Thread: Pro's and cons of using a torque-plate while boring a block

Is there a definitive up or downside with using a torque-plate while boring a block?

I've heard that NOT using them can make the block deform under stress of torquing the head and main caps.

Thoughts?

Cons: Cost

Pros: Everything else


Look up how torque plates work and why they are used. I'm surprised this question is being asked by you M0J0.
Topdog, is that you?

Yeah, figured as much. I was hoping someone would chime in and say you could bore a block without one, and still be ok.

Cause I think I had mine done without it.

The only reason boring our blocks ever became acceptable, was because JWT made a torque plate for them. Up until then it was a sketchy proposition. The tolerances are too tight on these "modern" engines. Sorry.

Okay. So re-boring them with a torque plate is the way to do it?

Here's the thing though. I've had the block bored to 86,5mm (size of the pistons), can I still use that diameter to re-bore them again, now using a torque plate? Or would I need new, larger pistons (say 87mm) and have it re-bored to 87mm?

That is a question I think only a bore gauge can answer after the fact. I don't think anyone who's tried something that shifty has shared their results.



Don't forget the transmission torque plate.

I think it's well worth the extra cost.

But if I have the block honed again, but this time with a TP, isn't there a chance that the cilinder will be deformed even further?

I mean, it is 86,5mm now without the head, and when the head will be mounted, it would deform into an oval shape, correct? Is this because the cilinders are stretched or compressed?

If they are compressed, I would say that I can just have them rehoned with a TP and 86,5, as the widest part of the oval cilinder would still be 86,5 and you would remove material from the narrow part of the cilinder.

However, if they are stretched, that would mean that the narrow part would be 86,5, and that honing them at 86,5 doesn't have any influence. I should then use 87mm pistons instead and have it rebored/honed to 87mm, using a TP??

Help?

Above shows you the EXACT reason why you use a torque plate and I will NEVER take any of my engines to any machine shop that does not use it when doing any sort of cylinder work

That is pretty much the reasons why 90-95% of the SR20s that were sleeved and re-sleeved over the past several years have failed. The sleeves would end up mostly "dropping" as the head and sleeve would "shift" under cylinder stresses.

If you bore without a torque plate, and then torque a head on, the cylinders don't deform into a a nice oval shape all the way up and down. They deform in the center the most, into a square shape I believe. Except the cylinder by the transmission can also deform on a different axis causing the bore to bow to the transmission side. There are tons of different deformations happening and they are not all on the vertical axis, and they are not uniform up and down the cylinder. There is almost no deformation toward the bottom of the cylinder for example. Things are much more complicated than you're imagining.