BLOCK GUARD

[dyingwish]

@cmross13

its an overly discussed/argued topic, much like underdrive pulleys.
the short answer is: yes, some can and will prevent the sleeves from moving/flexing/shifting. the cost of that “safety” is that they will block/slow/hinder coolant flow.

if you can’t afford to get your block sleeved, you could kick it old school and have a machinest put dowels in it

on an unrelated sidebar, if your wondering what the UDP referance is, its simple. crankshafts are designed to have a harmonic balancer to cancel out harmful vibrations and frequencies. if you remove the harmonic balancer in favor of a super light crank pulley, you are effectively re-intruducing those same harmful sonic pulses. the only acceptable solution is to have your stock crank pulley lightened or to drop a few hundred on an ATI or something.

Well stated, and yes adding UDP will allow harmful harmonic to resonate through your crank. Fluidampr makes a killer alternative to the OEM pulley. You can also shave your outer two beltways and have it balanced afterward…this leaves the OEM dampening substrate intact.