Oil Fed Tensioner Modification: ADD SPACER SURVEY

911 tweaks · 12-31-2008, 04:51 AM

i JUST COMPLETED THIS MOD ON AN ENGINE AND WAS CURIOUS WHAT OTHERS HAVE EXPERIENCED WHEN PERFORMING THIS TENSIONER MOD.
An excellent write up by George Aigel I believe back in 04' did a nice 3 pg write up on how-to.
Anyway, I performed the update resulting in installing a spacer of 0.146" on the right side and 0.166" on the left side ??
QUESTIONS:
1. did I screw up my measurements by getting different sizes ??
2. will the different sizes make a difference ?? (0.020" = a human hair thkns... can this be a problem??)
3. Is there an agreed minimum size to either do OR don't do the mod ??
***4. What have you all experienced in doing the mod??
Thanks and happy new year to all!!
Bob

Rusty 356 · 12-31-2008, 04:58 AM

Bob, if you are referring to the spacer between the tensioner and the housing you will be okay as long as the tensioner has a little float. Check the width of your old tensioner and compare with what you installed. my 2cnts worth.
Happy New Year,

Rusty

911 tweaks · 12-31-2008, 05:59 AM

actually Rusty, I am asking here about the "height or thickness" of the cut piece of 5/8" o/d bronze bushing that you slide down into the bore that the oil piston also rides up & down inside of the oil pressure fed tensioner.
I will post a pic in a bit to show all.
Thanks though for the info on the orientation/position of a complete tensioner, right ?? Is that what you are saying ??
Bob

911 tweaks · 12-31-2008, 06:19 AM

HERE IS THE PICTURE OF WHAT THE SET UP LOOKS LIKE.

***THE PART IN QUESTION IS THE BRONZE BUSHING... THE THIN ONE ~ 0.160" HEIGHT OR TALL... DEPENDING ON HOW YOU WANT VIEW THE SMALL BRONZE BUSHING...
Anyway, what have you all experienced at the "height OR tall" of what you installed ??
Thanks and I hope the pic helps to better present the info I solicite.
Bob

MotoSook · 12-31-2008, 06:34 AM

I don't think a 0.02" difference is anything to worry about. The intent of the spacer is to stop the tensioner from fully collapsing while providing enough travel for normal operation. I seem to recall seeing spacers that were thicker than what you have shown.

Without the spring, reassemble the tensioner, then install it on the engine as normal, then see if your chain has enough slack to skip the sprocket with the tensioner fully compressed. If so, then increase the spacer. You don't want the spacer too large as to preven installation and enough play to dampen the chain movement.

356RS · 356RS's Garage

Bob, I did the modification to a set of new pressure fed tensioners last summer and had about the same measurements as you. Like Rusty said, as long as there is some float in the piston you should be fine.

911 tweaks · 12-31-2008, 08:35 AM

thanks guys...glad o get the conformation all is well.
For those not well versed in this project, Souk highlites the procedure... a bit more info, best to check out the thread by George Aigel, and it basically says to remove tensioner... remove cir clip at top to allow tensioner piston to be removed... remove piston... remove spring... put piston back in tensioner... put tensioner back on engine... fully colapse(push down into) tensioner piston into tensioner... push chain sprocket away from piston to create gap between top of piston and contact point on arm/flange of chain sprocket... measure this distsnce - (subtract) 1/8" = height of cut pc of bushing that will be inserted into the bottom of the bore that the tensioner piston travels in.
Thanks again guys !
Bob

911 tweaks · 12-31-2008, 01:03 PM

*********** IMPORTANT QUESTION I almost forgot to ask****************... do I need to 'prime' the tensioners with oIl OR will the line feeding them take care of that either when I turn over the engine via the starter W/O fuel relay in OR when it is fired up at some point in the future ??
... I hope to get replies this PM as I would like to button this project up tonight...

Many thanks again guys !!
Bob

Rusty 356 · 12-31-2008, 01:31 PM

Put the pin back in and install. Engine oil will do the rest when you pull the pin and start the engine. Rumble in the exhaust the 1st day of the year.

rusty

911 tweaks · 01-02-2009, 05:40 AM

bump...
I find it hard to believe that no one has done this tensioner update & would then ba able to post what was the height/thkns (size) of their inserted tensioner bushing... ?

I thought this would be beneficial to all in that it would be a place to go and see actual data for engines with x # of miles, chains x # miles old, sprockets x # of miles old, ect.

Bob

Rusty 356 · 01-02-2009, 05:45 AM

Bob, I didn't read every post, but you asked in an earlier response about what I was referring to and you are correct. I thought you were referring to the spacer behind the tensioner when used on an earlier car. Quick question regarding new tensioner kits. Is this bushing stop already in place?
Thanks for sharing and apologize for my not understanding your question.
best wishes for the New Year,

911 tweaks · 01-02-2009, 06:23 AM

not a problem Rusty... I look at life in many ways and one of them is that their is no dumb question...
To answer your question regarding the spacer... the spacer does not come on the pressure fed tensioners. The insert/spacer bushing needs to be made and installed in each tensioner below the tensioner piston to prevent the piston from traveling too far down into its bore in the event of a oil pressure loss which "could" allow the piston to bottom out in its bore and "possible" allowing the timing chain(s) to jump a tooth on a cam or crank or both sprocket now quite possible allowing your valves to collide with the tops of your pistons... say 'ouch', thus why I did this as preventive medicine.
Good luck here Rusty and ask any q's you may have.

I hope others will post data here for reference.
Bob

sand_man · 01-02-2009, 06:32 AM

Hey tweaks, if you don't mind me asking, where did you source the material used for the spacer? Is that something you picked up from McMaster-Carr?

Now that my rebuilt engine has settled in, I need to fix a minor oil weep at the chain-box cover, and thought this would be a good time to perform this mod and re-set my cam timing.

911 tweaks · 01-02-2009, 07:33 AM

sand Man... I would agree that your timing is perfect... hate to see you cook an engine if for some crazy reason you had a tensioner collapse...
Anyway, I bought the bushings at lowe's @ about $0.89 each.
Least expensive thing one can do to a 911 engine and get the most "not-a-bang" for your buck !
Bob

911 tweaks · 01-02-2009, 07:34 AM

sand man... please post back here what sizes you wind up with after doing the mod.
Bob

sand_man · 01-02-2009, 07:41 AM

Quote:

Originally Posted by 911 tweaks

sand Man... I would agree that your timing is perfect... hate to see you cook an engine if for some crazy reason you had a tensioner collapse...
Anyway, I bought the bushings at lowe's @ about $0.89 each.
Least expensive thing one can do to a 911 engine and get the most "not-a-bang" for your buck !
Bob

Thanks for the info, Bob! Yeah, I had my tensioners thoroughly inspected by my Porsche machinist during my rebuild and they were given the clean bill of health. But with so much controversy swirling around pressure fed vs. mechanical vs. oil filled Turbo style...I think for peace of mind, having this "anti-collapse" spacer will go along way!