Slant Six Forum :: Closed chamber head....

Looks like a stock late 70s head and the bits needed to convert a mechanical lifter slant to hydraulic lifters.

According to the parts matrix:

https://www.slantsix.org/articles/parts-matrix/jpg.htm

Casting 3698447-9 is a stock 75-78 head. Nothing special to see. I suspect someone did some serious angle milling on the bottom of the head to make a pseudo-closed chamber head.

...I used this head in an engine build - set-up to have a.040 quench zone. (gasket thickness)
Had to use 7 inch 198 con rods and a special piston to get to zero deck height while keeping the compression reasonable. (9.2 CR & 8.0 effective CR)
A good running "street performance" engine but more sensitive to detonation. (pinging)...

Quote:

Did you enlarge the picture of the chamber I posted? It will actually enlarge twice. Click on it twice and look closely. Look at the edge of the closed side of the chamber at how it's not parallel with the edge of the head. That's impossible if it was milled to a closed chamber, because it would have been round there and would have been squared off with the edge of the head. Even more proof is the fact that the other three chambers face THE OTHER WAY! I believe it is still as cast and has never been milled. I'll know more when it arrives and will post as many pictures as yall would like. So stay tuned.

Could be the small bore that makes the quench area is pretty small.

The modified pistons could be the issue seeing that we left some material on the opposite side, to get the compression number we wanted.
The small bore may need a tighter quench space... .038, .020 instead of .040 but available gasket thickness is a driving factor, unless we resurface the deck and pop the piston above deck a little.
DD

Quote:

I did enlarge it twice. You do know that the stock combustion chamber is not a perfect circle, right It is slightly relieved around the intake valve to avoid shrouding. That supports my theory of aggressive angle milling because if enough material was removed from the head on an angle it would change the shape of the combustion chamber from a circle to a kidney bean shape with one lobe larger than the other. The larger lobe would be the intake valve side. If you look at the arrangement of the chambers and the angles, you see that the side of the chamber that appears higher is the intake valve side. The angle changes after the midline of the head because the slant six valve order from front to back is:

E-I-E-I-E-I-I-E-I-E-I-E

(Old MacDonald had a slant but dropped it on his toe......)

I still say this is a stock head that has been aggressively angle milled.

Quote:

Read Doug Dutra's reply above. That pretty much "unsupports" your theory.

Quote:

Read Doug Dutra's reply above. That pretty much "unsupports" your theory.

How so? I am talking about taking a stock cylinder head, which the casting number on your head indicates that it is, and then milling enough material off the bottom on an angle to completely eliminate the combustion chamber indent in the side of the chamber opposite the spark plug. Doctor Dodge posted a picture and discusses a factory prototype closed chamber cylinder head that was cast with a different combustion chamber shape.

You are obviously hoping to have purchased a rare factory prototype cylinder head. I hope you are right. I wish you the best. But the part number cast into the head and the shape of the chambers leads me to believe it is just a stock head that has been angle milled. But please prove me wrong. That much material being removed would make the head distinctly wedge shaped. Measure and post the distance between the bottom surface of the head and the valve cover sealing surface at all four corners of the head. If I am wrong I will be the first to admit it and congratulate you on your purchase.

Is it possible the detonation was from the sharp edges on the pistons?

Author:	StrokerScamp [ Wed Feb 10, 2021 2:41 pm ]
Post subject:	Re: Closed chamber head....
Quote: Looks like a stock late 70s head and the bits needed to convert a mechanical lifter slant to hydraulic lifters. According to the parts matrix: https://www.slantsix.org/articles/parts-matrix/jpg.htm Casting 3698447-9 is a stock 75-78 head. Nothing special to see. I suspect someone did some serious angle milling on the bottom of the head to make a pseudo-closed chamber head. Then explain how the chambers are tilted away from each other. If it was milled, that's just not possible. I JUST had an early head milled .155" (don't ask, it was actually an accident) and all the chambers came out straight and parallel to the edge of the head. Now you look at that head up there ^^^. Explain how, if it was milled three chambers can face one way and three the other? It's impossible, because the head was cast that way.

