Hi everyone,

 

My 2007 WRX Hawk potentially needs a rebuild, (overheating / HG?) I'd like to fit forged pistons and up-rated head gaskets. Is there anyone with experience of this that could give me a list of parts that I'd require for my model? I know there are Mahle pistons, but not sure which gasket set I'd need and any other components I should upgrade at the same time (looking long term to remap up to around 350 - 400 bhp)

 

Many thanks!

 

 

check the thermostat hasnt failed before you pull the whole engine apart - the standard wrx engine internals should be good for that BHP figure although I would uprate the oil pump and fit a decent sump baffle

Thanks Jay,

 

My hawk eye has been over heating and the oil dropped recently - hopefully it's not the head gasket, it's got a full service history from Subaru from new, fingers crossed!

hopefully not - what is the state of your expansion tank - any emulsification?

It's not unheard of but quite rare to get the emulsification when a Subaru head gasket goes. They normally go between the water jacket and the combustion chamber.

This leads to combustion gases getting into the coolant system and obviously the same in reverse which is why you lose coolant and why the temp gauge goes up.

One way to test is:

Take the car for a drive with the coolant levels correct. After the car has been up to normal temp for a few minutes, pull over, open the bonnet and turn the engine off. Open the expansion tank cap, not the rad cap. If you can see a lot of bubbling, it's due to the gases in the coolant which will mean head gasket/s have gone.

Standard Internals on that model are good for the level of power you are after. The weak point are the standard pistons. As has already been said, an updated oil pump would be good. Also, take the opportunity to change the timing belt kit and water pump, unless they have been done recently anyway.

It would also be a good idea to upgrade the cylinder head studs to safeguard the new build.

Personally, if you have to do the head gaskets and want to take the car to higher performance levels, and intend to track the car, I would always advise going the extra mile and refreshing the big end and main bearings too. The new pistons will need the new piston rings too.

The only reason to fit a baffle plate are if you intend doing track work of any sort.

Hope that helps a little

Thanks guys, much appreciated - would a 'sniff test' accurately detect a head gasket failure in an Impreza? 

Thanks guys, much appreciated - would a 'sniff test' accurately detect a head gasket failure in an Impreza? 

Yes, it should do. The sniff test is looking for the burnt combustion gases within the coolant so should be the perfect test

Cool, hopefully it's something else - we'll see!

Sniff test isn't always 100% accurate, but it's a good 95%

And on that subject... Mr Tlag, did you have my sniff test kit? Not worried if you did but I don't remember where it went in the chaos of the move!

I have it Adam :)

That's good. Better you have it for your new business than some playboy racing driver :)

That's good. Better you have it for your new business than some playboy racing driver :)

Not nice talking about Bip like that. And to his father,  ;)