Conrod/Piston weight matching

[Trondelond]

I'm about to go pick up my block and crank from machining. The crank, flywheel etc has been balanced, and I'm wondering if there's any point in having the conrods weight matched as well. I don't know how "bad" the conrods are in OE trim, and I'll be using JE pistons. Thus far I have no plans of upping the rev limit.

I've also had the block decked(?) to acommodate a steel gasket. Is it neccesary to have the head decked as well?

While we're at it, as far as I understand, the JE pistons (0.5mm oversized) will bump up the compression. I'll be running in the engine on the OE turbo, but will switch to the 3071 later on, and probably run more boost than the 1.1 I'm using now. What gasket thickness would be the sensible option so that the car will be somewhat functional off boost, but still be able to cope with.. let's say 1.5-1.6 bar of boost?

 

[Fast Guy]

I'd certainly have them checked to see if it's worth having them matched.

How much have you had the block decked by?

The head should just be checked for flatness and skimmed if needed.

 

[Trondelond]

I'd certainly have them checked to see if it's worth having them matched.

How much have you had the block decked by?

The head should just be checked for flatness and skimmed if needed.

What kind of weight difference would indicate that I'd need to have them matched?

I am not sure by how much, will have to get the details when I pick it up.

 

[campbellju]

IIRC, target less than 5g difference across the range. Just weigh them on anything reasonably accurate. My mate had a set of post office scales which were perfect.

 

[Trondelond]

IIRC, targart less than 5g difference across the range. Just weigh them on anything reasonably accurate. My mate had a set of post office scales which were perfect.

Thanks, will try to remove the pistons tonight, and take the rods with me to see if I can find a scale.

On a different note, I may have had a logical error with the pistons. I've purchased the following :

JE Pistons 245015 Forged 2618 T6 Aluminum Pistons SR20DET

• Bore: 86.5mm +0.020 Over
• Stroke: 3.386
• Rod: 5.366
• C/D: 1.253
• Head CC's: 46.5
• Compression: 8.5:1
• Dome CC's: -11.8
• Gram each: 334

But I'm unsure if these will give stock compression, as I suspect they're originally intended for the 200sx, and the combustion chamber is larger on our sr20dets? I found a post stating that they'd drop compression to 8.3:1 but I have no idea if this will have any practical effect.

 

[astarozna]

You should weight the pistons as well if you going to do the conrods. I have je pistons and they all weight different. And if you want to get anal then do them separate and together, conect piston to conrod and weight again.
All in all it won´t hurt the engine if you do them since you went through the trouble to do the crank!