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| Head gasket blown | Rate Topic |
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| Posted: 01-16-2025 09:01 pm |
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1st Post |
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stewart.wigg@gmail.com Member
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Hi, Attached is a photo of the head gasket that I recently dismantled. Engine overheating caused the head gasket to fail. I’ve not seen a blown head gasket before on an engine with liners, so I’m not sure what to expect, but this doesn’t look good! Next job is to clean the head up and check for true. Any other insight/advice very welcome. I’ve done a good few head gaskets, but not for this engine. I have been digesting Mr Engel’s advice pieces so I’m not coming to it cold. This is a LotusBits built 912 stroked to 2.2 with about 3 hours on it. Attachment: head gasket.jpg (Downloaded 38 times) Last edited on 01-16-2025 09:19 pm by stewart.wigg@gmail.com |
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| Posted: 01-16-2025 09:20 pm |
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2nd Post |
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stewart.wigg@gmail.com Member
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close up of head gasket Attachment: head gasket close up 1.jpg (Downloaded 37 times)
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| Posted: 01-16-2025 09:21 pm |
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3rd Post |
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stewart.wigg@gmail.com Member
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another close up of other cylinders Attachment: head gasket close up 2.jpg (Downloaded 36 times)
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| Posted: 01-16-2025 09:21 pm |
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4th Post |
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stewart.wigg@gmail.com Member
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head looks ok? Attachment: head.jpg (Downloaded 37 times)
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| Posted: 01-16-2025 09:22 pm |
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5th Post |
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stewart.wigg@gmail.com Member
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block looks ok? Attachment: block.jpg (Downloaded 36 times)
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| Posted: 01-16-2025 09:22 pm |
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6th Post |
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stewart.wigg@gmail.com Member
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block side of head gasket Attachment: block side of head gasket.jpg (Downloaded 36 times)
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| Posted: 01-17-2025 02:37 am |
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7th Post |
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vnavaret Member 
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Interesting failure. The pressure in each cylinder pushed the head gasket laterally, causing it to buckle. That to me says that the clamping force on the intake side of the gasket was inadequate to pin the gasket in position. I don't know what you may have noticed during disassembly (undoing the nuts on the studs) but it looks to me like the head nuts were inadequately torqued on the intake side of the head. This looks like an assembly error to me. Vance
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| Posted: 01-17-2025 06:41 am |
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8th Post |
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stewart.wigg@gmail.com Member
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I don’t have concrete measurement, but I was a little surprised how easily it was to undo the head nuts. The cam carrier bolts seemed tighter! The head and block look ok to you? Might the failure potentially cause an issue with the liners?
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| Posted: 01-17-2025 01:06 pm |
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9th Post |
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noomg Member
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Stewart, You picked a good source for information, I don't know of anyone who knows more about that motor than Tim Engle does. If he doesn't chime in here you can get him on the Jensen-Healey Facebook page, he's the resident engine expert.
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| Posted: 01-17-2025 07:10 pm |
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10th Post |
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vnavaret Member
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stewart.wigg@gmail.com wrote: I don’t have concrete measurement, but I was a little surprised how easily it was to undo the head nuts. The cam carrier bolts seemed tighter! The head and block look ok to you? Might the failure potentially cause an issue with the liners? The liners are iron, so if the aluminum block edges look OK, then the liners are OK as well. The iron is much tougher than the aluminum. If the head nuts were easier to undo than the cam carrier nuts were, it was indeed an assembly error, with the head being under torqued. Save that gasket and take it back to the engine builder. Whoever it was, they screwed the pooch if the engine blew a head gasket after three hours. Vance
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| Posted: 01-17-2025 08:03 pm |
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11th Post |
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stewart.wigg@gmail.com Member
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Thanks Vance. The engine was built in 2010 and sat around for a long time before being fired up last year, so I think the warranty is expired! I’ll make sure the head is torqued properly when it goes back together - I’ve seen the recommended rain dance using a torque angle gauge.
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| Posted: 01-17-2025 09:48 pm |
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12th Post |
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Jh092 Member
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You might want to consider new studs when you put it back together.
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| Posted: 01-19-2025 02:54 pm |
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13th Post |
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stewart.wigg@gmail.com Member
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sounds like a good idea given I don't know the history of them or which type they are and therefore the torque/technique I should apply!
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| Posted: 01-19-2025 07:28 pm |
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14th Post |
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vnavaret Member
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Jh092 wrote: You might want to consider new studs when you put it back together. Having just gone through disassembly of my engine, this may be much more difficult than it sounds. Admittedly my engine sat around in the rain for a few years before I started disassembly, but those studs were a B**** to get out. And of course one needs to worry about breaking one off, which would really ruin one's day. I would say DO NOT put a breaker bar on there and lean into it. Double nutting them will not work, the force required will simply back the nuts off no matter how tightly you you install them. Instead use a stud puller and an impact wrench (NOT A BREAKER BAR!). They will not come out instantly, but letting the impact wrench hammer away will eventually loosen them and they will come out. Be sure that your stud puller is rated to accept an impact wrench. If you get a cheapie, the impact wrench will break it. One factor in your favor is that the nuts were not tightened in the first place, so hopefully the studs will not have been wound too tightly into the block. Fingers crossed. When (re)installing the studs, remember that they are installed finger tight, and no more. Vance Last edited on 01-19-2025 07:31 pm by vnavaret |
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| Posted: 01-20-2025 12:12 am |
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15th Post |
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stewart.wigg@gmail.com Member
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I got lucky and the studs came out very easily. New ARP studs on their way shortly with the nuts, grease and washers. I didn’t get so lucky with the head though, it’s no longer flat :(
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| Posted: 01-20-2025 12:50 am |
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16th Post |
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vnavaret Member
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If the head is toast, I have a spare that's for sale. Let me know.
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| Posted: 01-20-2025 07:09 pm |
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17th Post |
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stewart.wigg@gmail.com Member
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I got a copy of an excerpt which documents the allowable tolerances for head warp. The head appears to be well within tolerances: Longitudinal 2&3 0.0025" (0.06mm) 1&2, 3&4 0.0025" (0.06mm) Transverse Rear less than 0.0015" (0.04mm) Front 0.0015" (0.04mm) So looks like I don't need to machine the head. However, I also checked the block. Longitudinal 2&3 Lower edge 0.002" (0.05mm) 2&3 Upper edge 0.012" (0.3mm) Transverse No discernable warp I don't have any numbers for the block tolerances, but the longitudinal distortion at the upper edge looks concerning. Anyone know the tolerances for the block? Attachment: head tolerances.PNG (Downloaded 10 times)
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| Posted: 01-20-2025 10:33 pm |
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18th Post |
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stewart.wigg@gmail.com Member
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Tellingly, the block distortion coincides with where the head gasket seemed to let go.
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