Hi guys,

i've had a look through the forum with the search but couldnt find the answers i was looking for to a couple of questions. My car has just suffered a big end failure and i am replacing the engine with another second hand unit. on the old engine, i upgraded to a td05 turbo from my vf12, which i would like to transfer over to the new engine.

However, is there a way i can clean/flush the turbo to make sure there's no swarf in there anywhere that could cause an issue? Does it need a full strip down?

and on a slightly different note, I was thinking of using later impreza heads which are better than the legacy heads but need suitable pistons to match the change in compression. I have the pistons available, but can they just be swapped over?

Some say that every time you swap pistons you need to hone the bores? But that would mean a complete strip down which seems a lot of effort for wanting to swap just the heads.

Anyone care to offer opinions or comments?

cheers,

 

With regards to the turbo, first and foremost change the oil feed line as you will get carbon build up in it which can come loose on handling and wreck a new turbo, so for the sake of a few quids it worth it.

Secondly, you'll need to prime the turbo anyway which will flush it out. This is done by bolting the turbo on and leaving the oil drain disconnected. Disable the ignition system and keep cranking the engine over, with a suitable container under the turbo to catch the oil, until you have about a pint of oil in the container. Once this has been done, connect the oil drain pipe, top up oil as necessary and run the engine to check for leaks.

With regards to changing standard bore pistons, you'll need to measure the bore to check for wear and use suitable sized piston rings otherwise you'll suffer from blow-by and end up burning oil. It's not often you can get away with swapping just pistons over unless its a very low mileage engine.

 

Out of interest what heads and pistons are you considering using Mark?

 

thanks for the reply Dan, thats cleared up my turbo issue and saved me needing to strip it unnecessarily.

Paul, the heads I was going to use were the ones that i swapped to on the last engine. I believe they are v1-2 heads, which arent the best, but it did mean no tappets and the ability to do the coil pack conversion which I now need to solder my ignitor back in as I'm going back to the two bolt coils

When they were swapped last time, the pistons wouldnt have been honed, but I can only presume that the bores were checked and suitable rings used. I didnt have any problems with them, but maybe that was luck? That was when I went to the STi Forged pistons.

I guess ideally if i were to swap them again in the future or on this new engine i would get heads that were the same CC's so the pistons didnt need changing. Unfortunately its hard to find out this info without taking them off and measuring them.

I dont know whether thats a job for the future, or whether to try and source some whilst its apart..

decisions decisions..

 

The problem you get is that, as the engine covers more mileage, the bores get smoother. This makes it very difficult if not impossible to bed in the new rings. You may struggle to get away with it a second time, you might be fine, but for the relative small cost of re-honing the block (if the bore measurements are still in spec), it's a no brainer as you'd only find you'd have to strip it down again due to poor oil consumption where the rings won't bed in.

 

Why are you going back to 2 bolt coils if you've already done the conversion?

 

Because i had swapped to Impreza single bolt heads on the last engine, but now getting a replacement Legacy engine which is the two bolt type, hence the questions of whether to swap the heads again for Impreza ones - maybe v3/4 if they are the same CC's as the legacy ones so that I dont have to touch the pistons.

Unless I can modify the single bolt coils to fit in the Legacy heads..

 

Just swap the heads mate, you don't really want to run Legacy heads anyway especially as you've already done the conversion If you are chasing bigger power get some sti 3 heads like I did but otherwise avoid Legacy heads and use the wrx ones

 

Well I'm only after around 300bhp in honesty, and swapping the heads with the ones i have comes with the whole issue of having to swap the pistons which is what i was trying to avoid as i dont want a full strip down to hone the bores.

So unless I can source some more heads that have the right capacity then i'm kind of stuck with the legacy ones for the time being..

 

Are you 100% sure that the pistons will touch the wrx heads? I didn't think there was an issue

 

Piston clearance isnt the issue, its the capacity of the heads which is. Some are 46cc and others are 49cc. If you dont match them to the right pistons, then the compression goes sky high which I think would risk damaging the engine..