964 - Repeat of Head Stud Woes

[captek]

My arp studs did not come coated,but I used the red 27140 Permatex thread locker on the studs.After they set up I tried to doublenut one of them to see how hard they had set in I could not budge it.How miles on those heads?Seems like a lot of oil.

[Porsche_monkey]

Paging Dr. House ....

I'm totally at a loss to explain this on an aluminum case with good studs. Aside from what Steve said regarding rates of expansion....

Waynes point that something else happened long ago doesn't explain the varying state of the studs today.

Were the studs ever re-torqued after assembly, or was this the first attempt to re-torque?

[sms1305]

I should have written it down when he told me, but the local Porsche shop did try to torque the heads recently. He said he only did some of them and then stopped when he encountered what he thought (and was correct) were pulled studs. I doubt he kept any kind of record, but I'll certainly ask. Still <30 - >60 is a big swing. I may not be an expert Porsche builder, but I've built my share of other engines and will testify that I know how to use a torque wrench better than that!!

Any theories on this mystery would be gratefully accepted...

[Porsche_monkey]

I would rule out 'faulty' torque wrench. I guess it could be broken, but it's not a calibration problem, the range is too wide.

And why is it a big problem to screw the studs in all the way to the bottom? Aside froma lack of nut engagement at the top end I can't see why this would be an issue.

[304065]

Only thing I can think of is that if the stud is threaded all the way to the bottom and gets torqued, it will try to push the threads out of the hole. If it's threaded to the proper height and the loctite sets, any excess torque will try to screw it in deeper. Have to check Carroll Smith's book about this.

[Porsche_monkey]

But they have red-loctite on them, and they are susceptible to that regardless, they can always get screwed in to the bottom if the nut binds a bit (without loctite).

[captek]

PBH,I have not seen arp studs come with any kind of coating on the stud end.If you call ARP directly they will tell you the same thing.In fact I called tech over at ARP and spoke to Paul,he has not heard of any problems with a stock motor with pulled arp studs.But again you have to use a tread locker. Steeve maybe the motor had been apart before and done incorrectly.Captek

[Porsche_monkey]

I guess in that case you could bottom out the studs and pre-load the threads, then put an additional load on when you torque the head bolts, and put a third load on when the head studs expand less that the cylinders?

Is that a plausible root cause?

[sms1305]

Thanks for the discussion. I talked to ARP and they said they hadn't had any complaints about the 964 studs. I believe them.

Loctite - It has been so long that I must confess not really remembering about the threads. If they don't come with a sealant, I probably used a Wurth thread lock, not loctite red.

Is there a bottom to the holes in the case where the studs go or do they go all the way into the case? Need to look at that.

[captek]

Maybe,but it seems to me that if you bottom out the stud you would feel it when it hits bottom.Maybe someone inexperienced in engine building,not that I would know how if this is the case but its plausible if he person doing the rebuild doesnt know the feel of the stud bottoming out and keeps cranking the stud down.Captek

[Porsche_monkey]

Originally posted by sms1305

Is there a bottom to the holes in the case where the studs go or do they go all the way into the case? Need to look at that.

The holes are blind, they do not go through the case.

[sms1305]

All the cylinders, pistons and head studs are out now.

Only the two on No. 1 were pulled.

I'm thinking about having them all timeserted anyway.

[captek]

Good idea its the best way to ensure it doesnt happen again and just be sure to have the correct height of the stud,you dont want to screw the stud down to deep and not have enough threads for the nut.Captek

[sms1305]

Engine is finally built. I got it started but had a major oil leak. Turns out the gasket at the front of the left side cam shaft was completely ruined. It looked like I put it and then had to twist it a little to get it aligned. Anyway, turns out that all I had to do was remove the rear tin, open the chain housing cover and replace it. All good.

But. . . now I see a small gasoline drip that seems to be coming from the fuel pressure regulator at the connection on the right (passenger) side of the engine. Any tricks of the trade for getting to the connection? It seems impossible to get to with the engine in the car. I hope someone has an idea. The thought of dropping it again is killing me!!

Thanks!

[captek]

Hey how you doing.I just replaced my fuel pressure reg.I thought I would have to remove the intake manifold,but did not have to.You just have to wiggle your hands in behind the intake.I removed the air mass senser and air cleaner,it was a little better.Its hard to explain but I used a bunch of different size wrenches diff lengths.I think you will need a 19 mm maybe a 17mm I forgot what sizes but you can definitely remove and replace or just tighten up a connection without all the fuss of removing the engine or the manifold.It just looks impossible but you can do it.

[sms1305]

Rebuild finished a few months ago, but major leak from left chain housing. Turns out that I totally botched the gasket between the plate and hte cam tower. All good now.
Fuel leak solved. Thanks Captek!
Correct temp sensor installed. Thanks, Glenn. ($50 Snapon tool wouldn't fit, but $3 socket and a grinder did the trick.)
Car is completely done, last night the rear bumber and new lights went on.
Then the start up . . .

On initial start up for first 20 minute run in after rebuild there was an incredible racket from the alternator / fan unit. I tried all variations of shims between the pulley halves, but it never went away. I then disconnected the alternator belt entirely just to finish the run in, and it was much, much quieter, but not silent. I ran the motor for about 5 seconds with no belts attached - silent.

I'm wondering if I should just replace the alternator and the hub assembly. I read here that the hub bearings are Porsche unique.

There is no indication of any contact between the fan and the housing/shroud.

After my last configuration of shims (I think only one shim between the outside pulley) the pulley was hot. Could that just be from being too tight?

I also noticed that when rotating the alternator shaft by hand that it seemed a little rough, though it never got stuck or binded.

I'm wondering what is the most likely cause of the problem - alternator or hub?

It's the original assembly. I'm thinking replace both.

Engine sounds great, though.

Thanks.

[captek]

the alternator sounds like the bearing is started to go.how many miles on the alternator?you sure there was nothing touching the fan blade?the housing maybe.If it does not spin smooth I would replace the alternator.they are not that much money,or have yours rebuilt.let me know.Captek Wyatt

[sms1305]

67K miles total . . .

[FL911]

Originally Posted by Twystd1

I just spent an hour with one of the PNA racing dyno guys. I posed this same question to him.

He said:

"The reason any stud pulls out on the early or late engines is because some idiot probably bottomed out the stud in the case when he installed them"

This assumes they were torqued to correct values.

So there is another option of why you may have pulled a stud. At least thats one mans opinion.

Clayton

In the rebuild book Page 136 figure 3-33 this is exactly what is says to do!
" Do not overtighten the stud; it should just bottom-out in its hole".

Is this not what to do? I seriously doubt Wayne would put this in the book if this is not an approved and or proven technique.

I want to know because I am in the process of a rebuild with ARP studs (or so I thought) and now I am more confused than before. Maybe I will use the steel studs.

Anyone?

[88911coupe]

I asked this before but I guess it did not "take". Anyway, what keeps the stud from rotating in the hole and potentially bottoming out when you are tightening the nut down on it? Do you use loctite and let it set, THEN tighten? I would have thought it would be best to torque it down before the loctite sets so you don't disturb the loctite once it is set. Or does the washer prevent this problem?