Hi everyone looking at buying some forged pistons for my ca18det rebuild what does the bore measure at,the guy that is rebuilding for me said to wait until the engine is apart because the bore could be 20 over or even under i know what he means but if the motor is in original condition wouldnt they all be the same.

the stock bore size is 83mm.
I would wait as well. Pistons generally go up in 0.020" Inch increments, with is 0.5mm.
If your bore is in bad conditions then they will hone the bore which generally puts you into the next ovesize category. I.e original bore + hone requires an 83.5mm piston.

hope that helps

Ah thanks mcgee now atleast i know where he is coming from i was going to put 84mm pistons in anyway with the spool stroker crank which is 87.6mm stroke.Can u do the honing yourself or is it a machine job

Get the machining done professionally, it can make or break a good engine.
Actually if you are asking these question (no offence intended) it would be worth paying someone to assemble as well, or if you want to learn get someone (pro) to help you with the build

why are so many people trying to go for the spool crank?
the stock ca18det crank is good enough for over 8500+rpm

more cubes = more torque/power i suppose.

I also suggest that if anyone is thinking of fitting forged pistons, measure the bore, if its still stock get the next size over pistons and the block machined to suit, even if the bore looks ok!

Alot of companies sell stock sized forged pistons (ie drop in), but with years of wear and tear on the engine they will very rarely have the right clearances.. which is cash down the drain

lot of money for extra cubes better spent on a billet dual ball bearing turbo or go just go to a rotary :)
On an interesting note, someone in the states has a 650+hp qr23de using modded sr20de crankshaft due to full counterweight design and cheaper than billet.

i thort that ca's dont like to be stroked??
bore to stroke ratio??? over square??
thats y thay go well,square ratio
my 2cents on ca stroking

Xactly but if you are going to stroke it
doesnt it make sense to use a taller block.
Even if its weaker the side loading on a short
ca18 block is not worth the effort of stroking.

+1 for money being better spent on things other than a stroker crank

And I wouldnt think that any good engine builder would put a new set of forged pistons in an old bore

But yeah, common sense to easier til the engine is measured up before buying pistons and bearings

One last thing, if buying forged pistons have a look at places in america for them. They were half the price of the exact same brand piston in australia when I bought mine and that was when the dollar wasnt as good