Should i get new head bolts for my corsa 1.0L z10xep when changing the gasket?

It somewhat depends on which engine version is fitted but the Vauxhall/Opel ohc engines need the initial angular torquing of the cylinder head bolts and after a warm up and cool down cycle a further small tighten. You will of course have to obtain the exact values from the applicable engine data though this is usually provided with a replacement head gasket.

After thoroughly cleaning of the parts including the female and male head bolt threads. Fit the new gasket and the head, etc. Preferably using new bolts but certainly replacing any corroded or stretched bolts, lubricate the threads and washers and fit the bolts and using a suitable torque wrench tighten in an outward spiral pattern to the initial figure (usually around 18 lb-ft).

Using the same outward spiral pattern the bolts are then further tightened in four stages that is something like 60 degrees + 60 + 30 and then after thoroughly warming up the engine and allowing it to cool for at least 6 hours, tighten a further 30 degrees.

No further tightening is required...

all heads are are torque from center out, clock wise , so think of it like a clock 12 then 6 center, then 1 and 5, then 7 and 11, then 2 and4 then 8 and 10. the best way is to torque 2/3 of the pounds (70 lbs) the first time around then do it again at full torque, (factory spect.) to keep from breaking head bolts. check with dealer about head bolts. ford ******* need new bolt for each install. I found out the hard way broke 3 before i checked with them. the next time you do this unbolt head from out side in to center, counter clock wise to prevent warp of head. for future repair.

Incorrect install of the timing belt.

i think the 1.6 ltr was only for some markets the engine i think it may be is! cyl head head with new bolts, 25nm +90 +90 +90 + 45 degrees the big end/conrod bearings 25nm +30 degrees thats if it a vauxhall/general motors engine. it may not be

failing head gasket

Drain antifreeze -DON"T POUR IT DOWN A STORM DRAIN - then remove valve cover, Remove exhaust from head assembly. On this engine the head is also the intake manifold - it's cast as a unit. Remove carb and remove heater hoses from carb base plate. Remove head bolts and discard. Break head loose from block - may have to smack it a time or two to break gasket loose. Get a buddy to help lift the head off the block - it's fairly heavy. Clean gasket surfaces on both head and block. Install new gasket onto block - pay attention to gasket orientation - it goes on only one way correctly. Reverse procedure to re-install - USE NEW HEAD BOLTS! Silly to try to save $20 bucks on bolts and ruin an engine.

did you have the head gasket on the wrong way around by any chance blocking off the oil feed through the gasket for cams

The heads will need to be shaved at a head shop, but should be $15 each or so. The block's gasket surface needs to be spotless also. When reinstalling the heads, make sure all the blots go in the same place they came from. The bolts also need to be tightened in steps in a cross pattern, so as not to warp the head under pressure.
You can remove the valves with a spring compressor and clean them out really good.
You will need an entire gasket set...the intake manifold and exhaust....etc...it all comes together.
You may want to use a tap & dye set on the bolts and block to clean the threds.
If you can remember how things go, or use a digital camera....you will do fine. BE CLEAN when it comes to the gasket surfaces. Start with a wire wheel on the block, and work down to some acetone to remove all oil.
Torque the head bolts to the specs!
Good Luck!

yes just undo all the rocker cover bolts remove the rocker and make sure that you remove all the old gasket material on the rocker cover and the cylinder head then get some gasket tack(a spray adheasive) put gasket in place and make sure you only tighten them hand tight with a nut driver.start with the inside nuts and work your way to the outside