where the starter hole is you use one
then the other on the same first vice grip
you can also use a bolt at the top of
the block with a small bracket and tube washer
for spacing then other end of bracket to the
flywheel clutch bolt up holes.
Ive split halve a dozen of CA18des this way
both manual and autos.

Hey D cant be done the flywheel sits to close to the block.

couple of vice grips on a flywheel do the trick

Good idea -- impact wrench has many uses. If you find the electric version not strong enough to break them loose, make your own holder from scraps as shown by the photos. Basically a piece of metal with two holes can be used.

Yeah already tried the jamming method but couldn't jam it enough,then thought about a flywheel locking device that hooks onto the dowl on the back of the block($85 from the States) then thought ill look into a electric rattle gun($85 on ebay)and would get a lot more use from a rattle gun than a flywheel lock for the same price.

Yes, flywheel bolts may be removed by jamming the flywheel, and then undoing the flywheel bolts as normal. Using a large screwdriver or small prybar on the teeth of the flywheel, wedged against a bolt or dowl will hold the flywheel. Sometimes it helps to use a mallet on the wrench to break the bolts loose. Or you can use a flywheel stop as pictured at Flywheel Removal

But an air wrench is the easiest way. Just don't use it to install the flywheel.

you dont need a rattle gun

Seems like you've got it under control, they are 14mm as DD said.

All sorted DD,i have arp flywheel studs to go on.I have stripped my engine but still have the crank,pistons and rods in the block and wont be using them.I have absolutely everything new and just want to get it down to just the block.Bit of a mission getting the flywheel bolts undone but have a rattle gun on its way so hope that will work.

they are 12-point heads. 14 mm I think. Do not use the 6-point bolts from the automatic flexplate. The flywheel needs the stronger bolts.