Torque Plate for Boring and Honing

Just to let the forum community know I have had a Torque plate made for boring and honing 6A13TT's





for those who don't know the purpose of a torque plate I shall try and explain

When head bolts/studs are torqued up to specification during engine assembly the load of the bolts/studs on the block pull the cylinders out of round which messes up any piston to bore clearances you try and set whilst boring and honing the block.
This is where the torque plate comes in. its purpose is to simulate the load of having a head torqued down onto the block whilst machining the block. this means although after machining the bores may measure out of round when no torque plate/cylinder head is attached but when the cylinder head is bolted back on the load of the studs/bolts will pull the bores back within spec.

This means the cylinders will be much closer to being perfectly round during operating conditions. meaning better ring seal. and better overall performance. A must for a performance engine such as one planning on forged pistons or high boost applications.

Also when using aftermarket head or main studs such as ARP it always pays to check all tolerances and the extra load from the aftermarket studs needing to be torqued up to a higher spec than stock will distort the bores more than just using factory bolts.

When I got this Torque plate made I specifically had the head bolt holes made at 12mm diameter as to accommodate those who are using larger than stock head studs.

Anyway for anyone wanting their block to be machined with my torque plate attached feel free to PM me and I'm sure we can work something out.

Will hopefully be torquing it down onto a block tomorrow so can update with how much the bores pull out of round.

 

Also works as a nifty drinks holder when bolted to the center console.

 

Torqued it up to a block tonight and measured with the bore gauge, showed the bores distorted up to 0.00175"

Not heaps but considering the piston to bore clearance on the wiseco forged pistons that a few people have been getting is 0.0035". if you were to hone the block without using the torque plate and had set piston to bore clearance to 0.0035" and then torqued down a head your actual piston to bore clearance could be as low as 0.00175", half of the recommended value! or up 0.00525", 50% more than it should be!

 

So the 1.75thou distortion that you measured was this an increase or decrease in diameter?

 

both, it distorts the cylinder.
For example it may be bang on size across one axis lets say a diagonal but a couple thou big across the front to back axis. and a couple thou small across the "inlet to exhaust side" axis
and the distortion varies along the length of the cylinder.

the 6A13 is a pretty solid block even with the ARP main studs and the A1 tech head studs the main tunnel and bores didn't distort anywhere near as much as the likes of a nissan RB 25/26/30. That being said Im still bloody glad I had this torque plate made!

 

Damn u for being on the wrong side of the ditch

 

No! damn the postage between NZ and Australia being so inexplicably expensive compared to anywhere else!

Torque plate only cost me 300NZD from memory. If some more of you guys over there get into building motors It may be worth all chipping in and getting one made to share around Australia. Kind of like a Club owned special tool. only to be lent out to engine builders for machining club members 6A13's

 

Honed a block on friday with the torque plate on. the attached picture illustrates how the block is distorted.

just below the torque plate you can see a dark patch in the bore directly inline with where the head stud is. all 4 studs in all 6 cylinders were the same they had all pulled out of round in the same way due to the load from the head studs.

 

How many lb/ft did you torque that up to? Going to look interesting at 120 lb/ft... lol

 

These 11mm studs do up to 90ft/lb

 

so you set them at 90ft/lb or thats the max they can go before they break?

 

Well since I'm one of the first guys in AUS to be doing this, maybe I'll get one made up. Need some specs though please @6A13TT TYPE S

 

Will draw it on CAD for you and post a .dxf file here so you can take it to get made. Just depends when I can borrow the work laptop with solidworks on it. Also 90ft/lb is what was on the spec sheet for these studs.

 

Ah ok great. Thanks a heap

 

Can do. will attach here when I have done it.

 

Christian, myself and possibly TJ will need a qld based one to share Lol

 

Yep will have to get onto drawing it on CAD for you guys.

 

Might even need a Sydney based 1 aswell. Few in the pipeline here too

 

Well it seems the forums software won't allow me to post .SLDPRT (solidworks part file ext)
so anyone who wants the drawings PM me and I will email it to you