DIY converting -86 block to 87+ tensioner?? - Rennlist - Porsche Discussion Forums

Notices

DIY converting -86 block to 87+ tensioner??

Old 10-28-2015, 10:19 AM
  #1  
V2Rocket
Rainman
Rennlist Member
Thread Starter
 
V2Rocket's Avatar
 
Join Date: Jan 2007
Location: Rancho Cucamonga, CA
Posts: 41,757
Default 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"
V2Rocket is offline  
Old 10-28-2015, 10:39 AM
  #2  
Dimi 944
Addict
Rennlist Member
 
Dimi 944's Avatar
 
Join Date: Feb 2008
Location: Frederick, MD
Posts: 1,263
Default DIY converting -86 block to 87+ tensioner??

Originally Posted by V2Rocket_aka944 View Post
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"
Have you checked if you have the bosses/provisioning to drill in on the '86 block?
Dimi 944 is offline  
Old 10-28-2015, 11:11 AM
  #3  
V2Rocket
Rainman
Rennlist Member
Thread Starter
 
V2Rocket's Avatar
 
Join Date: Jan 2007
Location: Rancho Cucamonga, CA
Posts: 41,757
Default

Yes the 86 block has the bosses, they are just not drilled/tapped.
V2Rocket is offline  
Old 10-28-2015, 07:34 PM
  #4  
Dimi 944
Addict
Rennlist Member
 
Dimi 944's Avatar
 
Join Date: Feb 2008
Location: Frederick, MD
Posts: 1,263
Default

Originally Posted by V2Rocket_aka944 View Post
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.
Dimi 944 is offline  
Old 10-28-2015, 07:42 PM
  #5  
gruhsy
Addict
Rennlist Member
 
gruhsy's Avatar
 
Join Date: Dec 2009
Posts: 2,164
Default

Are you getting a machine shop to do this?
gruhsy is offline  
Old 10-28-2015, 10:18 PM
  #6  
V2Rocket
Rainman
Rennlist Member
Thread Starter
 
V2Rocket's Avatar
 
Join Date: Jan 2007
Location: Rancho Cucamonga, CA
Posts: 41,757
Default

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"
V2Rocket is offline  
Old 10-28-2015, 11:25 PM
  #7  
fast924S
User
 
fast924S's Avatar
 
Join Date: May 2004
Location: CT
Posts: 1,807
Default

I wondered about this myself, but never moved forward, without an extra block to double check there wasn't much info around
fast924S is offline  
Old 10-28-2015, 11:47 PM
  #8  
michaelmount123
User
 
michaelmount123's Avatar
 
Join Date: Jun 2010
Location: Maryland, USA
Posts: 720
Default

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.
michaelmount123 is offline  
Old 10-29-2015, 12:18 AM
  #9  
V2Rocket
Rainman
Rennlist Member
Thread Starter
 
V2Rocket's Avatar
 
Join Date: Jan 2007
Location: Rancho Cucamonga, CA
Posts: 41,757
Default

Using the drill press to start the tap square is a really good idea!
Wouldn't have thought of that.
V2Rocket is offline  
Old 10-30-2015, 03:55 AM
  #10  
Kris H
User
 
Kris H's Avatar
 
Join Date: Dec 2010
Location: Warsaw, Poland
Posts: 238
Default

please post photos of the process if possible. This could help others a lot
Kris H is offline  
Old 06-12-2018, 10:26 AM
  #11  
V2Rocket
Rainman
Rennlist Member
Thread Starter
 
V2Rocket's Avatar
 
Join Date: Jan 2007
Location: Rancho Cucamonga, CA
Posts: 41,757
Default

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.
V2Rocket is offline  
Old 06-12-2018, 10:38 PM
  #12  
audisport
User
 
audisport's Avatar
 
Join Date: May 2010
Location: Iowa
Posts: 231
Default

Seems like a lot of work for no value.
audisport is offline  
Old 06-13-2018, 12:38 AM
  #13  
V2Rocket
Rainman
Rennlist Member
Thread Starter
 
V2Rocket's Avatar
 
Join Date: Jan 2007
Location: Rancho Cucamonga, CA
Posts: 41,757
Default

it has value to put a 16v hydraulic belt tensioner (968) onto a 951 block.
V2Rocket is offline  
Old 06-13-2018, 12:55 AM
  #14  
951and944S
Super User
 
951and944S's Avatar
 
Join Date: Dec 2001
Location: New Orleans/Baton Rouge
Posts: 3,026
Default

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
951and944S is offline  
Old 06-13-2018, 12:58 AM
  #15  
951and944S
Super User
 
951and944S's Avatar
 
Join Date: Dec 2001
Location: New Orleans/Baton Rouge
Posts: 3,026
Default

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

And yeah, '86 block should have bosses -



T
951and944S is offline  

Thread Tools
Search this Thread
Quick Reply: DIY converting -86 block to 87+ tensioner??


Contact Us Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: