24 replies to this topic

[AndyMiniMad.]

Your right of course...its all reletive...but would anyone actually bother? dont Miglia's run 130bhp and 8500-9000 revs with a centre main only?

[mini13]

I've never bothered with a strap, and thats on an engine that see's 7000-7500rpm.

If I was going to start messsing then I'd go for a 4 bolt main,

One thing I would recomend though, is a set of billet main bearing dowels from swiftune, 15 quid for the 6, and the fit really snug, and are thicker than the std ones, well worth it IMO.

[SAL 821X]

Chaps thought I'd bump this thread instead of starting a newy.

So I got bought a Main strap for my engine build im doing at the moment for chrimbo.

However I read somewhere about having them machined before fitting.

Is this true or can I just wack it on to the correct torque staight away?

[Artful Dodger]

i got this one, really well made and cheap (ish)

you have to machine the mini's main bearing cap flat otherwise the strap wouldnt fit. the cap has two flats where the bolt holes are and a raised section in the middle. they machine off this middle section and you get a nice flat surface you can bolt the strap on to.

[Cooperman]

The centre main strap is something which has 'fed down' from racing, mainly because the parts suppliers can make a few quid out of persuading owners that they are necessary. For a road engine they are really unnecessary.
You could list the special parts which are not necessary for road cars but which owners buy due to 'sales hype'. Typically these include 4-pot callipers, coil spring suspension, vented discs, beam rear suspension, and so on. Whilst these may be thought of as 'nice bits', for a road Mini they really are not vital. But the parts suppliers do make a lot of profit from selling this stuff so they will infer that all Mini owners desparately need it all! Cynical, me?

[SAL 821X]

i got this one, really well made and cheap (ish)

you have to machine the mini's main bearing cap flat otherwise the strap wouldnt fit. the cap has two flats where the bolt holes are and a raised section in the middle. they machine off this middle section and you get a nice flat surface you can bolt the strap on to.

Hhhmmm I see thanks for that, not quite as sinmple as I thought then.

Is this something they can do with the gearbox off but the crank in?

[Cooperman]

i got this one, really well made and cheap (ish)

you have to machine the mini's main bearing cap flat otherwise the strap wouldnt fit. the cap has two flats where the bolt holes are and a raised section in the middle. they machine off this middle section and you get a nice flat surface you can bolt the strap on to.

Hhhmmm I see thanks for that, not quite as sinmple as I thought then.

Is this something they can do with the gearbox off but the crank in?

Yes, just remove the centre main cap, take it to the machine shop and have it milled flat across the bottom face. Then re-fit it using gthe strap and the 2 new bolts supplied with the strap. You can't fit the 4-bolt strap with the crank installed as that involves drilling and tapping into the bottom of the block.

[AndyMiniMad.]

This is mine..Had the cap machined down to match the cap by a local machine shop..£10..make sure the bolts that came with your strap are of the correct tensile strength...the ones that came with mine wer'nt and I ended up buying a new strap with a certificate of conformaty for the bolts.

Edited by AndyMiniMad., 03 January 2012 - 08:29 PM.

[Guess-Works.com]

Also just milling the cap is not good enough, it should ideally be ground after milling... and likewise so should the strap, so there is as near as possible flat to flat contact, if there is any deviation from flat then your nice new mainstrap may not actually be supporting the main cap, or even worse, deforming it.

As for steel caps, very expensive, not only the initial cost of buying the caps, but then line boring of the block and caps true.

[SAL 821X]

Great thankls for the info guys, will pop down to the machine shop then.