iammulva

Saturday I finally got around to replacing plugs and coils (thanks to the DIY on this forum). Everything went reasonably well (better than expected actually) until I was reassembling things. I ended up cross-threading one of the two end-bolts on the manifold (going into the block). I didn't know if I would do more damage by trying to force the correct bolt in place so I got a shorter, stainless steel bolt and a couple washers and used that instead. I have it in probably 2 or 3 turns. The other 5 bolts on that side are fine and all 6 on the other side are fine too. Everything seems snug to me, I can't hear anything abnormal (as a matter of fact, from the inside, the engine seems a tad quieter now - which doesn't make sense to me unless the new gaskets had some effect). I used new manifold gaskets and bolts and torqued to 17ft/lbs.

What should I do?

1. Leave it alone
2. Take it to my mechanic and have him attempt to re-thread the hole
3. Something else

Thanks in advance

extanker

a good mechanic will look at it and give you his pro opine

Spiffyjiff

timeserts or helicoils will probably fix your problems. one question tho - manifold bolts...? why did you need to take off manifold in order to do sparks/coils? (or maybe i dont know what a manifold is...)

iammulva

USMC_DS1's writeup suggested removing the manifold to get a torque wrench positioned for the plugs. The manifold is item #1 in this link http://www.autoatlanta.com/porsche-p...=99611110755#a. I believe they are also often called headers, but I don't know if that's because the two are the same thing or just used interchangeably even if it is incorrect.


I called my mechanic, he will take a look at it for me when I bring it in. Likely will be a few weeks.

rsabeebe

we're talking exhaust manifold bolts here, right? i ask just as spiffy is inquiring - if you did plugs, why did you remove the manifold bolts? you apparently did though because you mention new manifold gaskets. i know it's too late, but this is why you always put bolts in with your hand or a socket using your hand - any resistance is felt right away. when going into aluminum, this is especially important. one thing you could try, if you are comfortable with it, is to remove the bolt and run a tap in there to possibly clear out any aluminum that may have been removed. if it's bad enough that you have to helicoil at some point anyway, this would not make matters worse. it's possible this would clean the threads and allow for a straight threading of the bolt again. this would be the approach i would take. i don't like the idea of a shorter bolt and washers long term.

rsabeebe

headers are typically tubular and manifolds are cast and generally just flow into a single exit as quickly as possible for space/location. they have the same function essentially, but they differ in appearance and efficiency. google each and you should see the fundamental difference.

mattyf

Tricky one...

I don't quite understand why you put the shorter fastener with washers.

Fasteners really only hold preload with 3 threads. So in general if you have three threads of full engagement you're good. Now for practical purposes the first thread on the bolt and on the tapped hole are not complete threads so add two more for those and you get a 5 thread engagement requirement. Figure out your thread pitch and you can count turns.

Assuming you didn't bugger up all the threads, I would pull the fastener and chase the hole with the proper tap and re-install. If you can get to the required torque then you're good. Generally if it doesn't break on torquing it should be good.

If you can't get to the torque and it strips more, then it's insert time. This assumes there is room to fit an insert. I prefer keenserts to helicoil or timeserts. That's what we use most of the time at work. In any case it's probably professional installation time, because you really don't want to mess up drilling the hole out larger and tapping it for the insert.

Of course you could just leave it as is and see what happens. Then address the issue later if you have to.

iammulva

Removed the manifold because the write-up suggested it would give clearance to get torque wrench in.

yes - i realize that. my brother did it. he knows this as well. not sure how he got it buggered.

me neither - gonna take it to my mechanic

To try to minimize the amount of thread damage.

Was considering that, but gonna let my mechanic have a look-see.

Spiffyjiff

yep, duh, you're correct. my brain fart - i forgot that both the intake AND exhaust can be referred to as "manifold". but as you point out, i usually refer to the exhaust as "headers".

in any case, good luck with your issue! if mechanic is any good, he'll fix you up in no time with a re-tap.

rsabeebe

running a tap up there is really an easy process if you have a tap-n-die set. if not, they're not that expensive. unless it's truly buggered, you could easily clear this with minimal expense and time - certainly less than having a mechanic look at it.

Fred R. C4S

As a retired Mechanical Engineer who once designed bolted joints at the Big Yellow Tractor Co., it takes more than three threads to hold preload. The recommended minimum thread engagement for a steel tapped hole is 1.5 x bolt diameter. For aluminum it's 2.0 x or greater.

Be careful out there........

iammulva

Good to know. Good reason to get it fixed.

mattyf

This is super conservative, but maybe that's just how Big Yellow operates since you probably don't worry about fastener mass. I wish I could post the flight fastener guidelines, but that would be an ITAR violation. You can search around the web and find similar information confirming the first three threads carry anywhere from 70% to 90% of the load. My point was to indicate that if the OP only messed up a few threads, he may still have plenty left to do the job.

USMC_DS1

#1... for now then #2 if you haven't done a tap and die repair previously.

Ugh... Sorry to hear this. Take your time to address it properly. You have 5 bolts holding the EM in place so you should be fine for the time being.

Last year my youngest son snapped one of the EM bolts when we installed the FVD exhaust system on my car. A miss comm issue between us... I said 17 ft-lb and somehow he heard 37 ft-lb. I assumed the worst and ordered some specialty back out tools to get the bolt extracted. I already had the tap and die on hand but we had to wait two wks for the back out tools to arrive. With tools on hand we finally tackled the job after a month. We soaked the offending bolt overnight with kano kroil and the next day it came out without the need for the back out tool afterall. Point being... I DD'd the car for 4-5 wks with 5 of the 6 bolts holding my EM in place w/o issue. So take your time, get all the tools you think is necessary and then tackle the issue properly.

Before you implement a helicoil I would try to repair it with a tap and die 1st. If you've never used a tap then have your mechanic address this. GL and let us know the outcome.