[stockhatch]

I see that the standard clearance from piston pin to rod bushing is .0002-.0004". The max clearance is specified at .002". That is obviously a huge difference. Would you guys shoot for the tighter, stock clearances, or something looser? If max wear is .002", would there be any issue if the clearance was something like .001 or .0015"?

Thanks for any input

 

[stockhatch]

Anyone have any ideas on this? I know that we want the mains and big ends of the rods a little on the looser side for big power, but I still wonder what you guys do on the small ends.

 

[stockhatch]

My machine shop said they usually shoot for around .001" .... Still no input on this one? Does everyone just run the stock clearances (.0002"- .0004") or is this secret squirrel stuff?

 

[twinturbosupra94]

I doubt any engine builders are going to share their clearances. Its pretty much secret squirrel stuff.

 

[Slow_Sc3]

is this secret squirrel stuff?

Its pretty much secret squirrel stuff.

id fallow the book unless the rods / pistons you got came with something saying different.

 

[stockhatch]

Gotcha, thanks guys. Why are all the 2JZ peeps so tight lipped? Plenty of builders in pretty much all other engine families share basic clearance information. It's not like I am asking for someones cylinder head CNC program or something, sheesh...

 

[Beau]

^ Becuase they aren't sure and don't want to look like a tool box.

 

[twinturbosupra94]

^ Becuase they aren't sure and don't want to look like a tool box.

Its about 50% this and 50% if they found something they like, they don't want to not get paid for their research and development.

To be dead honest, stock clearances will be fine since stock motors can go over 900-1000hp. The only thing I would change is the gapping of the rings. Run a little looser to hold better boost. Of course the trade off is wisping of oil at idle but almost all race cars have that.

If you are wondering my source, its a guy a dsm forum I met a while back. Build the 4AGE mid-Atlantic series motors so he knows his shit. He help me build my 4G63 and man does it run like a beast.

 

[Smaay]

how do you check that clearance? the wrist pin slides through the rod bushing, its not like you can get a gauge in there.

 

[stockhatch]

I'm no machinist, but it seems you would mic the wrist pin, and use a bore gauge in the rod bushing. The difference is your oil clearance...

 

[twinturbosupra94]

I'm no machinist, but it seems you would mic the wrist pin, and use a bore gauge in the rod bushing. The difference is your oil clearance...

Whoops thought you were talking about rod bearings. Read things too fast.

 

[stockhatch]

No way you can plastigauge in this situation. There is nothing to torque down.

 

[bimmerfreak 555]

You could do that or just buy plastic gauge. You basically torque it down and measure the squish. Either way will work. Just make sure you have a legit set of measuring calipers. I got lucky and my dad found a set they were throwing out at his old job. Shits cost like $1500 used :lol:

LOL... definitely cannot plastigauge wrist pins. Mic both pin and bore... simple math you end up with a clearance!!

You can use plastigauge for rods/main bearings. Its not really super accurate but will get you in the ball park. Best is to mic everything, issues as suggested is that mics are not cheap!

 

[twinturbosupra94]

LOL... definitely cannot plastigauge wrist pins. Mic both pin and bore... simple math you end up with a clearance!!

You can use plastigauge for rods/main bearings. Its not really super accurate but will get you in the ball park. Best is to mic everything, issues as suggested is that mics are not cheap!

Whoops I thought he was looking at the bearings. Didn't know he was looking at wrist pins. Disregard what I said.

 

[Janz99]

When i did my build, mine were .001-.0013". I talked to a couple local machine shops and they all agreed that this would be more then acceptable. I havn't run the engine yet, but will be in the next few weeks.

Ryan

 

[stockhatch]

Great, thanks. I am waiting to hear back from the machine shop regarding where mine end up.

 

[SupraTuRD]

Run it on the tighter end of the spectrum since the GTE's have oil jets that cool the pins.