cylinder head removed - seeking opinions

[js86944]

I am working on a 1986 951 and seek guidance and knowledge. The problem was already known to be a blown head gasket and so the disassembly began. Everything was going smooth, each bolt bagged and tagged, pictures taken and so on. Unfortunately, when it came to removing the bolts from the water neck and the head, three of them snapped. After using many types of bolt extractors, drill bits and many other methods, it became apparent that this head did not want to come off. It was time to sacrifice the head in order to continue. Here are some pictures of where I stand as of now.


This is what is left of the bolts. What would be the best way to remove them from the block?


Here is another shot.


This is where the head gasket blew, piston #4. I would like more details on how and why it blew on #4.


View from the top. What is the best way to flush all that coolant and oil out? Turkey baster?


Close-up of #3,4. Anything I should be taking a closer look at?


Close-up of #1,2. Is the one on the top the coolant temp sensor and the other one the oil pressure switch?

I need to know what to do next. What should I be inspecting now that the head is off. What is the best way to clean the block surface? Where can I buy new allen head bolts? That's all I have for now, will have more questions later. Thanks.

[Techno Duck]

What did you end up doing to the head to get it off?? Those broken allen head studs do not need to be removed to get the head off. You just need to use a pry bar on the lifting tabs, there is one on the front and back. Just need to break the seal on the headgasket and it will come right off.

Those two broken allen heads are very common due to the threaded holes going right through the water jacket. I liberally soak the area in penetrating oil a night before, then heating the area with a torch (heat the actual block, not the stud). I then use a pair of vice grips to tightly grip the stud and have always gotten them out without too much fuss. I have had the same problems on disassembley and only had half a vice grips jaw length to work with. You can get new bolts from BoltDepot.Com or McMaster.Com . Get cadmium plated if you can (at the very least zinc plated) and liberally use antiseize on them on reassembly.

To flush out the water jacket, i remove the block drain plug which is located inbetween the #3 and #4 cylinders. With the plug removed, i just stick a garden hose nozzle in the water jacket with your broken studs and flush it out.

The left sensor is for the dash board gauge, the right sensor is for the DME temp sensor which triggers the DME to go from open to closed loop.

To clean the block surface you have a few options. Carefully scraping away with a razor blade, brillo pad or 3M makes rotary discs specifically meant for removing gasket material without damaging mating surfaces. I recommend the 3M disc method.. they are expensive, but will save you ALOT of time. I would estimate almost 1/4 of the time i spent doing the headgasket was devoted to cleaning everything.

As for why the gasket blew, there is a theory which i believe has some good merit to it. Basically the cylinder head water jacket is not a great design and can suffer from an air pocket in the back of the head. This pocket of air causes hot spots from boiled over coolant which can deform the gasket. There is a fix called the steam vent, which is basically a fitting tapped into the back of the cylinder head, allowing an exit path for air and coolant back to the expansion tank. I think this is a great modification not only for the likely fix of the air pocket, but it makes bleeding air out of the cooling system incredibly simple. Normally its a major pain in the butt. I feel this is a modification every 944 owner should do if they have the cylinder head off.

Check this page out for detailed info..

http://www.lindseyracing.com/LR/Parts/STEAMVENT.html

Check this thread for some info from when i did the head gasket on my 951..

Phase one of my project - Rennlist Discussion Forums

As for your next step, i would bring the head to a machine shop to have it rebuilt (new valve guides, stem seals, valve job if you choose). Have them check the mating surface for flatness and deck it only if necessary. Also have them hot tank the head and it will come out looking brand new.

[js86944]

Thank you very much for all the answers, it is very helpful. You will most likely become angry and disappointed once you read and see the following.

The inside of one of the allen head bolts stripped and we were able to get that one off with an Irwin bolt-grip, still it broke. The other one snapped the same, just easier.




After many days of PB, and not having any luck, we started to drill and use a bolt extractor. This didn't work as the bolt extractor snapped and it became stuck in the hole we had made. This repeated itself later and it was becoming apparent that the head might need to be sacrificed. A week of failed attempts resulted in the following:



Ashamed as we were and guilty in our approach, we were relieved that the head was finally off and we could continue on.

Having no idea of what, if any, maintenance had been done the car, obstacles were expected but never like this.

A new cylinder head needs to be sought after. We want to purchase a used one and send it off to LR for machining. What should we be looking at when choosing one?

Would you agree that this vehicle never had any serious maintenance done to it? It has 87,xxx miles, old style water pump, very messy under the hood (dead-end hoses, unbolted brackets, harnesses unplugged). It was a running car up until the head gasket went. The PO had some modifications done to it, not sure really what. I plan on taking pictures of some things I am not familiar with under the hood to see if you might help me identify them.

Also, can the following piece be purchased new?


This is the coolant pipe that runs off that water neck. It is very rust and poor in condition.


Here you can see the nasty hiding underneath the hose. Is this a sign of poor maintenance or old age or both? If you have questions about the car let me know.

I will try to post tomorrow with some more information. Thanks.

[Techno Duck]

The coolant pipe is part # 951 106 091 00, im sure you can find a good used one from someone on here or Rennlist.

When shopping for a 951 cylinder head, just make sure the ceramic liners in the exhaust port are in good condition and not cracking. That is a very common issue with them.

If everything was as bad as you say under the intake, i would consider replacing all the rubber vacuum hoses and replacing all the vacuum lines also.

[JoshB]

Wow - wonderful pics. Makes it much easier to get an idea of what is going on.

What you are experiencing IMHO is normal for a 24 year old performance vehicle. I would say that what you are looking at is all original and hasn't been worked on.

That head is still probably usable. I would check and see if the ceramics are still ok. If you get a chance take a pic of the underside of that water passage that you had to cut some. Any aluminum welder could probably patch that up and since it has to only withstand the pressure of the water system it would be fine.

