My 26/30 Is Rooted

[Marko R1]

Indeed, the fun of a full build is... challenging at the best of times

But hey, he got warranty, that's not a bad end of the deal!

i had the same deal as well its always good to deal with engine builders who keep their word!

[aerofocker]

at such high rpm the valves are getting smashed open very fast,im sure this can induce oscilation and vibration and if the frequency/resonance ect was right eg 9krpm!!! then it may rattle round in the guide support and fatigue it rather quickly,especially in a ported head where the guide is unsupported by the head casting for the final portion,and of course that final ingreedient that makes all our lives so great POT LUCK the primary cause of engine failure!lol

Edited April 14, 2010 by aerofocker

[James_03]

I still think it's det related. Your number 2 on the list below.

We pulled a mates 25 head off that we knew had died due to det, and it was a very simlar picture.

Detonation causes three types of failure:

1. Mechanical damage (broken ring lands)

2. Abrasion (pitting of the piston crown)

3. Overheating (scuffed piston skirts due to excess heat input or high coolant temperatures)

Taken from here: http://www.streetrodstuff.com/Articles/Eng...tion/Page_2.php

Edited April 17, 2010 by James_03

[D_Stirls]

It's quite deep for Det' though.

Having said that I was thinking that it was Det'.

You mentioned that some rods were longer than others?

I noticed on you #2 piston that there was some similar marks, were the #2 and #5 rods longer than the others?

If this is the case then #2 and #5 cylinders would be running higher static compression than the rest so they will Det' before the others.

[Marko R1]

I still think it's det related. Your number 2 on the list below.

We pulled a mates 25 head off that we knew had died due to det, and it was a very simlar picture.

Taken from here: http://www.streetrodstuff.com/Articles/Eng...tion/Page_2.php

that link is a good read, thanks for sharing

[tridentt150v]

^^^^agreed, good read

[STATUS]

I still think it's det related. Your number 2 on the list below.

We pulled a mates 25 head off that we knew had died due to det, and it was a very simlar picture.

Taken from here: http://www.streetrodstuff.com/Articles/Eng...tion/Page_2.php

It takes 2 seconds to tell, if the damage on the piston is mirrored on the head it IS NOT DET.

[rockabilly]

cheers for all the input guys, been stranded in portugal till today, hence why i have have not been on. to answer some questions.

all the plugs are completely intact, no electrodes or tips missing

all the valve guides are intact too

had a light skim on the head and its like new

also stripped the gt4094r down no blades damaged on either the compressor or exhaust wheel

also the is no signs of any seat damage on any valve or valve seat.

gonna start the rebuild soon as i know have a crank and collar,tomei oil pump and 1000bhp ati damper, gonna use acl race bearings this time too.

will update as i build..bernie uk

[Marko R1]

Good to hear you're on the road to recovery so soon

[T04GTR]

at such high rpm the valves are getting smashed open very fast,im sure this can induce oscilation and vibration and if the frequency/resonance ect was right eg 9krpm!!! then it may rattle round in the guide support and fatigue it rather quickly,especially in a ported head where the guide is unsupported by the head casting for the final portion,and of course that final ingreedient that makes all our lives so great POT LUCK the primary cause of engine failure!lol

pitty with bucket lifters there is ZERO sidways load on the guides..

[Sheriff Wan]

Its not DET as has been said - you would in no way get the marks on the head from DET full stop.

Looks like its eaten something, what though remains unknown. Ever pop a cooler pipe or do anyhing with the throttle?

[rockabilly]

Its not DET as has been said - you would in no way get the marks on the head from DET full stop.

Looks like its eaten something, what though remains unknown. Ever pop a cooler pipe or do anyhing with the throttle?

hi mate, checked the butterflies, nothing odd there. intercooler is an old hks drag 4" thick one, all pipework is hks stuff, not homemade..bernie

[James_03]

Its not DET as has been said - you would in no way get the marks on the head from DET full stop.

Looks like its eaten something, what though remains unknown. Ever pop a cooler pipe or do anyhing with the throttle?

Can someone please explain to me why he wouldn't see these marks on the head with det? I simply cannot understand why this would be so, sure everyone is saying it can't be because of the pitting on the head, but tell me why?

From my understanding, there is STILL no evidence to say something has got into the intake system.

