6 Hour Pain

[Colin Byrne]

Hi guys, as many of you may have heard I didn't have a good weekend at the 6 hour, don't get me wrong great event as always, just had a few engine troubles...
I went up on Friday and run the open practice, engine seemed good but was getting a bit warm (which should have been my first warning sign), we continued the day lifting the max revs with each session and changed oil and filter half way through. finished off Friday all good and let the engine cool down overnight and re-torqued the head the next morning.  Went out for my first qualifying run on Saturday and was all good for 2 laps then I suddenly lost power and the O2 sensor went very lean, I thought I'd drooped the fuel pump but then spotted steam pouring out the exhaust.  I knew I'd done a head gasket but unfortunately that wasn't the end of it.  After I got in off the track we pulled the head off in the pits and found that pistons 1 and 2 had broken ring lans of which the pieces and done some damage to the head.  Vin suggested the cause was detonation, possible due to running lean ( I didn't have the O2 sensor in on Friday) or incorrect ignition advance.  I did get the dizzy re-mapped to suit but have since run that dizzy in a different engine and am concerned that It may be advancing way to quickly, so thats to be continued. 
Anyway we only had three cars this year and I didn't want to stop the other guys from running so we loaded the car onto the trailer, drove the 3 hours to Castlemaine put my dad's old engine in the car with my carbies and exhaust, put the car back on the trailer and drove back to Wang on Saturday night.  I had made a lot of other changes to the car, new 8211 Koni adjustable dampers, changed rear spring rates, changed brake and clutch Master cylinders, close ratio gearbox and rose joint steering linkages so was pretty keen to get out there and see what it could do.
The car felt awesome and managed a 1:44 (in traffic) with the old engine, best its done is a 1:47 previously.  The new dampers we're very noticeable on undulation and the close ratio gearbox was just fantastic, I wish I'd done that mod earlier, in fact I thoroughly recommend that as an upgrade and I did happen to see a few boxes of those gears at Vin's place the other day.
   With only 2.5 weeks till targa high country looks like I'll be doing the event with the old engine and get onto the engine re-build for Targa Tas, but as nearly everyone I spoke to over the weekend said to me, that's motor racing.

[hmd]

that's motor racing.

I broke 2 of these, $/lap this had been the worst event for me.

[alfagtv58]

$/lap this had been the worst event for me.

Never ever do this equation - it serves no purpose and no good can come from it.

[hmd]

$/lap this had been the worst event for me.

Never ever do this equation - it serves no purpose and no good can come from it.

Spoken like a true racer that you are.

[pancho]

Sad but good to hear Colin!

Did you get the Ultra close or the close unit ? I assume they are the OSG ones. - If possible (when you get a chance) would you be able to do a real world mini write up on the GB itself - how it performed in comparison to a std unit?

[Sheldon McIntosh]

Awesome work Colin.  Man, you came flying past me, the old engine must still be pretty good, can't wait to see you with the new one.  Bloody upsetting getting caught by 105s in a straight line, I thought my 3 litre was supposed to stop that?  Bring on Phillip Island....

[jimnielsen]

Very sad to hear Colin, but amazing that you got it going again for the next day. I would simply have headed home with my tail between my legs. Have you considered switching to E85 as a means of assisting detonation control?

jim~

[Colin Byrne]

Hey pancho, yea I might do something for the magazine regarding the gearbox, i'm actually in a training course at work today so I might get it started, and yes it was the standard close ratio gearset

Yea bring on the island, hopefully have the engine fixed by then, will be very interested to see the times there.  But like you said sheldon the old engine goes ok, I think the new extractors and exhaust breathed a bit of life into it.

Unfortunately I'm limited with the type of fuel I can use during the rallys so E85 not so much an option

[vin sharp]

Very sad to hear Colin, but amazing that you got it going again for the next day. I would simply have headed home with my tail between my legs. Have you considered switching to E85 as a means of assisting detonation control?

jim~

Changing fuel type is not the answer to this one. Fuel mixture/jetting was the most likely culprit; BUT the cheaper imported pistons should not have given up like that! I never did think they were made with enough thickness thru the back of the top ring groove when I saw them new, certainly I would be afraid to go that minimal. The piston should never be the detonation fuse in the engine; a head gasket or even a cracked liner; -remove & replace, not rebuild a major amount after bits of piston come off.....
Col, your new Australian designed and made pistons are in the works...... 

