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MG MGB Technical - High compersion pistons

Does any one make high compresion pistons for the 1800 cc MG engine? If so how high and the name of the company.
Shaddy MG owner

How high do you want to go? Compression depends on many things besides just the pistons. JE can custom make any kind of piston you desire if you can't get it ready made from a regular company. Check this link out for more info on the subject.

http://mgbmga.com/tech/mgb11.htm
Jared Snider

With stock head cc I am looking for 11.1 comp.
Shaddy MG owner

Shaddy- With a stock CI head , you're going up to 11:1???? Why would you do that? Live next to an airport using airport transfers tunbridge wells, eh?
vem myers

I'm not aware of any pistons that give 11.1 to 1, or is that 11:1 compression. Seems that I've seen some 10:1 piston somewhere. However, which stock head are you using? I believe earlier heads had a combustion chamber size of about 43cc while the later 18V heads had chambers of 39cc. If you spent some time poking around the site I last posted a link to you would have found this article

http://mgbmga.com/tech/mgb25.htm

Sorry I can't be of more specific help, but I'm just trying to make you more aware of the fact that it's more than a matter of simply one size fits all. Of course you can increase compression by milling the head too. So at least there are plenty of ways to arive at your desired destination. My best suggestion is to find a qualified machinist who is familiar with the B series and talk to them about your options.
Jared Snider

Easy,
Not sure why however. Overbore to .060 use later small chamber 18V (42-43cc) style head with early HC pistons, any will do 6cc dish type. Compression will be between 10.5 to 11.25 to 1 depending on any decking done on head or block. Be sure if you use a early block to have the exhaust valve cut-outs installed/milled. Av gas would be a good thing.

HTH

Ron
Ron Smith

Ron, are you sure about that process? I have a big-valve small-chamber head which has been skimmed a few times, with +.060 6cc pistons, and my engine does nothing to suggest that it's running at a higher than stock compression ratio. The only reason it knocks a bit is because I've got 10 (crank) degrees more timing advance than I'm supposed to, to make it scream at high revs. I use 95 RON unleaded. I could believe 9.5:1, but any more than that I think would result in an unusable engine with cheap fuel.

Maybe supermarket fuel is better than I thought :o)
--
Olly
Oliver Stephenson

I don't have the books to hand at the moment, but the 10.5 to 11 to 1 ratio is what I came up with when I built my last engine. .060 overbore 18GB block with later HC small dish pistons and a small chamber alloy head. I had to open up the chambers to around 50cc to get the ratio down to 10 to 1. Gas maybe better in other places, but here in CA even with the alloy head over 10 to 1 would be a problem.

Ron
Ron Smith

Shaddy,
Try Malvern Racing at http://www.malvernracing.com/who.html they have Cosworth domed pistons for MGB.
Leland Bradley

This thread was discussed between 10/03/2003 and 14/03/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.