Are turbo crank and rods better?
Turbo Mini Forums

.... are they better than std A+ and if so, how?

Any thoughts much appreciated.

Nick.

Hi,
The Turbo crank was apparently hardened, but the rods are the same.
Also a large proportion of turbo engines had a standard crank in them anyway.
Cheers,
Gavin :)

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Thanks.

So no real benefit if I'm going for a rebuild and getting the crank re-ground/ wedged/ hardened etc.

NONE! dont bother hardening the crank

they are up to the job but ...... if you have loads of cash! ...........go for it

Edited by BENROSS on 26th Apr, 2007.

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What revs can the std stroke crank take reliably? I k've done a few searches and seen some of you boys are going over 8k rpm...

PS I'm going 16v BMW head so want to get the cams right.

Proper "Turbo" crank is part no. 6581. If your lucky enough to find one of these, the do seem very hard wearing.

WWW.TURBO-MINI.COM

thats what i was aiming at carl 6500 rpm turbo applications the standard ones do survive

you need one made out of EN 9000 carl ....lol

with the RPM you take them to

i have one of those cranks phil in the garage in excellent condition

Hi Nick - nice to see you on here - as mentioned above the rods/cranks in A+ form are all. If you want a little more peace of mind from the rods you could run Innocenti ones - the ones with the littlte bridge across the centre of the rod - these are according to Viz en19 rather than the a+ en16 (I run them in the 1380) - but most people are happy with the stock A+ ones.

crank - for revs, wedged, cross drilled, hardened, fully balanced

cheers

JK

If Carling made Mini engines
it would probably be like this one!

Hi John,

Was wondering if my old turbo crank was a better bet in the short term than my 84mm offset ground crank. Would still need new pistons and rods of course.

Probably best to stick with what I've got and start saving for your crank and rods......

Mine regularly seen 7000rpm + and never had any issues.
Std turbo crank and rods, std main bolts.

Max rpm I used was about 7500rpm, although a brief bad cam choice seen that above 8000rpm.

Reading recent threads here...you could almost think the standard crank and rods are good for almost any power level !!!

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

the x- drilling is a bit dubious though:

this is a bit by David Reher (of Rehermorrison):

I’ll begin with a rather bold statement: Don’t use a cross-drilled crankshaft. There are a few exceptions to this rule, but under most circumstances, a cross-drilled crank is going to cause big problems.

Unfortunately cross-drilling is one of those terms that’s become part of the jargon of hot rodding. People who know very little about racing engines have heard of a “cross-drilled crank,” and mistakenly believe they’ve got to have one. In fact, cross-drilling simply refers to the position and routing of the holes that carry pressurized oil from the main bearing journals to the connecting rod bearings.

In a cross-drilled crankshaft, oil feed holes are drilled completely through the main journals so the passages are open on both ends. Holes from the rod journals are then drilled at an angle to intersect the holes in the main jouranls at the centerline of the crank. This system was thought to ensure a continuous supply of oil to the rod bearings because one end of the passage drilled through the main bearing is always exposed to the pressurized oil in the upper main bearing insert.

So what’s wrong with this picture? The pressurized oil that enters the feed hole through the main bearing journal must overcome the centrifugal force created by the rapidly spinning crankshaft before it can reach the passage to the rod journal. If the pressure created by the oil pump is not strong enough to counteract the centrifugal force that is pulling the oil away from the rod journal feed hole, then the rod bearing is starved for lubrication. Since the pinwheel effect of the centrifugal force increases with rpm, when the rod bearing does run dry and seize, the resulting carnage is usually catastrophic.

I learned my lesson about cross-drilled crankshafts the hard way. Back in the early ’80s we started to turn our engines faster. We’d been running stock Chevy cranks in our 287-cubic-inch small-blocks and B/ED motors without any problems. Eventually the supply of usable cranks became exhausted, so we ordered aftermarket cranks – “California cranks” as my Texan friends called them. These cranks were much prettier than the factory forgings, and they all had trick cross-drilled main bearings. It didn’t take long for those cranks to turn blue when the rod bearings burned, sometimes on the first or second dyno pull. Then we’d bolt in an old 283 crank and the engine would live forever. So what was the difference? The difference was the cross-drilling.

Today most racing crankshafts have a “high-speed” oiling system, which is essentially just how Chevy drilled those stock cranks. The oil feed holes for the rod bearings intersect the main journals at or near the surface of the journals. The pressurized oil does not have to overcome centrifugal force to reach the oil feed holes for the rod bearings, so the supply of lubrication is constant even at high rpm. There have been some refinements made to the angles and positions of the oiling holes to “time” the oil supply, but the basic design hasn’t changed significantly.

It’s easy to spot a cross-drilled crankshaft. Insert a piece of welding rod or coat hanger wire into the oil hole drilled in the main bearing. If the wire comes out the other side, the crank is cross-drilled. My advice is not to use it.

It is possible to crank up the oil pressure high enough to overcome the negative effects of cross-drilling. However, excessive oil pressure creates its own set of problems, increasing parasitic losses due to windage, excessive oil on the cylinder walls, and the power that’s consumed by turning a high-pressure oil pump.

It’s possible to manufacture a 5-inch stroke big-block crankshaft without cross-drilling the main journals. However, as the stroke becomes longer than 5 inches, the overlap between the main journals and the rod journals is reduced to the point that there is insufficient material for the oil feed holes. The crank manufacturer must then change the angle of the holes and drill them to intersect a cross-drilled passage in the main journal. When using this type of long-stroke cross-drilled crankshaft, it’s absolutely essential to increase the oil pressure and install a big dry-sump tank, because this engine is going to circulate a lot of oil.

It’s critical for anyone assembling an engine to inspect the crankshaft carefully. The first thing we do with every crank that comes into our shop is get out a pen light and a welding rod and check the oil holes. It’s not uncommon to find an oil feed hole that’s blocked or not drilled quite far enough. When assembling an engine, make sure that every oil passage is open and drilled where it is supposed to be."

Edited by Sir Yun on 27th Apr, 2007.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

Ive just got an NI-tempered crank, its seen 8k many times when it was used in the N/A phase of my engine a few years back.

Fingers crossed had no problems!

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1/4mile in 13.2sec @ 111 terminal on 15psi

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Everyone has their opinions - for very high revving n/a engines - ie all mine (a series)for the past 17 years have used cross drilled cranks, I've only ever had to change a crank once and that was due to flywheel fretting. So for turbo style engines it may not be necessary, for the high revvers the crank needs all the help it can get (even though drilling extra holes in it may not be the best thing either)!

JK

If Carling made Mini engines
it would probably be like this one!

as matter of interest wat would you guys say the rev limit of standard rod bolts?

i let my rip up to 7000rpm when on the rollers or on the track, but lower it on the road as the rod bolts are standard?

Anton - its held together this long!!! - that may be the answer. the bolt is only part of the equation - tightening up technique, oil under head of bolt, oil on threads. etc all make a difference to the stretch in the bolt - as does the finish of the cap "spot" facing where the bolts sit. If I'm not using new rods I always have these points re faced and the chamfers to the holes enlarged so the rad on the bottom of the bolt doesn't sit on a sharp corner.

JK

If Carling made Mini engines
it would probably be like this one!