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safe
Joined: 18 Mar 2017
Posts: 698
Location: Sweden
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 Posted: Thu Jan 26, 2023 12:52 am Post subject: |
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Ports and valves are the same in the AMC head? I thought I read somewhere that it was smaller, on the other hand you should not trust everything you read.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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Cedric
Joined: 27 Aug 2004
Posts: 2805
Location: Sweden
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| Posted: Thu Jan 26, 2023 2:21 am Post subject: |
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| safe wrote: | | Ports and valves are the same in the AMC head? I thought I read somewhere that it was smaller, on the other hand you should not trust everything you read. |
The port entry looks a little bit different to my ol n/a pics, could be just hard to see on the pic
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1980 924 Turbo
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Mike9311
Joined: 14 Dec 2004
Posts: 1798
Location: Chicago-ish
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| Posted: Thu Jan 26, 2023 2:29 am Post subject: |
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| safe wrote: | | Ports and valves are the same in the AMC head? I thought I read somewhere that it was smaller, on the other hand you should not trust everything you read. |
I better make sure I answer that question then so we know for sure! Thanks for that. They look the same but looks can deceive
Time to break down a true 924 NA head and get it cleaned up
Let me simplify what I said earlier today. I just want to figure out if there is something holding back these heads no matter what level of boost is being pushed through them. Is there something in the port 'dragging down' the ultimate performance capability of these heads? Initially it started by having to port to match the new larger offset valve but something was discovered (hopefully anyway) that just might be a win win. Maybe its eliminating a turbulent area that would effect a NA and a boosted motor. Maybe its free because its inefficient in the first place. Like an anchor holding us back
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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F3ARED
Joined: 14 Feb 2022
Posts: 29
Location: Melbourne, AUS
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| Posted: Thu Jan 26, 2023 12:26 pm Post subject: |
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| safe wrote: | | F3ARED wrote: | Holden V8s ran a bunch of different valve sizes on the inlet from 45mm up to 50mm. Not sure if they are available in a 6mm stem but length is 132.5mm which is .5mm shorter than a 931 valve.
I wonder if adding a curve to the clay vane could possible promote swirl? |
In the NA the valves are 137mm long! |
Am aware the NA head has a longer valve, hence why i specified 931 when comparing lengths  When I was looking at modifying the original engine before deciding to switch to a 1.8T, I was looking at machining a combustion chamber into the NA head [which would then allow the use of the Holden valve] as the heron-style head is a real drawback. Looking at the cut-away posted however there may not be enough material before breaking into the water passages etc behind it. 931 casting may be different here?
Mike if you are looking at Holden cylinder heads as ideas, keep in mind the early heads [cast iron] are completely different to the later VN alloy heads. Iron heads have a Siamese 2-3 exhaust port so the port shaping may not give you comparable images. In any event, jump on performanceforums.com and search PORTING with TK as the user/poster. TK is Tony Knight Engines, builds a lot of good stuff - but also freely posts photos, info, calculations etc. Depending how far down the rabbit hole you are, some of it may be like telling you how to suck eggs - but there are also lots of stuff like welding in material, or using epoxy etc to reshape or resize ports to try and increase port velocity.
https://performanceforums.com/forums/forum/general/general-discussions/203685-doing-really-really-stupid-shit-with-a-9-port-holden-head [discussing moving valves, repositioning head on block, using dividers etc to alter and increase airflow because the old Holden 6cyl engines had the pushrod running through the port]
https://performanceforums.com/forums/forum/general/general-discussions/197186-basic-holden-vn-heads [bit on epoxy filling in here]
N-
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1977 Porsche 924
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safe
Joined: 18 Mar 2017
Posts: 698
Location: Sweden
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| Posted: Thu Jan 26, 2023 5:31 pm Post subject: |
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| F3ARED wrote: | | When I was looking at modifying the original engine before deciding to switch to a 1.8T, I was looking at machining a combustion chamber into the NA head [which would then allow the use of the Holden valve] as the heron-style head is a real drawback. |
The draw back of the head is the valve angle, comparing it to an old 911 2.2 with a bore of only 84 mm, that head crammed in 46+40 mm valves (and that is not the maximum). The hemi head isnt't the greatest design either but its way better. It also allows for a decent port that hasn't got to turn 180 degrees.
I don't think you have much to gain in machining a combustion chamber into the head. I think you could improve the combustion chamber by using another piston design, moving it closer to the head for squish and adding bigger valve pockets instead.
Vizard has a section in a book about modifying heron heads I remember.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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morghen
Joined: 21 Jan 2005
Posts: 9095
Location: Romania
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| Posted: Thu Jan 26, 2023 5:47 pm Post subject: |
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I think its time to start testing with 3D printed models.
