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For the L-series, that my friends is perfection… zomp.gif

 

Very nice MONZTER. I am glad you found it in your heart to publicly post more info and pics of that sweetheart. bgiorno.gif

 

Thanks Paul,

After this last round of CNC work I can see the areas that I think need to be changed, so back to the computer. I will probably add epoxy to the low spots I don't like, and hand finish one of the chambers to flow test it. At my speed it will be another year, so I figured I would finally show it. I have some other things coming together which I will be posting soon.

Have a good one, Jeff

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Couldnt u still be able to take the P-90 or p-90 Head and polish the intake and exhaust ports ? using a fine dremle polishing tool ? just an thought or ideal what do yall think ?

 

Im in the process of Rebuilding a 1983 280zxt 2+2 digital dash with a P90A head but it has Soild lifter no joke ! im dumbfounded i have pictures.!

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Couldnt u still be able to take the P-90 or p-90 Head and polish the intake and exhaust ports ? using a fine dremle polishing tool ? just an thought or ideal what do yall think ?

 

Im in the process of Rebuilding a 1983 280zxt 2+2 digital dash with a P90A head but it has Soild lifter no joke ! im dumbfounded i have pictures.!

Go back and read the whole thread. I think you'll find the answer to your question.

 

Some P90A's have solid lifters, I think it was theorized that they were the Japanese import motors that were built like that.

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I presume that the ridge line parallel to the flow of air through the ports, that is bisected by the valve guide, is there to enhance swirl? Or is that simply tapering the existing valve guide ie, "streamlined leading and trailing edge" rather than totally grinding it down?

 

Grasshopper ask simple question, and smile politely. :)

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I presume that the ridge line parallel to the flow of air through the ports, that is bisected by the valve guide, is there to enhance swirl? Or is that simply tapering the existing valve guide ie, "streamlined leading and trailing edge" rather than totally grinding it down?

 

Grasshopper ask simple question, and smile politely. :)

 

I have read that completely removing the guide bosses can actually hurt flow. The idea was to thin them out, as thin as the guide, and then give them a leading and trailing edge to enhance the flow around the guides. They are also directed them with the shape of the port to enhance swirl. I have also heard that the trailing edge rib remove the possibility of the air expanding behind the guide and slowing down the flow, as well as the wet flow of the head being improved.

This is all just what I have read, so we won’t know until I finish the port work and flow test it, then run it.

Braap, do you have anything to add about your experiences with the shaping of the guide bosses

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I have read that completely removing the guide bosses can actually hurt flow. The idea was to thin them out, as thin as the guide, and then give them a leading and trailing edge to enhance the flow around the guides. They are also directed them with the shape of the port to enhance swirl. I have also heard that the trailing edge rib remove the possibility of the air expanding behind the guide and slowing down the flow, as well as the wet flow of the head being improved.

 

This is all just what I have read, so we won’t know until I finish the port work and flow test it, then run it.

 

Braap, do you have anything to add about your experiences with the shaping of the guide bosses

 

Thats about what I figured, but I had to ask. makes perfect sense, now that I have seen it.

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Hi All,

 

Great, now hopefully revived, thread!

 

Though anti-reversion has been discussed already, what are your thoughts when relating to turbo engines?

 

In turbo applications, pressure in the exhaust manifold can be much higher than in NA apps, so I'm wondering if exhaust port liners could keep the combustion chamber cleaner (better scavenged due to blocking the burnt mixture from re-entering up the exhaust port).

 

Is it more black and white than in NA apps? Or is the answer still "It depends on .... Helmholtz, ..... turbine specs, etc?"

 

Thanks.

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Any updates on your head MONZTER?

 

No, Nothing new. I got it to the point where I need to get some temporary guides and seats in one chamber and flow test it to see if it is worth finishing. I have not been working on my turbo car much since I got my bike. The NA motor has been running strong. I will be getting back on it after the first of the year and things slow down. I'll keep you posted when I move on with it.

