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Location:
Finland
Registered:
November 2002
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Can cylinders be bored eccentric???
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Thu, 29 January 2004 20:56
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What I mean is can cylinders be moved in the block?
I have this interesting project in my mind but only real obstacle what can ruin my plans is that bores in the block are bored oddly and the head (which Im going to pimp to this block) has compression chambers evenly. After rough measurements, I need to move cylinders 2 and 3 (both) 1mm closer to each other and 1 and 4 (both) 0.5mm closer to each other. There is enough meat in the cylinder walls(according to me   ).
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Location:
Melbourne
Registered:
October 2003
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Re: Can cylinders be bored eccentric???
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Thu, 29 January 2004 21:13
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I don't know what engine block your using, I'm not sure if other people do. But it might help if you put that in.
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Location:
Finland
Registered:
November 2002
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Re: Can cylinders be bored eccentric???
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Thu, 29 January 2004 21:39
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Put what in?
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: Can cylinders be bored eccentric???
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Thu, 29 January 2004 23:41
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I think he means put in the name of the engine you're referring to.
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Toymods Club Treasurer
Location:
Sydney
Registered:
May 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 01:15
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i've heard of Minis (the original) being bored offset so that the capacity could be riased past 1400cc, but these were all offset to the side not along the crank.
So short answer, yes it could be done, but I think the machinist would have to be a real expert.
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Location:
Northgate, QLD
Registered:
July 2003
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 04:06
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A read from a couple of different places on the web, how they had to move the bore on mini engines to fit the BMW 1100K motorbike twincam heads onto the block.
Yes, it can be done.
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Location:
Mentone
Registered:
May 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 06:23
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You dont have to but it is better. guy in queensland has a pretty interesting site but i cannot remember the url
Brad
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 06:30
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id be talking to the machinist you plan on using, not us, as they will be more familair with their individual machining capabilities than us 
also, how is the con rod going to line up with the crank journal? are you using floating piston pins etc? even so, the rod will still be offset 1mm from the centreline of the piston body (though that might not really count for much)
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Location:
On your mum!
Registered:
May 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 07:07
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Ed is dead correct in stating that the problem will most likely lie with the conrod to journal alignment posing the biggest problem. The rebuild books generally point to about .25mm side clearance for the rod big end - moving it 1mm will certainly cause this to bind.
As a matter of interest, a lot of engines have different spacing between the cylinders. This is usually due to where the thrust bearing is placed.
In a Toyota 3T the cylinders 1&2 are the same spacing as 3&4 but the spacing between 2&3 is greater (about 2mm I think).
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Location:
1st street on the right
Registered:
November 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 07:49
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Yes it can be done, it's called align boring, usually to align the bores over the crank though. Not to align the bores with the head chambers. It's done to reduce side loading on the rod bearings. The machinist needs to assemble the whole bottom end assy and measure the location of the rod bearings in relation to the bores. It also uses some wizbang machining technique and must go oversize for the obvious reasons.
I'm yet to find someone wiling to do it.
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Location:
Menai area of Sydney
Registered:
June 2003
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 08:23
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Given the add-on effects of offsetting the bore along the line of the crankshaft already mentioned, wouldn't it be easier to weld up and remachine the headspaces ? 1mm would hopefully not affect the valves so nothing else would need to be changed other than the shape (and hence position) of the headspaces.
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Location:
qld
Registered:
December 2003
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 09:32
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to a search for mini on google.com.au aus sites only. you should come up with a qld site owned by "mad matt the mini man" he has a link to the bmw bike head on mini block page. he is also doing the conversion himself, so i guess you could ask him what hes going to do, ive called him before in regards to other things, hes a nice and helpful guy.
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Location:
Finland
Registered:
November 2002
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Location:
Finland
Registered:
November 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 10:38
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http://toyotacover.50megs.com/cgi-bin/i/oldmuck.jp g
Here it is! Glorious 18R. As you can guess, Im not planning OHC head . Anyway I get more pics when my friend gets to his computer and sends those pics to me.
