Originals, pretty sure they weren't broken for some time as the car felt down on compression after my 25 PSI methanol fuelled 500 BHP chasing Porsche baiting episode when it also blew all the water out the header tank Could hear it all gurgling when I pulled up.

I think cylinder pressure from too much advance (even without det) killed it. The 2.5 motor doesn't like or need much advance.

I'm running a bit more respectfully on the same setup again. After all it was fine for several thousand miles until I went silly. And I didn't even need all that power to sort the Porsche out, 150 BHP less in T-uk's Scooby was also enough although it was only a 993 normally aspirated model which didn't like landing after yumps very much

 

John

Is this the type of cracking we talked about previously?
Do you think that if you had been using the piston I showed you recently this may not have happened, due to the thicker ring land ?

Mark

 

Possibly not, but I think the issue is cyl pressure not internals strength. ie I cocked it up tuning it with too much timing. The headgasket went on the other side. It had to get out somehow. However, chasing 500 BHP (more importantly the absolutely silly torque it was running - showed 390 wheel torque on Delta Dash, which is about 450-460 lbft on a conservative dyno I reckon) I don't think I did too bad on a standard engine that is supposed to be good for 350 BHP according to the experts because of risk of picking up. Also not sure it is through the ring land, need to pull all the pistons some time to check before reassembling and putting it in the Legacy.

 

If you want set of CPs let me know.

Mark

 

Tuned Porsche GT-2s make better targets!

Paul

 

Never seen one though

 

That's because there always in front........A target's always in front of you.............and an EVO5 is always in front of me let alone a GT2 or 3!

Stop bullying 911s. You know they are always ready to bite (their drivers) back. That's why I don't race mine anymore. Too bloody frightening.

911

 

Think i have joined the head gasket clan, need to do a check tonight

 

oh bu99er!

 

$hit Steven!! No! What a PITA. Let me know what you find please...

You had genuine ARP standard sized studs and which gasket?

Is the header tank emptying through the overflow? Were you battering it at the time?

 

John, it has been receiving the usual abuse, and is just shy of 8000 miles now.

I need to do a full check, but i have become increasingley concerned over the last 2 weeks.

I topped the water up 2 weeks ago, when it took nearly a litre, and put that down to recently draining the system, and not checking since filling.

Anyway, arrive at work today, and when i got into the office and looked down at the car, there was the tell tale rainbow water running away from the car, so something is leaking/spilling. I know there is an oil leak, but not that much.

Prompted me to go have a look at lunch, and the tank is empty, as is the over flow tank!

Standard ARP studs used and the thicker gasket (cant remember whether its 1.2 or 1.6 ).

Anyway, will have to do a check to night, but may top up and leave while weekend, as that is when i had planned to do an oil change and coolant drain down.

Fingers crossed it isnt, but you never know.

 

Just have to hope it is leaking from somewhere else...

A gas analyser over my coolant header or expansion tank showed lots of hydrocarbons, and the second time when bad it was bubbling in both.

 

Don't run it too long Steven if you are in any doubt. I have seen pics of one engine where the block was ruined when the gasket went, the hot gasses had dug a trough in the block surface where they were escaping through to the waterway.

Andy

 

why are u guys blowing headgaskets ?..... doesn't seem to be an issue on the other side of the ocean, and the few conversions we have here which still use the stock head studs don't seem to have a problem either.

Carlos H.

 

Maybe we have pushed peak pressures higher due to running pump fuel ? IIRC most of the big power USA builds (not many) were run on C16 or similar which will produce much more power but with lower peak combustion pressure.
FWIW the Sti6 I mapped recently in the USA would accept more timing running on their 93 octane 'pump gas' (R+M/2) than an identical model here would on optimax and that was at 85/90 degree ambient.

Andy

 

Andy, I think u may be right, out of 5 conversions I have seen here in Peru, 4 of them are used only for competition purposes and use race gas. Maybe with regular pump gas it is better to go for higher boost and lower timing to achieve the HP goals.

Carlos H.

 

"Maybe with regular pump gas it is better to go for higher boost and lower timing to achieve the HP goals"

My thoughts exactly for a road car used where fancy fuel isn't easily or cheaply available. It sounds from NASIOC that C16 is about the same price as our Optimax and available at the pump. Maybe then I would have an easy 500 BHP even with my present turbo?

Andy, any comments on the peak cylinder pressures with Optimax/10% Methanol compared with C16 for similar power? Because mine let go both times using methanol and lots of timing, with relatively small increases in boost.

 

Going to have a look at it tomorrow Andy. Congrats btw (think i read it somewhere).

Steven

 

We're talking on two threads Steven, but assuming it is the gaskets, what are your thoughts on how to stop it happening again?

