Welcome to K20a.org
@yaggs. I am sorry to read about the engine issues you suffered.
It’s 40 degrees out and I’m using Castrol Edge 5w-30… oil pressure steadily decreased from 35 down to 3 when coolant temp reached 180.
As a general suggestion. First, I never would use Castrol oil, neither non- nor synthetic, even not for the first installation lubrication. It has a low capacity to build up a stable oil film compared to the top dogs in the field of engine oils. High revving engines need a proper and stable oil film. Second, anytime an immediate oil pressure pressure drop happens, the oil filter check, oil level check, oil leak check are causing obligation. And 3rd, anytime a part of the oil system has signs of seizure oil was missing already there.
For your specific case. The seizure of the relief valve shows already signs of missed oil flow, which means an insufficient sucking or pressuring of oil flow. What would happen it that valve was always open? Oil pressure on lower engine speeds up to around 3000 rpm would be lower then normal. What would happen if it was always closed? Oil pressure would have been increased over 5 bar at higher engine speeds and the efficiency of the oil sucking would have decreased. The possibility of insufficient oil supply to bearings would have been dramatically increased at higher engine speeds.
For me it is not clarified where the relief valve stuck, either in the open or closed position. The symptoms you have described would indicate finally it has been stuck in the open position, means oil pressure was to low at higher engine speeds, what would match those lately observations you have described. But it is not for sure, I would like to see if there are also signs of seizure in the fully open position of the oil pump housing. The seizure signs in the pictures above show only closed stuck position, which contradicts the observations you have described. My conclusion, both sticking positions might have had happen.
On the journal bearings there are signs of pitting on the cap side and little scratches on the rod side.
- pitting on the cap side: lack of scratches on the cap indicates more a oil driven then particle driven pitting, lack of oil flow or insufficient thermal stability of the oil film
- wear on the rod side egdes: all bearings show one-sided wear on the low load areas, which may are signs of out of spec or excessive engine spinning under worn axial washer issues
- scratches on the rod side: the lack of wear in combination with scratches indicates those scratches can't be to old, what would be also a possibility for 1.
I have no history of that engine and no live observations of the issue (sound, feeling, signal trends, ...), just a stomach feeling of what is behind the gathered above. That tells me something caused the relief valve to seizure and this caused the stucking of the relief valve in both position and drove finally the damages of this engine. A lack of oil level? Or a low level and hard cornering? Or a low level of oil niveau and excessive engine speed?
@yaggs maybe you have some ideas on that?
Please don’t suggest power making parts unless it maintains reliability and is cost-effective
Buy a good used 86x86 bottom end and go with it. The stock header manifold restriction will stop any worth benefit on intake and exhaust side and cause further budget demand. Just my two cents.
Edit: there is a lot of excessive engine speed indicators, this doesn't mean 9000 rpm or more, it means the system was run faster that it was capable of. If the weakest link is low enough, 6000 rpm could have been that excessive engine speed already, just duration of it would work out the damages.
. I check it almost every time I am going to start the engine. Yeah, for an DD are 1000 miles/check quite good, but think of it, an oil change every 7500 miles would be a good thing, it is an high revving engine and earns only best maintenance.