 

MONZTER

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Hi,

 

I'm after some more information on valve un-shrouding,

 

I found this nice link with some good info,

http://www.gofastnews.com/board/technical-articles/1181-porting-school-6-secrets-reduce-valve-shrouding.html

 

but I'm after more information on the 'L' type heads

 

1. is it a right angle cut, or a radius cut between the valve seat and the outer part of the head on the un-shrouding, ( yellow line on picture),

 

2. should the martial that's shown by the red line, be smoothed to the top of the seat ?

 

3. how much martial should be removed ( but still stay with in the head gasket, blue line )

 

4. should I remove the edge where the green line is, and make it a smooth flat surface

 

the pictures is of a E30 head, I'll be wanting to do this on a N47 head (second picture), I don't mind loosing some cc s since it will be put on a turbo engine.

 

thank you for any information

 

Nigel

100_6646-1024_thumb.jpg

100_4653-1024_thumb.jpg

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rumble...rumble...rumble... I hear a big info dump coming :burnout:

 

:lmao: Yeup! How'd you know that? azzolina.gif

 

 

Hi,

 

I'm after some more information on valve un-shrouding,

 

I found this nice link with some good info,

http://www.gofastnews.com/board/technical-articles/1181-porting-school-6-secrets-reduce-valve-shrouding.html

 

but I'm after more information on the 'L' type heads

 

1. is it a right angle cut, or a radius cut between the valve seat and the outer part of the head on the un-shrouding, ( yellow line on picture),

 

2. should the martial that's shown by the red line, be smoothed to the top of the seat ?

 

3. how much martial should be removed ( but still stay with in the head gasket, blue line )

 

4. should I remove the edge where the green line is, and make it a smooth flat surface

 

the pictures is of a E30 head, I'll be wanting to do this on a N47 head (second picture), I don't mind loosing some cc s since it will be put on a turbo engine (see picture)

 

thank you for any information

 

Nigel

 

 

Nigel,

You are on the right track.

This thread talks a little about the techniques and approach to valve unshrouding as applied to the L-series heads;

 

http://forums.hybridz.org/showthread.php?t=110269

 

 

 

When I started learning performance cylinder head work, it was Vizards work that I studied most. His approach makes the most sense to me and after many years building custom cylinder heads, one of which Rebello Racing flowed on their flow bench, (that head was documented here in the L-6 section), and then ran on their dyno matching the power level of one of their custom heads, to me just confirmed what I gleaned from Mr. Vizard seems to be on the right track, (regardless of the actual power numbers Rebello claims from their Dyno, their engines are reknowned for being some of the most powerful and successful L-series at the track, as such I have a great deal of respect for their work). Last year I had the opportunity to speak with Mr. Vizard on the phone, what an honor it was to pick his brain on other aspects of engine design and thank him for sharing his knowledge.

 

Back to your questions;

1) Radius from the seat itself to the chamber wall. Lay the chamber wall back to just shy of the fire ring of the head gasket. With the L-series, I will undercut the chamber wall where the valve head is closest to the chamber wall, yellow and baby blue lines in your pics.

 

2) Sometimes, depending on the casting, that region in red will have a lip just like your intake side does depicted in green. In that case, yes, blend it to be a smooth transition from the chamber roof to the valve seat itself.

 

3) Referring back to #1, remove material out to just shy of the gasket fire ring. Using the gasket you intend to run, place the block deck dowels in the cylinder head and lay the gasket on the head, (the deck dowels positively locate the head gasket for accurately locating the fire ring in relation to the combustion chambers). Now lightly trace the fire ring of each cylinder with a scribe of very fine point felt pen onto the deck surface. The unshrouding process will be a multi step process starting out with a very aggressive cutter to rough shape the chamber, then a fine cutter to blend the rough cut, then coarse sanding wraps to blend the fine cutting, then a fine sanding wrap to blend the coarse sanding wrap and even finer wrap or Scotch-Brite style buffer for polishing in some instances. Keep in mind that each step is a process of material removal, so don’t take the valve unshrouding out the to the fire ring in the first rough cut phase. Leave enough material so that by the time you get to the final chamber prep/blending/polishing, the chamber wall will be "just shy" of the fire ring so as not to compromise the fire-rings sealing ability. wink.gif

