More questions about Head Removal

[Rodney Nelson]

Okay, I am replacing the head gasket on my 86 951 and I have a lot of questions, so I hope some of you guys could help me out here it goes:

1. Below in the pictures you will see a valve of some sort with three openings, one of which broke off during the surgery, what is it?

2. I need two gaskets for one of the coolant lines going to the top of the head, where do I get those (noted in picture)?

3. I need new Exhaust Header Studs, is there any special ones to buy and where do I get them along with the nuts?

4. There is a connector which is frayed, it looks like it only has two wires that go to it, what is it and is it easy to repair or do I need to replace the entire wire assembly?

5. There is a lot of build up on the head in the valve regieon and on the top of the cylinders, what type of cleaning can be done at this stage?

6. What is the best way, chemicals, tools to remove the residual head gasket material from the head?

Thanks, for all of your help, please enjoy the bonus pictures.

[Rodney Nelson]

[Rodney Nelson]

[ae1969]

1. cycling valve - controls boost .... frankly it may be worth it to do a simple upgrade at this point and get rid of it all together. www.gururacing.net ..... Highly recommend their chip set, mbc etc..... For what you will spend on the cycling valve I would upgrade.

2. the coolant gaskets come in all the head gasket kits. Pick one up. Pelican would be my first choice. You will need many little pieces in the set....intake gaskets, camshaft housing seals, exhaust gaskets etc....

3. I bought the studs and nuts at the dealer but I am sure pelican can help you out as well.

4. Thats your knock sensor plug thats frayed. It is a shielded wire. Becarefull. You can clean it up but take your time. The signal that goes to the KLR must be a clean signal.... Make sure none of the shield braid touches the inner wire.

5. In the head gasket kit you get a set of valve stem seals which you should replace. I would pull that head apart and see how the seats are on those valves.....
I use a hard brush on the end of my drill to remove the carbon deposits. Just dont use anything that will gouge the aluminum.....I use brake clean and the blow it all out a few times...

So far so good!

Doing your headgasket is your right of passage into the 944 world.

P.S. and I have passed it more times than I care to mention.

[Rodney Nelson]

Alex,

Thanks for all of your help.

I have heard a lot of good things about guru in this forum, so I will look into that upgrade.

What about the valve stem seals? How do I replace those, I can not find anything at clarks-garage on that.

Thanks,

[helowrench]

If you are having to do the head gasket I would take the head to a machine shop and have them check/surface it for you. While it is there for a nominal fee they will chenge out any studs and the valve guide seals for you. You might consider having a valve job done while you have it all apart. Same machine shop will do that. For a local machine shop look up your nearest NAPA and ask them.
Rob

[SoCal Driver]

Don't trust marking the belts and pulleys with paint. The engine should be set back up on TDC when you put the cam (set up to TDC) back on it and bolt it down.

Is the timing belt new? If not replace it and the balance belt.

[ae1969]

The valve stem seals are in the head gasket kit....

You will need a valve spring compressor to pull the springs off ... You compress the springs, remove the keepers and you are there.

Make sure you note the order of the shims underneath the spring. Keep the springs and valves together for each respective hole.

Check for wear on the valve guides and valve seats. If they are in bad shape.... may as well get them re-done.

The re-surfacing is questionable. Good shops would only need to take a couple thousands of the face...but unfortunately those are few and far in between and the majority can go an shave a hundredth off the face..... If the face is flat and square I wouldnt worry about it...... but its your call. If the shop knows what they are doing you will be left with a great head.

When you pull the valve stem seals off you may find that the stems are smooth. The factory used adhesive on that style so you are better off swapping them for ones with ribbed edges......

Dont forget to check the surface on the camshaft housing side as well.

[Rodney Nelson]

Okay, I took the head to a machine shop today. He is going to call me back with prices on Thursday.

So, atleast that descision is over.

Hugh,

the part that you said, not trusting the white paint. This is the part that scares me the most....when bolting everything back up.

What is the sequence of events? How do I reset the engine back to TDC? I'm confused? Could you please spell it out for me?

