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Old 08-05-2021, 08:09 AM   #1
Chilm
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Default What if I do this?

Hi all,

I've got a question: what if I do the same (hemi like) as in the picture below with my 531 bowls?
Yes the static compression will drop significant but does that matter with a turbo on 1 bar?

Gain imho is more cc's and better flow in the head especially when going for tight squish.
The picture is a project on the tube from "Stav-Tech" very interesting video's and experiments.

Picture is from a 530 head and personally I would do this a bit more even (without the humps).

Thanks in advance for you goeroe's input

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Old 08-05-2021, 01:07 PM   #2
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Couple questions first: are there any measured performance/fuel economy gains from this? How similar to your combination was the one that was tested?

I will tell you I don't like it, but that's because I like as much compression ratio as any given combination can handle. If you're at 1bar, and drive the car every day or almost every day, I would be looking for about 9:1 depending on tune and camshaft and fuel availability. Opening the chamber too much will make the CRs too low, making the engine extremely lazy and yielding poor fuel economy. If you wanted to run 2.5bar and had to stick with a stock head and a relatively short duration camshaft, it might be worth looking into.

Basically, if you do this and lose 1.5 points of compression, let's say, you're going to lose about 6-7% of your power. That means the change in the chamber has to yield a 6-7% power gain just to get you back where you started! Not impossible but highly unlikely.

Now, if you just want to do this to see what happens and you have the time and ability, I'd say go for it.
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Old 08-05-2021, 02:57 PM   #3
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Originally Posted by shoestring View Post
Couple questions first: are there any measured performance/fuel economy gains from this? How similar to your combination was the one that was tested?

I will tell you I don't like it, but that's because I like as much compression ratio as any given combination can handle. If you're at 1bar, and drive the car every day or almost every day, I would be looking for about 9:1 depending on tune and camshaft and fuel availability. Opening the chamber too much will make the CRs too low, making the engine extremely lazy and yielding poor fuel economy. If you wanted to run 2.5bar and had to stick with a stock head and a relatively short duration camshaft, it might be worth looking into.

Basically, if you do this and lose 1.5 points of compression, let's say, you're going to lose about 6-7% of your power. That means the change in the chamber has to yield a 6-7% power gain just to get you back where you started! Not impossible but highly unlikely.

Now, if you just want to do this to see what happens and you have the time and ability, I'd say go for it.
Clear answer, especially cuz it IS my daily driver with a mild (V) cam, some port work on the turbo and in/outlet, chipped and 1 bar max. The picture from the head is indeed from a guy who pumps 2.3 bar and revs to 7500 rpm. Looking at your answer it's probably a bad idea for my tune, never to old to learn, thanks

P.s. it's probably cuz I love porting and working the head so much, I'm heaving a couple of 530's laying around, maybe I can work them like above picture and sell them =P

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Old 08-05-2021, 03:07 PM   #4
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B230FT/FK engines have 8.7:1 CR stock using dished pistons. If you covert your chambers to this hemi-style chamber design you could compensate for the loss of compression by changing to flattop pistons (i think from a B230e) I think you would end up with more or less the same CR running your desired hemi-style head.
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Old 08-05-2021, 03:24 PM   #5
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B230FT/FK engines have 8.7:1 CR stock using dished pistons. If you covert your chambers to this hemi-style chamber design you could compensate for the loss of compression by changing to flattop pistons (i think from a B230e) I think you would end up with more or less the same CR running your desired hemi-style head.
Hi Jan, long time no see.

If so (flattops) will I gain more torque and speed (because better flow) in your opinion?
And having the flattops in mind the deleted material from the bowls is more then 2 times as much (compensate wise) imho.

Good tips and nice discussion.
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Old 08-05-2021, 04:04 PM   #6
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The flattops deliver 10.3 compression, you'd want around 9.0. The chambers come in at 53cc for a 530 iirc, so I'd guess you could port 10cc away.

I'd mostly focus on deshrouding the valves and taking a look at Chevy racing engines. Hemi's also have hemispherical pistons, Chevy's don't and have the same heart shaped chamber for flame propagation
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Old 08-05-2021, 04:40 PM   #7
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I think that you might be confusing "tumble" with "flow". A cylinder head's chamber design helps to induce "tumble", that is, turbulence in the air/fuel mixture to help burn characteristics. A true hemi head (like a 426 Chrysler from the 60's) has improved flow mostly because it can have HUGE valves, not from the chamber design. The massive dome on the piston to get appropriate compression ratio adds weight, is not good for flame travel, etc. As I understand it, the best chamber is the smallest one you can have with the correct valve size that does not impede flow in or out, that does not need a domed piston to get the desired compression ratio, and where all points are equidistant from the spark plug.

It's a lot to ask!

I'd agree with Swedbrick, if you want to look at excellent 2-valve chamber designs, look no further than the GM LS and LT series engines.
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Old 08-05-2021, 05:03 PM   #8
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I'd agree with Swedbrick, if you want to look at excellent 2-valve chamber designs, look no further than the GM LS and LT series engines.
Mkay, I have to look in to it then, and you are right I mean "tumble" as you call it.
If I'm honest, it strikes me every time how well designed the head is, especially the 531. Never understood why they were not standard on the for instance B230FK's. Allthough the outlet port design could have been better size wise.

