Cylinder head chamber without a beak - does it run ok?
Turbo Mini Forums

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?

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.

WWW.TURBO-MINI.COM

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.

i gotta beak.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

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

So this is not a good chamber mod?

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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

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

Outside the box

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.

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?

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

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.

Need to have another look at the head.
And maybe try to build it back up with MIG...

Welding cast with a MIG might not be the best idea in the world.
Cast welding is a specialty job.

I remeber turbo Nick had a crack in his head welded up. I can't remember who done it but I think it got him running again until her got a new head.