33 replies to this topic

[minilee94]

Right getting my engine machined by mini speed and he said i should have knife edging done and blading ?the crank will be re ground aswell

What is this is ?
Is it worth doing
It's a 1380 fast road race spec engine

While im at cranking aswell i want to get it lightned and balanced do i need a fly wheel etc to do so and does the bottom end have to be assembled to be lightned and balanced

Thanks lee

Edited by minilee94, 08 January 2013 - 06:28 AM.

[OfMini&Men]

IIRC blading and knife edge just help it cut though the air alot smoother and rev more freely

[minilee94]

Okay so do you think it worth it

[A-Cell]

The whole bottom end is dynamically balanced as an assembly (crankshaft, front pulley/damper, flywheel assembly) to reduce vibrations at high rpm. IMO this is essential for performance, high revving engines, changing the shape of the crankshaft webs (blading) is a nice to have feature, depends on the cost, your budget. I would also add unless done by someone very experienced it could weaken the crank. Any mods to the crank including regrind ing are done before the balancing.

[Cooperman]

It rather depends on the cam you are going to be using. Full balancing is good on engines which will be taken to much over about 6000 rpm on a regular basis, which implies quite a 'hot' cam, such as a 286 and hotter. The same applies to blading/wedging the crank webs where a real benefit will only be noticed when racing.
For a road engine, and especially a 1380, you maybe don't want to be using 'mega-revs' all the time as it leads to rapid bore wear (OK for a competition engine) and with a 1380 when the need to re-bore arrives it can cause a big problem.
If using, say, a Kent 266 cam, which is about ideal on a 1380 road engine as it will give fantastic torque and enable quite a high final drive ratio giving excellent cruising revs combined with good acceleration on standard gear ratios.
What you do need with a 1380 is a really well gas-flowed cylinder head to allow the additional volume of mixture to flow in efficiently.

[OfMini&Men]

to be honest 1293 has alot better performance outputs and more relieable than a 1380 now, plus still got a fair way to go, bigger dont always mean better.

[R1minimagic]

Agree with the above, also FYI - there are new techniques available now which have replaced blading and knife edging.
MED can do these for you

[Cooperman]

Interestingly, I'm re-building an engine which is at 1330 cc and needs a re-bore. It is having sleeves fitted to take it back to 1275 which effectively fully re-lifes the block. Sleeves are just over £30 each and as the bores are not offset, it's not expensive to bore.
When a 1380 needs re-boring, which with a high-revving unit in a road car won't be too long, it becomes very expensive to re-life and special sleeves are needed to fit to the offset bores which still have very little 'land' between 2 & 3.
A 1380 on the road will show little advantage, unlike on a track where the extre 4 or 5 bhp at very high revs will knock a bit off the lap time.

[minilee94]

The head will be totally flowed out the head and i am going for a key 286 cam

So basically i have the e fine lightned and balanced one e bottom end assembled

And is it a yes or no for blading and knife edging

Cheers

Edited by minilee94, 08 January 2013 - 12:56 PM.

[pickupmad87]

as a warning to you a 286 cam is very lumpy at low revs ive got one in my 998! but once you let the tthrottle go t like **** off a shovel!!!

[minilee94]

But it would be very lumpy in a 998 than a 1380 surely !
And things like being lumpy dont bother me its a toy not a everyday day car were I'd need to worry ) thanks for the warning anyway

[Cooperman]

A cam will always be 'lumpier' in a smaller engine and when we used a 286 in a rally 998 it had nothing to speak of below about 3500 rpm.
In a 1380 it will pull from about 2800 and will have strong power from about 4800 to 6800 rpm. To get the best out of the engine it will need to be revving at above 5000 rpm with upwards gear changes at around 6500 rpm. This equals high bore wear and the need for fairly frequent re-builds if performance is to be maintained.
Fit a centre main strap and have the whole lot accurately balanced. If running standard gear ratios I would suggest a FDR of 3.44:1 although you might get away with a 3.2:1. If running SC CR gears then a 3.76:1 would be better, although that will only give 15 mph/1000 rpm in 4th gear (i.e. 6000 rpm in top = 90 mph).

[minilee94]

Ok yeah im having a center main strap fitted too and i was going to leave the gets alone an just fit straight cut drops

[bmcecosse]

As others have pointed out - you won't be revving over 6000, so don't bother with the blading and knife edging....even the balancing is debatable.. To be any use you need to balance the pistons and rods too..... A slightly lighter fly will be useful - but don't go to 'race' weight. I would always use a pre-verto fly.

[minilee94]

Yeah it will be all balanced up and what other mods can i do to the crank other that x drilling as that weakens the crank