10 replies to this topic

[benspickup2011]

I'm building a 998 with a 286 kent cam, 12g940 head and twin su's. The question is- is it best to go down the route of fitting a centre main stap, or as ive recently been told by a few companies, not to fit one and allow the crank to flex, The engine will be used sparingly in my pick up! many thanks, ben

Edited by benspickup2011, 07 February 2011 - 08:37 PM.

[MRA]

It's more a case of the max revs you are thinking of ?

With your combination I would be more interested in a cross drilled crank to get better reliability....

[Cooperman]

A 998 with a 286 cam will really need to rev, so a centre strap is might be a good thing to have. Of course, the 998 being a shorter stroke than a 1275 will not present the same problems and the old Cooper 998 used to rev freely right up to around 7000 rpm in bursts. My son had a 1967 Cooper 998 with a 286 and he didn't have a centre strap and had no problems.
It's up to you really.

[bmcecosse]

I fitted one on my 'race' 998 - it worked well. No idea if it would have been ok without - but why take the chance? And I agree - a 286 cam on a 998 will want to be revved! The 'flex' idea is nonsense. The strap is there to support the main cap - which is cast iron - and doesn't flex.....

[jamie@thefatgarage]

I have a main strap that I got for my 1293 Turbo. I've found it very useful indeed. I use it as a paperweight to hold down all the invoices for the rest of the car, or when I open the office door they all blow around.

[benspickup2011]

It will need reving and im sure it'l get plenty. It might be ok but then if the crak snapped id be kicking myself. For the cost of fitting one, i might just do it. I assume its simply a case of taking my main cap and getting it milled flat?

[Cooperman]

It will need reving and im sure it'l get plenty. It might be ok but then if the crak snapped id be kicking myself. For the cost of fitting one, i might just do it. I assume its simply a case of taking my main cap and getting it milled flat?

Yes, that's all there is to it. Do buy from a reputable supplier as the new bolts must be the correct quality.

[MRA]

Cast iron does flex, just not as much as some other metals.

What lets most of the centre main straps down is the grade of bolts some companies choose to use...... including a certain person who is doing an engine build in Mini Magazine this month

************Just look at the photo in the magazine, you will see SAE 5 bolts used on his main strap**************

They should be SAE 8 not grade 8.8 which is about SAE 5

Edited by mra-minis.co.uk, 08 February 2011 - 09:46 AM.

[MRA]

No not milling........... the surface would not be good enough, it must be finish ground, and then to a high surface finish, typically we grind to um Ra 0.2 or better...

[benspickup2011]

There about a tenner from mini spares- surely they'd use proper bolts? whats the rough cost of getting the bearing cap ground flat? Its sadly not the sort of thing i'd want topost to acompany to do, if it vanished, the engines scrap because they're line bored.

Edited by benspickup2011, 07 February 2011 - 09:55 PM.

[Sprocket]

There about a tenner from mini spares- surely they'd use proper bolts?

All Minispares center main straps and four bolt caps should now come with the correct grade bolts denoted with 6 lines on the head of the bolts.