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BMC A series bore spacing?

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ditchdigger Part of things Posts: 567	BMC A series bore spacing?ditchdigger @ditchdigger
	Nov 18, 2010 5:50:35 GMT Select Post Deselect Post Link to Post Back to Top
	I have long been interested in the BMW K100 head swap for the A series motors, but I think it woud actually be a better fit on a Fiat 850 block. Similar bore sizes, similar sized blocks and most importantly the fiat block has no water pump on the front so there is no need to extend the cams and run a belt. The BMW cam chains could likely be used with minor mods. Anyway....before I go out and drop some coin on BMW parts I might not be able to use I am trying to do some research. My blocks have 65mm bores so I am thinking of the 8 valve K100 head as that is what is used on similar bore A series. My google-fu is apparently weak and I cannot find the bore spacing of a K100 motor so I turn to you, oh knowledgeable retro-riders in hopes to find the bore spacing on the A series motors that use pistons in the 65mm range. This has been on my mind for a year and a half or so but I could never think of a suitable and inexpensive way to deal with the cam timing on a counter-clockwise rotation of a Fiat 850 motor, Well today I sealed the deal on a 1958 fiat 600. It will be delivered in two weeks and the 600 transmissions work with clockwise rotating motors, so this plan is back in planning. Some 600's for your trouble


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TurboDieselWeasel Posted hell of a lot I like fully mechanical fuel processing Posts: 5,188	BMC A series bore spacing?TurboDieselWeasel @dieselweasel
	Nov 18, 2010 11:00:11 GMT Select Post Deselect Post Link to Post Back to Top
	Took some quick measurements: - 998cc A-Series (64.58mm bore): cyl.1&2/3&4: 5.5mm, 2&3: 18mm - 1275cc A-Series (70.66mm bore): 6.5mm The smal-bore engines (848, 948, 998, 1098) have paired bores, hence a bigger spacing between 2 and 3. The big bore engines have even spacing (970, 1071, 1275). P.e. 848cc vs. 1275cc: img23.imageshack.us/img23/4454/smalbigboretv4.jpg If you need very accurate measurements, or any other, I can take them again as soon as I find my caliper... To give an impression on how good the bores of a 1275cc A-series line up with the K engine's 8V head: As you can see, the valves are allready close to the walls with a 70.66mm bore; a smaler bore would probably need pockets for the valves. Bore alignement is about 2mm out (1275cc block). Cheers, Jan
	88 124 Diesel Coupé \| 84 Mini \| 89 124 TAXI \| 79 Clubman Estate motofreibeuter

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Jackman Part of things Posts: 217	BMC A series bore spacing?Jackman @jackman
	Nov 18, 2010 11:49:25 GMT Select Post Deselect Post Link to Post Back to Top
	I am going to be doing a 16v conversion for a mini. I'm not sure with fiat blocks but with the mini I'm going to be lining it so I can get the pistons directly in line with the head chambers. I wont be the first to have done it succsessfully either. Third time lucky with pic.
	Last Edit: Nov 18, 2010 11:52:15 GMT by Jackman

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ditchdigger Part of things Posts: 567	BMC A series bore spacing?ditchdigger @ditchdigger
	Nov 18, 2010 14:49:48 GMT Select Post Deselect Post Link to Post Back to Top
	An 850's cylinders are equally spaced. I think I just need to get a hold of a K100 headgasket to place on the block and see 850 gasket K100 from a BMC 850


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ettorebugatti Posted a lot Posts: 3,417	BMC A series bore spacing?ettorebugatti @ettorebugatti
	Nov 18, 2010 20:38:22 GMT Select Post Deselect Post Link to Post Back to Top
	K100 are also equally spaced if I rememerbered correctly it is 75mm. I'm building a 1293 A+ with a k100 head. Go over here: www.efiminis.olicentral.com/index.php They can confirm or decline my memory.
	Click picture for more

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