Gte Conrod stretch

Evening ladies and gents,

I am currently rebuilding my 2jz gte engine, not because it has failed, but because i am planning on going for just over double stock power (700hp aim) running a borg warner sxe 362. The engine has 130k miles.

Anyway back to the point. I have measured the internal diameters of my stock rods. Across the horizontal point, it is measuring up at 55.032-55.038 which is within spec. Upper limit of size 3 rods is 55.042.

However, vertically, it is coming up at 55.060 and some at 55.068.

These are measured using a DTI bore gauge and cross ref with micrometers.

My question is, has anyone ever measured their stock rods? If so have they ever seen measurements/stretch like this?

Many thanks in advance

Andy

I admire your attention to detail Whats the vertical measurement limit?

Checked all my saved resources, can't find any Toyota published data for those measurements.

I've never bothered measuring those diameter on a stock rod, wouldn't surprise me if most were a bit out of wack after 25 years. Stock components with big power is always a bit of a roll of the dice. One thing I will say is to upgrade the stock rod bolts as they can snap before the rod bends in some.

Edit: might be worth measure stretch on stock rod bolts. see if any variances on the bolts matches what you are seeing on the rod itself.

I admire your attention to detail Whats the vertical measurement limit?

Cheers man,

I am very anal to say the least, and being an engineer makes you want to know. It also helps me to understand how and why things are made to certain sizes.

As far as im aware, the conrod should be perfectly round. But i am not an engine builder, nor have the contacts to see a brand new one to measure it.

Maximum that Toyota made them to out the factory was 55.042mm as described in the manual (rod size 3)

Its less than this in horizontal axis measurement, but over 0.025mm bigger in the vertical axis measurement. Which is worrying but im not sure if this is anything to worry about.

I wont throw money at parts if the originals are perfectly fine. Im a yorkshire man so we have deep pockets and short arms

Checked all my saved resources, can't find any Toyota published data for those measurements.

 

I've never bothered measuring those diameter on a stock rod, wouldn't surprise me if most were a bit out of wack after 25 years. Stock components with big power is always a bit of a roll of the dice. One thing I will say is to upgrade the stock rod bolts as they can snap before the rod bends in some.

 

Edit: might be worth measure stretch on stock rod bolts. see if any variances on the bolts matches what you are seeing on the rod itself.

Hey mike,

The engine has always been stock. I dont even think it has ever been fully BPU.

I have checked all the rod bolts and all of them are within spec. Says replace them if shaft is under 8mm. And most measure 8.15-8.20 so cant see any issues with them.

I guess most people just chuck the stock rods without measuring like you say. Im not after crazy power so i was hoping to keep stock parts to keep the cost down.

Fingers crossed someone else has measured one to confirm from a lower milage engine.

Can you still get brand new oem rods?

Just for closure on this thread for any future people wondering the same question.

Bolts do need to be torqued up to manufacturers specs in order for the parts to measure correctly. Same with the main crank bearing sizes. The crank caps need to be torqued to spec.

As an engineer i could not understand the difference it would make. A clean mating surface should be the same no matter what. And the whole reason behind torquing the bolt is for taking it to its strongest clamping point before it gets to its yield point. So it doesn’t stretch in use.

Somehow it does change the size. I can only assume the rod bolts deform the conrod into its correct shape.

For any future people. Please follow this rule and do not fall foul like i have done. Measuring accurately has been a great tool in order for me to understand this and not just ‘because xyz says so’

Thanks Andy