Technical Plugs on engine block

[Luke W]

Hi All,
I was wondering if anyone can tell me what these two plugs are for exactly. I took off the clutch plate and flywheel to inspect and clean up the grease and grime behind the flywheel and noticed them. There seems to be some old silicone or some type of sealant that was applied to the area. I was wondering if I need to reapply some new sealant and if so does anyone have any recommendations.
I did not see any significant leaking in that area or the crankshaft seals but there was a fair amount of built up oil and dirt. I don't think the engine was ever rebuilt so I am assuming it is just 50 years of build up since I did not see any real evidence of leaking.
Thanks for any advice,
Luke

 

[Goldnrust]

I'm not 100% on the top plug, but the lower plug is blanking off the hole in the casting where the bore for the camshaft was drilled. I'm fairly confident the top plug would be similarly blanking off an access hole for when Fiat originally machined the crank case for the cam followers.

Both my engines have similar looking sealant, so I presume that to be factory applied. Unless you seem signs of leaking, or significant corrosion from the two plugs I'd leave well alone!

With you saying you presume the engine hasn't been worked on, I would question that. My reason being that the 3rd plug in the picture, the smaller aluminium plug to the left of the other two, appears to have been beaten up. It should look like the attached image, with a hex key head and threads showing.

This plug blanks off the end of the oil gallery drilling, and removal of it suggests that someones had the engine apart and internally cleaned it, which would be practice if you'd had a bearing failure or similar and had debris through the insides of the engine.

Or it could mean the plug was leaking at some stage and someone's made a ham fisted job of trying to force it in more...

 

[Luke W]

I'm not 100% on the top plug, but the lower plug is blanking off the hole in the casting where the bore for the camshaft was drilled. I'm fairly confident the top plug would be similarly blanking off an access hole for when Fiat originally machined the crank case for the cam followers.

Both my engines have similar looking sealant, so I presume that to be factory applied. Unless you seem signs of leaking, or significant corrosion from the two plugs I'd leave well alone!

With you saying you presume the engine hasn't been worked on, I would question that. My reason being that the 3rd plug in the picture, the smaller aluminium plug to the left of the other two, appears to have been beaten up. It should look like the attached image, with a hex key head and threads showing.

This plug blanks off the end of the oil gallery drilling, and removal of it suggests that someones had the engine apart and internally cleaned it, which would be practice if you'd had a bearing failure or similar and had debris through the insides of the engine.

Or it could mean the plug was leaking at some stage and someone's made a ham fisted job of trying to force it in more...

Hi Goldrush,
thanks for the info, I guess I will leave the two larger plugs alone and maybe clean up the third plug and see about trying to remove and replace it with a screw extractor.

 

[Goldnrust]

Unless you're in the middle of an engine build and are going to strip it down to a bare crankcase, then if it's not causing a problem I'd leave the plug alone and just make a mental note of it.

It's an aluminium plug in the aluminium crank case, add in a bit of corrosion and it could be very difficult to remove cleanly. Any debris coming from the threads, either removing or refitting, would go into the main oil gallery and could do all kinds of damage to the insides of the engine.

 

[Luke W]

Unless you're in the middle of an engine build and are going to strip it down to a bare crankcase, then if it's not causing a problem I'd leave the plug alone and just make a mental note of it.

It's an aluminium plug in the aluminium crank case, add in a bit of corrosion and it could be very difficult to remove cleanly. Any debris coming from the threads, either removing or refitting, would go into the main oil gallery and could do all kinds of damage to the insides of the engine.

Yes, your right. The compression is good and it was running well when I removed it so I think I may just JB weld it to stop any potential leaks and revisit it in the future if I end up doing a rebuild at some point.
Thanks again,
Luke

 

[the hobbler]

Yes, your right. The compression is good and it was running well when I removed it so I think I may just JB weld it to stop any potential leaks and revisit it in the future if I end up doing a rebuild at some point.
Thanks again,
Luke

If there are no signs of leakage (and I can't see any in the picture) leave the "beaten-up" plug alone. I have used "JP Weld" on a number of occasions, it is a very good product, but covering the plug in 'JP' will make any future extraxtion a real bugger of a job. These plugs are quite soft,and even using the correct 'metric'allen keycan cause distortion of the female hex. One way to overcome that problem is to use an 'imperial' just SLIGHTLY bigger, and it put in firmly (which means with a hammer)--a bit brutish, but sometimes that has been the only way that I have been able to extract a recalcitrant plug.

 

[Luke W]

If there are no signs of leakage (and I can't see any in the picture) leave the "beaten-up" plug alone. I have used "JP Weld" on a number of occasions, it is a very good product, but covering the plug in 'JP' will make any future extraxtion a real bugger of a job. These plugs are quite soft,and even using the correct 'metric'allen keycan cause distortion of the female hex. One way to overcome that problem is to use an 'imperial' just SLIGHTLY bigger, and it put in firmly (which means with a hammer)--a bit brutish, but sometimes that has been the only way that I have been able to extract a recalcitrant plug.

Hi Hobbler,
I think I will take your advice and leave it alone for now, hopefully it will come out with a little elbow grease in the future.
Thanks for the help,
Luke