@swedbrick: right, deshrouding is allways the first thing I do, I've even made a Perspex template that I use for it (to scribe with a fine felt tip pen) so the shape is even at every bowl.
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Old 08-05-2021, 05:11 PM   #9
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This is what you mean, exept the direct injection incorporated here?




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Old 08-05-2021, 06:11 PM   #10
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Yes basically, I looked up a lot of pictures of various 2 valve combustion chambers, thought of how the spark would propegate from the plug, and changed the chamber up from there (very little, only around the valves to deshroud. The aim is to make the combustion first go across the chamber, and then top to bottom, in a nice even push. When this flame is not nice in even, it will bump into itself, or explode in patches, which is the knock we hear.

This hemi design might be countering that, since it removes the squish area reducing chamber mixing. That is also the idea behind tight squish, first you light the chamber as quickly as possible with a homogeneous mixture, such that when the piston is going down your pushing straight on it. This artice on chevy's might be a bit clearer:
https://www.motortrend.com/how-to/94...earance-guide/

These are the pictures I used for reference, with the my own at the end:
Volvo 530/531 porting inspiration/own work



Erland Cox's website also has a good example, found here on the waybackmachine:
https://web.archive.org/web/20190902...olvo8v531.html

PS: I have a head core left over for practice if you want to experiment with a bit more freedom, that one will never see a b230 again. It's still waiting to get sectioned to create some good pictures of the 530 ports for reference, so I'd want it back eventually;)

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Old 08-10-2021, 02:31 PM   #11
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Nice Swedbrick, yeah I know Erland's website he is my Hero as is Stealth fti (no longer amongst us). I had a regrind camshaft of Erland I just sold it lol. I think the dent in the wall of the 530 and 531 is to propagate that flamefront. Also I'm thinking of dimpling the underside of my inlet valves as done with golf balls to quicken the airflow.

Your head is exactly the way I did it too (531 head):



And... I noticed a lttle ridge at the underside of the inlet valves and dunno what is the use of that? Should I make that flush or is that a dumb idea?

Also we must meet once to chit-chat about our bricks =P

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Old 08-10-2021, 02:50 PM   #12
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Adding a bowl/dish in the piston is a better approach to lowering compression, because of the propagation issues mentioned already.
Deshrouding can be good, but quench is very important. Turbulence helps a rapid burn, and the slower the burn, the more heat you lose.
The ridge is from a fast (cheap) machining process at the factory, but you shouldn't remove it completely. A contour in the bowl, especially intake side, helps low-lift flow.
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Old 08-10-2021, 03:54 PM   #13
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Originally Posted by mikep View Post
Adding a bowl/dish in the piston is a better approach to lowering compression, because of the propagation issues mentioned already.
Deshrouding can be good, but quench is very important. Turbulence helps a rapid burn, and the slower the burn, the more heat you lose.
The ridge is from a fast (cheap) machining process at the factory, but you shouldn't remove it completely. A contour in the bowl, especially intake side, helps low-lift flow.
Thanks for your input Mike, I might diminish that ridge then without the sky falling down on me. And what about my idea to "dimple" my intake valves underneath, has this been done before with good results or is it a bad idea?

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Old 08-10-2021, 05:25 PM   #14
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P.s. interesting article about dimples and race cars I just found:

Click

And this but what must be the conclusion:



Picture stolen from Click

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Old 08-10-2021, 06:45 PM   #15
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I tried it in the port, it was mostly a lot of work, no idea if it worked. In the V8 racing scene it's more common to grind ridges in the back of the valve, it's easier to do with a Dremel and a drill press.

Some inspiration;)
https://www.allpar.com/threads/prepp...rmance.229040/
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Old 08-10-2021, 07:38 PM   #16
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Old 08-10-2021, 07:47 PM   #17
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The return of the somender grooves...

This should be fun.
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Old 08-10-2021, 07:50 PM   #18
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Haha, those pics are very old. They are to show unshrouded valves
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Old 08-10-2021, 09:41 PM   #19
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Dimples don’t speed up golf balls. They slow the ball. But that drag on the underside from backspin gives the ball lift, keeping it from hitting the ground right away, so it goes farther.

A groove above the face of the exhaust valve supposedly helps control reversion at low lift.
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Old 08-11-2021, 03:20 PM   #20
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Yup, but no go for me
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Old 08-11-2021, 03:51 PM   #21
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Erland Cox's website also has a good example, found here on the waybackmachine:
https://web.archive.org/web/20190902...olvo8v531.html
Hi Heime, you don't need the wayback machine, just go directly to his website:

https://www.topplocksverkstan.se/
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Old 08-11-2021, 05:40 PM   #22
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Hi Heime, you don't need the wayback machine, just go directly to his website:

https://www.topplocksverkstan.se/
Cool, didn't realize it was back up, it was gone for a while if I recall correctly
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Old 08-11-2021, 07:22 PM   #23
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Dimples don’t speed up golf balls. They slow the ball. But that drag on the underside from backspin gives the ball lift, keeping it from hitting the ground right away, so it goes farther.

A groove above the face of the exhaust valve supposedly helps control reversion at low lift.
Boost keeps it from doing that haha
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