I would no rush getting those studs out of the block. It would be well worth it if you aren't having luck to have the car towed to a mechanic who has more experience with crabby studs.

Jon's (Techno Duck) advice is spot on. I would also replace all the rubber lines. I would inspect the battery cables and engine wiring harness as well. Also your exhaust manifolds are probably cracked - look just inside the inlet flanges.

[js86944]

Originally Posted by JoshB

Wow - wonderful pics. Makes it much easier to get an idea of what is going on.

What you are experiencing IMHO is normal for a 24 year old performance vehicle. I would say that what you are looking at is all original and hasn't been worked on.

That head is still probably usable. I would check and see if the ceramics are still ok. If you get a chance take a pic of the underside of that water passage that you had to cut some. Any aluminum welder could probably patch that up and since it has to only withstand the pressure of the water system it would be fine.

I would no rush getting those studs out of the block. It would be well worth it if you aren't having luck to have the car towed to a mechanic who has more experience with crabby studs.

Jon's (Techno Duck) advice is spot on. I would also replace all the rubber lines. I would inspect the battery cables and engine wiring harness as well. Also your exhaust manifolds are probably cracked - look just inside the inlet flanges.

Thanks for your answers. The head is being sent off to LR where it will be repaired, machined and have a steamvent kit installed per Techno Duck. Hopefully all goes well and a new head will not be needed.

I have some pictures of some things you might help me with.

First, here is a picture of what I mentioned earlier regarding the mess. You can see dead-end lines and a lot of zip ties. I would like opinions on what you see. Is there a factory diagram of what goes where?



Is that a fuel filter in between the top two arrows?

What is this piece?



And this?



Where does this harness plug into?



The one one the left connects to the TB, but the other?

Also, those two studs are OUT after about an hour of working with them. We used a propane torch and heated the block around the studs and used a nice set of vise grips to take them out. Very satisfying to say the least.



I guess I will use this thread as a rebuild thread. Thanks again for the answers and support.

[Techno Duck]

No fuel filter there, its in the back of the car right above the right CV joint. Those two lines were for the cycling valve which was removed on your car. So i am guessing it has a manual boost controller hooked up somewhere. You can actually remove that entire mess of metal pipes and replace it with 1 19mm silicone tube from the top of the oil fill tube (air oil seperator) back to the j-boot. This cleans up alot of the clutter under there. I think i have pictures of that in my build thread.

The 3rd picture is the idle stabalizer valve, not sure what the 2nd picture is.

2nd to last picture is for the airflow meter connector i think, either that or the throttle position sensor on the throttle body.

For sorting out your vacuum lines, Lindsey Racing has a couple of nice diagrams showing the basic layout of everything. Personally if i were working on this engine, i would basically remove everything that was done by the previous owner and whatever is left of the factory stuff. Buy about 30ft of silicone vacuum line and reroute everything as per the diagrams on LR's page.

http://www.lindseyracing.com/LR/Parts/VACDIA.html

[JoshB]

Looks like the PO might have had a electronic boost guage on there?

Like Jon said you need to get the hoses etc to do a venturi delete and manual boost controller. Lindsey's website does have all the diagrams.

You might want to read up on rennlist.com about the steam vent option. I am not knocking it but there are a variety of opinions about it and I don't have it on my car.

Congrats on getting those studs out!

[Techno Duck]

Any links to the threads about the steam vent on RL? I do not remember reading any negative views about it with the exception of possibly the cost and how much you could piece it together for yourself. Seeing the bubbles in the line while reving the engine is enough proof to me that it does work and vent that void in the back of the head. I also have not really needed to even crack the bleeder open to get the air out of the head.. it basically bleeds itself now by pushing all the air back out through the expansion tank.

[JoshB]

Originally Posted by Techno Duck

Any links to the threads about the steam vent on RL? I do not remember reading any negative views about it with the exception of possibly the cost and how much you could piece it together for yourself. Seeing the bubbles in the line while reving the engine is enough proof to me that it does work and vent that void in the back of the head. I also have not really needed to even crack the bleeder open to get the air out of the head.. it basically bleeds itself now by pushing all the air back out through the expansion tank.

Hi Jon,

I just did a quick search but couldn't find anything. I might have just been thinking of the opinion a long time 944 owner had given me a while back. In all the threads I found on Rennlist folks seemed satisfied.

Didn't mean any harm - just wanted to get the OP to use the search function some and perhaps discover a more traveled forum for this model car.

I will say that reguardless of how much I've searched my most valuable lessons (like never buy a used or rebuilt turbo) have come from personal experience

[Techno Duck]

Just curious. I always like to read opinions coming from both sides.

[nize]

the head gasket failing at #4 is common, and can be eliminated with the steam vent mod as already mentioned. lots of info and tips in another thread here. check the link in post#16 for the extensive steam-vent write up;
Head gasket advice needed

i have personally blown the head gasket at #4 several times before the steam vent installation, and i can attest to that it works. i've never blown the head gasket at #4 since after this mod.

for head rebuilding, you may want to search for my thread here on the custom big-valve head. if the ceramic is undamaged, it's possible my machinist can salvage your current head.

[mamica]

Here's a hint an old man thought me about drilling out bolts. Do not use any oil on the drill bit. Instead use vinegar and a slow drill speed. Don't ask me how or why it works,but it does. A grade 8 bolt will drill right out.

[oldass31]

My guess is that that part on the plastic green background is a pressure/vacuum sensor. The shape suggests to me that there is a diaphragm inside.

[Arizona_928]

Originally Posted by JoshB

Like Jon said you need to get the hoses etc to do a venturi delete and manual boost controller.

What's a Venturi delete?