mulik51

Hey. I am changing a block on my 1979 928 5speed from M28.03 to M28.20. Right now, I came to the head removal (it might look a little bit slow, but I take each pulley, bracket off, clean it, and paint it.). So, Here are the questions:
1) The new block which I got has some minor carbon build-up(around 1-2 mm thick maybe) on the pistons. First, I wanted to get it off, then I talked to some folks, and discovered that it will be nearly impossible to get all the debri out of the cylinder, and scratching of the walls will be inevitable.Plus, it is OK to have a carbon buildup, and shops do not remove it on regular basis. But, on the other hand it came all the way from Ca to NJ, a lot of moving and vibrations, so I am afraid that it might be allready loose. So, the question is what is the best cleaning procedure on this kind of project?(I DO not have compressed air, but can get 12A vacuum cleaner).
2)Is there a a need, and then a safe way to clean the water jackets?
3)When I will remove the heads, I don't want to disassemble them. Can I clean the carbon build up on them with the valves installed?
4)In WSM it says that it is very important that the washers on the head bolts don't move as you tighten the nuts. The advise to regrind them if they move. So, can I reuse my old washers, or I will need to grind them with sand paper? WHy is it important so that they don't move?
5)In WSM, they also state that it is very important not to have any oil on the nuts and washers, but stud threads MUST be given light coat of motor oil. Why? Is that necessery and very important?
6)Can I reuse the rubber plugs on the cam housing?
7)If there are any special precations of which you are aware, please tell me, becouse this is my first project like this, and I don't have the correct mechanical education. For example, what if there will be coat of oil between the head gasket and cylinder "sleeve"? It might look funny to somebody, but I don't have this info.
This life and death question for me and my shark, so, please be resonsible
Thanks a lot in advance, I had always gotten a great help on this forum, and hope for it again,

Klim

P.S. What size will I get for my own web space on Rennlist? Becouse I planning to create 928 society usefull website, but I need a lot of space.(I plan to put the WSM out. I have them on my PC, and I think it will be very helpfull. More, I take notes and make pictures of each action on dissassemliing and asemliing of the engine, which I will edit and post). Any advices on where I can get the right webspace?

BC

So did this car come from, say, Oceanside, CA or thereabouts? I can't quite see the interior.

Dennis Wilson

Mechanical or chemical cleaning of the carbon on the pistons would be wise. I would rather risk a small particle left from cleaning than a large chunk of carbon dislodged during the head replacement. Just make sure you clean/flush the ring gap with something like carb or brake cleaner. Also, seal off the water jackets so the residue from the pistons won't fall into them.

If the washer moves during torquing of the head bolts,the readings (torque) will be incorrect and risk over tightening. Use rough sandpaper. The light coating of oil on the threads is to insure the friction is measured at the top of the washer instead of at a carboned thread.

The water jackets are probably clean except for mineral desposits unless it was run with a leaking head gasket. Recommend a cooling system flush be used after you get the engine back together.

The rubber plugs could be reused if they are still flexible and have no cracks/nicks.

If you have carbon on the face and inlet side of the valves this should be cleaned by a machine shop when you have the head resurfaced. BTW both the block and cam cover sides of the head should be resurfaced prior to reassembly.

Dennis

mulik51

Dennis, thanks a lot for a very helpfull info. Is it absolutely necessary to resurface the block and the head surfaces? Where is it done? How much can it come to?
Brendan, no, the car came from Miami FL. The new block came from CA, bay area. The interior is all brown leather.
Thanks a lot,

Klim

GlenL

1) I'd vacuum out the cylinders. Then squirt with oil, crank the engine around and vacuum again and wipe dry. Might chip off a few loose flakes. Don't get crazy as the engines run with that stuff in there.

2) Not really and not with the crank and pistons in. The typical way is to hot tank the block. I'm sure some folks drench ith brake cleaner or whatnot.

3) Sure. Might leave a few grains. Check them when tey're off.

Editorial: The heads are key to success on the project. Can cost $$$ but taking them in for a head job is worth it. This includes inspection, dis-/re-assembly, cleaning, a nice surface cut, seat and valve grinding and any mechanical replacements like valve guides or valves. Might run $400 to $1000.