[MD]

hmd

Two possibilities:

1 Poor casting examples of the clutch housing or
2 You have a bad alignment of the transaxle to the engine flywheel.

I once had to lower the rear mount 12mm from its standard height to get this right before I broke a few as well.

(assuming prop shaft balances and components are good)

[djm411]

Colin,
Sorry to bring up an old topic but if you remember that far back, Can i ask What brand were the pistons? By the look of the photo, that failure was under the inlet port was that correct? Did the failure look simply like a brittle fracture of the piston or was there any pitting around the fracture area

I've just had a similar failure on the ring land of one piston (lucky for me the broken piece went out the exhaust port leaving very little damage to head or liner), I am sure it was detonation/incorrect ignition timing but the failure does not appear to be a simple brittle fracture from overheating. I'll post some photos when I get them (on dad's camera) bet there is some very strange pitting on the piston around the ring land AND also on the head around the inlet port.

By the way how are the new Ausie made pistons going too?

[Colin Byrne]

In my case there was no pitting on the piston or the head, although I have seen that in my dad's old engine, and it was caused by detonation from low octane fuel,  how did the head gasket look, was there any dimpling around the steel edge of the liner sealing ring? 

I actually ended up breaking one of my new pistons before I found the problem. Here's a bit of the story

Broke 2 pistons at winton 6 hour

Replaced all 4 pistons with ones from Vin, fixed up the head put it all back together and took it to Benincas for a dyno run.

Got a phone call saying engine was making good power but had begun a piston had begun to pick up in the boar.  Took the car home, pulled the head off to find another broken piston and liners 2 and 3 had started to score.

Replaced pistons 2 and 3 and took the car to V&HR for a dyno run, all was going well until we noticed smoke/steam coming out the breather on a power run, stopped the run pulled the scope out and had a look into piston 2.  Initally sore nothing but after some time noticed a small amount of coolant seeping past the head gasket into the combustion chamber and some new scoring in the boar.

Took the car home, pulled the head off and noticed that there was a slight discoloration of the aluminium in the head where coolant had been seeping in past the head gasket (a white colour like when aluminium becomes corroded). 

After some careful measurement determined that the liners where not protruding out of the block enough to seal up against the head.  This was causing coolant to enter into the combustion chamber, turn into super heated steam which was causing all sorts of trouble.  Liners where getting cleaned of oil, causing the rings to pick up and causing higher combustion pressures that the pistons couldn't handle.

Anyway a quick "block swap" was performed, some new old liners where obtained and SS O rings machined into the sealing face, back to the dyno with no problems and then didn't miss a beat for the entire 2000km of touring and 600km of competition of the targa just been, so I think we can safely say we found the problem and it had nothing to do with piston material or construction. 

So the pistons from Vin are running very well now, they are a much nicer looking piston, overall lighter but stronger in the area around the valve pocket.

[djm411]

Thanks for the info Colin, another little pitfall to look out for when rebuilding another engine.

The head gasket was showing no signs of dimpling at all.

With coolant leaking into the cylinder would't you be seeing both an increase in coolant going to the reservoir due to excessive coolant system pressures and also loosing coolant?

Also have you got a photo of the stainless o-ring you were talking about?

[djm411]

Here are the photos of my damage, Notice the pitting on the head near the valve. It's also chipped the valve seat too.

This also shows the brittle fracture and pitting on the ring land

[Colin Byrne]

It was such a small amount of coolant it was impossible to notice the level drop, and these engines where not lasting a long time!, and as far as pressurising the cooling system, not sure why that wasn't the case yet.

The pitting on the head your photo shows looks very similar to my dads head i would be saying that there has been detonation for some time in that engine?

Photo of SS o'ring in liner