engine balancing

[swedge]

ok so my new build will be

c20xe
early crank just been reground and using ACL duraglide bearings
ARP's
early 86p xe pistons with the valve cutouts deepened for cams
p&p gasket matched head head with porous mod
288 cams with verniers
r1 carbs
4-2-1manifold
lightened and balanced flywheel (flat type - 5kg)

my engine builder guy says he will balance the complete bottom end for £120

is it worth getting the bottom end balanced?

he says he needs the crank, pistons, rods, flywheel and clutch

[novasrikev]

i would at that money

[Bubba]

thats cheap! i was quoted £200+vat to do it with just the crank and fly (with a regrind)

[swedge]

mines has already been reground, mine was £160 for a regrind and polish and new ACL duraglide bearings supplied

[C612DNM]

Get it balanced, at that money, it's a bargain.
I assume that's the full rotating assembly - flywheel, crank, rods, front pulley, and pistons?

[MK999]

Rotating assembly at that price would be less pistons and rods I imagine. Especially since the pistons and rods reciprocate, so they aren't part of the 'rotating assembly' usually.

edit: Nvm says full bottom end rather than rotating assembly in the original post... that's a really good price for that.

[swedge]

Well he told me he would need the crank flywheel pistons rods and clutch

[garyc]

I thought it is usually done with pistons off the rods.

[C612DNM]

Yep. Balancing the pistons is getting them all to the same weight. Balancing the rods is done by making them weigh the same end-to-end. The rest is done rotating. My machinist usually asks for the front pulley as well as the clutch cover, to be 100%. Though he is a perfectionist and produces FIA championship winning engines!

[mowgli]

for proper balancing of the pistons/rods, the pistons would need balancing end to end seperately, and the rods would need balancing end to end seperately, and the pins would need weight matching too.

i think on a road engine that has been made since they really went mad on the whole factory cnc machining thing, so that tolerances were way better than some brummie with a hangover knocking cranks out by hand, an engine is less likely to need it balancing than, say a pinto, A series, or x-flow type engine, but if you want to do it, for peace of mind, why not.

for competition use, where the revs will be way higher, and every little thing helps to make it faster, it is a very good idea