Thanks

[Taz's Master]

Whatever Hugh's advice is is what I'd follow, but checking Clark's Garage for his precedure isn't a bad idea. He's done much of the spelling everything out, and has a sequence of events for most procedures.

[Porsche944]

You can find TDC for #1 cylinder by looking through the "window" in the bell housing near the speed and reference sensors.

The flywheel is mark with a line and the letters OT. Align the mark with the "finger" and you are at TDC. Align the timing marks on the cam gear and the gear housing to set the valve timing. The balance shafts have marks in the rear timing belt cover at 1 O'clock for the upper shaft, and at 7 O'Clock for the lower shaft.

[ae1969]

Rodney....

I am sure Socal will chime in soon.

But what you did by marking the belt to the camshaft housing is what I do when I am looking for a short cut as well..... lets just say by doing it this way you can save lots of time...

As I recall from your first pic you had the engine at TDC. Markings on the flywheel matched up with the camshaft housing mark.....and all you did was slip the belt off.
It also looked like you left the balance shaft on as well as I recall....

Well once you put the camshaft housing back on you will be able to slip the belt back on where the marks line up. You tighten the belt and then turn the engine by hand. The belt needs to be 2-3 teeth off before it binds (valve hitting pistons).... but I bet you.... you will be off only one tooth MAX if that....

Your balance shafts will probably be lined up as well.

Turn the camshaft once around and it should line right up. If not, slip the belt off and adjust.

Tension the belt following proper procedure and you are done.

[robm-951]

Does the top of this piston have a smooth bowl dish to it or is the edge of the bowl melted/pitted away from detonation? Or is it just how the picture came out?




Are these marks or pitts in the combustion chamber as well?

I was just wondering since your knock sensor cable is damaged.

Rob

[Rodney Nelson]

Rob,

All of that junk you see is basically just build up. I used everyones advice.

1. I took to head to a machine shop my buddy is good friends with, he machined it, cleaned it, and did a valve job and it was only a $100 and it is the most beautiful thing I have ever seen.

2. I used a wire brush and cleaned up the tops of the pistons, but I found something very disturbing. Underneath all of that build up were indintations where the valves must have hit the tops of the pistons at one time. My valves were fine, so one of the previous owners must have done a valve job at some point. If it was me who hit the valves the indintations would be at the top of all of the build up and my valves would have been bent, right?

I still have more questions about TDC, I know it seems simple but it scares the heck out of me.

I took the belt off and rotated the engine so I could clean off all of the pistons.

So.... do I just simply line up the mark with the finger in the housing at the rear of the engine, line up the gear on the camshaft assembly with the mark at the front and slap it together and that is it?

It has to be more complicated than that isn't it? What about what porsche944 said about the 1 o'clock and 7 o'clock position, what is that?

And finally, do I have to get the $400 tensioner tool for the belts? There has to be a better way to set the tension.

Thanks for all of your help.

[Porsche-O-Phile]

Yes the crud on the pistons is just combustion scaling, probably just hardened carbon build-up, it can be (reasonably) safely removed with judicious use of a wire brush. Just remember to vaccum the cylinder you're brushing before turning the crank and scoring your cylinder walls with the junk you just dislodged.

With regards to the "notches" in the pistons, this is standard. I have seen what look like "valve impact dents" in the pistons on numerous 944 pistions and although it looks like impact marking, it isn't. I think the "dents" are just to give the valves slightly more clearance during normal operation, but maybe SoCal or someone could verify this. In any event, I'm 99% sure that what you're seeing / describing ISN'T piston-versus-valve damage. You could smack a hammer into that piston head and you wouldn't dent it in that way. Even in a busted t-belt situation, you're going to bend the valves, but I seriously doubt there'd be enough impact energy to bend the metal on the top of a piston enough go distort it the way you're describing. The valve gives before the piston head metal ever does.

Find some pics of 944 piston heads and you'll see what I mean. If I can dredge some up from somewhere, I'll post them for you.