M20 Pistons

[Smrtpunk]

Where have all the pistons gone?

I've been having a heck of a time finding the pistons I need for my rebuild, stock bore PN: 11251287039

I called BMAparts, they have 5 Mahle's available and 1 Kolben - Schmidt.

I'm a little reluctant to run 5 of one piston and one of another. Are these pistons basically the same? Do you forsee and issues if I were to install them in the same engine?

Just for shits and gigles I tried investigating larger bore pistons to see if availability was easier, It was not, if anything it was harder. Is it really that hard to find pistons for the M20 do any of you have a site where pistons are available?

Thanks,
Ian

[jlevie]

Don't even consider using mixed pistons. The odds are that they won't be weight matched.

Unless the ring grooves are worn or the pistons were damaged I would not replace them on a street engine rebuild if I wasn't going 0.50 over. In which case I'd use MaxSil pistons as they are better than the OE part.

rmeuropean.com has the Mahle 0.50 pistons at $111 each.

[5Toes]

Venolia pistons arent too bad on price I hear

[MR 325]

Why in the world do you need brand new pistons? Find a used set of find a good bottom end. They're easy to come by.

[Smrtpunk]

Why in the world do you need brand new pistons? Find a used set of find a good bottom end. They're easy to come by.

Well, I'm rebuilding my engine as it was in pretty bad shape and the intent for the car is to run gravel stage rally.

Upon tearing down the block my father who is an engine builder advised that the skirts on the pistons were scuffed pretty bad but the cylinder walls seem OK. So the mindset was to keep the stock bore and just replace the pistons.

Good find on the Maxsil site! I've e-mailed them some questions and hopefully will hear back shortly.

Basically, The car will be getting a severe beating pretty much constantly so I want to make sure I build the engine well, without skimping on anything.

[jlevie]

New rings mean that you need to have the block cross hatch honed. Otherwise the new rings may not seat.

[MR 325]

Re-using pistons is not "skimping". Find a good used set.

[scrowner]

I run dirt rally with the '87 325E - did nothing to the engine after buying the car for $400. It has been running now 1.5 seasons and has 4 drivers pounding on the car. We run 2 mile dirt courses in fields - fantastic. We have been through several front control arm bushing and several front sway bar links and bushing. Even lost a oil drain plug - car ran out of oil and was squeaking funny at the start and we pulled it to check it out. Had a spare plug, filled it back up with oil and finished the event and that was about a year ago. 325 engine is solid. Change the fluids often and have fun. Running stock and prepared classes - but not much competition in RWD.

[Smrtpunk]

I run dirt rally with the '87 325E - did nothing to the engine after buying the car for $400. It has been running now 1.5 seasons and has 4 drivers pounding on the car. We run 2 mile dirt courses in fields - fantastic. We have been through several front control arm bushing and several front sway bar links and bushing. Even lost a oil drain plug - car ran out of oil and was squeaking funny at the start and we pulled it to check it out. Had a spare plug, filled it back up with oil and finished the event and that was about a year ago. 325 engine is solid. Change the fluids often and have fun. Running stock and prepared classes - but not much competition in RWD.

Very cool and good inspiration! I wish I could have gone ahead with the engine as it but it was in way rough shape. Once I do the rebuild the hope is that I will have the same kind of reliability as you've had.