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to a search for mini on google.com.au aus sites only. you should come up with a qld site owned by "mad matt the mini man" he has a link to the bmw bike head on mini block page. he is also doing the conversion himself, so i guess you could ask him what hes going to do, ive called him before in regards to other things, hes a nice and helpful guy.
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Thanks for that but I didnt find those pages YET. I'll keep looking.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 10:40
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what in gods name are you planning on doing with it  ???
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Location:
Finland
Registered:
November 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 10:50
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what in gods name are you planning on doing with it ???
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Believe me! you dont wanna know!
*cough* 16v *cough*
BTW. miniman.com.au
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 11:01
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As far as the mini conversions are concerned, the blocks were machined to give a very narrow (say 1-2 degrees) V in the block. What you are trying to do is to streach the block or head to matchthe cylinder spacing. This will be a huge job and for an 18R, more money than the boat anchor is worth.
Offsetting the conrods is about the worst thing you can do for them. This will build in an eccentricity and bend them quicker than any other mod ever could.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 11:13
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If you want to truly spend the $ you could always get a custom crankshaft made up 
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Location:
Finland
Registered:
November 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 12:06
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As far as the mini conversions are concerned, the blocks were machined to give a very narrow (say 1-2 degrees) V in the block. What you are trying to do is to streach the block or head to matchthe cylinder spacing. This will be a huge job and for an 18R, more money than the boat anchor is worth.
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I'm a studying machinist so I have time (5 days in a week) and I can do everything myself exept boring and balancing of crank and flywheel. I mean every thing, cam belt gears(adjustable of course), block and head machinings to fit, inlet and exhaust manifold, even dry sump system and I only have to pay for material(wholesale prices of course). I can get forged pistons (90mm) 16v turbo head (turbo cams) 18r short block and clutch housing for less than 100¤(or 160AUD). I will have to spend something like 100¤ for gaskets, bearings and rings. As you can see Im not willing to put too much money in this project. So far this would cost some thing like 300¤ and I cant get 18R-G for this price here, not that I would find one. Of course theres going to be unexpected expenses but hopefulle these dont hurt much since this is long term project. I can get turbo and clutch in friend discount.
Ok! back to original question.
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Offsetting the conrods is about the worst thing you can do for them. This will build in an eccentricity and bend them quicker than any other mod ever could.
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I'm not doubting this but I cant understand how it would bend the conrod if the conrod is in the middle of piston centerline and conrod would be plumbd otherwise.
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 12:15
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Heck, if you're going to make them a little off-centre, go crazy!
Honda NR750 bike engine, with oval pistons, eight valves per cylinder, two spark plugs, etc.
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Location:
Finland
Registered:
November 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 12:37
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That's too grazy  .
Have you seen that square piston engine? (was it some sixties Daf???)I have magazine a composition about it somewhere.
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Location:
tallahassee FL usOFa
Registered:
May 2002
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Re: Can cylinders be bored eccentric???
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Fri, 30 January 2004 14:31
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if it'll bolt together right now, just do it! i think the performance loss from the "non-centered" combustion chamber will be slight if measurable at all. and compared to the machining hassles & piston costs, i really don't think it's worth it. i'd weld up the head if there's a bore->gasket->head alignment problem.
i wouldn't call it align-boring, except for multiple holes that have to line up with each other. crank & cam bearing caps/saddles.
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Location:
1st street on the right
Registered:
November 2002
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Re: Can cylinders be bored eccentric???
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Sat, 31 January 2004 12:08
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The single most important thing is that the rod is aligned longitudinally over the crank as and offset (beyond allowable tollerance) WILL bend it. So allign the bores over the crank (along and across) then machine/fill the head to match the bores.
Original specs for Repco Brabham F1 engines was for <50thou offset any way for bore to crank. And this was when they used to be machined by hand not CNC'd. So someone should be able to do more than just a half assed job.
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Can cylinders be bored eccentric???
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Mon, 02 February 2004 02:18
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Just to clarify my previous statement and confirm what clubagreenie said. Looking at the side of the engine, if the centreline of the piston is not inline with the centre of the crank journal you have an offset. The compressive loads on the conrod multiplied by this offset is the size of the bending load. Conrods are not designed to resist bending loads, only tensile and compressive loads.
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