If you want to go with the insert idea, i think the easiest and quickest would be the key-slot option where you would just drill at a specific angle and position into the port and 3D scan that area, build the flow improving feature and print it to fit the drilled head, then you can do some precise adjustments to the geometry. This would be super cool if we would get away with just one fairly simple drill and sliding in some inserts and get 20cfm more. I mean thats good value / effort.
This could be a super popular and easy to do at home thing for all of us.
You could provide a set of 3D printed / Plastic machined jigs to help position and orientation of the the drill and it could even be done in a simple pull down drill machine with some proper discipline and those jigs.
You would just ship the jigs and the inserts, we would use the jigs to drill and slide in the inserts. Additional peace of mind we could tack the end of the inserts on the heads but its a simple job and would probably not cost a fortune either.
This could be a pretty cost effective relevant yet easy to do upgrade for these engines.
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Mike9311
Joined: 14 Dec 2004
Posts: 1798
Location: Chicago-ish
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| Posted: Fri Jan 27, 2023 12:28 am Post subject: |
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Thanks for the links F3ARED
I really like seeing what others do with their issues and obstacles
Safe, its funny because I see similar volvo heads with the same sort of issues. Naturally I feel like we should be able to match the the volvo numbers. I just have this 'itch' (thanks Jacob  ) that there is something more
Morghen, I am close for sure. I need to take better scans. Plus I want to test the concept on the NA head and map the velocity readings to see if we can get more info. 10-15cfm is easy in the 931 head.
A while back I knew this day was coming so I started a test scan-arm probed port. Still getting a hang of that process. Going to keep working on the scanning process
The key process does seem like the way. Of course I like the idea of putting in a locking slot of some sort that holds it. Letting my mind play with that idea. Needs to be simple so anyone can do it.
Would be awesome if the NA reacts the same way and a 15-20cfm insert is all that's needed
EDIT: I wish I had all day and night to work on this My mind is!
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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Mike9311
Joined: 14 Dec 2004
Posts: 1798
Location: Chicago-ish
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| Posted: Fri Jan 27, 2023 12:53 am Post subject: |
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I want to add something I forgot. The chamber
My chamber is supposed to help the flow from the long side radius and center port. The flow here is at its greatest and I have opened up this side as well as directed it by curving (hopefully into the piston pot). All modern heads are done this way. I have see 931 heads done the opposite way, with the short side (by the notch) ground away and shaped. Vizard speaks to this idea as well, to open up the chamber on the long side radius. He shows this over and over and isn't the only one
I visualize this part of the chamber as part of the 'nozzle' as the valve opens
I have yet to finish the chamber. In the past up to recently, I was a squish/quench guy but this change is because you have to get it right or not at all. If it isn't right it can cause issues. I will be softening those areas strategically. One idea is to help slow the quench reaction that pushes against the long side radius flow.
Its complicated in a way because the spark plug is opposite of most examples
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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F3ARED
Joined: 14 Feb 2022
Posts: 29
Location: Melbourne, AUS
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| Posted: Fri Jan 27, 2023 7:54 am Post subject: |
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| safe wrote: | | F3ARED wrote: | | When I was looking at modifying the original engine before deciding to switch to a 1.8T, I was looking at machining a combustion chamber into the NA head [which would then allow the use of the Holden valve] as the heron-style head is a real drawback. |
The draw back of the head is the valve angle, comparing it to an old 911 2.2 with a bore of only 84 mm, that head crammed in 46+40 mm valves (and that is not the maximum). The hemi head isnt't the greatest design either but its way better. It also allows for a decent port that hasn't got to turn 180 degrees.
I don't think you have much to gain in machining a combustion chamber into the head. I think you could improve the combustion chamber by using another piston design, moving it closer to the head for squish and adding bigger valve pockets instead.
Vizard has a section in a book about modifying heron heads I remember. |
My thinking was along the lines of trying to replicate the 931 head out of an NA so that off the shelf 931 parts could be used AND getting the squish area to be in the chamber. While the hemi-style chamber isnt exactly cutting edge it is still a decent improvement and gains are there to be had. As far as heron heads go and using the piston as the squish area, a lot of modern diesels including the Isuzu 4JJ1 still do this.
| Quote: | | My chamber is supposed to help the flow from the long side radius and center port. The flow here is at its greatest and I have opened up this side as well as directed it by curving (hopefully into the piston pot). All modern heads are done this way. I have see 931 heads done the opposite way, with the short side (by the notch) ground away and shaped. Vizard speaks to this idea as well, to open up the chamber on the long side radius. He shows this over and over and isn't the only one |
My understanding of it [and I could be wrong] is that the majority of the gains are always on the long side for a reason; it essentially gives you the benefit of increasing the CSA AND allows the port path to be raised at the same time. The flow also tends to be able to have a higher velocity in this area and stay laminar as the path is smoother so its less likely to separate from the port and become turbulent. Most of the work ive seen tends to limit the work on the short side of the port to blending/smoothing the short turn radius and removing any "hump" that some engines have in the port floor.
