ALH ported head - "free hand"

[burpod]

this is my 3rd head i've ported - it's going to go into @braddies alh mk4 when we do an in-car rebuild (hone, maxpeeding rods, new rings).....

gasket matched.
left the swirl in the intake ports, just enlarged a little bit towards the bowl, shaved out a bit all-round.
exhaust ports opened up quite a bit, but kept the shape expanding in volume outward.

comments welcome. it's hard to get good pics of this stuff, did my best with my phone

it could use a bit better polishing, but i think is good enough. this one i was able to get done in <8hrs.

next head, i'm going to try and find some better bits and techniques for getting the final round a little more even and polished

tools used were mostly my 3000rpm drill + carbide burrs, but i did use makita 1/4 die grinder with a rough cut carbide bit to more quickly get the exhaust ports opened up. also a little bit of dremel for polishing, but it's really too weak, so i mostly used the drill + die grinder

 

[GlowBugTDI]

What determines how much material you remove? In other words, how do you know how much you can remove before issues arise?

 

[jmodge]

One comment, reversion dams rather than gasket matching due to valve overlap. I firmly believe in them

 

[ducatipaso]

have you tried doing volumetric measurements of each port? not flow, just actual interior volume?

 

[burpod]

have you tried doing volumetric measurements of each port? not flow, just actual interior volume?

no, i have not. i've used very basic method of using a medium stiff pipe brush and comparing visually and by feel

i've thought about using some silicone molds or something on a completed victim to be able to get a better idea how i'm doing, and then use those on the next head in order to get things more even/perfect, and then repeat that another time to achieve more "reasonable perfection".

i'll be testing this soon, on braddies car, as well as a similarly ported head on my ahu

i'm not sure what "reversion dams" are - i'll have to google that....

 

[TDIMeister]

One comment, reversion dams rather than gasket matching due to valve overlap. I firmly believe in them

There is no valve overlap to speak of...

 

[jmodge]

There is no valve overlap to speak of...

Not sure what you meant by that, but I'm pretty sure you have a well above average education on TDI's from your posts and history. So I'll bite. Maybe I'll learn something new.
I don't have the cam specs for the TDI handy. Pretty much any internal combustion engine I am familiar with the closing of the intake and the opening exhaust valves overlap, as well as the valves overlapping peak or start of the stroke. Especially true with performance cams. This is what prompted the theory and application of reversion dams in head porting, from what I studied some 40 years ago.
From what I understand that valve overlap is intended to help start the flow of the next stroke cycle within the cylinder. The reversion dam buffers that action of back flow within the port, particularly at higher rpms, when porting has been modified.

So, is my understanding incorrect in your point of view? Do you not believe reversion dams are necessary or useful, and if not, why? Or am I missing something else?

I an also interested in your opinion on grinding out the guide where it protrudes into the port. In my thoughts it reduces the support of the valve and probably the guides and valves life expectancy, having friction take effect on a smaller amount of surface. So I would think in an engine built for longevity, No. Performance where it is torn down and inspected frequently, Ok. Doesn't seem the loss of support justifies the gain in volume, since the stem is still there. Some of my theories on porting, FWIW.

With due respect, looking forward to your thoughts

 

[[486]]

One comment, reversion dams rather than gasket matching due to valve overlap. I firmly believe in them

tdis got negative overlap

 

[burpod]

@jmodge - if yo're referring to the grinds i did on the valve guides - those were the old valve guides which were of course going to be replaced with new ones. i just left them in there for machine shop to r&r - certainly not going to be grinding those

 

[jmodge]

@jmodge - if yo're referring to the grinds i did on the valve guides - those were the old valve guides which were of course going to be replaced with new ones. i just left them in there for machine shop to r&r - certainly not going to be grinding those

Yes and no, it also reminded me of the video of a guy porting ALH heads. He was dimpling them, then he ground out the guides, then I quit watching....because iirc he was doing it on purpose. So maybe I missed that part in the video also. Yeah, you did it the logical way.

 

[jmodge]

tdis got negative overlap

I did not know that. So no valves open at the same in a given cylinder, no valve durations, exhaust or intake, overlapping into or from another stroke?

Are performance cams like that also? @Franko6

 

[jmodge]

tdis got negative overlap

BTW, any funky projects going on up there nowadays?

 

[GlowBugTDI]

I did not know that. So no valves open at the same in a given cylinder, no valve durations, exhaust or intake, overlapping into or from another stroke?

Are performance cams like that also? @Franko6

You can see this when you set the cam for TB replacement. Both lobes on cyl one are forming a v not pushing valves.

 

[jmodge]

You can see this when you set the cam for TB replacement. Both lobes on cyl one are forming a v not pushing valves.

valve overlap happens at the bottom of the piston stroke.

 

[GlowBugTDI]

valve overlap happens at the bottom of the piston stroke.

