Just got back from dropping off part and visiting the MINI. First off, I forgot my camera, I will be back there again on Tuesday with more parts and since the tech cannot really do anything till these parts are in hand all will be the same as today. The cause of the low compression in Cyl was found. The ring gaps all lined up again. This is the second time this has happened. The first time the cyl was honed, the piston re-ringed and it ran fine 25K or so miles. Note that the first instance of this issue was at about 25K miles as well. I will have pictures of this next week. Other issues found.... Vacuum Leak - The "sight glass" of the M7 Oil Catch Can was again broken. This is was just repaired less than 2000 miles ago. Going back to NO catch can when reassembled. This thing has caused more problems than it has been worth. Chain Tensioner - A chunk of the plastic has broken off. Wayward chunk was found in the oil pan. Replacing the part. Item # 3 in the image below. And the affected part. Chunk is missing from left side. Exhaust Gasket - The copper exhaust gasket leaks. To be replaced with a crush-able type gasket that PGT had made.
Thinking about this? You are saying the top two ring gaps lined up correct not the 3rd which is the oil controller? If that is the case then your bore/hone may be incorrect? Piston rings (mostly the 1st and 2 nd ring) will rotate in the bores and settle in a similar location if the the bore/hone is not correct. In theory?? I have never seen this happen but I called a friend who still has his performance engine shop and he claims to have seen this a couple times but says it was the installers improper end gap measurements and gap position in the bore.
Called the tech and asked him to send me a picture. This is off a phone. Will get better ones when I go back over there.
Have a better image of the piston rings now. The plan is to measure to bore to make sure it is round. I did take a lamp to take a good look at the hone marks and all the cross hatch marks are nice and even around the entire cylinder. I'm starting to think the piston may be slightly deformed. A bit more detail of the area.
Update time! Besides the fun of getting an incorrect part and having to wait for the correct one due to a communications snafu we had the Memorial Day holiday, so things were on hold for a few days. Since the head was off the thinking is why not clean out all built up carbon, there really wasn't a lot. Twas going well...till this... Now mind you, I did blow up the photo and enhance the colors to make it easier to see. The stem ain't that dandy looking either... The coating is worn, they tell me this could be an issue with the valve guides too...oh goody. That one is the worst of the 3 obviously damaged exhaust valve. The head is off to the machine shop for a full tear down and inspection. Darn good thing we have such great MetroplexMINI.org members too. The loaner from a club member is a real lifesaver. It's an R53 at that... :cornut:
:crazy: Good thing you tore her down when you did with everything ya found. Have a party when you're done and put more then 2 bolts in your facia devil: made me say it) Mark Group4
Machine Shop Report time.... At least 4 Exhaust Valves need to be replaced. Since we are in there the full set of exhaust valves will be replaced. 2 Intake valves are very suspect and will be replaced. Springs, guides, seals and seats have all been given a clean bill of health. They found a very small V shaped crack in cyl 3 between the 2 exhaust valves and the spark plug hole. This will be filled and a helicoil installed. The crack does not extend to the water jacket. Please keep in mind that this is not an indictment of the quality of this head. It has 45K miles on it and it is a race type head that has seen more than it's fair share of track days and runs to 8K rpm. The take away here is that things things happen when you enter the realm of the extreme. I'd also like to thank all those that have offered help, support, parts and guidance along the way with this latest adventure in MINI modding.
Point taken, so this falls into the realm of normal wear and tear on an aggressively driven tracked car. Are you going to change all the intake valves as well, or just the two suspect ones? Reason I ask is if you're changing the valves, are you going to go with a different valve set, or just replace the originals with identical valves? Just asking for selfish reasons. Eventually, whenever a tuner makes it this way (or if I can find the time to drive to a tuner, which is doubtful), I'd like to do a head/cam combo, but I want to maximize the endurance of the setup. But with the luck I'm having, it'll probably never happen anyway...
Well no, some of this is due to head design and the stresses experienced with an aggressively driven tracked car over the long haul, emphasis on over the long haul. We have to remember that these are parts that are beyond the OEM design specs, have not been long term tested and are tasked with creating more power that the original OEM design yet use the basic casting to achieve these goals. Just the two solely based on budgetary concerns. This incident has put a big dent in the wallet. I would prefer to replace all of them but since I like a roof over my head that's just beyond reach right now. That has yet to be determined. I see this as a learning experience myself and am focused more on moving forward and getting it as right as I can at this point with the focus being endurance over flat out max power.
One of the things that has been spouted out about the Newman cam (that's the cam you run, right?) is that it's harder on the valves (I think it's high lift short duration--not an expert on these things). Wonder if this is a manifestation of that or totally unrelated? It's stuff like this that scares the contents of my intestines into my BVD's...
Cams do not in the case of a MINI have an effect on valve wear or anything that might have happened here with Nathans engine. Newman cams do not have high enough valve lift or duration that would cause any concerns with Nathan engine or anyone's engine using those cams. If it did valve spring issues would have been addressed which is not the case. Although I know an upgrade spring kit that would be of benefit but not necessary in Nathan case.:smilewinkgrin:
Ah contrare' mon ami... Cam is as it left the MINI factory in Oxford. There was no good solution at the time I did the engine and the confluence of a tuner on hand, sufficient cash and quality camshaft has yet to happen.
Ok, good to know. Newman cam is the one I'm leaning toward putting in... Jan, now if you'd quit messing around with that racing crap, get off your ass and come to the midwest, then maybe I could finally get a head/cam/tune in....
Good luck with the rebuild Nathan. How are the head and block surfaces? Still true or are they to be resurfaced? Jeremy