Arp Bolts, Bottom End Mods

[dom604 0]

Is the arp bolt number I need 117-6101? I have found couple sets.

 

Anyone know?

[kyepan 291]

Correct me if i am wrong.

 

But shouldn't a well balanced crank / rod & piston assembly / flywheel / pulley / and clutch cover mean you can rev it harder on the standard bolts?

 

taken from here

 

Balancing and blueprinting are relative terms, all engines; Ilmor V10"s to Rover K Series engines are balanced and blueprinted to a specified required level. This level depends upon the engines use and its maximum speed of rotation. If an engine is outside its balancing tolerance it will vibrate " like an oscillating hammer, and the faster an engine rotates the more violent the hammering. Any rotating mass " crank assembly will do this, the tolerance simply reflects a maximum limit. The graph below shows how required levels of balance are derived. The lines on the graph denote the use to which the engine will be put, the lower the line the better the engine. The vertical axis denotes the vibration a system exhibits, against engine speed on the horizontal axis.

 

[graph placeholder] graph missing

 

Point D exhibits the point that a factory balanced K Series crank is toleranced to for a 7000 rpm rev limit. Point C is the intersection with an engine speed of 9500 rpm that is required of a modified K to make this rev limit possible. This equates to a required tolerance of 40 gm/mm. Point A indicates the tolerance of the aftermarket cranks as measured to an engine speed of 7000 rpm and B the same cranks to an engine speed of 9500 rpm. In other words all the steel crankshafts are at least 10 times out of tolerance for a standard engine and more that 20 times out of tolerance for an engine with a raised rev limit. It is a similar story for the flywheels measured. Points A and B mark a tolerance that is appropriate only for agricultural diesel engines!

 

Now it is worth pointing out, that a tolerance represents merely an "acceptable level", and that any engine builder worth his name will realise that the tighter the tolerance the better. A badly balanced engine causes vibration, this stress within the reciprocating elements and engine block, noise and heat. All this is lost power. A recent test measured a 5 litre V8 on a dyno, then balanced and blueprinted the engine to a race tolerance, without the addition of any non OE parts, subsequently the engine was found to have gained 12 bhp on the dyno, why, because internal stresses were minimised.

 

The fact that some of the cranks and flywheels measured, come from engines that had been built by specialist tuners, indeed one from a car manufacturer, is nothing short of breath-taking and is the cause of all the bottom end problems that the K has been suffering. Quite simply suppliers and engine builders have been using components that are wildly outside the tolerance for a standard factory engine and exacerbating the problem by then raising the rev limit. This is why all these tuned engines are so rough when compared to a standard factory engine. They rev more freely with less advance in the mapping, lightweight flywheels and clutches, but put back-to-back, the modified engines are rough. The degree to which these engines actually see this unbalance depends upon the relative position of unbalance of flywheel and crank. Opposite and they will cancel these forces out to an extent, if they coincide they combine, and I have seen resultant bearing loads as a result of these F3 forces top 120 kgf @ 9200 rpm, this compares with a standard factory crank and flywheel measuring 6.7 kgf @ 9200 rpm.

[brumster 135 1 Cars]

I guess that will help, but I think the standard rod bolts are basically limited in the loads they can take, full stop. So if you want to extend the rev change - particularly with any regularity - I was under the impression that uprated rod bolts are effectively a must. All the balancing in the world won't reduce the stresses a fast-moving piston assembly will put on the big end caps, surely? Particularly when those stresses are beyond the original design limits (not sure what the standard rev limiter is on an mi16 as I've never had standard management, but bet it's not much more north of 7k is it?).

[kyepan 291]

All the balancing in the world won't reduce the stresses a fast-moving piston assembly will put on the big end caps, surely?

 

 

 

I also thought the counterweighting on the crank is also a factor, for example the counterweighting on the diesel / 8v crank, is different to (less webs on 8v) the 16v crank. And the design / placement of the counterweights has something to do with the maximum rev limit of the engine. Those may have been calculated to help

 

I remember reading here that inline fours have lateral vibration that is unbalanced, because the con rods are moving sideways without balance. And the centre of the engine (pistons 2 & 3) moves down whilst the outside moves up (pistons 1 & 4) leading to a wobble along the crank.

 

But i don't pretend to understand it, so perhaps someone who does.

 

Rev limit on a standard MI is around 7200

[kyepan 291]

All the balancing in the world won't reduce the stresses a fast-moving piston assembly will put on the big end caps, surely?