My thoughts are:

1. Turn the power down - my present solution whilst it is my only daily driver or until someone else proves a method... and it does take quite a mileage to do so!
2. Consider less timing and more boost (but how do you decide how much of each as we are no longer then tuning to knock limits which makes it tricky)
3. Try and get some measure of cylinder pressure profiles (too expensive? Optrand, experimental ion sense, both practically beyond me)
4. O-ring it
5. Reconsider 14mm asymmetrical studs such as from RCMS (standard size in heads because of proximity to water), Quirt says they are no better though
6. Speak to Cometic as they sent me the following info:

"The main issue most of the time is that the torque on the motor must be even all the way across the motor in equal increments especially a steel gasket. They are by far the most picky of all gaskets they require a very smooth finish of 50 RA or finer along with a flatness tolerance of .005". Any sort of sleeve stepping or o-ringing completely defeats the purpose of the gasket."

Job said in response, "As I thought about the multilayer steel gaskets. They might not be truly suitable for a ‘wet’ linered block. The liners will expand at a different rate to the block. That might be the reason why Alfa Romeo never used steel layered gaskets."

Role of composite gaskets?

7. Use another engine that doesn't pop gaskets - which one?? Some of the 2.3s have also lost gaskets?

If I had a solution I would do it and change my pistons to something that could take the pressure if I wanted to go further.

So much conflicting info.

Quirt mentions cooling, I've already tried water wetter, this time I also have a 1.3bar rad cap. Quirt is concerned about hot spots near the long exhaust ports in our engines. Whilst my coolant temps according to Delta Dash don't get so high I might not have logged them in the heat of the moment. I do of course have a radiator that is getting preheated air from my FMIC Andy has a point here with a TMIC, no A/C rad etc, his oil temps were astonishingly low.

Let's get the thinking caps on?

 

John, i will try and talk on this thread , but here is my plan.

1. Speak to Cometec about some gaskets, as i was discussing with DW today, and think this is the weakness (dont know why, i am not technical in that sense)
2. Improve cooling to radiator, 2nd fan
3. Measure water temps

I cant do anything else, i drive them t-uk style, and they should be able to take the abuse, thats my logic anyway.

 

Ducting the gap between the rad and fmic, so the air goes through it, not to the side?

 

I have never tried C16 John, the race gas that Daniel had on the US car was 110 ron, this allowed more timing than the engine needed from 4500rpm upwards, even below 4500 I could still run 30 degrees at 1.5 bar on a 20G, it ran clean as a whistle at 38 degrees at 6krpm but made most power at 34 deg.

From this I'm making the assumption that the higher octane C16 (116ron ?) will allow an even greater margin.

Has anyone lost a gasket on a virgin CDB ? ie one which has not been relinered ?

Andy

Thanks Steven think I should start acting a bit more mature now

 

Its gone

Compression test
1, 3 and 4 = 9.5 ~ 10 bar
2 = 7.5 ~ 8 bar

spark plugs
1 and 3 normal expected soot, and shiny tip
4 soot and a bit of orange
2 rusty orange

the litre of water put in on thursday, has gone, header tank is bone dry

oh well, engine out

 

Not good news Steven Not just for you but all of us really if these high output big capacity conversions are not going to do the miles ?

What boost level were you running at peak torque and what sort of timing advance ?

Andy

 

Not sure on where peak torque was, as once it came on boost it was just a head rush, and its never been on the dyno. Due to the persistant boost problems, boost varied so much, but never went above 1.6bar. Ocassionaly it would hold 1.6 in 4th from about 3800 to near the red line of 7500, and it would simply take off.

latest ign table here www.stevend.org/uploads/darley29ign.xls

dont know how they compare to others?

it is a bit worrying as the only 2 people to my knowledge that have done high mileage, is me and John, and we have had problems.

 

The timing looks very 'safe' to me, I presume you have some temperature, knock and gear compensations adding to those base figures ? I have 20 degrees more than that in some load zones although every engine has different requirements.

 

Steven, I think mine is quite similar on (what is my full load - ie 1.4 bar) assuming your reference is BTDC, probably about 3 more across the board at 1.4 bar, which is knock limited on Optimax with a safety margin. Differences - I have slightly higher compression I think and a smaller turbo, going the other way P1 heads. So all ties up and looks very reasonable to me.

 

Andy, i thought they were low too, compared to my 2.0l, but i may be wrong. My gut feeling is, i still think there is more to come from it, Pat and i just ran out of time, and the ability to stay awake. I have been too content with driving it, to bother looking at it since, plus i didnt have the means for a while, as i lent pat my can cable for the motec.

There are no compensations yet, so thats it. Mapped on a plain Optimax, with a residue of BP Ultimate (sh!te).

This time when the engine goes back in, its going to be set up right, how it should have been in terms of fuelling etc. I am not happy with the 850's and think 740's would be better suited.

 

I agree with you on the 850's I'm also pulling mine out and fitting 740's but I'll need to add a second fuel pump to keep the pressure up.

 

I also have 2 new walbros sat at home to do exactly that Andy.