looking for a certain dimension pistons..

[zuruzuruz]

hello all...

does anybody know any pistons from any engine which has bore around 78-79 mm n stroke around 83-84 mm and can withstand a compression ratio of 11:1?

I know, some might say this might be a 'long shot' search n I'm better off with a custom pistons. However, im trying to reduce cost in rebuilding my engine. Sharing of any info regarding above is greatly appreciated..

thanks in advance..

 

[mines998]

For 78 to 79mm bore I think you do not much choice. Maybe to can try use 6A12TT piston cos it consider as semi forge piston but for stroke I not so sure.

 

[zuruzuruz]

hi mines998,

thanx for the heads up. yeah, ive been looking up in the internet and found the same thing too.. the closest to my desired bore (excluding pistons from some unknown french cars) is the 6A12. And the most intriguing part of it all, (quoted from wikipedia) it says that

6A12
Displacement — 1998 cc
Bore — 78.4 mm
Stroke — 69.0 mm
SOHC
Engine type — V type 6 cylinder SOHC 24 valve
Compression ratio — 9.5:1, 10.0:1 , 10.4:1
Fuel system — ECI multi
Peak power — 107–110 kW (145–150 PS; 143–148 hp) at 6000–6750 rpm
Peak torque — 179–181 N·m (132–133 lb·ft) at 4000–4500 rpm

Applications
1992–96 Mitsubishi Galant/Eterna/Emeraude
1992–94 Mitsubishi Diamante

I'm interested with the CR of 10.4:1 part. So, is it true that engine from car models of Galant/Eterna/Emeraude and Diamante can have three types of CR? If it is true, I definitely would like to see it and compare it to my stock pistons and see whether it is interchangeable or not.(10.4 is almost to 11, good enough for me :D)

If there are any 6A12 meister out there, your help is really much appreciated.

Thanks a bunch.. :)

 

[mines998]

Can you share with us which engine you going to place this piston?

Here is some technical spec and piston photo. Hope can help you.

 

[^pomen_GTR^]

probably u need to find mitsubishi diamante piston..(newer model shud explain higher CR for better low rpm torque)

or from toyota family engine 1zz which use 79mm bore...model example: toyota celica gt,toyota mrs and lotus elise S

 

[zuruzuruz]

mines998: its for a kia spectra engine :). btw, the pic u attached, is it a set of custom JE Pistons? How much did u buy it? including custom conrods?

^pomen_GTR^: although a 1zz's bore might be a little bit too much for my first bore up, I will still consider ur recommendation as one of my options.. thanks..

 

[mines998]

Ya is a custom made piston for 6A12TT engine 6pcs a set I think around 4k including freight cost. Con rod is made by other shop about 4k aswell. Need to wait for 2 month and send yr original parts to them for fabricate.

 

[zuruzuruz]

wow.. that much huh? so that really assured me that custom pistons is LAST option.. huhu.. btw, i would like to confirm on something mines998, after installing the set of pistons, does the sound made by ur engine is more 'garang'?

 

[mines998]

I not very sure about that but my engine totally different compare to stock. My mech tell me the cam made the sound different. Now my car sound like Ferrari engine.

 

[zuruzuruz]

nice... i just browsed thru a thread of yours.. admire the work done.. good job bro..

 

[mines998]

Mod engine need alot of patient and money. Suggest don't use yr daily car for heavy mod. My car spend about 2years complete this is no joke. Car stay in workshop about 1year

 

[zuruzuruz]

will keep that in mind.. thanks bro

 

[mines998]

Good luck bro keep us post on yr project it seem interesting. Hardly see ppl mod on korean car.

 

[zuruzuruz]

sure.. will keep that in mind.. i only gonna do this project next year.. when my engine is due for full overhaul.. in the mean time, save up some money.. huhu

 

[zuruzuruz]

sorry for the late update.. but here's the update of my mod which i had done 2 months ago.. For the pistons, I just took an oversize piston of kia specra that is already sold in parts shop, which has a bore of 78.5mm. Sadly enough, the piston is not domed at all.. :( My foreman prefer taking this option rather than finding other engines' pistons. Since this is really made for kia spectra.

So, my foreman advised me if still want to have a bigger CR, maybe can skim head to 0.5mm to have a higher CR. After asking this and that, I finally agree to the idea. After taking measurements here and there (I dunno what my foreman told me, chamber clearance blah blah) he said my CR shud be 11.3.

However, the sad part is, after all that CR increase from 9.5 to 11.3, prior to dynotuning and all, my whp just increased 6whp.. Now im stick with RON97 because of higher CR, but the whp increase is just... what u call.. doesnt cut it.. Anyone can give their opinion or experience after increasing their CR?