Knackered shells - Advice please!

[madpugger]

Not sure if I have posted yet to say, but on the way to the ring the S2 started knocking so I stopped it, called dad to get over pronto with the trailer as I had a ferry to catch! Luckily I was 10 miles from his!

Anyway, long story short, I started it, he say big end, turn it off, we winched it onto trailer. Stripped it and the number 1 shells are gone, almost completely. I have only taken off the number 2 cap to have a look, not done the others yet but it is also scored.

Firstly, what are your opinions on why? The shells were in the correct positions, torques were correct, oil pressure was good at around 2 bar idle, 4 or 5 fast idle etc. My suspicion is shyte oil (a GM/Vauxhall fully synth) I have used the semi synth for years and its been excellent but never used this stuff till now.

Secondly, what are my options?

Has anyone had a crank sprayed and ground back to original size? Are undersize shells ok to use on a 500hp setup? What engines use the same crank and does anyone have one?

I hope Aron has a spare rod as one is goosed

TIA
Mike

[driftin jo]

I have been told that swapping oil from normal / semi synthetic to some fully synthetics can cause baked on carbonised oil to fall off as flakes , this can obviously be very bad if they get into the wrong place.

The fact that you had good oil pressure doesn't really mean anything other than the sensor was seeing good pressure I.E a single part of the engine , a bearing for instance, could have oil starvation and you would see no drop in oil pressure on the gauge . The only thing the gauge does for certain is tell you the pump is good, but it cant tell you if one of the oil galleries is blocked .

[madpugger]

I have been told that swapping oil from normal / semi synthetic to some fully synthetics can cause baked on carbonised oil to fall off as flakes , this can obviously be very bad if they get into the wrong place.

The fact that you had good oil pressure doesn't really mean anything other than the sensor was seeing good pressure I.E a single part of the engine , a bearing for instance, could have oil starvation and you would see no drop in oil pressure on the gauge . The only thing the gauge does for certain is tell you the pump is good, but it cant tell you if one of the oil galleries is blocked .

That is an interesting point. I hadn't heard of the carbonised theory, I know you have to flush changing from one to the other, which i did by virtue of the engine being stripped in the first instance, built up with fully on all the shells etc and run, drained and re filled with new filter etc.

I know for sure I wont be using it again! I just don't know what to do with this crank.

[twenty valve]

get the crank re-ground and then order some oversize shells from 034. Thats pretty much your only option unless you replace the crank all together.

[driftin jo]

I just had a quick look online to see if there was anything about what I was told and found this.
It seems to back up what I was told , not that I doubted it as the person that told me has been tuning race bikes for 30 years and knows his stuff .


"When switching to a fully synthetic on an older engine, or one with a higher mileage, it is the ester that can cause problems when one changes from mineral to synthetic. Ester base oil used alongside PAO base oil in lubricant formulation has excellent natural detergent. In other words, it will clean up deposits on component surfaces as a result of thermal and oxidative degradation of the lubricant. When one switches from typical mineral-based engine oils to a typical synthetic-based oil, the varnish layer will be removed by the ester in the synthetic oil and become suspended.
This suspended material can rapidly clog filters and can potentially block oil flow passageways and lead to component starvation. The same is true for gearboxes and other industrial machines. So think twice about switching to synthetic oils in applications where the engine or other machine has been operating for some time with mineral oils. It can be done but be aware of the potential for creating more harm than good."

[s2_wot]

That story about switching to synthetic needs to be a sticky. There's been a few cases of engines letting go shortly after a rebuild, could that be the cause?

Avantus has a thread running about a noisey RS2 bottom end. In that thread s2central posted catalogue excerpts from a replacement bearing supplier, kobelschmidt or something like that.

[madpugger]

That story about switching to synthetic needs to be a sticky. There's been a few cases of engines letting go shortly after a rebuild, could that be the cause?

Avantus has a thread running about a noisey RS2 bottom end. In that thread s2central posted catalogue excerpts from a replacement bearing supplier, kobelschmidt or something like that.

That is a good point, there should be a sticky!

I saw that post (and posted on it) but the difference is I am going to be running 500+ hp with the associated torque increases. I guess ideally i'd like a new crank for free, but realistically I need to weigh up the options.

[s2_wot]

IMO the diameters that you're reducing are not the smallest diameters or section sizes on the crank, so if the bearing fit is appropriate then the crank should be able to transfer whatever power a new crank could carry. Just thinking out loud.

[Error404]

I've got a good 7A bottom end inc crank if its any use?

[madpugger]

I've got a good 7A bottom end inc crank if its any use?

The bottom end is the same is it not? Except shells I'd guess. How much?

[madpugger]

IMO the diameters that you're reducing are not the smallest diameters or section sizes on the crank, so if the bearing fit is appropriate then the crank should be able to transfer whatever power a new crank could carry. Just thinking out loud.

I would think the same. I've rebuilt a few engines but never really tuned anything so...

[Error404]

Yeah the crank is the same
Was asking £40 for but the shipping is the killer as it must weight the best part of 100kg

Are you in a rush for it? As I could strip the crank out and send you that (circa 25kg IIRC)

Cheers
Alex

[madpugger]

Yeah the crank is the same
Was asking £40 for but the shipping is the killer as it must weight the best part of 100kg

Are you in a rush for it? As I could strip the crank out and send you that (circa 25kg IIRC)

Cheers
Alex

If you could that would be great, or I could get a courier to collect if need be.

[Error404]

PM'd you

[fish]

Would you have the same problem going from Fully synthetic to semi synthetic and vice versa or does this only occure when going from mineral to any synthetic?