Blown headgasket - Printable Version

Blown headgasket - Printable Version

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Blown headgasket - Cloud9...68 - 06-25-2012

I'm sure doing a cam R & R without the cam blocks is perfectly fine, but I was shocked at the amount of stress the cams are under during the process (at least it looked that way to me). 99% of the time, it's probably OK to go without them. It's the 1% thing that worries me. But I guess you could argue that if a cam snaps during install, it was probably weak anyway. A darwinian thing, I suppose...

Blown headgasket - tamathumper - 06-25-2012

I've seen someone's post using cam blocks made of maple? I believe on another site, though.

Blown headgasket - Nosferatu - 06-25-2012

I done my head without the cam blocks. It is easy to remove and install as long you're patient. Just undo the bolts slowly like a quarter of a turn each one at the time. What the blocks allow you to do is undo the bolts at once without care for the cam carriers to bind.

As for redo the head as long you don't have a bent valve or extremely excessive play between the valve stem and the guide you can do it at home. Remove the head from the car and disassemble it marking all the pieces. You can use a bit of valve grinding compound on each valve along with a simple valve lapping tool. Clean and reassemble. It will not be 100% but it will be extremely close to 100% and way better than what you've now. I'm sure you're not going to race the car and loose 1HP will not make you loose any sleep.

To disassemble the valves you can use a socket and a rubber mallet. To put it back together I used a rented tools from Autozone. Since there is no such thing in Chile my suggestion is for you to build a tool using either wood or steel. If you look at the design of the Porsche valve compression tool you will see that isn't too complicated to make something that will work in the same way.

Chances are there is some corrosion on the head surface. Don't bother to do anything unless it is on the firing area. In this case you will need to take the head to the machine shop. Mine was fine and all I did was clean, replace the gasket and bolt it all back together. I will try to post the picture somewhere.

Blown headgasket - Nosferatu - 06-25-2012

Here are the pictures of the head. I may have some pictures from the disassembly, if I find I will upload to the same album http://gallery.me.com/piresz#100174

Blown headgasket - flash - 06-26-2012

wow - pretty ugly

Blown headgasket - tamathumper - 06-26-2012

And in the eventuality that something is wrong with the block, and someone suggests machining or boring it, bear in mind it cannot be machined like a "normal" cylinder as the bores are impregnated with silicon and special etching processes are required to properly repair or resurface them.

Blown headgasket - mbardeen - 06-26-2012

Thanks Tama, I was aware of theAusil coating. The machine shop that I was recommended does work on 911s and other high end sports cars. I'm assuming (maybe wrongly) that they'd know about the issues associated with working the material.

I'm praying that nothing's wrong with the block. I can't afford to shell out the cash for a new one any time soon.

Blown headgasket - mbardeen - 06-30-2012

Yesterday I did the bypass for the throttle body, changed out the fan switch, then refilled & bled the cooling system. I ran it (with white smoke pouring out the tailpipe) until the fans turned on, then let it sit. By the time the I turned it off, the white smoke had stopped. I let it sit for a half hour, then checked the coolant/water level. It was low (below cooling tank level) I topped it up and restarted the car. White smoke again...

I guess I've exhausted all other possibilities and am left with the original diagnosis of coolant in the cylinder.

I've decided that I will pull the engine and do everything that's needed at once. My 20 minutes of driving last week will have to tide me over for the next year or two, while I gather the tools and parts, build the garage, and do the work.

Blown headgasket - flash - 06-30-2012

ugh. i sympathize. $20k later, i am almost done.

Blown headgasket - mbardeen - 06-30-2012

What should I do about coolant in the short term? I'm using plain tap water for testing purposes, but that doesn't set well with me for storage. I plan on keeping it semi-mobile, so I don't want to drain the water entirely.

I was thinking something like 3/4 distilled water, 1/4 antifreeze. Would that be enough antifreeze to protect against corrosion? I don't really want to use that much expensive antifreeze, knowing that it's just going to be lost one way or another.

