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4 bolt main cap
https://www.ausmini.com/forums/viewtopic.php?f=5&t=6745		 Page 1 of 1
Author:  Metalfab_101 [ Fri Apr 29, 2005 12:28 pm ]
Post subject:  4 bolt main cap
Has anyone had experience with these? Are they worth the money & effort?

I have heard a few people mention crank whip and thought that this would probably help on a performance tuned engine.

Cheers,

Damo.
Author:  TK [ Fri Apr 29, 2005 12:45 pm ]
Post subject: 
Not worth the effort or money.
A centre main strap will do. Use ARP main studs too.
The extra drilling for the four bolt mains actually weakens the block.
It's like those old cons like roller cams in the 'A' series Ha Ha Ha.
Author:  drmini in aust [ Fri Apr 29, 2005 8:04 pm ]
Post subject: 
Re the centre main caps, you are only ever likely to break them on deceleration if you downshift too soon and buzz the engine REAL HIGH.
S caps are a bit stronger than the others and don't ever need a strap anyhow.
Many people are racing without a strap with no problems.

I have one on the 1310 (which will be a 1430? stroker next year) but my newly built 1360 is getting by without one. :wink:
Author:  TK [ Fri Apr 29, 2005 8:40 pm ]
Post subject: 
Doc,
those pics that you see in the Mini in Motorsport section with the title Fred Sayers. His crossflow 8 ports, twin 45s, offset ground big donks are ALL run without straps or 4 bolt mains. Just set up correctly.
Ty
Author:  TheMiniMan [ Sat Apr 30, 2005 9:59 pm ]
Post subject: 
anyone who`s anyone in the mini racing scene will have known about "allowing" the crank to flex,,, by givng way more clearance between the crank & the cap,,,we set them up with even more on the lower half so that the crank doesn`t "push" against the cap when reving hard & flexing heaps,,,let em flex i say, let em flex :-)

I`ve never used a centre strap or a 4 bolt cap, no need to simple as that!!!!!!

i just love the facts :-)
Author:  drmini in aust [ Sat Apr 30, 2005 10:38 pm ]
Post subject: 
Confession-
Only time I ever broke a centre main cap (1098) was when running my 1st Mini on a shandy of petrol and diesel... :shock:
My defence, your honour- I was an apprentice, I was broke, dad had an (empty) petrol drum and a (full) diesel one on the farm..
nudge nudge :wink: :wink:
Soooo... I made a new cap from axle steel, courtesy of NSW Dep't of Railways. 8)
Author:  Metalfab_101 [ Mon May 02, 2005 7:51 am ]
Post subject:  More dribble from me
Interesting. A lot of what you guys are saying flies in the face of convention. Not that i'm saying you're wrong, just an observation.

Just so we're comparing apples with apples though, is this train of thought consistant across all engines and cranks? I mean, if you were to build a performance 998 and a 1400+ stroker would the same thing apply? And does the type of crank make a difference? Would you build it the same with a EN16T? EN40B? How about a brand new billet crank? (yeah dream on, like i'll ever buy a billet crank!!! cha-ching!!! :lol: :oops: )

Thanks for the input fellas, it's always more interesting when you get an answer you dont expect :P

Cheers,

Damo.
Author:  drmini in aust [ Mon May 02, 2005 8:30 am ]
Post subject: 
I'll just say most of the motors GR builds for comp or road use DON'T have a strap or a 4 bolt cap. And, they don't break. I'd be more concerned when you're doing a rebuild about the bolts being used.. how old etc.

To fit a strap to most centre caps usually means machining the cap flat first. IMO this weakens it to begin with. The later 998 caps (99H motor) are thicker in the middle than early ones, even more reason not to do it.
If the strap is flat (like most I've seen), when the bolts are tightened it will tend to bow away from the cap, so it's doing bugger all anyway. I guess it will hold the 2 bits in if/when the cap breaks..

I don't think the type of crank matters, they are all whippy anyhow. :lol:

BTW a billet crank is no stronger than a forged one, but those being made in Melbourne are very pretty, 8 counterweights and all. Material spec of these is 4140, nitrided. But their hardness depth is very shallow.
Author:  Metalfab_101 [ Tue May 03, 2005 4:00 pm ]
Post subject: 
drmini in aust wrote:
... those being made in Melbourne are very pretty, 8 counterweights and all. Material spec of these is 4140, nitrided. But their hardness depth is very shallow.


Who is making these? I was talking about them out of UK, didn't know anyone over here was making them.

Damo
Author:  TheMiniMan [ Tue May 03, 2005 6:34 pm ]
Post subject: 
i set them up the same , No Matter What motor, big or small, slow or fast.

if/"WHEN" the crank whips/flexes, then with the std clearance between the crank to the main cap thrusts, the crank will push on the cap,,,both sides alternating,,,that`s a fact!!!, simple as that & especially(or more so) at high HP outputs & revs,,,just works on the cap the whole time, push one side then the other, then over & over & over again,,,,

if you allow more clearance (like 8-10 Thou) to the "cap" (leaving the upper thrusts at STD clearance, then, there is less chance that the crank will "work" on the "CAP",,,all the thrusting is then happening on the stronger part, being the block.

therefore less chance of the cap &/or bolts breaking...the blocks have been known to break there also,,,,but!!!!!,,,,>>> way way less than the cap does, if nothing is done to help prevent it,,,

I would also guess to say that if it`s built this way, then there would be more HP avaliable (or rather less HP loss) as there will be less friction wearing on the lower/cap thrusts & less "strain" on the crank,,,simple physics in my books :-)

ah well,,,it`s just what my dad has been doing since way back when,,,& what i`ve been doing cause he said so from way back when & """NOT ONE""" of our cranks/blocks has ever broken & i can say that i`ve """SEEN""" many many other peoples cranks & Blocks broken

Just think,,,i`m 42 years old & been born & bred in the mini racing/parts/service industry my entire life,,,so lets work that out,,,oh,,,yeah well,,,approx 42 years of watching & doing mini stuff,,,HHhhhmmmm,,,,may not be as much as some people,,,but who ARE those people ????? :-) I`ve seen LOTS & LOTS of stuff ups in my time :-) some people say,,,Bugga that, doing it that way costs more money & time & really isn`t necessary,,,hee hee,,,well...guess what happened to those cranks & caps

read the stroker thread & see the way we treat the stroker cranks too,,,,a little more time & money spent in these places saves a heap of money & grief at a later date ,,, there`s a method in my dad`s madness :-) i`ve watched learned & listened to it all my life, as much as dad will tell you otherwise :-)
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