Engine Dilemma
06-13-2021, 04:09 AM
#1
Three Wheelin'
Thread Starter
Engine Dilemma
Hi All,
Hope everyone is well. Have a 4.5 that at some point in the past had 4.7 pistons fitted. Well...the car sat for 25 years with coolant in it. Got one head off, but the other head has fused itself to the block. In an attempt to get it off, I've cracked the block. I still want the pistons. I've got the crank etc out, but obviously can't get the last four pistons out. Any ideas?
Cheers
Scott
Hope everyone is well. Have a 4.5 that at some point in the past had 4.7 pistons fitted. Well...the car sat for 25 years with coolant in it. Got one head off, but the other head has fused itself to the block. In an attempt to get it off, I've cracked the block. I still want the pistons. I've got the crank etc out, but obviously can't get the last four pistons out. Any ideas?
Cheers
Scott
06-13-2021, 09:46 AM
#4
Three Wheelin'
Thread Starter
Fred, the head gasket had been eaten away, all that was left was the alloy rings.
06-13-2021, 09:50 AM
#5
Rennlist Member
Well what a surprise that is!
Any pics of the head to managed to remove?
You could try semtex to get the other one off!
06-13-2021, 10:12 AM
#6
Three Wheelin'
Thread Starter
To late Fred. The block is cracked in multiple places, snapped a piece from the crank girdle and have taken a chunk out of the block as well. Safe to say it's rooted. (Aussie slang for effed).
06-13-2021, 12:13 PM
#7
Rennlist Member
Trending Topics
06-13-2021, 03:41 PM
#8
Former Vendor
If the head is loose, at all, use a Sawsall, between the block and the head to cut the studs which are stuck in the head.
06-13-2021, 06:18 PM
#9
Nordschleife Master
DeWolf, not sure if Aussie slang has that one in it.
It's what we call a reciprocating saw here in the US (some folks spell it with an "S", some with a "Z").
https://www.google.com/search?q=sawz...hrome&ie=UTF-8
06-14-2021, 09:06 AM
#11
Rennlist Member
Scott,
That really is well and truly fubarred!
Looks as though you had the head partially loose and pryed the thing upwards on one side and that caused the block to shear on the other side.
The difficult thing to understand is why the head put up so much resistance to being lifted off- one presumes that you could not undo the head stud in that section that snapped off- is that a reasonable prognosis?.
The corrosion damage is typical of what I have referred to previously but I cannot resolve sufficient detail on the head surface to confirm such but my expectation is that when viewed up close you will find the surface is pitted.
Close inspection of the photo of the head shows in the bottom left hand corner of the image a couple of well illuminated sections of the inner surface of the head and that suggests the inner surfaces of the head are in perfect condition. Similarly the cylinder external walls also look to be in excellent condition with some deposition but no obvious corrosion and that tells us that the original coolant fill was not the problem.
Unfortunately the gasket not only seals the cylinders and the external coolant passage ways, stud chambers and cam tower drains, it also has to block off many of the open transfer passages where coolant flow is not required. For the latter there is no counter compression on the block side of the gasket and thus there is nothing to stop coolant migrating into the "crevice" that is formed. This may seem harmless enough but that is far from the case. The coolant that is trapped is stagnant and over time the coolant loses its ability to protect, the glycol/water mix in there goes acidic and that then creates a situation wherein there is an electrolyte [the coolant] outside the crevice and a different electrolyte is formed inside the crevice and at some point electrons start flowing and a chronic form of corrosion sets in. The corrosion pits formed are the indisputable evidence of what is happening and that is known as a "crevice corrosion" attack. That in essence is the "what" as in "what happens". The "why" it happens is what i have been trying to resolve and the common perception that it is the "wrong coolant" or "ransid aged coolant" are quite understandable but in the cases I have seen they are false perceptions. I reckon that engines that are used regularly generally do not experience such problems but even that is not a complete explanation. I suspect that the heating and cooling down cycles allow the trapped coolant to be replenished through the process of diffusion.
The acids formed in this process also appear to attack the gasket binder material. The fibrous material [aramid fibre] is totally inert but the rubber binder material is attacked and then the acids permeate the body of the gasket that is a two sheet construction that is pressed together onto a barbed galvanised steel mesh - the acids eat through the galvanised coating and then attack the underling steel to form ferric oxide and that is why one sees the orange staining in your photo.
What I suspect has happened in your case is that the attack has breached the seal formed around the stud orifice and the evil brew has then entered the "normally dry" head stud chamber and attacked the steel to threaded block interface and in effect has "welded" the steel stud to the block thus why you might not have been able to remove it.
Bad as the corrosion is I see no evidence that the heads have in effect been welded to the block per se but needless to say I only have limited visual evidence of what has happened.
Trust the above analysis is of interest even though it is of little practical use to you.
That really is well and truly fubarred!
Looks as though you had the head partially loose and pryed the thing upwards on one side and that caused the block to shear on the other side.
The difficult thing to understand is why the head put up so much resistance to being lifted off- one presumes that you could not undo the head stud in that section that snapped off- is that a reasonable prognosis?.
