9 replies to this topic

[Wessie28]

hi
i've just stripped down my 2 engines that i used last year - both went bang and i couldnt work out why, both were fully balanced, timed up properly, rolling roaded etc
i had one L/C 1275 +40 AE 21251 and one H/C 1275 +40 AE 21253 built and i used AE pistons in both (as we are restircted by the rules) BOTH engines have had a piston break up in the same place
so has anybody else had this problem? or heard of anyone with this problem? or is it just my bad luck with BOTH engines
if other people have had a problem with these what are the alternatives ? bearing in mind these are my rules "No machining of pistons except for balancing purposes and this can only be carried out on the inside surface of pistons, and they must not protrude above block face, but some manufacturers have pistons that protrude as standard, so particular vehicles will be checked on their merit, according to manufacturers tolerances, for that specific vehicle. One piston and one con rod must remain as standard. Competition pistons are not permitted. Casting and/or forging marks to remain."

thanks
tom

Edited by Wessie28, 09 February 2008 - 12:01 PM.

[langers2k]

Your album is set as private on photobucket so we can't see them!

[Wessie28]

Your album is set as private on photobucket so we can't see them!

photobucket buggering around so i'll get some pictures up tomorow

[Sprocket]

Depends where the pistons have broken, and if anything has contacted them. if there was no contact with anything then piston failures would be down to detonation when broken, and pre ignition when melted.

Detonation at the higher RPM is inaudiable and the most damaging.

[dklawson]

Search back over the past three months and you will find at least two threads discussing (at least in part) the two AE pistons you used. Repeating briefly part of what was in those threads, the 21251 pistons have a reputation for "coming apart" when pushed hard due to an issue associated with how their oil control ring drains. The 21253s are considered to be a little more robust in this area and are also designed for higher compression than the 21251s.

The 21253s are considered OK on a moderate performance street engine and I have some acquaintances who say they have used them in vintage race engines. However, for most full out race engines I thought they preferred to use forged pistons (which these two AE pistons are not).

[Wessie28]

Depends where the pistons have broken, and if anything has contacted them. if there was no contact with anything then piston failures would be down to detonation when broken, and pre ignition when melted.

Detonation at the higher RPM is inaudiable and the most damaging.

thanks for your reply

nothing has touched either piston, there both immaculate and one piston has only done about 5 miles of racing after been run in and rolling roaded
http://s89.photobuck...stonshit002.jpg

is the first two pictures

Edited by Wessie28, 10 February 2008 - 09:41 AM.

[Wessie28]

Search back over the past three months and you will find at least two threads discussing (at least in part) the two AE pistons you used. Repeating briefly part of what was in those threads, the 21251 pistons have a reputation for "coming apart" when pushed hard due to an issue associated with how their oil control ring drains. The 21253s are considered to be a little more robust in this area and are also designed for higher compression than the 21251s.

The 21253s are considered OK on a moderate performance street engine and I have some acquaintances who say they have used them in vintage race engines. However, for most full out race engines I thought they preferred to use forged pistons (which these two AE pistons are not).

thanks for your reply
i wonder if AE are going to change the design then ? i spoke to minispeed and they told me where my piston would come apart even before i told them it had even broken! unfortunatly im not allowed to use forged pistons, and its only autograss racing - hardly long distance endurance racing!

[Sprocket]

That is detonation failure and not the fault of the piston

http://www.mlcmotorf...rs/PistonTT.pdf

[Wessie28]

thanks, has anybody ot any recommendations for other makes of pistons ? i've found a set on ebay from an australian supplier ? anybody heard of or used these?

[Sprocket]

pretty much the same piston untill you get to the bigger non standard sizes.

you would be better runnig some Omega or MiniSpares Mega pistons, these are a better design. However, Investigate why detonation has happened, whilest the Omegas and the Megas are more tollerable of detonation, they will still fail. You must sort out the detonation probelm before you use the engine in anger.