Author:	StrokerScamp [ Wed Feb 10, 2021 2:45 pm ]
Post subject:	Re: Closed chamber head....
Quote: Looks like a stock late 70s head and the bits needed to convert a mechanical lifter slant to hydraulic lifters. According to the parts matrix: https://www.slantsix.org/articles/parts-matrix/jpg.htm Casting 3698447-9 is a stock 75-78 head. Nothing special to see. I suspect someone did some serious angle milling on the bottom of the head to make a pseudo-closed chamber head. Did you enlarge the picture of the chamber I posted? It will actually enlarge twice. Click on it twice and look closely. Look at the edge of the closed side of the chamber at how it's not parallel with the edge of the head. That's impossible if it was milled to a closed chamber, because it would have been round there and would have been squared off with the edge of the head. Even more proof is the fact that the other three chambers face THE OTHER WAY! I believe it is still as cast and has never been milled. I'll know more when it arrives and will post as many pictures as yall would like. So stay tuned.

Author:	Doctor Dodge [ Wed Feb 10, 2021 8:17 pm ]
Post subject:	Re: Closed chamber head....
Chrysler engineering prototype closed chamber SL6 head. I think the main focus here was to see if the closed chamber design could be used to improve emissions. The one I have measured 56 ccs so there is not much difference in the actual chamber size. Everything else is the same as the open chamber 75 - 78 head. I used this head in an engine build - set-up to have a.040 quench zone. (gasket thickness) Had to use 7 inch 198 con rods and a special piston to get to zero deck height while keeping the compression reasonable. (9.2 CR & 8.0 effective CR) A good running "street performance" engine but more sensitive to detonation. (pinging) I would use a little less compression if I were to build that combo again. DD

Author:	ProCycle [ Wed Feb 10, 2021 8:36 pm ]
Post subject:	Re: Closed chamber head....
Quote: ...I used this head in an engine build - set-up to have a.040 quench zone. (gasket thickness) Had to use 7 inch 198 con rods and a special piston to get to zero deck height while keeping the compression reasonable. (9.2 CR & 8.0 effective CR) A good running "street performance" engine but more sensitive to detonation. (pinging)... Interesting. I would have thought the quench area would make it less sensitive to detonation. Do you have an idea why it didn't work out that way?

Author:	Doctor Dodge [ Wed Feb 10, 2021 9:08 pm ]
Post subject:	Re: Closed chamber head....
Could be the small bore that makes the quench area is pretty small. The modified pistons could be the issue seeing that we left some material on the opposite side, to get the compression number we wanted. The small bore may need a tighter quench space... .038, .020 instead of .040 but available gasket thickness is a driving factor, unless we resurface the deck and pop the piston above deck a little. DD

Slant Six Forum https://slantsix.org/forum/

Closed chamber head.... https://slantsix.org/forum/viewtopic.php?t=65770	Page 2 of 9

Author:	Reed [ Wed Feb 10, 2021 9:16 pm ]
Post subject:	Re: Closed chamber head....
Quote: Quote: Looks like a stock late 70s head and the bits needed to convert a mechanical lifter slant to hydraulic lifters. According to the parts matrix: https://www.slantsix.org/articles/parts-matrix/jpg.htm Casting 3698447-9 is a stock 75-78 head. Nothing special to see. I suspect someone did some serious angle milling on the bottom of the head to make a pseudo-closed chamber head. Did you enlarge the picture of the chamber I posted? It will actually enlarge twice. Click on it twice and look closely. Look at the edge of the closed side of the chamber at how it's not parallel with the edge of the head. That's impossible if it was milled to a closed chamber, because it would have been round there and would have been squared off with the edge of the head. Even more proof is the fact that the other three chambers face THE OTHER WAY! I believe it is still as cast and has never been milled. I'll know more when it arrives and will post as many pictures as yall would like. So stay tuned. I did enlarge it twice. You do know that the stock combustion chamber is not a perfect circle, right It is slightly relieved around the intake valve to avoid shrouding. That supports my theory of aggressive angle milling because if enough material was removed from the head on an angle it would change the shape of the combustion chamber from a circle to a kidney bean shape with one lobe larger than the other. The larger lobe would be the intake valve side. If you look at the arrangement of the chambers and the angles, you see that the side of the chamber that appears higher is the intake valve side. The angle changes after the midline of the head because the slant six valve order from front to back is: E-I-E-I-E-I-I-E-I-E-I-E (Old MacDonald had a slant but dropped it on his toe......) I still say this is a stock head that has been aggressively angle milled. Or, on second thought, maybe someone spent the time and effort to actually fill in the combustion chambers as discussed by Doctor Dodge here: https://www.slantsix.org/articles/combu ... hamber.htm

Author:	slantzilla [ Wed Feb 10, 2021 9:19 pm ]
Post subject:	Re: Closed chamber head....
Is it possible the detonation was from the sharp edges on the pistons?

