aware it was always used with an A cam, the A has 10.5mm of lift and 254 duration. The 530 was used on the later cars with a T cam, 9.94mm of lift and 225 duration.
In other words, choose your head (and it's particulars) based on your objectives.
That actually clarifies a lot. Thanks!
Th 531 I used to have had a V cam in it.
Then presumably it wasn't a 531 which o0riginated on a turbo car?
Pretty sure it's a lot higher than that, but I'm not sure of the magic number.You need to use oversize cam followers to go above 12.5mm lift.
Bumped, because it appears people still do not get the point. But, in addition to maybe having better midrange, the LOW range and idle will be more efficient too... Velocity is very important at lower rpm for more complete combustion and torque production. The questionable thing is whether or not the 531's improved chamber design makes up for any of that lost port velocity(and chamber volume is greater than a 530...).The point is that a ported 530 will not give up the area under the curve that a 531 will. Stock for stock the 531 makes a little more power. Nobody's arguing that.
But, if you want to build something that is say, sub 400whp (Jon could comment better on what the actual output might be, I'm just guessing), and doesn't necessitate a gnarly cam, a worked 530 will not be a restriction, and will provide better midrange torque than a 531 will. All you are doing going with a 531 is costing yourself midrange. The 531 is only truly a better choice on a wild enough build where the power band and cam choice reflect the stage at which a worked 531 will have ideal port velocities, etc.
A worked 530 that will perform like a stock 531(better at lower rpm/midrange) may end up costing more than a workable 531. A workable 531 will just be harder to find and have less torque under the lower rpm power curve unless you have a cam and engine setup that is able to take advantage of the high lift flow.I guess the availability vs cost would be a factor in choosing a head. If you can't get a nice 531 at a reasonable cost (then work it) use a 530, as you see no real benefit. Is that the point?
531 on the B230FB and FX with a VX3 cam you get 20hp over a B230F. These motors are reasonably available here.
So with these motors and the B230ET what factor does the cam play in performance increase vs the head?
I just want to post this up so hopefully it will become internet lore.
We've been doing alot of head stuff and for turbo and NA folks using camshafts under 12.5mm of lift and for that matter stock unported intake manifolds, the 531/405 head is a waste of your time as it won't make more power, especially under the curve.
A well ported/filled 530 will make more power than a 531 anyday with a cam under 12.5mm. If going to a bigger cam, you bet, make the jump for the 531/405 heads, but you should also consider one of Nathan Kahler intake manifolds at that point.
Cheers.
Jonathan
Pretty sure it's a lot higher than that, but I'm not sure of the magic number.
edit: says 14mm lift, still with stock buckets
http://yhst-26451710505916.stores.yahoo.net/stagevturbocam.html
Yeah, it's somewhere higher. In the cam chart off the home page with the enem cams at 14.5mm lift the note on the right reads 37mm lifters required. The K15 is 12.5mm lift.
http://www.turbobricks.com/resources.php?content=camspec
If your going above 12.5mm of lift its also a good idea to get rid of the stock lifters and go with a shim under setup (in the stock dia)... much more stable for high lift cams.
Anyone on here sell the stuff to do that? I'm keen on a doing a nice base circle reduced regrind if its not cost prohibitive.