Abnormal combustion

When unburned fuel/air mixture beyond the boundary of the flame front is subjected to a combination of heat and pressure for a certain duration (beyond the delay period of the fuel used), detonation may occur. Detonation is characterized by an instantaneous, explosive ignition of at least one pocket of fuel/air mixture outside of the flame front. A local shockwave is created around each pocket and the cylinder pressure may rise sharply beyond its design limits. If detonation is allowed to persist under extreme conditions or over many engine cycles, engine parts can be damaged or destroyed. The simplest deleterious effects are typically particle wear caused by moderate knocking, which may further ensue through the engine's oil system and cause wear on other parts before being trapped by the oil filter. Severe knocking can lead to catastrophic failure in the form of physical holes punched through the piston or head (i.e., rupture of the combustion chamber), either of which depressurizes the affected cylinder and introduces large metal fragments, fuel, and combustion products into the oil system. Hypereutectic pistons are known to break easily from such shock waves.

Taken from wiki here: http://en.wikipedia.org/wiki/Engine_knocking

Granted this is not severe detonation, but it's obvious from that statement that both the head and pistons can be effected.

Other signs are there including potential contamination of the oil system which has also caused the bearing failure.

Edited May 1, 2010 by James_03

[GTRNUR]

The biggest giveaway that it wasnt detonation, and that it was a foreign partical is on page two where the pics of the piston crown are right next to the damaged squish pads on the head.

1. Part of the squish pad near the intake valve 3rd picture down (look for the clean intake ports in the first of the combustion chamber pics), has a dent right next to the edge of the valve seat. The distrtion of the aluminium would requre more force than detonation alone could do, AND detonation would not cause damage right on the edge of a combustion chamber. Combustion of the air-fuel mix would expand into the larger area within the combustion chamber. It would not localise all of its energy on a spot next to the combustion chamber and create a dent in the aluminium that has forcefully distorted the edge of the combustion chamber.

Also, if it were detonation, there should also be signs of damage to the combustion chamber itself (inbetween the squish pads), and also to the tops of the pistons between where the squish pad area. But there is barely any kid of mark at all on the piston crowns between the squish pad area, and the head combustion chamber has no signs of damage at all. The reason there was no damage in this area is that there is sufficent space inside the combustion chamber between the squish pads for particles to fit without causing piston/head damage.

2. The purpose of squish pads is to force the fuel air mix into the center of the combustion chamber so it is right next to the spark plug. The shape of the combustin chamber compression area (between the squish pads) is optimised to provide a complete and fast burn of the air-fuel mix, alowing the flame front from the spark plug ignition point to burn efficently to the other side of the combustion chamber. The most inefficent area of the combustion chamber, and the are that has the worst/most incomplete burn is right at the outer edge of the squish pad.

The reason this area is inefficent is because as the flame front tries to move outward across the top of the squish area between the piston and the crown, the energy produced from the burn and expansion of gasses push the flame front back into the combustion chamber. So very little/to nearly no combustion at all will occur out near the edges of the squish pads.

The further in you go, the less energy produced from combuston in the squish area. At the outer edges where combustion is at its worst, the energy produced is so low it could not cause any damage to the surfaces as is pictured.

Consider a 5lt petrol container with fuel/air vapor in it. If you were to ignite the contents you would blow your self up nicely. Now if you had two BIG sheets of glass that were set apart a few mm from each other so that the volume of that same area was 5 litres and you were to ignite that, you could watch the burn slowly move from one end of the sheets of glass to the other. The energy released from the burn would happen a lot slower and would not explode, and at no point during the burn woud combustion in one are be particularily more intense than in any other area.

A squish pad (deck height clearance) in a well setup engine will only be 0.035" - 0.060" from the head to the top of the piston squish area at TDC. I believe Bernie said the engine was running a 1.2mm head gasket, so 0.060".

Given this information, combustion or detonation (at least at a level that could cause sufficent structual damage as pictured) can not have occurred out at the very edge of the piston and combustion chamber.

3. The patterns of the impact events on the head seem to fairly closely match those on the piston. Pictures 2+3 on page two. There are 4 main dents in the combustion chamber that sort of look like a face and to the right of it is three marks in a line. A similar impact patern is on the piston above that picture. 4 big dents, with a row of 3 next to them.