 

 

 

I also thought the counterweighting on the crank is also a factor, for example the counterweighting on the diesel / 8v crank, is different to (less webs on 8v) the 16v crank. And the design / placement of the counterweights has something to do with the maximum rev limit of the engine. Those may have been calculated to help

 

I remember reading here that inline fours have lateral vibration that is unbalanced, because the con rods are moving sideways without balance. And the centre of the engine (pistons 2 & 3) moves down whilst the outside moves up (pistons 1 & 4) leading to a wobble along the crank.

 

But i don't pretend to understand it, so perhaps someone who does.

 

Rev limit on a standard MI is around 7200

[brumster 135 1 Cars]

I also thought the counterweighting on the crank is also a factor, for example the counterweighting on the diesel / 8v crank, is different to (less webs on 8v) the 16v crank. And the design / placement of the counterweights has something to do with the maximum rev limit of the engine. Those may have been calculated to help

 

I remember talking to Longman about cranks when they were building my engine; for example Andy Baker used to run a very-thinned-down 8v crank and I asked what the implications were and why they were recommending sticking with a 16v crank. They said for rally use it's probably not so much of an issue than it is for circuit racers that are spending more of their time at sustained high revs, unlike us rally boys that are more up-and-down over the rev range. But the suggestion was that an 8v crank would flex more, ultimately causing undue wear and stresses on the bearings/journals, I guess - it would need rebuilding more often, all other aspects equal. I'm paraphrasing, of course, as the discussion was quite some time ago.

 

I remember reading here that inline fours have lateral vibration that is unbalanced, because the con rods are moving sideways without balance. And the centre of the engine (pistons 2 & 3) moves down whilst the outside moves up (pistons 1 & 4) leading to a wobble along the crank.

 

But i don't pretend to understand it, so perhaps someone who does.

 

I remember reading a similar, but better-worded (for the idiots amongst us!) article. Very interesting, and I understood it particularly with respect to what balancer shafts are then doing. From memory it was to do with the fact that while 2 pistons might be in the same physical position in the block, one of them is on a forced stroke down (ie. expansion stroke) while the other is on it's induction stroke, and therefore not having the same degree of force applied downwards - it's 'freewheeling', being pulled down by the crank, rather than being pushed down by the forces of an explosion.

 

I should duck out now - I'm wading out of my depth, and the forums had enough hypothesis recently I'll have Baz on my case

[dom604 0]

Right... So I am going to order arp bolts. Will tht be ok? Or will I need anythin else to help the engine?

[dom604 0]

I know baffled sump ad the spring will help. But is it

Actually needed. It's only autograss. It's high revving

With couple bends for minute or 2. I want think as its a steel dump of makin my own channel just to help it. Won't be amazing it will just help.

[brumster 135 1 Cars]

I wouldn't risk an mi16 without one, not in competition use. I appreciate you're not going to get much lateral G on grass, but anything like a quick flick of momentum from one side to another (say a chicane, or a slide which you catch and then flick the car the other way violently) could see all the oil sloshing over to the other side of the sump pretty quickly... not sure I'd like to risk the starvation at 7200rpm :-)

[dom604 0]

Any pictures of the different baffled sumps you can buy? And this spring what is it? Seen people say u can just buy from pug... Wat is it wats it do?? Cheers

[Alan_M 66 1 Cars]

Right... So I am going to order arp bolts. Will tht be ok? Or will I need anythin else to help the engine?

 

I seem to recall you need to mod the rods slightly to allow the ARP bolts to fit.

[dom604 0]

I seem to recall you need to mod the rods slightly to allow the ARP bolts to fit.

 

How exactly?

 

I seem to recall you need to mod the rods slightly to allow the ARP bolts to fit.

 

How exactly?

[wicked 103 3 Cars]

They do fit, but I have check if the head of the bolt is not more conical and does clamp properly. Otherwise the torque applied may not be accurate.

But they do fit.

 

You can buy a Constella baffled sump of the shelf for the 1.9 Mi16.

 

http://www.constella.co.uk/index.php?option=com_virtuemart&Itemid=148&vmcchk=1&Itemid=148

Edited December 7, 2011 by wicked

[Alan_M 66 1 Cars]

How exactly?

 

 

MattSav told me some time ago. Some fit, some don't. You need to check the bolt head has seated properly.

 

ARP Bolts