4) I guess this is because the torque specs include friction between the nut and washer and not washer to head. Sand the washers and put them back. If they look squished then get new ones.

5) THis is the torque spec again. They want dry friction in some places and oiled in others. Use some oil on a rag to coat the studs.

Editorial 2: Re-torqueing the heads every day or two will get a better seal. Back of the nut 1/8 turn and then got back to the torque.

Editorial 3: In the manauls you'll find the torue method and the angle method. This is like religion. I like to re-torque and that works with the three-torque method best.

6) Yes, but I expect you'll mangle a few removing them.

7) The most important thing is to have the head and block as close to perfectly clean as possible. Get some Scotch-Brite pads (black or green) and lacquer thinner and get at it. I'll use razor blades and brushes but remember that the aluminum block is really soft compared to steel tools. Oil on the cylinder bore tops is waaay past acceptable. Dry, clean and shiney will get a good seal.

Search, read, study and give yourself enough time. Track where each part comes off. I use paper egg cartons, baggies and coffee cans to group the parts. Pre-order what you plan to replace and after dis-assembly order the other parts you need.

Dennis Wilson

Klim,

Check the tolerances in the WSM for head flatness. IIRC anything more than .002" out requires resurfacing. I've had heads resurfaced for about $50 per head but that didn't include the cam carrier (top) edge. If you skimp on this step, you run a large risk of blowing a new head gasket or blowing oil between the head and cam tower. Also, check the backs of your valves. If you have any oil buildup it indicates your valve guides/seals are leaking.

Dennis

GregBBRD

The replacement gasket that go between the cam carrier and the head (the ones with the graphite sprayed on each end for about 3 inches.....they have a 944 part number, now) can cause significant problems. They have a tendency to slip around. I don't have a clue why they decided to add this "coating" to the gaskets.....does anyone out there know?

Anyway, make sure you don't over torque the bolts that hold the cam carrier on...this makes the gaskets slip and split. It is also a disaster to use any type of sealant on this gasket. It needs to be clean and dry.

mulik51

Glen: Thanks a lot for thorough response. My heads supposedly have 15000 miles on them. When I look down the intake hole at the valve, it looks clean. You probably remember that I got coolant in the oil. So, I decided that it was a bad block(actually, now I see some leaks on the side of block under the heads, probably the head gasket, I will check later). So, that's why I am changing the block with 15000 miles on it. About torqueing the head: I heard that it is a good practice to leave at least 30min between the steps they talk about is WSM. THen on the next day, loosen the nuts 1/4 turn and retorque them to specs.(4th step) Is that right? And, if I understand you right, you advise me to do the same thing(...loosen the nuts 1/4 turn and retorque to specs.) couple more times with about 24hour period in between. Is that right?About the clean surfaces: first, what is consdered clean, when it is shiny and with nothing on it(oil, water, etc). Second, about the block, I should not do any meachanical cleanng to the cylinder "sleeves" I assume. Is that right? BTW, thanks for the advice on tracking the parts. I allready was doing it. Got a bunch of ZipLocks, and boxes. So, in Zipcks I put nuts, bolts, washers, and write where did they come from. Parts which I remove, I clean, and paint(if I think it will look better), and then put in large boxes, writing on the boxes what parts it contains. To know how everything was assebled, becouse on each step I have a "diary" and take a picture with my phone. This serves two purposes, first I will edit and post it, second I won't forget how everything was in the first place.
Dennis: Strange. Becouse I have Chilton's book also(with WSMs), and it has rebuilding procedure, and head reconditioning procedure. So, it only notes about resurfacing of the heads and/or the block if there is warpage which is out of limits(for heads they say it is .006in on overall length). So, I will check that. If that will be within the limits, will the head still be neede for resurface? Thanks.
Greg: Thanks for the response. I will keep that in mind. I used the sealant on the valve cover gasket on my Bronco II, and didn't know that couldn't use it here.

Thanks a lot to all, your help is really appreciated,

Klim

GlenL

Klim,

Sounds like similar advice you've gotten on head re-torqueing. Doing it over a few days just gives more time for the gasket to fully crush. It's always surprising to see how much more the nuts turn when doing it the second time. Then less on the third, less on the fourth. I use 1/8th back-turn (45deg) as that doesn't un-load the gasket as much. Stick with the sequence pattern for the bolts.