Then there is the piston damage at the bottom right of picture 2, and that matches the damage to the combustion chamber where right next to the intake valve in picture 3.

The 1st and 4th pictures are harder to match, as the first picture is a little blury. The main thing that stands out though is that there is only one BIG pit in the crown that seems to match the approximate location of the damage in picture 4.

Well thats my opinion.... Hope it makes sense.

[Marko R1]

If bernie doesn't find any fragments in the engine, that will be frustrating I'm sure. Not knowing the cause would drive anyone up the wall

[rockabilly]

cheers GTRNUR for that in depth and superb reply.

yes Marko your right mate. not found anything yet, crank will be back soon and then whilst i rebuild i will be even more meticulous on assembly than usual. lol Bernie

[James_03]

The biggest giveaway that it wasnt detonation, and that it was a foreign partical is on page two where the pics of the piston crown are right next to the damaged squish pads on the head.

1. Part of the squish pad near the intake valve 3rd picture down (look for the clean intake ports in the first of the combustion chamber pics), has a dent right next to the edge of the valve seat. The distrtion of the aluminium would requre more force than detonation alone could do, AND detonation would not cause damage right on the edge of a combustion chamber. Combustion of the air-fuel mix would expand into the larger area within the combustion chamber. It would not localise all of its energy on a spot next to the combustion chamber and create a dent in the aluminium that has forcefully distorted the edge of the combustion chamber.

Also, if it were detonation, there should also be signs of damage to the combustion chamber itself (inbetween the squish pads), and also to the tops of the pistons between where the squish pad area. But there is barely any kid of mark at all on the piston crowns between the squish pad area, and the head combustion chamber has no signs of damage at all. The reason there was no damage in this area is that there is sufficent space inside the combustion chamber between the squish pads for particles to fit without causing piston/head damage.

2. The purpose of squish pads is to force the fuel air mix into the center of the combustion chamber so it is right next to the spark plug. The shape of the combustin chamber compression area (between the squish pads) is optimised to provide a complete and fast burn of the air-fuel mix, alowing the flame front from the spark plug ignition point to burn efficently to the other side of the combustion chamber. The most inefficent area of the combustion chamber, and the are that has the worst/most incomplete burn is right at the outer edge of the squish pad.

The reason this area is inefficent is because as the flame front tries to move outward across the top of the squish area between the piston and the crown, the energy produced from the burn and expansion of gasses push the flame front back into the combustion chamber. So very little/to nearly no combustion at all will occur out near the edges of the squish pads.

The further in you go, the less energy produced from combuston in the squish area. At the outer edges where combustion is at its worst, the energy produced is so low it could not cause any damage to the surfaces as is pictured.

Consider a 5lt petrol container with fuel/air vapor in it. If you were to ignite the contents you would blow your self up nicely. Now if you had two BIG sheets of glass that were set apart a few mm from each other so that the volume of that same area was 5 litres and you were to ignite that, you could watch the burn slowly move from one end of the sheets of glass to the other. The energy released from the burn would happen a lot slower and would not explode, and at no point during the burn woud combustion in one are be particularily more intense than in any other area.

A squish pad (deck height clearance) in a well setup engine will only be 0.035" - 0.060" from the head to the top of the piston squish area at TDC. I believe Bernie said the engine was running a 1.2mm head gasket, so 0.060".

Given this information, combustion or detonation (at least at a level that could cause sufficent structual damage as pictured) can not have occurred out at the very edge of the piston and combustion chamber.

3. The patterns of the impact events on the head seem to fairly closely match those on the piston. Pictures 2+3 on page two. There are 4 main dents in the combustion chamber that sort of look like a face and to the right of it is three marks in a line. A similar impact patern is on the piston above that picture. 4 big dents, with a row of 3 next to them.

Then there is the piston damage at the bottom right of picture 2, and that matches the damage to the combustion chamber where right next to the intake valve in picture 3.

The 1st and 4th pictures are harder to match, as the first picture is a little blury. The main thing that stands out though is that there is only one BIG pit in the crown that seems to match the approximate location of the damage in picture 4.

Well thats my opinion.... Hope it makes sense.

Thanks for that mate.

Definately makes more sense to me now, Ill concede defeat with that lol.

Edited May 3, 2010 by James_03