 

4) Yes. grin.gif

 

 

Helpful thoughts…

As you are unshrouding the chambers, keep a scrap intake and exhaust valve in the chamber you are working on. Those scrap valves are your sacrifice valves protecting the valve seats, allowing you to hog in the chambers without fear of cutting into the valve seats themselves. For the final shaping, you will have to remove those valves to be able to blend the chamber into the seat, just be very careful and take your time, don't rush it. Run-away cutters happen to even the most experienced porters.

Also, try to visualize the air flow as it flows around the valve head. Lift the sacrifice valve off its seat slowly up to approx max valve lift for the cam you are using as you rough shape the chamber, taking note of the proximity of the valve head to the chamber walls. Keep in mind how air flows, boundary layers, how and why boundary layers separate, turbulence and its ill effects, etc. Ideally you want a flow bench to not only measure your gains, (not just maximum flow, but gains from strategic shaping), but also to replicate your efforts in the other ports. The flow bench numbers should never be used to compare one head to another. Static flow number are not equal to HP potential, only rough guidelines. The flow bench is a tool for the person porting the head, not a measurement of power potential.

 

Here are some pics that may help illustrate that a bit more…

 

Z car N-47 chamber, virgin with the fire ring in red felt pen, and after extreme rough shaping, prior to final smoothing.

N-47style.jpg

 

portedchamber2.jpg

 

 

Material removal areas, for valve unshrouding here; (P90 head shown)

Exhch.jpg

 

Intch.jpg

 

 

Good visual of the “unshrouding”!

ValveliftMedium.jpg

 

A very closed chamber that was unshrouded, coarse sanding wrap finish, (Welded N-42, similar to E30).

chamberMedium.jpg

 

Pretty P90, ready for assembly;

DeckSmall.jpg

 

 

Hope that helps,

Paul

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Thank you very much Paul,

 

The link you provided, I did read that again the other night, and was looking very closely at how the "bowl" area was done,

 

another question, on some of the pictures, the unshrouding work looks like it's radius on one head (first picture), and on another it a sharper angle (second picture), which do you think is better for flow ?

 

Is there anything special needed to be done with the spark plug area on the N47 head (third picture), and lastly, I also assume all sharp edges should be removed

 

Nigel

ValveliftMedium_thumb.jpg

Intch_thumb.jpg

16281_thumb.attach

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Thank you very much Paul,

 

The link you provided, I did read that again the other night, and was looking very closely at how the "bowl" area was done,

 

another question, on some of the pictures, the unshrouding work looks like it's radius on one head (first picture), and on another it a sharper angle (second picture), which do you think is better for flow ?

 

Is there anything special needed to be down with the spark plug area on the N47 head (third picture), and lastly, I also assume all sharp edges should be removed

 

Nigel

 

The first picture is modified chamber, extensive unshrouding performed. The second picture is an untouched virgin chamber, no work has been performed in that chamber, just highlighting the areas to be worked over.

 

As for the spark plug boss, I have played with reshaping it a few different ways over the years. My current approach for the early heads leave the intake side alone, and blend the exhaust side into the chamber wall, mostly just increasing the radius of the bump on that side to smooth blend. On the P-79 and P90 heads, I just make sure there are no protrusions and all radius are smooth and gentle. I'm sure there is spark plug boss shape that lend itself to superior turbulence in the chamber during the compression stroke or one that allows clean efficient flow in and out of the chamber, etc,. MONZTER's approach in relocating the spark plug and angling it as he did seems to be the ideal approach, though not an easy or inexpensive modification.

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1-2cc of material is what is removed from valve unshrouding.

 

A small portion of that, if not all, can be gained back during surfacing depending on how much material is removed during surfacing, which is dependent on how warped the head was or if the customer specifies a minimum of material to be removed during surfacing.

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