For heads to be clean it's got to be shiny. No crud and no oxydation. The Al will start to get grey if it sits for a week or more but a quick once-over will clean that up. There may be pits that are into the surface. Get those as good as possible. It they a really bad it needs to be machined. I have used a tiny dab of gasket sealer just on the pits around water passages but that is not acceptable around the cylinders themselves. Better using nothing there.

Some people will use the "paste" on the bores to etch the Al a bit but you don't have to do this. Absolutely no stone honing like on iron block engines. Sounds like you're leaving the pistons in the block anyways. Just wipe the walls with an oily rag so they're dampened. I'll give a tiny (1/4 tsp) squirt on the piston rings as well.

Sounds like you're more organized than I am. Lots of similar looking bolts and nuts on the engine. Also helps to not forget a bolt. For the water pump I draw the pump outline on a piece of cardboard and then make holes where the bolts are. Then stick the bolts into the holes.

I like doing a head resurfacing because it's an easy way to get them perfectly clean. Not too expensive either in 928 terms. Takes out any warp as well.

mulik51

Ok. Thanks a lot, becouse now I think I have an idea what I am going to do.
First, I am going to vacuum the pistons and water jackets. Then, I am going to spray some carb cleanning or brake cleaning fluid on the pistons, and on the block surface(I think brake cleaning fluid might work well, becouse it is under big compression to blow the dust off. I think this might be helpfull to get the debri off out of cylinders). Then I will vacuum the block again. Then I will squirt a little bit of oil in cylinders(what if I put oil on my finger a "massage" it in the cylinder wall?). Then, I will bring engine to TDC on the 1st piston. That's it for the block. Absolutely no mechanical cleaning of the pistons or surface. Any suggestions? As for the heads, I will remove them. Then I will try to clean the carbon buildup(not removing the valves). Can I use wire brush for this? Then I will clean the surface of the head with carb and brake cleaner and a rag. Then I will check for warpage. If it is withing the boundaries, I have two ways. I have a friend, he owns Mobil gas stations, and says that they rebuild the engines there all the time. If they will be able to perform the head recurfacing for less then 50$, I will go for it. (Is it hard procedure? I mean, should I get some Porsche mechanic to do this, or any qualified mechanic can do this?) Then I will grind the washers. Then I will put light coat of oil on the threads of the studs. Then I will install the heads on the block, as noted in previous posts( I will use 1/8 turn back). Any suggestions?

Thanks a lot,

Klim
P.S. Very cool idea about the water pump bolts! If I won't change the pump and the bolts, I will definitly use it.

GlenL

Sounds like a plan.

On the head surfacing, they'll most likely want to disassemble the head. This allows them to get all of the chips and flakes out afterwards. The cash factor starts going up quick. Definately a good place to spend the $$, though.

checkmate1996

Keep up the good posts...I'm right around the corner of doing the same thing!

Dennis Wilson

Klim,

Step number one on your rebuild should be to throw the Chiltons in the trash or sell it to a 924 guy. Use the WSM only. When and if you have the heads machined, take a copy of the head specs to the shop and have it checked for deck height. If the square indicators are at the limit (20mm?) you have yourself an interference engine.

Dennis

mulik51

Thanks. If I ordered the full engine gasket set, what more I will need if I will want to disassemble the head and then assemble it back? What procedures will I need to go through.(I mean, will I be able to get the head off, disassemble it, put parts in the bags, and then put everything back together?)
Chilton's helps sometimes to clarify. As a primary source, WSm rules ofcourse, but Chiltons has some information for less educated people.

Klim

Dennis Wilson

Klim,

Buy the full gasket set. I learned first hand that buying the individual gaskets cost about 50% more than buying the set. Why are you going to disassemble the head? Do you have the micrometers, dial indicators, valve seat tool, etc needed to properly check it and reseat the valves? A home mechanic can change the valve seals but that may be for naught if the valve guides are worn beyond tolerances. The shop I use will tear down, inspect, clean, surface and reassemble the head for the price of resurfacing. It's doubful he would even work on a head that has previously been disassembled.

Dennis