The corrosion damage is typical of what I have referred to previously but I cannot resolve sufficient detail on the head surface to confirm such but my expectation is that when viewed up close you will find the surface is pitted.
Close inspection of the photo of the head shows in the bottom left hand corner of the image a couple of well illuminated sections of the inner surface of the head and that suggests the inner surfaces of the head are in perfect condition. Similarly the cylinder external walls also look to be in excellent condition with some deposition but no obvious corrosion and that tells us that the original coolant fill was not the problem.
Unfortunately the gasket not only seals the cylinders and the external coolant passage ways, stud chambers and cam tower drains, it also has to block off many of the open transfer passages where coolant flow is not required. For the latter there is no counter compression on the block side of the gasket and thus there is nothing to stop coolant migrating into the "crevice" that is formed. This may seem harmless enough but that is far from the case. The coolant that is trapped is stagnant and over time the coolant loses its ability to protect, the glycol/water mix in there goes acidic and that then creates a situation wherein there is an electrolyte [the coolant] outside the crevice and a different electrolyte is formed inside the crevice and at some point electrons start flowing and a chronic form of corrosion sets in. The corrosion pits formed are the indisputable evidence of what is happening and that is known as a "crevice corrosion" attack. That in essence is the "what" as in "what happens". The "why" it happens is what i have been trying to resolve and the common perception that it is the "wrong coolant" or "ransid aged coolant" are quite understandable but in the cases I have seen they are false perceptions. I reckon that engines that are used regularly generally do not experience such problems but even that is not a complete explanation. I suspect that the heating and cooling down cycles allow the trapped coolant to be replenished through the process of diffusion.
The acids formed in this process also appear to attack the gasket binder material. The fibrous material [aramid fibre] is totally inert but the rubber binder material is attacked and then the acids permeate the body of the gasket that is a two sheet construction that is pressed together onto a barbed galvanised steel mesh - the acids eat through the galvanised coating and then attack the underling steel to form ferric oxide and that is why one sees the orange staining in your photo.
What I suspect has happened in your case is that the attack has breached the seal formed around the stud orifice and the evil brew has then entered the "normally dry" head stud chamber and attacked the steel to threaded block interface and in effect has "welded" the steel stud to the block thus why you might not have been able to remove it.
Bad as the corrosion is I see no evidence that the heads have in effect been welded to the block per se but needless to say I only have limited visual evidence of what has happened.
Trust the above analysis is of interest even though it is of little practical use to you.
06-14-2021, 05:07 PM
#12
Former Vendor
Once the head gaskets deteriorate to the point where coolant can travel up the hole in the head where the studs pass through, the aluminum and steel will corrode and "fuse" together.
I predict that this is going to be more of the "normal" and less of the "uncommon", as the years of coolant neglect pass.
06-15-2021, 12:12 AM
#13
Three Wheelin'
Thread Starter
Greg,
Had a friend fab up a steel plate to try and use the studs to force the head off. It ended up stripping the bolts out of the cam cover threads. I'll got a 4.5 lined up already. Can I turn a 4.5 bottom end into a 4.7. have the 4.7 crank, rods and pistons now.
Fred,
Yes to the mix getting into the stud holes. I couldn't get the studs loose either. Tried heating them till they glowed. Smacking the crap out them with a small sledgehammer. Sadly, one less 928 motor on earth now.
Had a friend fab up a steel plate to try and use the studs to force the head off. It ended up stripping the bolts out of the cam cover threads. I'll got a 4.5 lined up already. Can I turn a 4.5 bottom end into a 4.7. have the 4.7 crank, rods and pistons now.
Fred,
Yes to the mix getting into the stud holes. I couldn't get the studs loose either. Tried heating them till they glowed. Smacking the crap out them with a small sledgehammer. Sadly, one less 928 motor on earth now.
06-15-2021, 07:58 AM
#14
Rennlist Member
If I was going to leave my engine idle for a long time I would drain down the coolant from the block - not 100% sure it would stop this kind of problem but at least it might have a chance of doing so. The problem is defining what constitutes "a long time". I am thinking a couple of months but...?
Ethylene glycol and water is a horrible combination that presents corrosion challenges that I suspect were never envisaged. I recently did a google search using the criteria "Corvette head corrosion" and the first result led me to a forum like ours having seemingly identical issues and they had no clue as to the real cause of their problems other than the "wrong coolant type" or "ransid coolant" type of memes.
This corrosion problem is a real serious concern and if I were you I would look seriously into using the Liquid intelligence coolant that Mike [RAMCRAM] is proposing to use in his awesome build. Besides being indigenous to you chaps down under in theory at least it should ensure this type of corrosion problem is avoided never mind the other benefits it claims to provide. Cheap it is not but then if it prevents corrosion damage and strip down/rebuild costs then it should be well worth the incremental cost on that benefit alone. On a new build it really does appear to be a no brainer. The only reservations i had were with respect to its heat pick up capacity and pump-ability but if they really have broken down the boundary layer with whatever surfactants they use in the brew to do so then it is something that our community should seriously consider. If I could get the stuff over here I would seriously consider using it just for peace of mind regarding corrosion. Converting to the stuff might be tricky as getting every last drop of conventional coolant out without a heads off strip down will be difficult.