Pardon my ignorance and confused understanding of what I thought I knew. That makes sense 100%, Not sure what I was talking about, but now I understand.

 

[jmodge]

Pardon my ignorance and confused understanding of what I thought I knew. That makes sense 100%, Not sure what I was talking about, but now I understand.

You probably would have realized it after awhile, but wth, thought I'd point it out anyways

 

[dieseldonato]

Reversion dams are basically useless on forced induction engines. The exhaust side runs under pressure, ie back flow isn't really a concern. Low valve over lap also won't benefit from them. They only really need to be on the bottom of the exhaust port anyway, and again natural aspirated engines will benefit much more then forced induction.

 

[[486]]

valve overlap happens at the bottom of the piston stroke.

1 and 4 at TDC, 2 and 3 are at BDC

 

[[486]]

BTW, any funky projects going on up there nowadays?

Sadly I can't really post about anything much any more.
To put it bluntly, "political progress" is advancing to where I don't feel safe at all with the possibility of being deanonymized by someone taking pictures of any of my projects out and about.

 

[ducatipaso]

I have performance cams in the 24v - I love the exhaust burbles because of the overlap

 

[TDIMeister]

valve overlap happens at the bottom of the piston stroke.

No it doesn't

 

[jmodge]

Reversion dams are basically useless on forced induction engines. The exhaust side runs under pressure, ie back flow isn't really a concern. Low valve over lap also won't benefit from them. They only really need to be on the bottom of the exhaust port anyway, and again natural aspirated engines will benefit much more then forced induction.

I thought about the forced induction factor. I don't agree at the moment that RD would be irrelevant because to make boost the exhaust would be restricted by the turbo vanes and exhaust manifold pressure would be present at the same time as boost. And with boost decreasing, emp would also, seems they may negate each other. Also boost isn't always present, as in cruising. But I've thought about that point, and I do it anyway.
They get put on the intake side also, just in the other direction. But, yeah generally on the exhaust where the port meets the exhaust manifold. Some manifolds have them cast into the collector, such as Sanderson's. I had a set of 2 1/2" center dumps on the stroker in my "72 K5. They were good quality BTW, solid, quiet, fairly cool, and flowed well.

 

[jmodge]

No it doesn't

Made me stop and ponder, That's correct, thank you. TDC, just not on compression stroke. sorry @GlowBugTDI

TDC at the end of the exhaust stroke as it begins the intake stroke. That is the overlap to which I speak of, and that is why I do reversion dams rather than gasket matching.

Aside from knowing the specs of any particular cam, it's no more effort grinding them in than it is to port match. So personally, I will always put them in, generally speaking.

 

[GlowBugTDI]

Made me stop and ponder, That's correct, thank you. TDC, just not on compression stroke. sorry @GlowBugTDI

TDC at the end of the exhaust stroke as it begins the intake stroke. That is the overlap to which I speak of, and that is why I do reversion dams rather than gasket matching.

Aside from knowing the specs of any particular cam, it's no more effort grinding them in than it is to port match. So personally, I will always put them in, generally speaking.

No worries man. I have been blatantly wrong on several occasions recently, so I figured I was just wrong about what I thought made sense to me. Obviously I was able to be convinced otherwise so I wasn't completely sure.

 

[jmodge]

No worries man. I have been blatantly wrong on several occasions recently, so I figured I was just wrong about what I thought made sense to me. Obviously I was able to be convinced otherwise so I wasn't completely sure.

It happens, especially to people who are always trying to stuff 15 gallons of crap into a 5 gallon bucket

 

[GlowBugTDI]

It happens, especially to people who are always trying to stuff 15 gallons of crap into a 5 gallon bucket

I don't think I understand the reference...

 

[burpod]

I don't think I understand the reference...

i think he's referring to his brain capacity i can have a tendency to do that myself lol

 

[jmodge]

I'm convinced it's possible.

 

[GlowBugTDI]

i think he's referring to his brain capacity i can have a tendency to do that myself lol

I'm convinced it's possible.

Oh yes, same here. I am for sure a 15/5gal.

 

[dieseldonato]

I thought about the forced induction factor. I don't agree at the moment that RD would be irrelevant because to make boost the exhaust would be restricted by the turbo vanes and exhaust manifold pressure would be present at the same time as boost. And with boost decreasing, emp would also, seems they may negate each other. Also boost isn't always present, as in cruising. But I've thought about that point, and I do it anyway.
They get put on the intake side also, just in the other direction. But, yeah generally on the exhaust where the port meets the exhaust manifold. Some manifolds have them cast into the collector, such as Sanderson's. I had a set of 2 1/2" center dumps on the stroker in my "72 K5. They were good quality BTW, solid, quiet, fairly cool, and flowed well.

Possibly there could be marginal help, during certain conditions in a forced induction engine, I'm not seeing any in a turbo diesel with near zero cam over lap.