hi guys, Im having my 4x4 saph engine rebuilt by a local firm, they phoned me up today to discuss a few things and they recommended that i should balance my crank, is it a must? the chap doing my work owns a cossie 2wd and knows his stuff.
just would like to know everyones views.

 

And what have you done to disturb the factory balance ?

 

Yes of course, the thrown weight inside the engine is best off balanced, normally do crank, rods, pistons, flywheel and clutch when you have it done, probably do the front pulley on a yb as its a big lump.

 

Unless you plan on revving it regularly over 7500 rpm I wouldn't bother. The standard unit is ballanced well enough for this kind of teritory.... awaits the bombardment from so called experts (young and old lol)

 

Well i'd ask how much they want for doing it....if its cheap enough/affordable why not?

will you notice a difference? probably not...will it be worth it? who knows...

It could be a mile out, or it could be fine. Usually you balance the crank on its own, then with flywheel, front pulleys, clutch and cover...clutch always moves anyway so that part of it will never be balanced. mark all the bolts, nuts, flywheel so you know what was where when balancing. You can also weight match the pistons and rods.

I think a fair price would be somewhere between 150-200.

P.s. It's also worth doing if the crank has been ground, i've heard of a crank being ground offset and when put on the balancer, it nearly fell over

 

It's only really worth while if you balance the whole lot, flywheel and clutch included

 

its £95 to balance the crank, its £95 i didnt think i needed to spend only because im buying new pistons and bearings through out, the head is having a complete overhaul, it was a 400bhp engine setup by MAD and it was sound, i might just give it a miss on the balancing.

 

as said above if your only reving to 7500 then leave it as is,and if you do bother have the lot done ,rods pistons pulley flywheel etc

 

for a couple of hundred quid it may be worth doing if the crank has been reground for the sake of longevity. however the serial engine builders will give a true answer based on experience. its an all or nothing though, no point having rods balanced and ignoring pistons/crank/flywheel ect for any real benefit.

 

I'd sooner trust Fords ability to balance a crank than most machine shops.

 

its not likely to spit a piston out of the block then?

 

Not if you don't try to rev it too high....

 

the cylinder head usually prevents that.

I really wouldnt worry about balancing the crank. You really dont need it done.

 

It's not just the crank your balancing though, it's the whole rotating assembley. Who knows how in or out of balance it is until it's on the machine. for £95...is it really THAT big an issue not to check it?

 

He said £95 to balance the crank. Not the entire rotating assembly, part of which sounds like he doesnt even have yet.

And then there is the issue of whether they actually know how to operate the machine !

just because a machine shop says they can do something, and charges money for saying they are doing something, doesnt always mean they can !

There are some good machine shops out there, but there are 100x more crap ones. And the crap ones dont have a sign outside saying they are crap.

So as he has done absolutely nothing to the crank to warrant balancing it, I'd be leaving it well alone.

And as you've also said, you cant really do any single item, you need to do the heap.

 

Have to disagree here, if you use a good balancing specialist, and get the entire rotating assembly from the crank pully to the clutch cover plate done, it makes a huge difference IMHO, having personally done it a number of times. Much smoother at high revs, well worth doing if done correctly.

 

There is always that risk when using machine shops unless you know their worth from previous work. I know all too well machine shops that are good are few and far between, which Is why I travel a 40 mile round trip to mine when I could use a couple that are a stones throw away!

I assumed as they were doing his engine, he knew they were ok, and as they suggested balancing the crank they may have an idea what they are doing...but we can only speculate

The crank may be balanced, but is it still in balance with the flywheel/clutch etc as they've probably been off since the manufacturors done it, if they done the whole assembley rather than just the crank...

I wouldn't bother if your not going to do it right and balance it all. But on the other hand, you'll probably never notice it balanced or unbalanced! *edit* Unless you're RWD_Cossie_Will (joke!)

 

Ive had engines balanced by professionals, and Ive had engines Ive literally thrown together with all sorts of mismatched parts.

TBH Ive never felt any difference on them !

I'd say in extreme cases, it is more of a bearing longevity issue than anything else. But the higher you intend to spin it, then of course the more important it becomes.

 

I have had a number of people comment on how smooth the engines I have built run, but there you go...

 

Couldnt agree more (but it cost me a little bit more than £95.00)

You pays your money and takes your chance !

Here is my "rotating mass" prior to it going to Wilkinson Dynamic Balancing in Halesowen

Con rods and pistons were also balanced and weight matched to finish the job off !