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| Original von ChrisF-68 Hi, Steve and a warm welcome! Great mods you did! One of the main-problems IMHO of the 2,5-engine are the HG-failures. Seems, you solved that problem? Tell us some details, we´re all interested! Regards Chris (driving Lee´s former GT) |
Thanks for the welcome every one
Chris to answer your question
In stock form the 2.5 has a weaker thinner block than the 2.0.
I wouldnt push stock pistons above 400hp
And because therefore the gasket area is thinner, as it were, they can be more prone to head gasket failure.
however - most of the time it seems to be the pistons going. And on a previous 2.5 I destroyed two standard pistons.
(The problems with the newage hatch are different it is down to weak pistons combined with a poor map from the factory - subaru have lots of spare warenty engines tucked away as they wont admit there is a problem)
Anyway..back to my build. The 2.5 block is a semi closed block. so although a bit thin it is not as weak as people make out. Forged pistons are a must. Rods not so important and the stock crank is also good big power. A must however is the hand built strengthened liners flanged top and bottom to stop slip. This is a big part of making the engine reliable at big power. I then coupled this with the strongest heads that subaru ever made and had them reworked. These are V3/4 STI heads they are kings and comand a good price if they ever come up second hand.
I sourced the parts and got a very very good builder to build the engine.
Summary
So yes head gasket failure still a bit more likely than on a 2.0. The strength is mainly down to the quality of the build and componets used. However you are more likely to see a piston go than headgasket on a 2.5
A fully forged engine like mine sounds like it is broken when cold, It sounds like all the pistons are dead and mine drinks oil (some do some dont). Only when it is really warm and the pistons have swollen to fill the bores does it sound sweet and smooth.
The best big power build you can do is 2.3 on a closed deck block with Sti V3 heads - However that is big big money!!!
Best wishes
Steve
Just to add 2006 Hawkeye 2.5 Sti seem to suffer from this problem.
You got a nice car!
. Da kann meine Gurke nicht ansatzweise mithalten. Sein Auto hat übrigens den dicksten und offensten Endschalldämpfer, den ich je gesehen habE 
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