Zip sound when rotating engine by hand

Hi guys! I am wondering if anyone can tell me if this is normal before I proceed any further with my project. I recently had my heads rebuilt and started to install them this weekend along with new coolant pump, 4 new chain guides, new vario cam tensioner guides, low temp thermostat, new EPS clutch and pressure plate and headers. I decided to keep the IMS as I was happy to discover it had a dual row which seems to be in great condition. Here is my question, i have installed head and cams for head 1-3 and rotated the engine by hand to check for roughness and notice a Zipping sound does anyone know what this is, I feel slight resistance at one point during the rotation but I assume this is only the cam lobes because it is brief? I know the engine is dry but i did not hear this before i had them rebuilt. Also can someone tell me if I am supposed to fill the vario cam chain tensioner with oil before installation? I looked every where because I thought i read it at some point? Thanks guys!

BUMP, anyone???

Quotes source post: 16499816

Zipping sound like a coat zipper? Can you record and post. Resistance...don't think there should be, but others will have to comment on that.

I just had a mechanical binding issue with an engine (not a Porsche) that I rebuilt. I ended up using a torque wrench to turn the engine over and could tell where it was binding. Marked the cam lobes where it was binding and figured out it was twice per crank revolution. It was as much as 80 ft-lbs at the binding point, when I fixed it (flex plate between engine and transmission installed backwards) it took about 30-40 ft-lbs max to turn the crank. So I would at least be documenting the torque required.

You need to get with an engine expert. The tensioners and lifters should be soaked in warm oil overnight, then manually pumped up. Get with user Jake Raby with specific details about how to do this.

I soaked the lifters, the tensioners I did not, the shop manual did not mention this, oh well I guess I can remove uninstalling soak and reinstall. Sucks because she is all timed up. Another question ..does anyone know what these strange clear half capsule things are? They came with the gasket set and look like one half of a medicine pill I'm thinking maybe a type of shrink wrap /seal for a bolt? What bolts? I have no idea

Oh and thanks for all the replies!

Oh to clarify, I am referring to the variocam tensioner that sits in the head in between two cam sprockets , it has a solid void attached to it that has a electrical plug that feeds through the valve/cam cover. I hope it's the cylindrical ones that screw in that have to be submerge and pumped up as that will be easy peasy.!

Quotes source post: 16500317

The clear "half capsule thing " is a valve stem seal protector to use when installing new stem seals ( I guess you're not performing that task).. No need to oil the vario-cam actuator (or pump it up), it should have plenty of residual oil in it. You should make a video and sound clip of the " zip" noise if you want technical help, that seems like it could be a serious issue.

Thanks for the reply, Hoffman rebuilt and repaired both my heads. I was wondering what those things were. It would have haunted me forever. So the zip sound seems to be coming from the vario cam tensioners I suspect it will go away when they fill up all the way with oil. I took one out and the plunger makes that sound when It goes up an down. I took the other one out and it makes the same sound. I hope its normal. Does the engine oil pressure fill the tensioner? Also, there is no gasket that goes between the tensioner and the head is there?

Quotes source post: 16500949

Yes, as soon as the oil pressure builds, it will fill and pressurize the actuator/tensioner. It is a machine fit, no gasket required.

Quotes source post: 16501033

You are awesome thank you very much!

Boggles my mind that someone would go this deep into a rebuild and not change the IMSB because its a dual row and "seems to be in great condition." This is the second one this week. Good luck with that.

Quotes source post: 16501217

My first thought as well...Pinching pennies will cost you dollars down the road!

Quotes source post: 16501542

ok a 996 with 30k equipped with a dual row IMSB, info from 2 10 year porsche techs from 2 different dealerships reporting 0 dual row IMSB failures. What is it, a 1% failure rate on the dualbrow equipped cars? Hell I should have my perfectly good cylinders replaced with nickes as well right because they may get scored? Or just done an ls1 swap to avoid ALL potential failures.....What's with all the smart *** remarks. If you have something helpful to say the say it. I'm sure we can all do with out the smart *** comments.

Quotes source post: 16500317

It's best to "cook" the lifters in engine oil at 100 degrees while using a pushrod to compress the lifter plunger surface. This fills the lifter with engine oil so they will function properly on initial engine startup. Same for tensioners. I bought a cheap Walmart electric plug-in plate with cover for this. Teflon for easy cleanup!

[QUOTE=Sarc1218;16501883]ok a 996 with 30k equipped with a dual row IMSB, info from 2 10 year porsche techs from 2 different dealerships reporting 0 dual row IMSB failures. What is it, a 1% failure rate on the dualbrow equipped cars? Hell I should have my perfectly good cylinders replaced with nickes as well right because they may get scored? Or just done an ls1 swap to avoid ALL potential failures.... .What's with all the smart *** remarks. If you have something helpful to say the say it. I'm sure we can all do with out the smart *** comments.[ /QUOTE] Wow! This is a forum and people will offer their opinions that might be contradictory to your actions. Don't be so sensitive...just a suggestion.

Duplicate my bad!

