Timing belt reinstall - Another PK tensioner over extended?
05-26-2016, 01:05 PM
#1
Rennlist Member
Thread Starter
Timing belt reinstall - Another PK tensioner over extended?
I am in the middle of putting my car back together after my oil pump failure. The previous owner put on the PK black edition. I have recoated cam gears, Ed's pump and new steel oil pump gear and a standard gates belt with only 500 miles on it. After becoming aware of the timing death thread I figured it would be prudent to check my piston extension on reassembly.
I timed everything and rotated the engine by hand a few times to equalize the tension on the belt. I set the engine at 45 and measured 9.5 mm extension.
So obviously I need to modify the holes on the damper/tensioner. How common does this modification need to be done? I have had the heads off on my car and they don't appear to ever have been machined.
I timed everything and rotated the engine by hand a few times to equalize the tension on the belt. I set the engine at 45 and measured 9.5 mm extension.
So obviously I need to modify the holes on the damper/tensioner. How common does this modification need to be done? I have had the heads off on my car and they don't appear to ever have been machined.
05-26-2016, 01:54 PM
#2
Rennlist Member
Thread Starter
Pulled off the damper. Holes were at 7 mm and I drilled them to 7.8. Made sure bracket was aligned properly and retorqued, then reinstalled the damper pushed as far forward as possible. Measures just a hair over 7 mm now.
As Adam mentioned in the other thread, is there any worry of the Audi part slipping back?
As Adam mentioned in the other thread, is there any worry of the Audi part slipping back?
05-26-2016, 02:08 PM
#3
When I reinstalled a stretched belt on an 85 I had, the extension was up to 8. I felt that was safe. Usually these things install around 5-6.
05-26-2016, 03:33 PM
#4
Three Wheelin'
05-26-2016, 04:31 PM
#5
Rennlist Member
Ted,
When thinking about the current hot topic regarding the engine failure one thing occurred to me but whether it is relevant or not remains to be seen. The heads have a specified dimension but I have never noticed anything that states what height the block mating face sits at. Obviously such needs to be tightly controlled but it made me wonder just how tightly such is controlled given it is also has a machined surface.
One imagines that such will be controlled but to what tolerance? I cannot imaging such dimension floating by numbers like 1mm both sides but something has to explain why numbers like 8mm are suddenly emerging. Maybe there is also some tolerance on the crankcase centre boring for the mains- if they all fell at one extreme could we thus explain why there is a range of between 5mm to 8mm coming into the equation?
Put another way head shaving may be done but it is not all that common surely?
Rgds
Fred
When thinking about the current hot topic regarding the engine failure one thing occurred to me but whether it is relevant or not remains to be seen. The heads have a specified dimension but I have never noticed anything that states what height the block mating face sits at. Obviously such needs to be tightly controlled but it made me wonder just how tightly such is controlled given it is also has a machined surface.
One imagines that such will be controlled but to what tolerance? I cannot imaging such dimension floating by numbers like 1mm both sides but something has to explain why numbers like 8mm are suddenly emerging. Maybe there is also some tolerance on the crankcase centre boring for the mains- if they all fell at one extreme could we thus explain why there is a range of between 5mm to 8mm coming into the equation?
Put another way head shaving may be done but it is not all that common surely?
Rgds
Fred
05-26-2016, 05:03 PM
#7
Rennlist Member
Thread Starter
Ted,
When thinking about the current hot topic regarding the engine failure one thing occurred to me but whether it is relevant or not remains to be seen. The heads have a specified dimension but I have never noticed anything that states what height the block mating face sits at. Obviously such needs to be tightly controlled but it made me wonder just how tightly such is controlled given it is also has a machined surface.
One imagines that such will be controlled but to what tolerance? I cannot imaging such dimension floating by numbers like 1mm both sides but something has to explain why numbers like 8mm are suddenly emerging. Maybe there is also some tolerance on the crankcase centre boring for the mains- if they all fell at one extreme could we thus explain why there is a range of between 5mm to 8mm coming into the equation?
Put another way head shaving may be done but it is not all that common surely?
Rgds
Fred
When thinking about the current hot topic regarding the engine failure one thing occurred to me but whether it is relevant or not remains to be seen. The heads have a specified dimension but I have never noticed anything that states what height the block mating face sits at. Obviously such needs to be tightly controlled but it made me wonder just how tightly such is controlled given it is also has a machined surface.
One imagines that such will be controlled but to what tolerance? I cannot imaging such dimension floating by numbers like 1mm both sides but something has to explain why numbers like 8mm are suddenly emerging. Maybe there is also some tolerance on the crankcase centre boring for the mains- if they all fell at one extreme could we thus explain why there is a range of between 5mm to 8mm coming into the equation?
Put another way head shaving may be done but it is not all that common surely?
Rgds
Fred
Personally I think a damper/tensioner with a longer stroke would be a better option to make it a fail safe install, or making the bracket mount a few mm towards the belt. If the second option makes it too tight with a new belt install, string the belt and install the pinned damper after.
