Ok guys,

So i've heard different stories on the whole centre main strap mod. I am about to build up a supercharged 998 motor and would like to hear your opinions on whether i should do one or not? Vizard etc says yes, but from what i remember the Doc and theMiniMan seem to think its a waste of time?

Yes, the motor will be givin some crap, and thats why i'd quite like my bottom end to stay together

Cheers, Rob

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Mini - The Wizardry on Wheels!

For the sake of a little bit of metal that only adds 2-300 grams or so to the weight and doesn't affect anything else (rotating wieght etc) why not fit it as a bit of extra security ? Even if people are undecided it'll save you having to listen to the "I told you so" routine from people if you didn't fit a strap and the crank failed . If it still fails with the strap , well , you tried all you could to keep it together ..... Just my opinion anyway .

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if you can afford it, why not, i say....

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I say go for it

I asked about this to many people including the heavy weights Graham Russel and our resident Doctor. The consensus is no need. Main reasons against are:

1) You have to modify the old cap to fit a strap which in turn weakens the cap and sort of counters the stregthening of the cap somewhat
2) Cranks don't flex unless you are decellerating from extreme revs using the gearbox (ie, shift to 3rd at 100 miles/h to slow down ) in which case it is user error.
3) If you are going to do it right, get a good quality one and make sure it is fitted properly. This money can be spent elsewhere for much more gain...

Facts: Greig Malure's beast of a car does not use a strap. GR's 1400 stroker does not use a strap. And finally: Engines don't break caps, drivers break caps

Hence just get yourself some good ARP studs instead of bolts or something like that.

For my 1330 120bhp build I will be using the factory cap and bolts with confidence!

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Lillee - 1969 Morris Mini K

http://www.ausmini.com/forums/viewtopic.php?t=6745

What the Doc and MadMatt say makes sense to me! Let them whip.

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"Life is not like a box of chocolates... it's more like a jar of jalapenos. Whatever you do today, may burn your arse tomorrow."

Be very careful what bolts you fit these days. There are bolts out there (made in China) masquerading as Grade 8 etc when they are nothing of the sort.
I recently rebuilt a Mini diff, with NEW Grade 8 bolts. 2 of them peeled the thread off before they were torqued up to spec.
I had to go get 2 more...

BTW avoid PLATED fasteners for high stress applications, plating weakens then due to hydrogen embrittlement.

The stock BL 1275 main cap bolts with the 6 slots in them (this means they are `grade 8') are a good bolt.

Genuine Unbrako brand cap head bolts are real good, too.

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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.

Any point in going for ARP main studs? or is it overkill?

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Mini - The Wizardry on Wheels!

If you need bolts anyway there are a good option, I'm pretty sure you need to mod them a little to fit into the 1275 caps though. These ARP studs are really for Cooper S blocks.

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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.

I Put them on every engine and have never not once had a recall on them. The only reason i put them on is for the safety factor as i dont know how the dick head is going to drive once out of sight.
Rob i would say stick it on it doenst do any harm knowing you have a bit of added protection down there.
I discussed this subject in great detail with Graham russel when i was there and Keith when he came to visit the other week.
Yes cranks dont just break themselves people break them but you are not building a std motor with the normal conditions of stresses being put onto the main cap.
They are cheaper than a new crank and cheaper than a cap (which i have never seen break), usually when a crank lets go its pretty terminal and causes a lot more damage than you would expect.

Only thing i would recommend is once you have fitted the cap etc and tourques it down just get the bore checked out cos somewtimes they tend to puta little extra pressure on the centre of the bearing causing the bore to og out of round so a line bore or even a hone could be needed.

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www.minicranks.com add me to your watch list and come back again soon, under construction.

My old 1310 (soon 1412 stroker) has a centre strap fitted years ago.
I made it out of EN25 steel (tuff stuff!) and machined it to fit on the standard cap without milling the cap flat and weakening it.
I surface ground it so that it has .002" preload when tightened, bore of cap is still spot on.

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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.