Motor Trend tests heads on a SBF---

[Guest]

[Bossman]

https://www.youtube.com/watch?v=p1w8OU_8-JM

What are your thoughts?

[juiced coupe]

The first two are about what I'd expect, give or take a little.

I think the poor performance of the last is likely due to the valvetrain not being setup for such a small cam, combined with heavier intake valves.

Also, I think that they are correct that they made the wrong decision with the stroker Windsor. At least, for what they were trying to prove.

[knucklefux]

These head shootouts are dumb and they don't prove shit other than which head works best on a given displacement/intake/exhaust/cam.

To see real results, you would need for each head to be part of an optimised combo.  Anything else is just entertainment.

[69 Merc]

Helps to prove that spending a $100 more dollars for a custom camshaft is the way to go for performance.

[Bossman]

It's fun to think about what influenced what. 

Why did the largest head on a stroker motor actually make the exact same power as the small head?  Is it possible the 2.100 valve of the largest head was the problem?  AFR's own website shows they tested it on a 4.155 bore vs. the 4.060 bore of the 195 head.

Since the goal of the test wasn't to max out the heads, then testing 50 cams and intakes per head just isn't going to happen.   It's possible the AFR big valve head will never see it's potential on a small bore engine. 

[knucklefux]

they used an air gap intake and tiny cam on the more appropriately sized heads.  of course that combo fell on it's face.

the "test" didn't have a goal other than "let's see what happens if we throw THIS shit together".  the problem is now some internet hero is going to start screaming that the 195 makes more power than the 220.

is valve shrouding an issue?  likely so.  the bigger issue is the rest of the induction system was limiting the performance of the biggest heads.  just swapping on a box stock vic jr intake probably would have made a big improvement.

[Bossman]

Knucklefux--  I would "think" that the big ones should have at least made the same power as the 195's, but they lost power.  If the intake/cam truly was the culprit, which we know for sure was on the small side, the 220's shoulda at least matched the 195's.  I think it's something else, like the shrouding.

I remember when AFR's were never ever recommended over here because they still used the stock valve centers.  Now I don't know if they have changed in the last few years, but if that's the case, the 2.100 probably is heavily shrouded on a 4.030 bore. 

The torque and hp with those small heads and cam were alot higher than a bunch of 460 builds you can find.  Cost wise, probably not a fair comparison. 

[knucklefux]

with the small intake and cam, the ports on those 220s are gonna be pretty lazy.  the benefit of the bigger heads is going to come with higher lift and duration and less restriction on the intake.  lazy ass ports due to low lift/duration and a restrictive intake will certainly make an engine drop power.

[juiced coupe]

They had over twice the recommended coil bind clearance, with the heaviest intake valves. Not only is that not good, it's dangerous for the engine.

The port math between the 220 head and the street intake was likely horrible, causing reversion.

Small (relatively) headers for use with the bigger exhaust ports. More reversion?

[David Claflin]

That intake would need to ported to feed what the heads needed, pretty much an apples to watermelons comparison.

[Bossman]

That intake would need to ported to feed what the heads needed, pretty much an apples to watermelons comparison.

Should't the intake have been able to feed the same amount of air it fed the 195's?

[juiced coupe]

That intake would need to ported to feed what the heads needed, pretty much an apples to watermelons comparison.

Should't the intake have been able to feed the same amount of air it fed the 195's?

If the transition from the intake to head is bad, it will screw up the intake pulse.

[knucklefux]

the issue isn't whether the intake feeds the 220 as well as it does the 195.  it's about the pressure drop through the intake port.

the more air you pull through a passage of a given diameter, the faster it has to go.

in this case, the air would be moving really fast through the intake, then slow down as it gets into the head.  basically, you are creating a traffic jam in the intake port.

look at any sheet metal intake...you'll see it is biggest at the bellmouth, then gets smaller as it gets to the head.  these guys have unwittingly created a reverse taper.

again, i'm not at all surprised that a mismatched combo fell on it's face.  it should be expected.

i know the response is "ZOMG wat aboot teh scientific methodz!!!  only change wun variable and see wat happenz".  this really just highlights the ignorance of the testers, as changing the heads changes more than one variable.

the only test of value would be an optimized combination for each head.  if that test were performed, you'd see the peak HP increase with each set of heads, and the rpm @ peak would go up as well.  frame the test as an optimized engine of a given displacement to operate over a given rpm range.  if that was done, you'd get valuable results instead of what amounts to mild entertainment on a dyno.

[David Claflin]

That intake would need to ported to feed what the heads needed, pretty much an apples to watermelons comparison.

Should't the intake have been able to feed the same amount of air it fed the 195's?

If the intake was near maxed out at that power level it doesn't matter what heads are on there it won't make hardly any more power.