Is my block a goner?

[Andy8421]

The on again / off again restoration of my Sprint is back on. My 3 month house rebuilding project is coming to an end, so I had a look at the Sprint engine I took out before Christmas.

The engine has had work done on it by the PO, the head has been ported, VG3 Vegantune cams fitted and bored to +20. As far as I can tell from the invoices that came with the car, the engine has done less than 10,000 miles since its rebuild.

Counting from the front of the engine, bores 1,2 and 3 show no apparent wear. Bore 4 however has a pronounced wear ridge at the top of the bore. More worryingly, there appears to be an area of the cylinder wall that is discoloured and possibly indicates an area of porosity.

For those on here who have had experience of a rebore breaking into the water jacket, is this what it looks like, and would it explain the greater wear rate in this cylinder? It has been so long since the car ran, I cant remember whether it used water, or there were any indications of a cooling problem.

According to Tim, the engine is the correct engine number for the car, so if possible I would like to keep the block, but it will definitely need to rebored if I do.

Any comments most welcome.

Thanks.

Bore 4 discoloured area

edit: I am not sure why the picture is on its side. If you click on it, it appears the right way up.

[Donels]

Looks like a piston ring has corroded into the cylinder. Can you feel it? If it needs a rebore you can usually go to +.040 with no problems so the block is probably ok. It could also be sleeved.

[promotor]

The on again / off again restoration of my Sprint is back on. My 3 month house rebuilding project is coming to an end, so I had a look at the Sprint engine I took out before Christmas.

The engine has had work done on it by the PO, the head has been ported, VG3 Vegantune cams fitted and bored to +20. As far as I can tell from the invoices that came with the car, the engine has done less than 10,000 miles since its rebuild.

Counting from the front of the engine, bores 1,2 and 3 show no apparent wear. Bore 4 however has a pronounced wear ridge at the top of the bore. More worryingly, there appears to be an area of the cylinder wall that is discoloured and possibly indicates an area of porosity.

For those on here who have had experience of a rebore breaking into the water jacket, is this what it looks like, and would it explain the greater wear rate in this cylinder? It has been so long since the car ran, I cant remember whether it used water, or there were any indications of a cooling problem.

According to Tim, the engine is the correct engine number for the car, so if possible I would like to keep the block, but it will definitely need to rebored if I do.

Any comments most welcome.

Thanks.

IMG_3485 - Copy.jpg

edit: I am not sure why the picture is on its side. If you click on it, it appears the right way up.

Until some pressure testing is done it'd be hard to know for sure what is or isn't going off. If the block is not porous, then it could be the head or the block are not flat around cylinder no.4, causing the head gasket to fail; or the head could be porous.
That mark may be from moisture being trapped against the bore wall by the piston or a piston ring just from being stood for a while with valves on that bore being open and moisture somehow getting in.
However, if a fair amount of water had been getting into the block while it has been running - and washing the bore of oil, causing more wear than other bores - then I would expect the piston to be cleaner than the rest due to a steam-cleaning effect.

Either way, there's a bit more investigation to be done! You could be looking at two separate problems in one cylinder.

[2cams70]

I've seen a similar effect before on engines that had poor quality aftermarket air filters fitted. That cylinder looks like there's grit particles embedded in the cylinder wall. Did it have foam sock type filters? Were there air leaks on that intake that allowed air to bypass the filter? Did that cylinder supply vacuum for the brake booster? If so it might have sucked in both brake fluid and dirt. Did cylinder 4 supply vacuum to the pop up headlights? If so and that pipe was leaking and sucking in road dirt it would also cause this problem

[Andy8421]

I've seen a similar effect before on engines that had poor quality aftermarket air filters fitted. That cylinder looks like there's grit particles embedded in the cylinder wall. Did it have foam sock type filters? Were there air leaks on that intake that allowed air to bypass the filter? Did that cylinder supply vacuum for the brake booster? If so it might have sucked in both brake fluid and dirt. Did cylinder 4 supply vacuum to the pop up headlights? If so and that pipe was leaking and sucking in road dirt it would also cause this problem

All good questions.

The car as purchased by me in the mid 80s had K&Ns, but who knows what it had before then. The vacuum connection for brakes and pop up headlights was to the front cylinder, which shows no wear.

Having checked the invoices again, I am pretty sure the engine had done less than 8000 miles since the rebuild in the early 80s. It does seem strange that one cylinder would wear so badly in such a short period, with the rest OK.

Andy.

[Andy8421]

Thanks to all for the replies.

I am encouraged by the lack of "that's a classic example of breaking through to the water jacket". The car had been left unused (and un-started) for many years, so it is quite possible that this cylinder has a valve open and a piston ring had rusted.

If I get time, I am going to try to measure the wear accurately to see if +30 will do it. I am then going to need to find a quality shop to do the work for me. There was a recent thread about good machine shops, I will go and re-read it.

Andy.