can anyone tell me how to tell if an engine is 8.5 or 9.0 to one compression ratio.
are there any numbers or markings on the barrel or piston

Don't think there is anything on the barrel but I seem to recall the piston crown has it marked on it

they have 8,5 or 9 cast into the crown


ooh thats a bit tiny look here
http://www.flickr.com/photos/42745680@N02/5034148264/

The engine ID plate should give you a hint.

thanks guys ,the pistons in my engine have the number 9 cast in to them,so it must be a 9.00/1.
what is the benefit(if any) over the 8.5/1

should be "crisper" slightly higher power...but not so as you would notice a good 8.5:1 will be stronger than a tired 9:1

it will have a tendancy to pink more so you need to be familiar with what that sounds/feels like and how to set the timing up properly to stop it

sean

9/1's will give you bit more torque and bit of extra "oomph" ....pulls better in 4th at around 30-35 mph and feels quicker through the gears ....it prob'ly equates to a couple of exra bhp [thats wot mine felt like anyway after Uncle Ken rebuilt my engine].
Best to put Dyane jets in the carb too [I dunno wot "number" the Dyane jets are ....no doubt some-one who does know will be along shortly]
Deffo worth the investment [imho]

T.

if i am using 123 ignition,will that help with the timing issues(assuming it is set up correctly)

My car has [and had before] the Lumenition EI system.
FWIU Electronic Ignition needs setting with a strobe,the "peg in the flywheel" method is only a rough guide.

T.

It won't help the timing, you still need to retard it to prevent the pinking if it's doing so.