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Home > Technical Chat > Cylinder head chamber without a beak - does it run ok?

NDT

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Member #: 11884
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Many years ago I took the die grinder to an MG head.
I was tying to reduce the CR as much as possible and basically ground it so there was no “beak” left at all in the chamber - it was basically like a smooth round chamber.

Anyone tried running a head like this?
What are the downsides?


Turbo Phil

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4409 Posts
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Lake District

Not ideal but it will still work. Though a shape like you describe removes all the squish band and promotes poor mixture motion at low rpm.

Phil.

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dazibee

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TRURO, CORNWALL

Mine still has the traditional chamber shape at 8.3:1. Thought I was the odd one out as it seems everybody else had removed the beak to get the Cr down? Avonbar told me the beak causes hot spots and potential for detonation.


robert

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uranus

i gotta beak.

Bicester scramble ,Medusa enjoyed the trip. https://www.youtube.com/watch?v=Q-7I7-nA19U


Turbo Phil

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On the smallbore (non 295) heads I could see there being an issue as the “beak” is very pointed and they often crack from this point. On the 1275 heads the “beak” has a far larger radius. I’ve seen no issues keeping a more traditional shape in this area, in fact I’ve seen some of the best results retaining it.

Phil.

WWW.TURBO-MINI.COM


Chris.williams

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New Zealand

So this is not a good chamber mod?


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Turbo Phil

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My sister is so fit I won't show anyone her picture

Lake District

It’ll work just fine, is it optimum ? Probably not. It’s often a compromise in order to get the compression to a suitable level.

Phil.

WWW.TURBO-MINI.COM


monsterob

206 Posts
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Crewe

Looks like an alien that's had the probe turned onto him ........

Outside the box


slater

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Suffolk / Birmingham

Removing the beak is a bad idea yes.

The engine will still work but it's not ideal for several reasons. Swirl/squish etc. Its also completely unessicary in anything but the largest of forced induction aseries considering you can remove quite a bit of material from other places fairly easily.


Anthony30

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Rainhill, Merseyside.




On 5th May, 2019 monsterob said:
Looks like an alien that's had the probe turned onto him ........
*happy*

On 18th Nov, 2014 D4VE said:
went down to my local hydraulics place and he gave me a suitable replacement larger nipple *smiley*


Jack2eaton

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78 Posts
Member #: 9772
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Sheffield

I’m currently having fuelling issues and wondering if this maybe the route of my problem.

So I have no doubt that the head I have which that is built by Steve AKA Benross is anything south of perfect for creating what I was looking for. As we all are... a very powerful machine.
But does removing some of the squish and swirl promote poor fuelling while at tick over/low RPM while off boost?

My engine is going through spark plugs like nobody’s business and are all black and coked up. We have tested the head and everything else with no oil present. Swapped back to a standard head with full squish and suddenly seems to be running fine.
This seems to be my only conclusion. I am very limited on knowledge though to confirm that this is a definitive conclusion.

Any suggestions what I should try next?


Jack2eaton

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Sheffield



jukka

302 Posts
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Forgotten more than most ever know

Old farts claim that making the combustion chamber perfectly round made the fastest race engines around. That was of course verified with the famous butt dyno. But no hard evidense *smiley*

The first head I cut for my 1380 turbo head had about 42 cc and still retained the beak. I had an old Marina head to start with and the valves were pretty deep in the seats. So I machined the chamber deeper to make the chamber flat. This gave a nice increase in volume (and also screwed up the valve geometry big time)


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Edited by jukka on 14th Jun, 2019.

Home > Technical Chat > Cylinder head chamber without a beak - does it run ok?
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