14 replies to this topic

[vivalamini]

I'm trying to decide on what pistons to use in my engine build but I'm getting a headache!!

Assuming I need an 11cc dish as this is what is coming out as an acceptable compression ratio on the calculator for 10.5:1

Spec is as follows:

1380 pre A plus Block
Standard Crank
Oselli A600 Camshaft 288 degree
Full Roller Rockers
12G940 Head 21.4cc head 37/31
Etc etc...

Below is my shortlist, the information is what I've found of other people's experience/advice, which may be fictional... who's to know?!

Omega - supposedly the ring pack wears the bores very quickly??
Powermax - oil control ring sits very high can cause head gasket blow?? and oil control problems?
Mega piston - seem to be the best choice can't find any disadvantages but they are out of stock at Minispares are they still an available piston or have they disappeared?
Minispares Evo Piston only stocked in 9cc dish? Has wide rings at 1.5mm

Has someone got some up to date advice real world experience?

Attached Files

•  IMG_1951.PNG   90.72K   12 downloads

[ozz1]

I'm afraid I can't comment on real-life experience. Anecdotally, I have heard nothing but good things and use the same 64mm equivalent piston in my 998 race engine. 

 

So maybe another to add to your shortlist...

 

They are 1340 - more sensible than 1380 as you can have it re-bored in the future without requiring liners.

 

http://www.calverst....perior-quality/

 

Note: they are 6.5cc dish, but should have a lower crown height to allow for ample re-surfacing of the block  (10 thou if memory serves), so this will decrease the CR depending on how much needs taking off the block.

Edited by ozz1, 09 July 2017 - 10:20 AM.

[mini13]

How on earth would the oil control ring being too high cause head gasket issues? 

[nicklouse]

never had issues with Powermax or Omega forged pistons

 

never used the others.

 

and always had smaller dish than you mention.

[paul1380]

I am Running a 1380 A series engine with 735 OMEGA pistons I have just done a full rebuilt renewed the rings no sign of ware at all on the bores.

The rings were brought from Mini spares I also brought a Evolution 001 cam from them just changed the distributor from standard to a 123 electronic the engine has never run better. Also running hi lift rockers and a duplex chain all brought from Mini spares.

[Northernpower]

I'm afraid I can't comment on real-life experience. Anecdotally, I have heard nothing but good things and use the same 64mm equivalent piston in my 998 race engine. 
 
So maybe another to add to your shortlist...
 
They are 1340 - more sensible than 1380 as you can have it re-bored in the future without requiring liners.
 
http://www.calverst....perior-quality/
 
Note: they are 6.5cc dish, but should have a lower crown height to allow for ample re-surfacing of the block  (10 thou if memory serves), so this will decrease the CR depending on how much needs taking off the block.

I use these at 72.5 to give 1342. They have a high silicon content and as a result don't expand as much therefore the machining tolerance can be tighter. I run 10 to 1 compression and find it sufficient. It does give you the option of a further bore.

[Dusky]

Got omegas in the slalom mini. Cant fault them.

[ACDodd]

Omegas or calverst. No probs with either.

Ac

[Gr4h4m]

I have run two sets of calvers Pistons in a self built short stroke supercharged engine and so far they have taken some abuse

[minimans]

Never had a problem with Omega's use them for all big bores I've done. In fact I'm using a set of 73.5 with 11cc dish in my current build with the 8 port with sprint cam at 11:1

[Retroman]

Ac has it right above, you will no problems with Omega or Calverst...

I would consider +060" or 72.5mm or 73mm all allow another bore on the block and power wise there is little difference.

[govig]

Has anyone used these cheaper 1380 pistons ?

 

https://www.ebay.co....7?ul_noapp=true

[Tones61]

Omegas,
Just make sure you set the ring gap to spec ,
Mine came with no gap

[Tones61]

1293 omegas 10cc dish,
ring gap set to 14 thou,
3-5 thou out of deck
Comp set at 10.9/1
Sw10 cam
Race spec head

Attached Files

•  IMG_1820.JPG   42.21K   2 downloads
•  IMG_1823.JPG   21.93K   4 downloads
•  IMG_1826.JPG   25.69K   6 downloads
•  IMG_1856.JPG   44.01K   6 downloads

Edited by Tones61, 09 May 2021 - 01:50 PM.

[r.tec]

The ones you linked on ebay are the STR0310, AE 20659 Powermax pistons. As Federal Mogul concentrated piston manufacturing to Nüral (NÜRnberger ALuminiumwerke) the current number is 87-526600. Two years ago you could order them from all car part dealers here in Germany for a very good price, ca. €60.- per piston. Now they are not available over here but this will hopefully change as they seem to be manufactured in batches.

 

I have used them in competition and think they are very good. Dish is 9 cm³, piston rings are from Goetze another Federal Mogul company.

Edited by r.tec, 09 May 2021 - 02:57 PM.