Torquing head studs

[jstoezel]

Hi:

I'm having troubles torquing 8mm head studs on my engine. I'm following the 2 sequential patterns recommended, going in torque increments. But I'm stuck at 15ft/lbs. The head studs can't seem to keep anything more than that. Service manuals recommend 18ft/lbs.

Is it safe to leave it at 15ft/lbs? Any tricks to get the studs to hold the torque?

Thanks,
Jean

[SR Racing]

Jean,

Not sure what you mean by saying the 'studs can't keep anything more than that'. ?

They are either stretching and ready to break, or they are pulling out of the case. Yes, you really need to take them to 17-18lbs and not a pound more. (8mm studs)

If you have an engine that has had them for a long time, they may have been torqued dozens of times, in which case they made need replacement.
MAKE sure you are using a dial or beam type torque wrench. I will not allow clicker wrenches in the shop except for wheel stud use. They are terribly inaccurate and can go out of compliance.

After proper torqueing in proper sequence you should really do a leak down test. (Not a compression check).

[jstoezel]

Hi Jim:

Thanks for the reply. What I mean by it doesn't seem to hold the torque, is that when I go through the torquing pattern, each bolt requires a minimum extra torque (maybe 1/16 or a bit more of bolt actually turning) then the torque wrench disengages. And I could go like this all day. It seems every bit I put on the stud is lost.
Now this is a case that is 3 season old, with case savers.

I do use a clicker wrench but I'll pick up a dial one first hour tomorrow. Still I find it odd that the studs don't seem to hold the torque.

Jean

Jean,

Not sure what you mean by saying the 'studs can't keep anything more than that'. ?

They are either stretching and ready to break, or they are pulling out of the case. Yes, you really need to take them to 17-18lbs and not a pound more. (8mm studs)

If you have an engine that has had them for a long time, they may have been torqued dozens of times, in which case they made need replacement.
MAKE sure you are using a dial or beam type torque wrench. I will not allow clicker wrenches in the shop except for wheel stud use. They are terribly inaccurate and can go out of compliance.

After proper torqueing in proper sequence you should really do a leak down test. (Not a compression check).

[tiagosantos]

Are you sure the 1/16th of a turn isn't just the amount of rotation in the torque wrench's ratchet mechanism? Try making a mark in the nut/stud and see if it's actually rotating..

[SR Racing]

Hi Jim:

. Still I find it odd that the studs don't seem to hold the torque.

You will have to hit them each probably a couple times, but they should get to 17-18 and stay there. If you have paper shims under the cylinders they will compress a bit over time (secs/mins) and you might have to do it 3 times. I think if you get a beam type wrench you will get it right. (BTW, the dial type wrenches are also "beam" type internally and have a little more reading resolution.) Try and get a beam (either type) that has a max reading of no more than 50 ft lbs. That will be adequate for everything on the ACVW, except the gland nut. (We have a 500 lb torque wrench for them. It cost $1 / pound. )

[jstoezel]

Hi Jim:

Thanks for the reply. I think I got it alright this time. I think this was an issue with one of the cylinders not properly seated on the case...

Seems ok now. Now while torquing the heads one of the pushrod tube seals unexpectedly popped inside the heads. I find it difficult to get the pushrod tube seals to apply evenly. Reset everything and no seals popped in this time. Looking at the seals from inside the heads, I'm a bit suspicious of one.

What does a properly installed seal look like? What are clues to look for, for one that is going to pop out?

Thanks,
Jean

You will have to hit them each probably a couple times, but they should get to 17-18 and stay there. If you have paper shims under the cylinders they will compress a bit over time (secs/mins) and you might have to do it 3 times. I think if you get a beam type wrench you will get it right. (BTW, the dial type wrenches are also "beam" type internally and have a little more reading resolution.) Try and get a beam (either type) that has a max reading of no more than 50 ft lbs. That will be adequate for everything on the ACVW, except the gland nut. (We have a 500 lb torque wrench for them. It cost $1 / pound. )

[SR Racing]

You will have to flex the top of the tube a little bit so that it is straight into the head. The tube will not be precisely straight. When looking at the hole you should see an equal amount of seal around the tube at the hole.

I have never see one pop through the hole. You sure you have 1200 tubes and not 1600 ones right?

Hope that helps

[jstoezel]

Hi Jim:

I believe I have 1200 tubes. These are the tubes that came with the engine from the FV shop. What came through the head is not the tube, just part of the seal.

I would say I find it difficult to have an equal amount of seal around the tube and the hole. All of the seals are offset one side.

You will have to flex the top of the tube a little bit so that it is straight into the head. The tube will not be precisely straight. When looking at the hole you should see an equal amount of seal around the tube at the hole.

I have never see one pop through the hole. You sure you have 1200 tubes and not 1600 ones right?

Hope that helps

[SR Racing]

I would say I find it difficult to have an equal amount of seal around the tube and the hole. All of the seals are offset one side.

