This is the way the engine is set up know. Tag reads 99H889V H00741. My block is a 1275(12A497) but only bored for 998, block is made in 1990-91. The head has K7 marked on top, outside of valve cover. Inside has ECA?(N,H) 4004. Tranny reads A/BZ 3 DAM 2886 BC & M. Intake manifold 12G787. Carb cant find #. Engine is complete, not tore down, yet.

WHAT I WOULD LIKE TO DO

What i was told... i could take head 12G295( bigger valve, same size, shape camber), bolt right on, no modifications needed. but did have to change a gear???(one extra tooth, located behind bell housing) to match the new horsepower. Also have a duel carb set up that i want to put on, intake is 12A309 with Carbs H22(mowog 1 1/4" bore)Will this work? Which gear needed? Thanks

A 12G295 has big combustion chambers stock and will reduce your compression ratio. They are hard to come by too. You'd either have to skim the head or change the pistons to bring your compression ratio at least back to stock.

The 12A497 block is a 998 or 1098 block, not a 1275 block. Your engine number is 99H, which is a 998.

On my 998 I installed a "Stage one kit" which will improve performance a little, for further increases you'll need a new head/cam
http://www.minispares.com/product/Class ... STN17.aspx

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12A497 is 1098/998 thick flange pre A+ - made some time before ~1981

don't confuse the part number (12A497) with an engine number that might start with 12A

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As I told you recently on the Mini Mania forum, that is a 998 block, NOT a 1275 one.

A 1275 engine is not just a bored out 998, it is a heavier design, taller block with different bore spacing and bigger main bearings.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

If you google 12A497 you get this thread:
http://www.theminiforum.co.uk/forums/to ... ify-block/

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http://www.sw-em.com/SU_vs_disp.jpg

I love this chart. You can put the twin carbs but they're not really necessary for a fast road 998. They are complicated to tune and have twice as many parts to refurbish or upgrade. They are hs2 not h22.
Su carbs suffer badly from worn spindles, to stand any chance of tuning them properly get them checked out and refurbished if neccesary.

Absolutely no idea what the gear is about, more info needed.

The 12g295 is not an instant upgrade, you have to carefully measure the compression ratio of the original setup to at least stand a chance of achieving the same compression ratio. If you don't it could be a step backwards in terms of power.

What comes in must go out, have you put thought into exhausts? Is the current engine in good condition? Can you even use it or will more power put it under too much stress?

Don't be offended but I am sensing you're new to building engines and minis in general? They are fun little cars and a lot of people out there have the information you need. They just cost coin, so find a good specialist and pay for some of their time.

Listen to the doc, you have a small bore, not a 1275. If you bore out a 998 too much best case you get horrendous oil consumption, worst case you get a door stop.

Call me old fashioned...but...if I had a 998 and wanted to breathe on it...I would be having a good hard look here:

http://russellengineering.com.au/projec ... gine-pt-1/

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