The 998 block in my '65 Deluxe is running +0.060 and it is due for a rebuild. I've got a couple of wrecked 1098 engines I can rob cranks out of, and I'm thinking I wouldn't mind having a go at boring it to take standard Hillman Imp pistons a la Steve Vizard.

Has anyone ever done it? Got any clues as to where I can source suitable pistons? I know that JP Pistons will make just about anything you want, so theoretically you get Hillman Imp pistons made with the extra 135 thou gudgeon to crown height to save decking the block (or 998 mini pistons made to 2.677" dia. for that matter). Pricey though.

The worry is probably the crank - the 1100's are the weakest of all mini cranks. Got any suggestions besides stop dreaming and get a SH A+ 1275 for $800 and use that.

You shouldn't have any problems using an 1100 crank, IMO.

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I've bored 3 of these blocks to 68mm for Imp pistons over the years.

1100 crank is fine if kept below 7000, but crack test before you fit it. It is not the weakest of all Mini cranks- that accolade goes to the early `thin tail' 850 ones.

Forget the JP pistons. I would try for Imp pistons in NZ or UK. More of 'em still running there...
If you fit Imp pistons I would use Teflon buttons instead of Imp circlips- which break in a Mini at high rpm...
Put the pistons around the right way- gudgeon pins are offset. Valve cutouts go to RH side looking from fan end of motor.

Taking 0.140" off the block is no problem, just watch the clearance between the front of head and top of the water pump (if running a 940 head). Grind pump away a bit if you have to.

You do need to offset the bores as it says in Vizard's book. Don't be surprised if you break into #4 cylinder bore. If that happens you need to sleeve the oilway with a steel bush, then relieve it where it comes into the bore.

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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.

Thanks dr,

I realised after I posted the question that it'd be far cheaper to deck the block the 140" thou than have special pistons made. Are you saying that JP pistons are not much chop?
Getting suitable pistons seems like it might be the most difficult part of the excercise.

It'd be running a 295 head. What's the performance like? I'm presuming that the long stroke crank would make it fairly torquey

The other thing to consider is what cam to use. They all seem to raving about the SW5 for the small bore A series in the UK. Anyone used one?

I won't criticise piston manufacturers in public- but pm me if you like.

Imp pistons are available, somewhere. Just find out who.
The Imp GT pistons have thicker pins than the standard ones, but use whatever you can get.

Camwise it depends what you want. There are good cams available here frome Russell Eng, Wade, Tighe or Camtech, without getting in from UK.
I'd suggest a cam around 270* or so duration, much more and you'll like revving it too much.
With twin HS4s and a 295 or 940 head it will blow a stock S away.

My first one used a works 544 cam with a 12G940 head. It spun to 9000. Don't do this- the crank won't like you...

<edit> bit more good reading on this conversion here-
http://www.minormania.com/html/mods_aseries.html

For Imp parts, go to URL below and check some of the links there.
http://www.imps4ever.info/tech/supply.html

ENJOY!

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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.

[quote]With twin HS4s and a 295 or 940 head it will blow a stock S away.

I like the sound of that!

I just noticed I put Steve Vizard in my first post. Wasn't he that guy that did the TV show?

Oops! Wrong Vizard (Sorry David)[code][/code]

Note that the Imp gudgeon pins are 5/8" diameter like a Mini, but are about .001" bigger. Get the Mini 1098 rods' bushes honed out to fit at any engine reconditioning shop.

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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.