Head gasket or more?

[Joe L.]

Re: Head gasket or more?

I decided not to start the car before driving to the garage. However, I pressurized the coolant system to 14-15psi and took more pictures. Based from the attached picture I would guess it is the gasket because there are no coolant drops above the separating line between block and head.

Oliver

[ATTACH=CONFIG]99206[/ATTACH]

Oliver------


Have you checked the intake manifold bolt torque?

[Oliver S.]

Re: Head gasket or more?

I missed it ... I’ll check.



Oliver

[Oliver S.]

Re: Head gasket or more?

I brought the Corvette to my garage. Today I have received a call in which I have been told that there is neither an intake manifold nor a head gasket issue after removing the parts. From pure visual inspection nothing is to be seen as the cause of the leakage.

Based on what I have described ... is there a crack pattern on 327 blocks that shows these symptoms described or do they rather point to a head crack - the head has hardened valve seats? Can a mix of antifreeze/water cause corrossion on the cylinder wall - according to the shop there are traces of coolant visible on the cylinder wall when it accumulated during storage and cause increased oil consumption?



Oliver

[Joe L.]

Re: Head gasket or more?

I brought the Corvette to my garage. Today I have received a call in which I have been told that there is neither an intake manifold nor a head gasket issue after removing the parts. From pure visual inspection nothing is to be seen as the cause of the leakage.

Based on what I have described ... is there a crack pattern on 327 blocks that shows these symptoms described or do they rather point to a head crack - the head has hardened valve seats? Can a mix of antifreeze/water cause corrossion on the cylinder wall - according to the shop there are traces of coolant visible on the cylinder wall when it accumulated during storage and cause increased oil consumption?



Oliver

Oliver------


If there is visible coolant on the cylinder walls that has to be occurring during the period when the engine is not operating. It could not be a case of the coolant being deposited while the engine is running and observed immediately after shut down.

When you say that the shop has determined it's not an intake manifold or cylinder head gasket leak "after removing parts", do you mean that they have removed the intake manifold and cylinder heads to make this determination? Even if they have, some leak paths can be subtle and not easily discerned by inspection of the gaskets.

Also, are you asking if the engine has had hardened exhaust valve seats installed or are you saying they have been installed and could they be the source of the problem? Of course, no one on this board could answer the question as to whether or not these inserts have been installed. If the heads are off, though, it's easily discerned. If they have been installed, could they be a source of the leak? Absolutely, yes. Improperly installed they could easily be a source of a leak and improperly installed they could be the root cause of a crack in the cylinder head which could also be responsible for a leak.

Can coolant leakage into the cylinder cause cylinder wall cause corrosion during extended periods of non-operation? Absolutely yes. Can this result in higher oil consumption? Eventually, yes.

[Oliver S.]

Re: Head gasket or more?

I was at the garage. The cylinder wall is smooth without any palpable imperfections. So the discolored areas are just visual. After removing the valves the only visible, potential cause (at the moment) is the area indicated by the red arrows. Is this area prone to crack? I will do a non-destructive/penetration test, which can be done with 3 different spray (cleaner, penetrator, developer). In parallel I will look for a machine shop that can pressure test the head.

Oliver

BTW: I was told by the previous owner that the head has got hardened valve seats, which is not the case as it turned out.

[Patrick B.]

[Joe L.]

Re: Head gasket or more?

Isn’t that a hardened valve seat that the red arrows are pointing to? The appearance of a crack may be the meeting line of the valve seat insert and the cast iron of the head.

Patrick------


I don't think so. At least, I've never seen a valve seat insert that wide. Plus, this looks like an intake valve position. Hardened inserts are usually only installed on the exhaust valve positions.

[Owen L.]

Re: Head gasket or more?

I will do a non-destructive/penetration test, which can be done with 3 different spray (cleaner, penetrator, developer). In parallel I will look for a machine shop that can pressure test the head.

Agreed. I think a pressure test and magnaflux is the next step to eliminate a cracked head. Visual inspections only indicate major failure and what you seem to have is a long-term issue without a catastrophic symptom.

[Oliver S.]

Re: Head gasket or more?

