I was looking because I was working on my 300ex and the piston looked scored bad and was not sure why it's air cooled it had oil when it failed the engine was hot. I don't want to pit a new one in to just fail again. Did you find out what caused your piston to look like the first one?
It doesn't take much skirt wear to turn newer engines into real slappers when cold too. Slapping causes more slapping because you're tearing the skirt up more each cold start.
Cold Starts is the the Issue.. The next Motors I Build I will use a Freeze Plug Block Heater on Both Sides of the Block ..Older Chevy V-8,s and a Electric Oil pump Pre- Oiler.
I’ve had weird situation in my last engine only slaps when warm I’ve ruled everything out It’s almost comical no slap when cold only when hot and especially when the oils really hot never seen anything like it and no it’s not the bearings
depends on the the cylinder position too, for instance a flat four engine will obviously wear the bottom of the skirt out faster than the top because of gravity. and also what the vehicle is being used for i.e hill climbs, time attack, rally....
I would think force due to gravity would be very negligible compared to the other forces the piston sees while running (inertial force, resultant force from cylinder pressure, etc.)
how much piston scoring is too much? I had a flat tappet cam failure and my Mahle forged pistons are scratched from the debris in the oil. These pistons weren't cheap and I'd like to use them again if possible. Mine aren't as bad as the third piston he picked up, but still have many fine scratches. I will replace the rings.
Hi, I am building a Mercedes ALUSIL engine from the mid 90's and the cylinder walls are aluminum that has been polished. Can I get a piston made that would be compatible with this type of block that would prevent galling?
Does the first ring (top ring)needs to be more clearense then the 2nd ring or contrary . Or which one should be more clearence then the other??????. Could you tell me please
I also have never seen a coated piston coming out of a hole with much coating left on it. Everything from a 1/3 of the coating to almost all the coating gone. I don't buy coated pistons anymore if I can avoid it. There is something to be said about the coating rubbing off and embedding in the cylinder wall providing some extended protection however I have never seen proof of this.
The Skirt Coating acts as a cushioning property. It is simply trying to soften the contact vs bare skirt on cylinder contact which is not healthy for the motor. Several OE's are now using our pistons for vehicles that are daily drivers with GRAFAL skirt coating.
My wear pattern looks like the second from the left but the finish looks faded since its not worn through yet. Only 500 miles or so and its got oily/gummy carbon residue on top of the pistons. I figure it never seated
4 inch is 100 mm... For every 10 mm they apply 0.01mm clearance.... Would be around 0.1mm clearance. (I guess)... But I think the overall use would be a factor to....
@Christs Revenge i can t tell you… so your new piston did not last that long,ore are you talking about your 1st (Original)piston???are you sure that your oil pomp is working oke,because piston lubrication is one of the first lubrication a dieing engine will suffer... if you check the inside from your piston there is most of the time a casting stamp from the manufactuor,(like art for some japanese bikes) i edit because now i understand your question.....!!!!! anyway if yo question that piston just measuring the piston on the lower part lets say 10-15 mmm from the bottom from that skirt,lets say the borediameter is about 75mm tan your used piston should not get much smaller than 74,92mm(15mm from the bottom skirt!!!) what do you mean by "flare out"?
@Christs Revenge is the discolaration caused by blowby ?you can also check the gap the pistonrings have in the cilinderwall,so get them from the piston put the 1st ring in the cilinderwall and check the gap in the top,then middel and then bottom...dont know exactly but when the gap is bigger then 0,4mm than you have a problem i guess,in this way you also can see the difrence between top and bottom bore (without caliper!)maybe its a good idea for you to buy an haynes manuel ore download it somewere on line...there are lso specs for the room the pistinrings should have,gap clearance and also up and down.
@Christs Revenge well,first of all if there is any friction thats a nono.so the piston cant be stuck in the bore if you lift the cilinder(without the rings of course).what you can do (but its not waterproof methode)put the cilinder upside down on a table with a straith cardbord under the cilinder,when you drop the piston in the bore(without rings and with the ringgrooves pointing down)then the piston has to drop but not insantly,more gradualy. if the bore is to small then your engine will not idlle and sees up soon i guess… if the bore is to big ,off course with your forstroke it wil make to much blow by,but even worse because there is no coolant for the piston(because of youre big bore!)...because there is to littel contact with your cilinder liner your piston can t get rid of the heat,then your piston gets so hot it will expand much harder then your cilinder liner so it can sees up (while youre bore is to big!!!) piston can also go rocking with big bore and that why you cant have your piston to small in diameter... check for a castingstamp on the inside from your piston......
@Christs Revenge yes oké.... Think the xt 250 can handel at least 2 oversises from. 0.5 mm each, maybe now you learn the hard way but Don 't get discouraged... Anyway if you need some tips when mounting just ask.... And buy a haneys Manuel.......
I am just a simple mechanic not an engine builder but I am pretty sure it was one of this 3 reasons: 1- Too much piston to wall clearance. 2- A design flaw on the piston (basically piston was too short and made it rock too much even when with clearances within specification) 3- Used on the wrong build (basically those kind of pistons are aimed at low boost high RPM type of engines. I think high boost engines are more susceptible to piston rocking but once again I am not an engine builder and I don't have much experience with this) If it was too little of a piston to wall clearence the piston would look more like the first. At the very least I think it would have some "blueing".
No, at 2:05 he even says they were working on shape issues (piston was not uniform to the bore as good as it should have been). So it's a weird one-off situation there
I realise you guys make hypertectic pistons for nissan td42 have you ever considered making forged reason i ask is as far as i know ross are the only ones that do and because of the expansion and clearances required alot blow by seems to be the norm
We can make custom, but if there is enough demand we would make a shelfstock version. For more information our custom piston program it is linked here. www.us.mahle.com/en/motorsports/custom-piston-sets/
I'm not sure why you didn't say the the skirt being screwed up wouldn't cause oiling issues that's a no brainer that's what it's for and lack of oil in tern can cause the piston to seize in the bore
Isn’t the purpose of a skirt coating to buffer the expected known contact that Will be made on cold starts? That’s their very purpose. Their only purpose.
The wear on each of those pistons would still be there even without the coating; the coating just makes it easier to see. You would otherwise need to have the parts in-hand to really see it in detail. Or high resolution, zoomed in shots.