Sarc1218, I'll offer the same experience I had to you that I offered to the other poster whom said he was not going to change his IMSB while doing clutch/pp/to brng/rms. My experience relates to my 1999 986 Boxster which has the same engine architecture as the 996. My plan was to do the clutch/pp/to brng/rms and IMSB. The car needed a clutch and the rest of the work was preventative in nature. The car had 70K miles and, when I pulled the original dual row IMSB, it was rough and the center stud was wobbly. It was probably less than a couple of thousand miles from failure which would implicate catastrophic engine failure. I had bought the car with 52K miles and had religiously changed the oil every 4K miles with high quality oil, although not synthetic. Didn't get much in the way of service records from the PO so the frequency of oil changes prior to my purchase was unknown. Put the car back together with Vertex cylindrical roller bearing and 18K miles later all is well. My point is that dual row bearings do indeed fail, and if my memory serves me correctly, the lower mileage cars are particularly susceptible. It's often the case that preventative maintenance can save your bacon as was the case for me. Wouldn't it suck for you if you did all that work, then had the IMSB fail suddenly? Apologies if my original post offended you, but I stand by it. As the saying goes, sometimes the truth hurts.

A professional mechanic who has not seen a Dual Row IMS Bearing fail is someone who has not worked on enough Porsche 996. I have seen one fail on a 1999 996. It came out wobbly and probably a few hundred miles from an engine blow up. Still, this is your car, your wallet, and your risk to take. Good luck.

Ok guys I do actually want to apologize. It is solid advice, I am active duty and this Covid crap is stressing us out beyond belief. That and I already dropped about 5k on it ot more o lost track after 5k. But I see now 600 more is cheap insurance. I really do not know which one I should go with. I like the roller style but read it's not as good as the ln products due to lateral stress resistance or something like that. It's been a long project due to uncle Sam's demands and I guess I'm just being unreasonable anxious to put her back on the road, I see that now thanks for not tearing into me.. Again please accept my apologies guys.

Welcome to owning a Porsche,, term maintenance items cost a lot. Its just part of the game,, There are MASSIVE amounts of info on here about the IMSB ,, Dealer mechanics are the last reference you should use,, other than warranty work they wont see most of these. The 996 Indi shops will have seen way more of them. When you consider that for almost half the life of the car,, Porsche denied there was a problem at all.. There is NO cheap exit out of this game, and Straight replacement is good for approx 60 to 80 K just like the average clutch life.. Good luck and we have all been there or are going there..

Sarc1218, I researched the cylindrical roller bearing prior to installing it and was attracted to the fact that it has 5 times the radial (side to side) load capacity as a ball bearing. I did, however, read anecdotal accounts that it did not possess the same axial (front to rear) capacity as a ball bearing. I am an ex-machinist from the former Philadelphia Naval Shipyard, and it was my experience that cylindrical roller bearings were the preference for heavy duty applications, that's why I chose the cylindrical roller bearing. In our application on 986/996 series Porsches the cylindrical roller bearing is captured axially by the IMSB cover plate at one end and the IMS shaft itself at the other end of the bearing. I don't expect that there is much axial stress on the bearing from the IMS shaft because that shaft is connected to the crankshaft and to the cams by chains which are under tension. If there is axial stress on the bearing from the IMS shaft moving front to rear, the engine has much greater problems than axial stress on the IMS bearing. Also, from the research I did, It was apparent that radial stress and poor lubrication are the killers for the original ball bearing design. I am happy with the choice I made, and was going to put the cylindrical roller bearing in my 1999 dual row ball bearing 996 as well, again as preventative maintenance while doing the clutch, only to discover it had a replacement engine that the PO did not disclose to me which contained the later large single row bearing which requires splitting the cases to replace. I did remove the oil seal from the bearing for added lubrication, and change the oil and filter religiously every 4K miles, including dissecting the oil filter looking for ferrous material. Anyway, best of luck with your project, and a salute to you and all of our men and women in uniform all of whom I hold in the highest regard. I retired after 38 years as a Department of Defense employee and had the good fortune to work with and for many fine military personnel, we are all lucky to have you protecting our country.

Quotes source post: 16503682

Hi Weazer, thanks for the kind words and good advice my thoughts were the same regarding the roller bearing. Which one did you go with I have seen them made with steel cages, brass like cages and plastic/polymer. Anyone have any thoughts on which one they would suggest. Hopefully this thread doesn't turn into one of the countless imsb vs. Imsb threads lol! I think LN partnered with one manufacturer at one point and has not entirely endorsed, I suspect due to their own product line but they definitely did not knock it down. I've heard good things.

The LNE "Solution" is the best way do go!

Quotes source post: 16503450

Thanks for your service. Take care of your mental health. The wrong kind of stress is not a good thing...at all.

Quotes source post: 16504034

Yes, go with The IMS Solution and NEVER worry about it again. https://lnengineering.com/products/i...s-my97-01.html

Sarc1218, I went with the Vertex cylindrical roller bearing (brass cage), again due to the 5X radial load capacity, and also due to the lower cost (approx. $500 if memory serves me back in 2017). My personal situation, mortgage payment, paying for college, child support and a wedding, was/is such that I attempt to maintain these cars on a budget. While the LN "Solution" may be the preferred lifetime remedy, at 4X the cost of the cylindrical roller bearing I just couldn't swing it. I'm confident the Vertex cylindrical roller bearing will last me until the next clutch job (conservatively, 60K miles per clutch) at which time I'll change it out as a routine maintenance wear item. I'd have to go through three more clutches for the LN "Solution" to have been cost effective for me. Such is the life of a retired DoD employee, I blame myself. BTW, TexSquirrel, that car is boss, love the headlight covers and aero kit!