Author:	StrokerScamp [ Wed Feb 10, 2021 9:24 pm ]
Post subject:	Re: Closed chamber head....
Quote: Could be the small bore that makes the quench area is pretty small. The modified pistons could be the issue seeing that we left some material on the opposite side, to get the compression number we wanted. The small bore may need a tighter quench space... .038, .020 instead of .040 but available gasket thickness is a driving factor, unless we resurface the deck and pop the piston above deck a little. DD What camshaft did you use? If it had a fairly early (40* or less) IVC event, there's your detonation sensitivity issue. Thanks very much for chiming in, Doug. It's much appreciated. My long engine utilizes the 2.2 non turbo flat top piston with the trough valve relief. I plan on a camshaft with a pretty late IVC event (at least 60) and probably north of 250 duration @ .050" so I don't believe detonation will be an issue there. Of course I won't know until I mock everything up with actual measurements. Thanks again for chiming in. It is very much appreciated.

Author:	StrokerScamp [ Wed Feb 10, 2021 9:26 pm ]
Post subject:	Re: Closed chamber head....
Quote: Quote: Quote: Looks like a stock late 70s head and the bits needed to convert a mechanical lifter slant to hydraulic lifters. According to the parts matrix: https://www.slantsix.org/articles/parts-matrix/jpg.htm Casting 3698447-9 is a stock 75-78 head. Nothing special to see. I suspect someone did some serious angle milling on the bottom of the head to make a pseudo-closed chamber head. Did you enlarge the picture of the chamber I posted? It will actually enlarge twice. Click on it twice and look closely. Look at the edge of the closed side of the chamber at how it's not parallel with the edge of the head. That's impossible if it was milled to a closed chamber, because it would have been round there and would have been squared off with the edge of the head. Even more proof is the fact that the other three chambers face THE OTHER WAY! I believe it is still as cast and has never been milled. I'll know more when it arrives and will post as many pictures as yall would like. So stay tuned. I did enlarge it twice. You do know that the stock combustion chamber is not a perfect circle, right It is slightly relieved around the intake valve to avoid shrouding. That supports my theory of aggressive angle milling because if enough material was removed from the head on an angle it would change the shape of the combustion chamber from a circle to a kidney bean shape with one lobe larger than the other. The larger lobe would be the intake valve side. If you look at the arrangement of the chambers and the angles, you see that the side of the chamber that appears higher is the intake valve side. The angle changes after the midline of the head because the slant six valve order from front to back is: E-I-E-I-E-I-I-E-I-E-I-E (Old MacDonald had a slant but dropped it on his toe......) I still say this is a stock head that has been aggressively angle milled. Read Doug Dutra's reply above. That pretty much "unsupports" your theory.

Author:	Reed [ Wed Feb 10, 2021 9:33 pm ]
Post subject:	Re: Closed chamber head....
Quote: Quote: Quote: Did you enlarge the picture of the chamber I posted? It will actually enlarge twice. Click on it twice and look closely. Look at the edge of the closed side of the chamber at how it's not parallel with the edge of the head. That's impossible if it was milled to a closed chamber, because it would have been round there and would have been squared off with the edge of the head. Even more proof is the fact that the other three chambers face THE OTHER WAY! I believe it is still as cast and has never been milled. I'll know more when it arrives and will post as many pictures as yall would like. So stay tuned. I did enlarge it twice. You do know that the stock combustion chamber is not a perfect circle, right It is slightly relieved around the intake valve to avoid shrouding. That supports my theory of aggressive angle milling because if enough material was removed from the head on an angle it would change the shape of the combustion chamber from a circle to a kidney bean shape with one lobe larger than the other. The larger lobe would be the intake valve side. If you look at the arrangement of the chambers and the angles, you see that the side of the chamber that appears higher is the intake valve side. The angle changes after the midline of the head because the slant six valve order from front to back is: E-I-E-I-E-I-I-E-I-E-I-E (Old MacDonald had a slant but dropped it on his toe......) I still say this is a stock head that has been aggressively angle milled. Read Doug Dutra's reply above. That pretty much "unsupports" your theory. How so? I am talking about taking a stock cylinder head, which the casting number on your head indicates that it is, and then milling enough material off the bottom on an angle to completely eliminate the combustion chamber indent in the side of the chamber opposite the spark plug. Doctor Dodge posted a picture and discusses a factory prototype closed chamber cylinder head that was cast with a different combustion chamber shape. You are obviously hoping to have purchased a rare factory prototype cylinder head. I hope you are right. I wish you the best. But the part number cast into the head and the shape of the chambers leads me to believe it is just a stock head that has been angle milled. But please prove me wrong. That much material being removed would make the head distinctly wedge shaped. Measure and post the distance between the bottom surface of the head and the valve cover sealing surface at all four corners of the head. If I am wrong I will be the first to admit it and congratulate you on your purchase.

