DIY converting -86 block to 87+ tensioner??
 

Anybody have tips or a template or anything regarding drilling the holes for the 87+ belt tensioner onto an 86 block, to make sure its exactly in the right place?

Just use a drill-stop for the depth or what?

Or is it as simple as "center the tensioner plate over the block bosses and drill through the holes to match"

DIY converting -86 block to 87+ tensioner??
 

Have you checked if you have the bosses/provisioning to drill in on the '86 block?

Yes the 86 block has the bosses, they are just not drilled/tapped.

I guess you got your answer. Place the tensioner so all the mounting wholes are centered on top of the bosses, mark, drill and tap would be my approach.

Are you getting a machine shop to do this?

I did get a referral by someone to a semi-local shop that can do this but glancing over their site they appear to be quite pricey, at least for parts...no idea on services.

That said, I do have a drill press tall enough to fit the block on the deck and go to town. Looking at another block I have (S2) the tensioner studs are more or less centered on the bosses, so "how hard can it be" :)

I wondered about this myself, but never moved forward, without an extra block to double check there wasn't much info around

I say go for it on your drill press. It will get your holes square enough for sure. Drill smaller pilot holes, perhaps 1/8 or 3/16, first and your final holes won't have wandered. Then chuck up the 8mm tap and hand turn the drill press to start the threading so the tap stays square. Use a new (sharp) decent quality tap. The tapped bosses are only securing the tensioner, so absolute precision is not necessary.

Using the drill press to start the tap square is a really good idea!
Wouldn't have thought of that.

please post photos of the process if possible. This could help others a lot

revisiting this...
anyone know how long overall the 3x tensioner studs are, and how much thread is engaged in the block?
PET doesn't appear to list the studs as separate parts from the block, and im all out of late blocks to compare with.

i would guess ~12mm into the block would be sufficient for an 8mm stud.

it has value to put a 16v hydraulic belt tensioner (968) onto a 951 block.

Just picked up my block from bore/hone today and had all studs removed because I was highly considering nikasil.
Will ping you dimensions of studs.

Against the norm here, I would set the tensioner and use a bit same size as the holes in tensioner.

Just kiss the aluminum boss with that size bit to mark it for all three holes then remove tensioner and proceed from there.

The bit of mounting hole size will self center your holes and will have created a divot that will keep your 1st drill size from walking when you proceed up in bit sizes to reach the recommended 8mm thread tap size.

T

Now, where do you find one of these tensioners...., I hear they are pretty rare...:D

And yeah, '86 block should have bosses -

https://s22.postimg.cc/8mq3dhx7l/tensioner_bosses.jpg

T