Thread: Mahle pistons,the coatings

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For my 383 stroker I have almost decided to buy the power pack Mahle pistons.All of what we have done over the yrs has been pretty much on race engines.This is a street engine and I was wonder if anyone has had experience on the long term with the coatings on these pistons???.

Please and thank you,

Gary

yep i have

Originally Posted by pat mccarthy

yep i have

Pat,any problems with them??.Could you please explain??.

What I am looking for is if the coating is any cause for concern of wearing out and then contaminating the oil causing problems.Or any other problems.


Anyone???.

i used it on race and street pistons that had it on them i feel a top coat under side of piston may help more on the street then the grafal skirts if you do not prep your bores good its all off very fast i feel the mahle is a good piston for making power but not a piston i would use in a every day street van with it contact reduction skirts .i seen it on many stock pistons for every day use but most all the times. i have taking them out or seen them used its off . i can get the mahle /pbm with out the coatings

Originally Posted by pat mccarthy

i used it on race and street pistons that had it on them i feel a top coat under side of piston may help more on the street then the grafal skirts if you do not prep your bores good its all off very fast i feel the mahle is a good piston for making power but not a piston i would use in a every day street van with it contact reduction skirts .i seen it on many stock pistons for every day use but most all the times. i have taking them out or seen them used its off . i can get the mahle /pbm with out the coatings

Pat,while I waited to see a post on this topic,I did a search on the net and did find one reply on a web page that stated the coating is worn off by 50,000 miles.So I am thinking that the engineered rings are set for the coatings and the piston to bore clearances are set to the coatings too,made me wonder about it.It does keep the temp's down so you set the bore sizes alittle tighter,but after the coating wears off,then what??.

I don't mean to come off sounding like the doubting son.All I am doing is my homework on parts so I am sure I know what I am buying.

well thats why i do not care much for them coating i feel its better to know were the piston stops and the coating starts i feel the same and even more so with crank .rod bearing s they give you a bore size to finsh the block to your should not size the bore to the piston coated skirt the HARLEY SCREAMING EAGLE PISTON S have a spot were there no coating so you can mic the REAL piston and set size . other do not and like i said your taking there word on the real size were i have put them in but bit bigger 0005 so if they want 001 piston to wall i bump them out to 001.5 race stuff its not a big deal were .001 more or less may not hurt were you can be at 003 to 008 piston to wall if coating there fine if wears off thats fine .but if the bore is to small then the coating go to come off just as fast . i do not under stand what you saying about the rings ? the bore s if not prep good is what i mean is the bore bottom of bore edge breaking this so you do not shave the piston s as there moving farther down the bores and skirts can come out of bores

Pat-here is what I found on the rings:

http://www.mahleclevite.com/p_heavyduty_pistonrings.asp

i used many sets of mahle rings have 4 more to file fit for a 427 today and JE for big bore 4.600+.I use the hell fire for Nos use for mild use and oem i like hasting.theres i new line of rings re box i am sure that use a steel top ring for the 043 ring looks to use the vent flex 3mm oil expander like mahle

During looking at the Mahle pistons which are the part number SBC425030I26 I was concerned with making the wrong choice and ending up with too low of a compression ratio.<it's a dished piston>.Still wanting to run 87 gas threw it because it is basically a towing van for my business(costs of gas is a concern somewhat),but wanting to have some fun with it when the trailer isn't behind the van.

Mahle suggested the following:

-0- deck with a .040 gasket

RHS 64 cc heads cast iron with a 180 cc intake runner and a cut of 12 to 15 thousands to get to a ratio of 9.21.About 62cc end results after the cut.

Well I was talking to the machine shop telling them the costs was $693.95 for these pistons.They checked their cost and it wasn't much different.

The machine shop called back suggesting these TRW pistons with 5/64's rings.Part number L2256F30.With a 64cc head would be 9.6 compression ratio.
Man,I keep going back and forth on the compression ratio.I am thinking to cross over the line of 9.5 is a point where 87 gas isn't in play any longer.Yep,I know I could cam it to work,but I am thinking a smooth idle is also apart of my intension.

The cam is a GM roller part number14097395 that is:

288/308 duration @ .050 tappet lift

196/206 max lift 1.51 rocket ratio

431/451

center line of 109.

why do you want to spend so much money on pistons for a van engine ?when cast pistons will go past 100.000+ miles i could see going to a hyper speed pro the 5/64 is a thick ring .078 did you say you wanted to run 043. rings in it ? you can buy a head with a bigger chamber srp are $458 speed pros are $320.if your pulling any thing heavy your never going to know the quality of the fuel is till it is in the tank. so i would keep cool on cr not a hi cr engine any thing over 9to1 would be more then i would want to do you should not need any more your building a stroker and that cam will not need any more cr to work good .did you try that piston in the PBM brand may be abit less if you must have the mahle piston. is your machine shop going to be cool with you walking in with your own new pistons ? i would think my cost is better on them pistons but the guy at your machine shop i am sure wants to make some money on parts?

Pat the machine shop guy is a cousin to my partner in the race car deal.So I am expected to walk in with the parts so he doesn't have to deal with ordering anything.He's just helping out with the machine work picking up some extra bucks for that work and giving advise.In fact he tried to see the cost of the Mahle's to see if at his cost he could get them cheaper than me.He found them to be $679.00 plus shipping and that was what he was going to charge me.I would pay $693.95 from Competition Products with free shipping.Not any real savings.

Ok abbreviations???.PBM Brand??.Tell the truth,I am not trilled with the low tension Mahle rings on the part number I spoke about.The TRW's on the other hand have a ring pack that is more I think in line with my use.Now the compression ratio is 9.6 with 64cc heads.If only I could get this part number L2256f30's compression ratio under control with maybe 72cc heads,don't deck the block(far as I know it is flat not needing to be cut) and a .040 head gasket,my search for this stroker pistons would be over.So Pat what do you think the compression ratio would be???.

Please and Thank You,

Gary

i think i went over this with you pbm has a piston line there made by mahle .smaller top ring like a 1/16 or .043 may help. it is the low tension oil rings i would stay away from and you can get them both ways hi or low . the srp piston 139628 is a dish and with a 70.cc head 5.700 rod you have 9.2 cr i would think that would be max cr for what your doing ? i would think getting 9to1 is the srp piston is a 16cc dish so with a 9.1 cc head gasket looks if your down in the hole .005 you should be at 8.989CR or about . thats a felpro f1003 head gasket. the money your throwing at this. there s no way i would not tru-deck the block so cam thru crank main is in the center of the block and decks are in the right angle then i zero the boring bar off the deck so bores are tru front to back and side to side my machine comes off the oil pan rails this is not good enough for me so i shim the block fixture till the boring heads O to deck then bore the block

You Irish guys are pretty ok.Thanks Pat.