Blown headgasket - flash - 06-30-2012

do NOT run the engine. if water or coolant gets into the oil, you can foul a bearing and have worse problems than you have now, not ot mention the mess it will make inside the engine that will make the work that much harder.

it takes very little anti-freeze to protect against corrosion. your ratio sounds fine.

Blown headgasket - Lear35A - 06-30-2012

My white smoke turned out to be a cracked cylinder wall. I hope yours is just a blown head gasket. Been messing with mine over 2 years, and I stopped counting the cost. OTOH I really know the inside of a 968 engine now. I can time cams in my sleep. Have fun and good luck.

Blown headgasket - mbardeen - 06-30-2012

That's my greatest fear, Lance. I'd probably just opt for grabbing a used engine from the US and shipping it in that case. It'd be easier & probably a little bit less cost. A cracked head would be the same scenario. Auto Atlanta has new heads for $2500. DC Auto used for $1000. Or maybe I can find one from a part out.. My last option would be a repair.

So yeah, I'm hoping for the best. But I'm preparing myself for the worst. It's a long term project (my mantra now), so I can take my time and think about what I want to do and how I want to do it.

Blown headgasket - RS Barn - 07-03-2012

I've seen quite a few cams ruined without cam blocks-and the right instructions. There is an inherent problem with removing the cams. Let me see if the DIY guys can advise you how to not damage your cams.

This is a test-come on guys-you're on the clock...

Blown headgasket - Lear35A - 07-03-2012

Over the past couple of years I have had my cams off and on at least 5 times. At first, I didn't know any better; now, I don't see the big deal.

All I do to remove the cams is slowly and incrementally undo the bearing caps. If one of the cams gets hung up in the lower bearing half, a light tap with plastic hammer frees it up. After the cams are free of their bearings I undo the fasteners holding the variocam in place and lift the whole assembly off the head. To put them back in, first I get the variocam in place and bolted in with the cams sitting up in place. I put the bearing caps on and slowly/incrementally tighten them down. This draws the cams into their proper place. You're working against some, but not all, of the valve springs. Frankly it does not seem like that much pressure. I have looked closely (magnifying glass) at the bearing surfaces in the head and the cams every time. I see no evidence of any problems.

I would like to know what damage others have seen by doing it this way.

Edit: By the way, I would like nothing better than to have the long and expensive list of Porsche tools at my disposal to assemble this engine. On the other hand my experience shows me that many of them are just a convenience or a little bit of a time saver or something that would be useful for OEM mass production of the engine. Whether or not the cam tools are a nice to have or a necessity is the question here. I have done fine without them.

Blown headgasket - Nosferatu - 07-03-2012

This is exactly what I did recently and no issues whatsoever. Just do 1/4 to 1/2 a turn at time and you will be ok.

Blown headgasket - RS Barn - 07-03-2012

It's very easy to have the #1 intake cam bind while removing, cracking the flange on front of cam. When people send them to me to repair sprockets there is a high incidence of this. The cam blocks are just as important when installing cams back in. The preload of tensioner pulls the cams together preventing correct alignment. The cam block allows the cams to be drawn down evenly from a higher position than cam caps allow.

It is nice to have the factory tools...

Blown headgasket - mbardeen - 07-03-2012

I've been chatting with the wife, and have negotiated the use one of our spare rooms as a place to store/work on the engine. However, there's a catch -- namely 40 meters of gravel, uneven paving stones, and a 10cm step that I'll need to traverse with the engine.

So, the $64K question.. how heavy is the engine block? I can remove all the unnecessary bits prior to transportation and enlist the help of some burley friends, but I'd like to know how feasible it is first.

Blown headgasket - tamathumper - 07-03-2012

Is this the magical tool? It doesn't look that hard to make...

[Image: camshaft_bridge.png]

Blown headgasket - mbardeen - 07-03-2012

[quote name='RS Barn' timestamp='1341332933' post='128877']

It is nice to have the factory tools...

[/quote]

Checking out possibilities, it seems 928 Specialists list the blocks for $180. Then you still need the tensioning bolts (which seem to be only part of a $550 kit). In lieu of buying these, does anyone have a set that they'd be willing to loan for a few months? Or maybe provide the basic measurements so I can get one made up?