The above of course assumes that said hypothetical port is able to have material removed from the roof of the port and there arent any galleries above it that will rear their head when a die grinder is run over it!
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1987 Range Rover Classic 3.5L V8 |
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Mike9311
Joined: 14 Dec 2004
Posts: 1798
Location: Chicago-ish
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| Posted: Sat Jan 28, 2023 12:41 am Post subject: |
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| F3ARED wrote: |
My understanding of it [and I could be wrong] is that the majority of the gains are always on the long side for a reason; it essentially gives you the benefit of increasing the CSA AND allows the port path to be raised at the same time. The flow also tends to be able to have a higher velocity in this area and stay laminar as the path is smoother so its less likely to separate from the port and become turbulent. Most of the work ive seen tends to limit the work on the short side of the port to blending/smoothing the short turn radius and removing any "hump" that some engines have in the port floor. |
So far I can say this seems to be the case in the port when I stick something into it while flowing. It isn't so much right at the opening ceiling but slightly in a bit. You can feel it with a finger and hear it as you do it. I suspect the vel readings will bear all this out
Once this particular head is finished, someone will likely have me do a NA head or I could do another one for the '80 I have in assembly right now. Would like to flow the head that's on that one since I did a really simple clean up on that one waaaay back in the day
Yesterday I started tearing down a NA cylinder head (really think 924 NA and AMC are the same by the looks of it) and I also disassembled a 931 intake. Both need major cleaning today.
The 42mm offset 931 head is on the bench with a raised cylinder so I can clear the intake to bench top which is still difficult. I am at the edge of height but it should work at least for comparison. The last test 'baguette vane' has not been removed for this reason
The NA head allows me to take some valve height readings from top to maybe the cam journal. Need to get grooves cut in the new valves. Don't want to screw that up
Edit: And Morghen, my stupid CAD example has the drill hole way too big
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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Mike9311
Joined: 14 Dec 2004
Posts: 1798
Location: Chicago-ish
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| Posted: Sat Jan 28, 2023 12:55 am Post subject: |
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One thing we have not talked about, an injector. Tests so far are without an injector. Would like to see what happens when part of the system
Will get that tested as well
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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fblade
Joined: 06 Dec 2020
Posts: 43
Location: UK
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| Posted: Sat Jan 28, 2023 4:05 am Post subject: |
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| Mike9311 wrote: | One thing we have not talked about, an injector. Tests so far are without an injector. Would like to see what happens when part of the system
Will get that tested as well |
Have you done a test with the injector hole filled in/blocked off somehow to see if that makes any difference to flow? |
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Mike9311
Joined: 14 Dec 2004
Posts: 1798
Location: Chicago-ish
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| Posted: Sat Jan 28, 2023 4:38 am Post subject: |
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| fblade wrote: | | Mike9311 wrote: | One thing we have not talked about, an injector. Tests so far are without an injector. Would like to see what happens when part of the system
Will get that tested as well |
Have you done a test with the injector hole filled in/blocked off somehow to see if that makes any difference to flow? |
That is how the testing has been so far. Just closed with clay. This is why I am making sure that whatever is done in the end reflects all these additional factors. Going to make sure it is tested
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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fblade
Joined: 06 Dec 2020
Posts: 43
Location: UK
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| Posted: Sat Jan 28, 2023 5:24 am Post subject: |
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| Mike9311 wrote: |
That is how the testing has been so far. Just closed with clay. This is why I am making sure that whatever is done in the end reflects all these additional factors. Going to make sure it is tested
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Ahh nice one, can't wait for the balls to the wall turbo version, I'm hoping for 200+ cfm on an 87.5-88mm bore. |
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Mike9311
Joined: 14 Dec 2004
Posts: 1798
Location: Chicago-ish
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| Posted: Sat Jan 28, 2023 5:49 am Post subject: |
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| fblade wrote: | | Mike9311 wrote: |
That is how the testing has been so far. Just closed with clay. This is why I am making sure that whatever is done in the end reflects all these additional factors. Going to make sure it is tested
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Ahh nice one, can't wait for the balls to the wall turbo version, I'm hoping for 200+ cfm on an 87.5-88mm bore. |
My opinion is that we can get 200cfm with street friendly performance. Given how close I am now already, it seems totally possible. BUT, and its a big BUT, the high flow number so far needs higher lift which is strange given that its over the curtain area criteria. I wonder if its my 42mm valve going beyond the chamber as I have it shaped now? I do have 'cc room left with which to play
If you want no torque, just shovel it in there max flow that's different Not sure I want a donate a head to that project lol
Edit: (Pic is old but close to how it is now) Long side port radius is on the side of the weld bead opposite the spark plug location. This part of the chamber is not yet finalized
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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