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MG MGB Technical - combustion chamber surface

This question really needs to be directed to Peter Burgess. I thought I would open it to general discussion. I have almost finished my porting and combustion chamber Mods, according to Peters' book ( thanks Peter)But, of course I have to get some repairs done as well,( the hole in the push rod tube, oops.)And I have a bad,,,,,,,, let me get this correct, ' BLING ', problem. My combustion chambers are very shiny. I use dental instruments, (that's why it's taken so long, try using little stones and buffers,and a 5 ml plastic syringe to measure the cc volume! I learnt from the push rod hole saga see!)Anyway, would it be harmful Peter, if, to dull off the surface, if I used my small dental Aluminium oxide blaster to as it were sand blast the surface,(50 micron Al particles.) Note, none of the valve work, seat inserts,guides have been completed. To be honest I am sorely tempted to send it to you, but the postage would be ruinous! What do you think? Thanks Mike
J.M. Doust

I have also used a dental shotblaster for cleaning up small metal bits. The 50 micron dust will just take the shine of your polishing! Why do you want to lose the shine?
I have had a couple of heads ( not MGB) polished and ported in the past and they have always been sent back very shiney!
I thought the idea was to help gas flow and also to stop carbon from sticking to the surfaces?
AdrianS

Adrian, What is you surname? It's not Slaney by any chance? Mike
J.M. Doust

Go for the 'flat' finish, if you are brave you can do the top of the pistons too. You will get a rapid light carbon build up which acts as a thermal barrier to keep heat where it needs to be during combustion.

If the inlet ports are 'too' shiny you risk droplet separation. 'Our' Jordan loves a shiny finish and I have to get him to roughen the ports up a little when he has finished, especially with ally heads and manifolds.

I hate to tell you but the work to the valve seats, throats and valves will have more of an effect than the porting.

Raising CR is 'good' too.


Peter
P Burgess

Thanks Peter, no gathered that about the ports and seats being more productive. Let's just say it was fun doing the work, and I can now dull it off a little. But you are quite right, it is good for individuals to carry out some of this work, so that they then appreciate the time professionals put in, and realise where their pounds, or dollars go! Thanks for your input. Mike
J.M. Doust

This thread was discussed between 18/11/2011 and 09/12/2011

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