4age 16v piston options

[pen15]

ok all here is my question i know all 16v pistons will work across all 16v heads and i also know that the 20v silvertop piston will wotk with the 16v head and still not be an interference motor apparently but has anyone used 20v blacktop pistons with a stock 16v head obviously it will be an interference motor but will it have issues in the timing cycle running the 20v bt piston with the 16v head?

cheers
mat

[Sam-Q]

You would have to dummy fit it without a head gasket in place and rotate it. It really wouldn't be good for your combustion though.

Why not smallport pistons + 0.8mm gasket that would get you very close to what the blacktop pistons would give you.

[pen15]

the reason im opting for a blacktop piston is because i have a set sitting around for free so i thought why not i also have a set of silvertops laying around but one is .002 undersize from the rest and the blacktop set is perfect

i was just wondering if anyone has tried to use blacktop pistons in their 4age 16v before

[Dilsy]

20v piston pin size is 20mm, and 16v are 18mm or 19mm? so might have to make a couple of changes to fit them

[xero]

dilsy, early bigport 16v had 18mm wrist pins, all other iterations of 4age had 20mm wrist pins which includes smallport 16v.


matty the only think i can think of is the that the centre cut for the middle valve on the intake side might be a clearence issue, as you say it isnt with a silvertop but due to the different shape of the valves on the blacktop it might be a bit of a tight fit.
can you throw it together (or borrow a bottom end from your boss) and check clearences?

[pen15]

ok have found blacktop pistons are interference in a 4age 16v bigport or smallport so if your looking to do it be warned

[Sam-Q]

they are are inteference even in a blacktop engine, unless you mean they hit the head

[pen15]

they clear the head but as for what i mean the valves hit the pistons if the timming belt snaps when in time there is no issues the valve reliefs dont suit and the lift is to great on the bt pistons in a 16v head it will be bent vale heaven if you loose a timing belt

[Sam-Q]

that's the case for both 20v pistons, but as I said same story even in the blacktop unmodified

[86coupe]

Reviving an old thread here, but Sam might find this interesting.

I've just pulled these pistons out of a bigport that came from a late model jdm ae86.

I'm not sure if it was the original engine, and has obviously been modified, but it has a 7 rib block and what look like blacktop pistons that have been modded to be non-interference in a 16v.

http://www.ae86drivingclub.com.au/dcimages/7/5/1/406457.jpg

http://www.ae86drivingclub.com.au/dcimages/7/5/1/406459.jpg

[Matt]

Tbh that looks like a silver top piston, blacktop is much higher dome in the middle

[pen15]

No that's just a stock Toyota piston looks to be Smallport

[86coupe]

http://i.imgur.com/hhCAP.jpg

Notice the double valve cut outs on the exhaust side on my pistons. Here's a better picture, with stock bigport piston for comparison.

http://i.imgur.com/YHCRg.jpg

And here's a stock smallport piston

http://i.imgur.com/s2QpX.jpg

[timbo]

Blacktop maybe? Also those pistons on the last page look like they have had the skirts cut off, for squirter clearance or weight, I don't know.

[Sam-Q]

notice the pins as well, those are far from original, look how thin they are

[pen15]

pins would be tapered but those pistons on the last page are a cheap like hyputec piston the reason they have 2 exhaust valve cut outs is because those pistons also suit another model of engine like maby a Honda or something the rods on the last page are smallport so i would imagine that the block and botomend are smallport and the motor has been bored .5mm and they used cheap pistons rather than forged i see it all the time