Well a bit of offset is ok. The way we do it is before torquing the head (it is in place, but not bolted down yet.) push the tubes around by bending slightly at the bellows section until it is centered in the hole with the seal. Start torquing down the 4 center studs (under the rocker shaft) (about 5-6 lbs) and rebend the ends if needed to keep the tubes centered. Complete torque of the 4 center studs (the ones under the rocker shaft) to 6lbs. Then follow the full VW sequence to 17-18 lbs. After the 6 lbs we normally go through them at 6, 10, 14, then the final. Before you do the first 6 lb, check at the head / cylinder mating area to make sure they are lining up right.

[sharplikestump]

I think Jim has this covered pretty well, BUT being the budinski that I am, I will add this: Over the years, I have seen some longer 1200cc P.R.T.s. Additionally, with the decking of the heads and case, trimming of cylinders, it can all compound the situation. I built a fixture for the press, where I compress every PRT, collapsing one end, and then I flex the accordian on that end. Recently, I've started putting a light coat of racing Hylomar on the tubes prior to installing the seals, and I only use the pure silicone (translucent) seals. Years back, I had some of the red harder ones crack, and then it IS possible for them to push through into the rocker box.
On your "torque creep", my GUESS is that you either had a cylinder o-ring pinched, or you have some of the super cheesy junk head studs that stretch.....right up until they break. Chrome Moly studs, only.
Mike P.

[jstoezel]

Hi Mike:

Thanks for the reply, I apologize for missing it, this site doesn't have automatic email notifications.... I've switched to Apexspeed which is much easier to use to follow discussions.

Last summer I did get to install and remove the heads several times. I think 6 times total? I ended up getting quite a bit of practice. The issue with the seals blowing inside the heads: I used the white type seals, and got red ones when I ordered new ones from CIP. I haven't used the red ones just yet so I'll only say what I know about the white ones.

The white ones popped up inside the heads about 3 times, always when I wasn't paying attention in the initial stages of torquing the heads. Or I should say in the first stage where you pre-tension the studs just after you install the head and the tubes. During this stage it seems very critical to tension the studs very carefully and readjust the tubes so they are perfectly perpendicular to the heads.
Once I noticed that I never had a seal pop up.

Now as for the sealant: I was using Permatex... Hum I forgot the number. It's whatever is specified in the VW manual. Some kind of aircraft seal, smells good (to me) and looks like molasses. It's very sticking and never seems to dry. After all these re-assembly I have yet to see any leak. however, this product is very difficult to remove, which makes reassembly very time consuming, since it requires quite a bit of work (and acetone) to remove the old coat.

What sealant type exactly do you use? I'd be interested to know.

As for torquing the heads. I torqued the studs as 15lbs, that's what my engine builder had them at. I have yet to send my engine to Vallis, we will see what he says about the studs. Engine needs total overall anyways.

Jean

I think Jim has this covered pretty well, BUT being the budinski that I am, I will add this: Over the years, I have seen some longer 1200cc P.R.T.s. Additionally, with the decking of the heads and case, trimming of cylinders, it can all compound the situation. I built a fixture for the press, where I compress every PRT, collapsing one end, and then I flex the accordian on that end. Recently, I've started putting a light coat of racing Hylomar on the tubes prior to installing the seals, and I only use the pure silicone (translucent) seals. Years back, I had some of the red harder ones crack, and then it IS possible for them to push through into the rocker box.
On your "torque creep", my GUESS is that you either had a cylinder o-ring pinched, or you have some of the super cheesy junk head studs that stretch.....right up until they break. Chrome Moly studs, only.
Mike P.

[SR Racing]

The white ones popped up inside the heads about 3 times, always when I wasn't paying attention in the initial stages of torquing the heads. Or I should say in the first stage where you pre-tension the studs just after you install the head and the tubes.

Strange. The white seals are silicone and the most of the red ones are rubber (or a close facsimile) We always use the silicone (white) and have great results. They stay softer longer and seal well. Never had any push through the holes in the head.

Now as for the sealant: I was using Permatex... Hum I forgot the number. It's whatever is specified in the VW manual. Some kind of aircraft seal, smells good (to me) and looks like molasses.
What sealant type exactly do you use? I'd be interested to know.

Sounds like the right stuff. We use the Permatex Aviation sealant on the case halves, base of the heads, case portion of the oil pump and any place where tolerances are important. We use RTV on most everything else. Just be carefull with excessive RTV on the valve covers and sump etc. It can block an oil passage.

As for torquing the heads. I torqued the studs as 15lbs, that's what my engine builder had them at.

A little light but better on the low side than over 18. We take them to 17 lbs with a calibrated dial gauge making sure that the nuts are very free on the studs to insure a real 17 lbs. (8mm studs) This is pretty critical due to the different expansion factors in the case, cylinders and heads. On a vee, if good stock studs are used you usually won't have a problem, but better aftermarket studs are available.

[billinstuart]

1) I never used paper gaskets under the cylinder..added a few thousandths' to the clearance above the piston.

2) I would assemble the jugs/heads and lightly tighten the studs. Then I would turn the engine over a few times, and line everything up perfectly.