Piston choice - budget build

[Dave.TAS]

Hi,

Rebuilding a 16v 4age, 3 rib, big port head with tvis, 42mm rod journal crankshaft, oil squirter hole 20mm pin+circlip rods.

Parts i already have -
Complete engine (was running great, many oil leaks tho)
TRD 0.5mm headgasket
Complete gasket kit
ACL race series mains, thrust and big ends (STD sizes)

My bores need to go oversize due to some grooving, so i need new pistons. This is a budget build, will be run on standard ecu for now likely recieve aftermarket ecu later.

Im open to suggestions, but the two types of pistons im looking at right now are:

http://www.precisionintl.com/online/Part.aspx?CID=16268606
http://www.precisionintl.com/online/Part.aspx?CID=16268596

Both pistons linked above have 20mm circlip pins. One is for ae82, and the other for later model ae92, which i assume is big port vs small port. Please correct me wherever im wrong

The later model piston has 1.5mm dome, versus the early piston 1mm dish. I assume this is where the small port gets its higher comprssion from.

What i need to know is, which piston should i use in this build, can i get away with a 1mm oversize small port piston in my big port engine for more compression, or will it munch the valves/head. Pros and cons of either piston?? Has anyone done this before?

Cheers, look forward to some good answers.

Dave
Devonport, Tasmania
Discotune - performance auto works

[Sam-Q]

wouldn't bigport pistons be incompatiable due to the 18mm pin?

[Dave.TAS]

I have 20mm pins in this engine, i have already come to conclusion it is a bit of a frankenstein

Both pistons i linked have 20mm pin

[Sam-Q]

yes I got that bit, what I mean is one of the two pistons you say is for an ae82 which had an 18mm pin and hence incompatiable

[Dave.TAS]

if you look at the links provided, both pistons shown are 20mm circlip types. They may not be to suit ae82, my corolla knowledge is low haha.

Whats the story with using the 1.5mm domed pistons in place of the 1mm dished variety?

[fantapants]

i just wanna dance to the





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[Dave.TAS]

No answer? Thought you would had it in the bag Sam :)

[Deeken]

dished = turbo. domed = na :p

domed probly like 10.5:1~ and the dished slugs would be 8.5:1 or something.. you want high comp NA ;)

[Sam-Q]

No answer? Thought you would had it in the bag Sam :)

I went to sleep, lol

one of them looks like a bigport ZE piston, they are 20mm still

[Dave.TAS]

yeah do not want ze piston, will check mine again tomorrow but fairly sure they are slightly dished, hence this thread asking if domed ones will work without issues...

[Matt]

yes I got that bit, what I mean is one of the two pistons you say is for an ae82 which had an 18mm pin and hence incompatiable

someone correct me if I am wrong, it seams you have smallport/20v crank, 16v smallport rods and pistons already

[Dave.TAS]

Worth noting that the ae92 piston with the domed crown also has cutouts in skirt for block mounted oil squirters, the other ones dont appear to

[Dave.TAS]

I would agree matt, i did hint that it was frankenstein engine, and thats the only reason i gave so much detail in my first post, because i was under the impression that bigport should have had small crank and rods. Was a very good engine while it was running but leaked oil at every gasket lol

[slydar]

use the "domed" pistons. extra CR will run fine on a big port stock ecu. ive done it heaps of times. i actually didnt think the other piston that site lists existed. good to know. would seem to indicate the 7 rib big ports must still have the proper 20/42 rods. i always assumed they ran a unique rod with the small wrist pin.

anyway if you DEFINITELY have the big wrist pin. then you DEFINITELY want the higher CR pistons.