Choice of Pistons ROSS or JE

[supraguy31]

Well, I have a friend of mine that has a Set of ROSS stock bore pistons for sale and I have a Current forum member that has a Set Of JE .040 overbore pistons for sale also. Both are asking the same Price but I want to know what you forged internal guys think is the better Piston or Option. Ive never ran Forged internals so this would be a great help in Decided what way to go.

Thanks
Robert

 

[Mr.PFloyd]

Aren't Ross's the ones with the super high comp ratio?

 

[jdub]

Cyro - Ross are 8.5:1 - JE are 8.4:1. You might be thinking of Wisco...they are a 9.0:1 CR.

Both are excellent pistons.

The JE's will require the max over bore you can safely do...it will be the last time that block will be bored.

To use the Ross, you will need to check your cyn bores...iirc stock pistons are 83mm...Ross "stock size" are 83.1mm. For Ross pistons you will need 0.0035" - 0.004" piston to bore clearance...more than that and you'll get warm-up piston slap. If your bores can be made true and meet the above spec, I'd use the Ross.

 

[NewWestSupras]

0.040 is alot of bore on these blocks. They are thin-walled to begin with. If you don't need to bore it, then I would'nt. I don't know the comp. ratio offhand on these Ross pistons I have, but my compression numbers aren't extraordinary with them. You do have to be careful about piston to bore though. They can diesel a bit till they warm up...

oooops, jdub beat me to it while I was typing, what he said...

 

[supraguy31]

Got this off the JE website.
http://www.jepistons.com/cat/je/sport/toyota/7mgte.shtml

The block that these Pistons are going into has only 68,000 miles on it so Im sure its a good canidate. Do JE pistons Expand that much?

Since these are 83.1mm, How much boring do you need or are you just Honing the Cylinders until you get the correct Clearnace Specs.

 

[jdub]

So...this is a 2J?
Would have been good to know...esp since this is in the 7M GTE Tech Section

 

[supraguy31]

So...this is a 2J?
Would have been good to know...esp since this is in the 7M GTE Tech Section

Changed the Link... Try again, Still same Place just didnt click on the right one

 

[jdub]

Interesting...JE lists the CR at 8.8:1. That's quite a bit higher than what I was looking at (another web site)...you might want to consider how much boost you're planning on

JE pistons are significantly lighter than Ross.

You'll have to take the block to the machinist and have him measure the bores for roundness. The "stock" Ross pistons will require a very small amount of bore to meet piston/bore clearance, but it's going to depend on how much wear is present in the cylinders.

 

[supraguy31]

Im planning on running just enough boost to get into the Low 12s/High 11s in a MK2. Im running a 67mm Turbo with on it right now so I just want the Issurance that my Internals are going to hold up under lets say as a Guess 18 to 20 psi

 

[supraguy31]

I have a Block at home what Im going to a few Pics of J and let you see it. It has .040 pistons installed and as soon as I got the engine in the car and started, I instantly got a Very Faint miss like I was loosing compression. I ran it for 300 miles and I started to get Blowby. Pulled the engine out and pulled the head, If you look at the engine from the Side and look down into the cylinders, Everyone of them have about a 1/2" of area that looks like the rings arent even touching. If you look at it from the front of the motor its the east and west side of the Cylinder on all 6.

 

[starscream5000]

An aquantance who has experience running both of these pistons has advised me that ROSS would be the better route for a DD, high HP street car . ROSS are heavier, true, but IIRC, they are lighter than a stock piston as well .

 

[jdub]

The higher compression pistons are great for bottom end, but you risk detonation at boost due to dynamic compression. You'll have to pay close attention to the tune and run premium gas

Sounds like the block was bored without a torque plate and/or without the main bearing caps torqued down
Boring without the timing belt tensioning pulley torqued down will do the same thing to the front of the #1 cylinder.

BTW - that's a case in point...that block is done. Boring it out any more (say for a .050 oversize) will push the cylinder walls way too thin IMO.

 

[supraguy31]

That block is pretty much toast I agree which is the reason for the 68000 mile block that I have sitting on my stand. It came off a JDM engine and I knew the guy pretty well that owned it.

So from what Im getting, the Ross Pistons would be a great way to go due to not having to bore the cylinder out so much and they are lighter than stock Pistons.

JE Pistons are even lighter but you have to hope that the Machinist does the Job correctly the first time around or your block is pretty much toast.

Robert

 

[jdub]

Take a look at these specs...take the block to the machinist to make sure the ones you're looking at will work. The 2nd sheet list the piston to wall clearance as 0.006"...that is too large. Use 0.004"

http://www.rosspistons.thinkhost.com/uploads/toyota.pdf

http://www.rosspistons.thinkhost.com/resources/ROSSRACINGPISTONINSTALLATION.pdf

 

[supraguy31]

Im pretty sure they will work as I have the Stock Pistons that came out of it sitting in the Garage. They have the #2 Stamped on them and Im sure that doesnt mean anything but I just want to let ya Know.

I printed out the Sheets and thank you for the Link. So best recommendation is go 0.035 if Possible but if not, Use 0.004

What about ring Gap, What would be a Recommended ring gap Size based on Boost Pressure as I dont see it in on the ROSS website.

Thanks

 

[jdub]

I'm thinking the Ross pistons *should* work, but actual measurements will tell-the-tale.

If you plan on coating the pistons, def use 0.0035". If not, I would lean more toward 0.004" to account for expansion. You may get a small amount of slap (Ross skirts are fairly short) at start, but that's better than a locked up piston

 

[supraguy31]

They are already coated so I will be using the 0.0035 as you recommended. Now I just need to figure out this Ring gap thing and I should be good to go.

 

[supraguy31]

Jdub.....

Pics from last block

They are on Every Cylinder the same way, Some wider than others but Im sure you get the Picture

 

[jdub]

Not good!

No wonder you got blow by so fast.

 

[supraguy31]

I would say I had 500 Miles on it. Thats why I havent taken anything back to the Machinist that did it. Its all good though as I have another block sitting here waiting to go. Does that look like he bored it wrong or it Cylinder isnt completely round or what?