Fortunately, I found a shop specialized in cylinder head work close to where I live. The head is already there and will be pressure tested on Monday. If the head doesn’t have a crack it will be resurfaced. The guy there pointed to some areas where the visible imprint patterns of the removed head gasket weren’t to his satisfaction. My current plan is to install either the resurfaced head or a remanufactured one. If it was not a cracked head, my hope is that it might have been a very minor issue with the head gasket in conjunction with suboptimal surface of the head. The symptoms - i.e. only few water (mainly small coolant drops on the wall acummulating in the piston pockets) in the cylinder, loss barely noticeable in the expansion tank, engine runs perfectly, starts perfectly after longer time - seem to be uncommon in GM V8s as far as I have read - I found nothing similar in the Internet. The owner of the garage with long time experience in US cars was also surprised.

Oliver

[Oliver S.]

Re: Head gasket or more?

Today I have received the call from the shop that did the pressure test: the head has got a tiny hole explaning the minimal water in the cylinder #6. I will replace both heads since the traces left by the valves in the seats might point to a suboptimal valve job done during the last engine overhaul.

Oliver

[Joe L.]

Re: Head gasket or more?

Today I have received the call from the shop that did the pressure test: the head has got a tiny hole explaning the minimal water in the cylinder #6. I will replace both heads since the traces left by the valves in the seats might point to a suboptimal valve job done during the last engine overhaul.

Oliver

Oliver------

One problem: you currently have a set of used heads. If you buy another set, they will be used heads, too. In addition, if you are to buy heads of the original configuration, they will be very well used heads, 50+ years old. Sure, you can have them checked just like you did the heads you have. But, if what you are saying is that you think the heads you have suffer from some problems that are indiscernible, how ill you know that any heads you buy don't have the same or other indiscernible problems?

[Oliver S.]

Re: Head gasket or more?

Joe,

I aware of this problem. My plan is to order and install two of those:

https://www.rockauto.com/en/moreinfo.php?pk=3754008&jsn=3

I considered buying alu heads with similar visual appearance. However, they have 2.02 intake valves and mine have 1.94.

https://www.ebay.com/itm/Aluminum-GM-3782461-Chevy-327-SBC-Camel-Back-Double-Hump-Cylinder-Head-Assembled/133375642692?hash=item1f0dcecc44:g:WZAAAOSw59heg5hr

Using 2.02 instead of 1.94 on a 300hp is apparently not optimal as I’ve read here ... and recall correctly.

Furthermore I don’t know if they are good. Ideal would be perhaps a set of unused NOS heads ready to bolt on. However, I’m open for suggestions. So what would you do?

Oliver

[Joe L.]

Re: Head gasket or more?

Joe,

I aware of this problem. My plan is to order and install two of those:

https://www.rockauto.com/en/moreinfo.php?pk=3754008&jsn=3

I considered buying alu heads with similar visual appearance. However, they have 2.02 intake valves and mine have 1.94.

https://www.ebay.com/itm/Aluminum-GM-3782461-Chevy-327-SBC-Camel-Back-Double-Hump-Cylinder-Head-Assembled/133375642692?hash=item1f0dcecc44:g:WZAAAOSw59heg5hr

Using 2.02 instead of 1.94 on a 300hp is apparently not optimal as I’ve read here ... and recall correctly.

Furthermore I don’t know if they are good. Ideal would be perhaps a set of unused NOS heads ready to bolt on. However, I’m open for suggestions. So what would you do?

Oliver

Oliver------

If it were me and I had an engine with original heads that I wanted to keep original, I'd have a good machinist disassemble the heads and carefully inspect the valve seats for problems. If there is excessive recession (e.g too many previous valve jobs) or wear of the valve seats, the only solution is the installation of valve seat inserts. This can be problematic but can be successfully done on 1.94/1.50 valve heads. Otherwise the heads are scrap metal. However, if the valve seats are OK, a 3 angle valve job can be performed. I'd also install new valves.

As far as the leak in one head is concerned, it depends what it is. You mention a "pin hole". If so, that can usually be easily repaired by the installation of a tapered, threaded plug.

[Oliver S.]

Re: Head gasket or more?

Joe,

I meant that the hole is small. Based on that I assumed the head is scrap ... the guy didn’t mention any repair option despite doing (all possible) head-related jobs for a living. To be sure I call him again.

Oliver

[Joe L.]

Re: Head gasket or more?

Joe,

I meant that the hole is small. Based on that I assumed the head is scrap ... the guy didn’t mention any repair option despite doing (all possible) head-related jobs for a living. To be sure I call him again.

Oliver

Oliver------


I'd like to see a photo of the hole.