Author:	StrokerScamp [ Wed Feb 10, 2021 9:44 pm ]
Post subject:	Re: Closed chamber head....
Quote: Quote: Quote: I did enlarge it twice. You do know that the stock combustion chamber is not a perfect circle, right It is slightly relieved around the intake valve to avoid shrouding. That supports my theory of aggressive angle milling because if enough material was removed from the head on an angle it would change the shape of the combustion chamber from a circle to a kidney bean shape with one lobe larger than the other. The larger lobe would be the intake valve side. If you look at the arrangement of the chambers and the angles, you see that the side of the chamber that appears higher is the intake valve side. The angle changes after the midline of the head because the slant six valve order from front to back is: E-I-E-I-E-I-I-E-I-E-I-E (Old MacDonald had a slant but dropped it on his toe......) I still say this is a stock head that has been aggressively angle milled. Read Doug Dutra's reply above. That pretty much "unsupports" your theory. How so? I am talking about taking a stock cylinder head, which the casting number on your head indicates that it is, and then milling enough material off the bottom on an angle to completely eliminate the combustion chamber indent in the side of the chamber opposite the spark plug. Doctor Dodge posted a picture and discusses a factory prototype closed chamber cylinder head that was cast with a different combustion chamber shape. You are obviously hoping to have purchased a rare factory prototype cylinder head. I hope you are right. I wish you the best. But the part number cast into the head and the shape of the chambers leads me to believe it is just a stock head that has been angle milled. But please prove me wrong. That much material being removed would make the head distinctly wedge shaped. Measure and post the distance between the bottom surface of the head and the valve cover sealing surface at all four corners of the head. If I am wrong I will be the first to admit it and congratulate you on your purchase. The one Doug posted is the same head. I'm not hoping for a unicorn. I just wanted a closed chamber head for quench. And I found one. I have a trained eye and I know what I'm looking at. I did machine work for a number of years and can tell you that head has either been milled VERY little and long ago or not at all. After Doug posted the pictures above, I am inclined to say the head has never been milled. There is no question it left the foundry with closed chambers. Like I said, I'll post more when I get it here.

Author:	Reed [ Wed Feb 10, 2021 9:49 pm ]
Post subject:	Re: Closed chamber head....
OK, keep us posted.

Author:	StrokerScamp [ Wed Feb 10, 2021 10:03 pm ]
Post subject:	Re: Closed chamber head....
Quote: OK, keep us posted. I will.....good or bad. Don't get me wrong, I appreciate your input. I'm the one with the dough in it so I hope it is what it is more than anybody. LOL

Author:	Doctor Dodge [ Thu Feb 11, 2021 5:31 pm ]
Post subject:	Re: Closed chamber head....
Quote: Is it possible the detonation was from the sharp edges on the pistons? The photo of the pistons was taken right after machining. We rounded-off all the sharp edges before installing these pistons but the two raised areas are still pretty "proud" so I guess they could get hot and cause more pinging. As for doing any closed chamber / quench / squish area engine build, finding the right amount of clearance between the piston and head is key. Too little clearance and the piston hits the head, too much will lead to detonation issues. https://www.hotrod.com/articles/ideal-quench-height DD

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Author:	GregCon [ Thu Feb 11, 2021 6:23 pm ]
Post subject:	Re: Closed chamber head....
I think it's kinda cool if it is a 'factory' closed chamber head, and I tend to agree it does not look milled. But aside from that, I think the cool factor is all you get....I doubt the closed chamber is gonna drive any gains.