is this ported? Weird AMC head

[bastianshaw]

Stock 885 head intake port:


my weird AMD head intake port:


pic of the head casting mark where the 885 is usually stamped:


Anyone know anything about these heads?
it came off a 89 325i vert

[TurboJake]

It's AMC, Not AMD.

It's a spanish aftermarket head.

As for it being ported? Not sure. It's been said that they are better for it.

[The Humjet]

I wouldn't call it ported is still has a lot of rough casting. Real ported and polished heads have very smooth port finish so air comes in smoother rather than rippling over the rough casting.
As turbojake mentioned AMC is a company who make 885 cylinder head castings. I actually know of someone purchasing one when he found out his original head was cracked and couldn't afford to buy another genuine 885 cyl head. (885 heads are expensive here in Australia)

[jlevie]

Porting has nothing to do with surface finish as it is the practice of opening up the passage to eliminate choke or trip points and thus minimize turbulence. A polished surface isn't necessarily a good thing. The right degree of surface roughness allows a boundary layer to form. Air slides easier on air and if a boundary layer can be maintained there will be less friction and turbulence.

[ForcedFirebird]

That head appears to be a poorer casting mold and the ports needed to be milled to correct.

Porting has nothing to do with surface finish as it is the practice of opening up the passage to eliminate choke or trip points and thus minimize turbulence. A polished surface isn't necessarily a good thing. The right degree of surface roughness allows a boundary layer to form. Air slides easier on air and if a boundary layer can be maintained there will be less friction and turbulence.

This is so true. I have spent several hundreds hours on my flow bench testing textures, valve cuts, seat angles etc. Most head porters only pretty them up since people like shiny things. Usually polish the exhaust to a mirror shine to keep carbon from sticking so easily, even if flow suffers slightly.

[SkiFree]

Not even getting into the problems with polished walls while running a carb.

That head appears to be a poorer casting mold and the ports needed to be milled to correct.
.

I agree, it looks like it was done rather quick and efficiently.

[LJ851]

Here is my guess: AMC has one casting for all M20 heads and it's the smallest port one (eta). What is shown in the pictures is how they modify the casting to be a large port (i) head.

It doesn't look very nice, i wonder how well it flows?

[ForcedFirebird]

Here is my guess: AMC has one casting for all M20 heads and it's the smallest port one (eta). What is shown in the pictures is how they modify the casting to be a large port (i) head.

It doesn't look very nice, i wonder how well it flows?

Not sure about that one. If that were the case, the entire port roof would have to be machined, not just the corners.

[Kershaw]

right, if anyone doesnt quite understand what jim is talking about, look at a golf ball. they have a boundary layer of air, good aerodynamics.

[bastianshaw]

soo is this a good head? i just had it resurfaced at a machine shop

[MR 325]

I'd ditch it and run an OEM 885 head, but that's just me.

[7pilot]

soo is this a good head? i just had it resurfaced at a machine shop

Not a performance head. The transition from the port to the valve pocket is too abrupt.

m

[Sagaris]

right, if anyone doesnt quite understand what jim is talking about, look at a golf ball. they have a boundary layer of air, good aerodynamics.

This is true, however, I get cranky when people believe that the original casting texture of a manifold or head will generate the same results. Newer plastic/composite intake manifolds are smooth inside. A texture could easily be added to the mold without significantly increasing the cost of the mold.

ForcedFirebird, how smooth have you been able to make a port/manifold surface before you saw an increased pressure drop on the flowbench? Are we talking about pressure drops associated with anything smoother than what 600 grit could accomplish? I have my own ideas but it sounds like you have the resources and experience so I am all ears.

[ForcedFirebird]

This is true, however, I get cranky when people believe that the original casting texture of a manifold or head will generate the same results. Newer plastic/composite intake manifolds are smooth inside. A texture could easily be added to the mold without significantly increasing the cost of the mold.

ForcedFirebird, how smooth have you been able to make a port/manifold surface before you saw an increased pressure drop on the flowbench? Are we talking about pressure drops associated with anything smoother than what 600 grit could accomplish? I have my own ideas but it sounds like you have the resources and experience so I am all ears.

Plastic has to be smooth enough to release from the molds, not like molten metal that can have the oil/sand removed easily. The texture allows more flow without removing material. Having the most flow with the least volume removed from ports keeps velocity up. 600 is far too smooth and will lose flow over a properly textured port.