I think a lot of these get installed without the piston stroke being measured.
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05-26-2016, 05:34 PM
#8
IIRC my 87 was at 7.5 when installed. Now I'm paranoid with SITM next week.
Guess I'm pulling the belly pans this weekend for a look or maybe I can get a mirror down there from above and measure somehow with the covers on.
Guess I'm pulling the belly pans this weekend for a look or maybe I can get a mirror down there from above and measure somehow with the covers on.
05-26-2016, 05:51 PM
#9
Rennlist Member
Ted,
The interesting bit is that with the stock tensioner one winds in the piston until the tool says enough, you give it a pinch/waggle with your fingers to let the senses tell you it is now "ok'ish" and relax knowing you have done as much as you can and trust the warning light does not come on to suggest otherwise. With this approach one never really knows where the belt sits in relation to the tensioner because it is generally irrelevant. Our professional friends who do these jobs regularly can probably spot whether something looks suspiciously different from normal by eyeballing the thing or just looking at the position of the adjuster protrusion from the body. Us DIY types who only see one motor at a time probably have no idea - for sure I have no feel on such matters.
Not sure I like the idea of slotting holes to get the tensioner into the drop zone, science may tell us it will hold steady but that would not sit easy with me without something along the lines of the power steering pump belt tensioner to secure the traverse given the severe consequences of failure.
Maybe some kind of extender on the piston is possible to customise the installation into the correct operating envelope. There are many examples to build data on if everyone chips in.
rgds
Fred
The interesting bit is that with the stock tensioner one winds in the piston until the tool says enough, you give it a pinch/waggle with your fingers to let the senses tell you it is now "ok'ish" and relax knowing you have done as much as you can and trust the warning light does not come on to suggest otherwise. With this approach one never really knows where the belt sits in relation to the tensioner because it is generally irrelevant. Our professional friends who do these jobs regularly can probably spot whether something looks suspiciously different from normal by eyeballing the thing or just looking at the position of the adjuster protrusion from the body. Us DIY types who only see one motor at a time probably have no idea - for sure I have no feel on such matters.
Not sure I like the idea of slotting holes to get the tensioner into the drop zone, science may tell us it will hold steady but that would not sit easy with me without something along the lines of the power steering pump belt tensioner to secure the traverse given the severe consequences of failure.
Maybe some kind of extender on the piston is possible to customise the installation into the correct operating envelope. There are many examples to build data on if everyone chips in.
rgds
Fred
05-26-2016, 06:37 PM
#10
Yeah - you have the exact setup right there. That is an early version of a Porken tensioner and the belt should be a 196 normal one. The gears, if I recall, were pretty good. Take some pics. And remember (OT), those injectors are VERY large - so you will need to change them
05-26-2016, 06:40 PM
#11
NICE!. Even better than I remembered. That engine sang. Just *ripped*. Bad ***.
Can you turn it over? See if that extension changes? That probably has... maybe less than 8k on that belt install? I would have to look at my posts.
05-26-2016, 06:46 PM
#12
My number I posted was wrong - under 7 is visible on the exact motor I was talking about.
Ted,
When thinking about the current hot topic regarding the engine failure one thing occurred to me but whether it is relevant or not remains to be seen. The heads have a specified dimension but I have never noticed anything that states what height the block mating face sits at. Obviously such needs to be tightly controlled but it made me wonder just how tightly such is controlled given it is also has a machined surface.
One imagines that such will be controlled but to what tolerance? I cannot imaging such dimension floating by numbers like 1mm both sides but something has to explain why numbers like 8mm are suddenly emerging. Maybe there is also some tolerance on the crankcase centre boring for the mains- if they all fell at one extreme could we thus explain why there is a range of between 5mm to 8mm coming into the equation?
Put another way head shaving may be done but it is not all that common surely?
Rgds
Fred
When thinking about the current hot topic regarding the engine failure one thing occurred to me but whether it is relevant or not remains to be seen. The heads have a specified dimension but I have never noticed anything that states what height the block mating face sits at. Obviously such needs to be tightly controlled but it made me wonder just how tightly such is controlled given it is also has a machined surface.
One imagines that such will be controlled but to what tolerance? I cannot imaging such dimension floating by numbers like 1mm both sides but something has to explain why numbers like 8mm are suddenly emerging. Maybe there is also some tolerance on the crankcase centre boring for the mains- if they all fell at one extreme could we thus explain why there is a range of between 5mm to 8mm coming into the equation?
Put another way head shaving may be done but it is not all that common surely?
Rgds
Fred
05-26-2016, 07:03 PM
#13
Rennlist Member
Thread Starter
I am finding it is very tricky to measure when you have stuff in the way. If your caliper gets **** eyed even a little bit the measurement shows to be long.
05-26-2016, 07:58 PM
#14
Three Wheelin'
Extension varies by a couple hundredths at various crank positions when turning it over via the crank bolt.
05-26-2016, 07:58 PM
#15
Three Wheelin'