I think either could lift the heads. I once upper the compression on my air cooled Kwat Z1100. I bored it to 1170 and rased the comp ratio from 9:1 to 10.5:1 i think it was. I had to replace the standard studs with APE chrome molly and use a cometic hg to keep it all clamped.

Hmm so when considering a turbo I think I'll have to factor in compression ratio and HG thickness. Having a 79mm stroke crank will increase my CR but to what?

+1 on the above.
I've found a lot of the head bolts on the outer lower side of the heads have corrosion on the shanks of the bolts - another indication of coolant ingress.

Mick

Has anyone ever checked the torque on the head bolts prior to HG failure?

Achieved by been very oversquare -shortstroke

The pistons will smack the head if you don't have the pistons to match! :lol1:
We build to 8.5 to 1 by calculating based on a trial assembly, then machining to suit with our choice of deck height and gasket thickness.

Some combinations also require head machining to open up the chambers.

The difference between mechanic and engineering. Some peeps think it's just a case of bolting everything together and not realizing the maths and machining involved.:thumb:

Shorter rods will be used. So do you build, compression test and go from there?.

as above a dry-build so you can measure exact compression volume, etc. is the way forward.......

alyn

Just an update guys / gals, but everything seems to be ok now.

My PSi3 is giving normal temp readings, and after draining out the 750 ml of excess coolant, the level is behaving.

It rises an inch after a run, then once it cools down, the level drops back down to max.
No idea how all this extra coolant came about, but perhaps it was overfilled at some stage, and was gradually overflowing as it should.

Thanks again to David @ API, fantastic fellow to talk to, and gave me reassuring competent advice.

Panic over for me now, but will be keeping a closer eye on the overflow tank.

Did you take Subaru up on their Free winter check up a few months ago ? If you did then maybe one the the main dealer gimps over filled it.

Nice one Hawkeye D.

Kwik, I'm not into bike engines (I'd kill myself) but if you didn't realise, there is a nice free lunch from turbocharging an engine. Whilst you can double the cylinder charge with just over 1 bar of boost with good intercooling and an efficient turbo, the PEAK combustion pressure (which does the damage) doesn't double (goes up by about 20%), but the MEAN combustion pressure and therefore the torque assuming you have the octane to support the compression almost can.

No I never took them up on that offer. I think I was emailed about it though.

I can get all that done at were I work anyway (Volkswagen). Good oil change last week at work. Gulf FS 5w 40.

Seems like good oil so far, I rang Opie to buy 5L of Shell Ultra AG 5w30, and Matt recommended the Gulf.

It was cheaper, and had all the protection grades required. I got a sump plug washer posted out from my nearest dealer, and job done.

Do you think my 1L top up bottle of Shell Ultra will mix ok with the Gulf? Matt @ Opie said it would be fine.

:thumb: Get out there and enjoy the car!

Ut oh! Water level seems to be rising again.

I got home about 6.00 pm tonight, just went out to check my oil and the water is up high again like my pictures earlier in my thread.

It's now about 3 hours since I switched it off, so the water should have dropped by now shouldn't it?

The overflow tank still feels warm, so perhaps it will drop down again. I never usually check oil until the next day, so maybe it's always this high 3 hours after switching off?

Coolant looks a healthy colour, just like the last time. Temps on the needle and PSi3 have been behaving too.

I do sometimes hear like a bubbling / trickling noise from behind the heater matrix when I start the car, so maybe and air lock? Or would you say this is normal.

I feel another call to David @ APi coming on!!

I've just gone through this, only to really check is to boot it then test for hydro carbons I the coolant,

I caught mine really early temp never got over 100, but its there,

I have now got cosworth gaskets. Head bolts n other bits fitted and I'm £1300 lighter :)

Route the pipe that goes to expansion tank up to the wind screen by joining a longer pipe. rip tie it to the wiper to keep in place. Go for a blast and see if any coolant sprays on the windscreen. If it does you have issues, if not your probably being paranoid. The cure for paranoia is stop reading internet forums :lol1::lol1:

have you checked it when the engine is cold?

my overflow tank is 3/4 full if engine still warm/hot.

But even in a healthy engine, reading Alan's description a few posts above means that the heated coolant will expand and the one way valve of the header tank will let coolant enter the expansion tank; so if this pipe is routed to the wiper you will surely see coolant coming out when it heats up.

The other morning (stone cold) it was bang on the maximum.

Just looked again and it's still 3/4 full.
Will check again tomorrow, but if it's like the last time, I'll have to take approx 500ml out of the tank to get it down to max.

Fingers crossed that it's down where it should be tomorrow, but I'm not confident.

As said, I only ever seem to lift the bonnet up when everything is completely cooled down, so I may get a nice surprise.

Tank still lukewarm right now (just) and inlets still feel warm.
4.5 hours after switching off.

It's a great thing owning a standard 2.5, checking the coolant level after each journey, watching the temperature guage after each blast through the gears.

Get it forged so you don't have to worry about it!

It shouldn't push out coolant unless its under pressure. Think how much higher your wind screen is compared to the header tank. If it pushes coolant out that high its being pressurised which indicates a problem.

In a way you are right but even in a system under balance, the acceleration will move the liquid backwards so may spill.

Have you tried this on a healthy engine to see the results?

Not personally but i know some garages use this method for suspected head gasket leak under high boost.

When I first bought my impreza (2.0L) I had the bubbling noise from the heater matrix that you're talking about, Checked the overflow and it was completely empty! Needless to say I filled everything up to the right levels and then burped the coolant system, I got a fair amount of air out the system and since then it's not had any issues at all, so maybe try that?

The latest :

Extracted approx 500ml of coolant from the overflow tank by the radiator this morning. This took the level down to about 1cm below the max mark.

Gave her a life, took out an extremely enthusiastic Civic Type R in the process with ease on the A331, cooled everything down, got home and switched off.

Level has risen about and inch and a half or so (checked when hot) and has stayed there, engine now cold.

All in all I now have approx 750ml of coolant in a screenwash bottle (clearly marked COOLANT!), and may need to take more out by the look of it.

There must be a "void" of water somewhere, how would gases from a shot HG make water rise? Gas is gas and it would bubble out of the non pressurised cap wouldn't it?

So can't figure this out!

How did you burp it?

There are a few methods you can use, and no doubt there will be someone here saying my method is wrong :D but for my method you'll need a no spill funnel / funnel and some rags, and possibly some spare coolant (which you seem to have enough of already). personally I used a normal funnel and some rags, which I'll explain below:

1) make sure the car is cold, then open up the top reservoir cap and place the funnel in there. Get it fitting as tight as possible as you don't want any leaks! To help this, wrap rags tightly around the funnel to make a seal (bit of a bodge i know, but it worked for me).

2) With the funnel securely in place, start the engine, set the heater to maximum and put the cabin fans on (open the windows to let the heat out).

3) leave the car to idle until the engine is at operating temperature, you should see the coolant level rise in the funnel, and after a while dip when the pipes to the block open up (this rise and drop is normal). While all this is going on keep an eye on the coolant in the funnel for any rising air bubbles. They can either be big or incredibly small, small bubbles doesnt mean that there isnt much air in the system, it just means the air and water is cavitated.

4) To aid this process squeeze the s bend radiator hose that leads to the top of the radiator. This will make the coolant level rise and drop in the funnel, but should also help to push any air out of the system. Don't squeeze the hose too hard, you're only trying to move air, not flatten it completely, also remember this will get hot!

5) If the fluid levels are dropping considerably in the funnel simply top it up. A dropping fluid level during this process is probably showing that youre getting a lot of air out of the system.

6)Once you're happy that you've got all the air out of the system, turn off the engine and let everything cool down. The levels should drop down, meaning you'll be able to remove the funnel without making a mess. Finally top up the top reservoir and the radiator to the brim, and fill the overflow reservoir to the specified levels.

And that's that! It's easy to do, just takes a while. On a side note, if you don't mind the possibility of splashes, you can test the head gaskets with this set up as well. Once everything's up to temperature with the funnel in, open up the throttle a bit and check for air bubbles coming up through the coolant in the funnel. A lot of air bubbles shows that air is being forced in to the coolant system, which in turn means your head gaskets are gone.

there's a short video showing the setup and how the fluid will rise and fall

By basically filling the combustion chamber with high pressure boost it forces gasses out of the the cylinder either by lifting the head slightly or a buggered gasket into the water chamber, hence the blowing out of water.

if you take the headertank top off when its cool I dare bet there will be around and inch of water missing in there, this is what ends up in the expansion bottle.

Look around the edge of the caps near the seal for a build up of black scum this is a very clear indicator of a shot gasket.