Head damage...

[aspira]

Hi

Looking for a bit of advice please. I completed my first V8 rebuild but I’ve run into a few problems.
On it’s first few starts and when I bedded the CAM in – all was well. But after a few short trips it ran a little hot. I may have overheated it.
I’m now getting a lot of smoke – I thought it was slightly blue in colour. The longer it sits ticking over the more smoke I get.

Ran a compression text and #1 had dropped to 100psi. All the other at 125psi.
I used a chemical test to check if I’d blown the head gasket but looked okay.
I did buy a leak down tester, but it got nicked out of the car before I used it!
Decided I dive in and take a look at the head.

I was thinking that the smoke could be caused by a bad stem seal. But the head is a ERC 0216 came off a SD1 Vitesse, so only add the crappy rubber seal that usually gets pulled off. My other thought was a leaking valve that I didn’t bed in properly.

I found that the head gasket looks like it had blown
https://1drv.ms/i/c/f2cf483bba82bf78/IQ ... g?e=dNOchf

I’ve also damaged the top of the piston.
https://1drv.ms/i/c/f2cf483bba82bf78/IQ ... k?e=Le1paE

I’m not sure what has happened here and how this damage has happened. What could have caused this damage?

I wondered if I hadn’t measured and set the preload correctly. I fitted a new CAM with slightly more lift. I had the heads machined very slightly, fitted composite gaskets and added some shims under the rockers to get it all in tolerance.

I’ve tested the head to see if the valves are leaking – all seem to hold liquid fine, including #1.
Could this have been caused by overheating and what actually caused that groove into the piston?

Any thoughts on what I should do next guys?

Many thx

[scudderfish]

Something hard has repeatedly smacked that piston. If it was a valve, it could have bent it and broken the stem seal. I think the gasket was OK as there doesn't seem to be any damage around the circumferences, just some stuck gasket around the water way. No evidence of combustion gases getting out.

[aspira]

Many thanks for the thoughts...

It doesn't have any fitted stem seals - just those useless rubber ones.

But you're right something may have been sucked in via the intake. Could it have been blown out of the exhaust without damaging the valve?
Also if the head gasket isn't blowing as I thought, that would explain why the chemical test didn't highlight any problems.

That all makes sense, but I do have a lot of smoke - slightly blue - exacly what you'd expect if oil was getting passed through a stem seal. And also, this cylinder had a 25 psi drop in the compression test. Maybe I need to take a closer look at the valve. I just checked the head was holding liquid so i know it seals okay, but I guess if the valve is very slightly bent, it could remain working but be passing oil back through the valve guide. Explaining the smoke?

[Ian Anderson]

You have it that far apart and if I was in the same position I would definately have the valves out and check them for bends and also check the seats for pitttimg etc and lap them in again.

The piston shot seems to show a lot of oil in the 9 o’clock position.

Turn the engine over ….spanner on crank bolt and check the bore for scoring as it could be a ring not bedded or broken.

Some rings take a few thousand miles to bed in ciorrectly how many have you done since rebuild?

If the bore is scored time to remove that piston and check further.

Ian

[scudderfish]

Holding liquid at 14.7psi is a lot less of a challenge for a seal than a gas at 100 psi. Take the valves out for that cylinder, and another one (for reference) and examine them closely. Post photos here so we can have a look as well. You can attach them directly if you use the 'Attachments' tab directly below the 'Save draft/Preview/Submit' buttons

[aspira]

I've pulled the valves out and I've added a few shots - thx for the attachement hint!

The two shots of the head - #1 (with the damaged piston) has what looks like cone type gouge near the spark plug. The others, inlcuding #7 which I've attached, look normal.

The two valves, #1 and #7 look identical. They both look strraight but are quite pitted considering there's no real milage on the new engine. No marks on the valve heads where #1 could have hit the piston. The stem seals (rubber washer type) have no ware and were both in place.

I tried putting them in my drill and spinning them. Maybe a tiny bit of movement on #1 but my drill is pretty old.

I'll lap the valves in again. They do look quite pitted considering I haven't done an real milage, although a lot of time spent running on the drive could have been a conttrubuting factor I guess.

See what you think. I'll check the bores this evening.

[aspira]

The other valve pics...

[stevieturbo]

Maybe my eyes are getting too old, or it's the blurry pics. But I can see impact damage on that first pic there, where something has tried to ram into the valve seat from the plug hole.

The piston in the earlier photo, definite impact damage too. Probably not a 10mm socket, but something has been in there.

Question is, do you know what and where from ?

Not really seeing a lot in the other photos though ?

Nothing that looks difficult to clean up and repair though.

[aspira]

Yes, you’re right. So looks like something probably got in there, otherwise the valve would be more damaged. And whatever it was, it was probably pushed out of the exhaust port.

If that’s the case, I was pretty lucky.
I’ll take a look at the bore this evening re Ian’s point.
If that looks ok, it sounds like the cause is debris.

I’ll lap in the valves again, and clean up the head. Assuming it probably was a leaking valve that caused the white/ blue smoke and the lower compression on that cylinder?

Should I do anything about the gouge on top of piston #1?
Should I take off the other head, and replace both gaskets or is it ok to leave that and just fix the damaged head?

Thx for all your help.

[aspira]

Checked the bore and all looks okay. No damage.

[scudderfish]

Should I do anything about the gouge on top of piston #1?
Should I take off the other head, and replace both gaskets or is it ok to leave that and just fix the damaged head?

Thx for all your help.

I'd use a dremel to smooth out the damage on the piston, but I wouldn't worry too deeply about it afterwards.

[stevieturbo]

I'd be more concerned about that valve seat

Try a quick lap in of the valve, if the seat does not clean up quickly and evenly you may well need to get a new valve seat installed.

Also check that valve is straight and hasn't suffered damage

A quick burr on the piston to smooth it over should be fine.

[aspira]

The valve isn't showing any sign of damage and looks pretty straight.
I take your point about the valve seat though. On the pic you can clearly see that the debris has caused some distortion to the head where it hit, around where the valve seat is inserted. Even though the valve seat itself doesn't look affected, it's quite close and must have been quite a bang.

Hopefully as you’ve suggested, some light lapping of the valve might just work, but I won’t know until it’s reassembled.
Obviously if it does leak, it’s a much bigger job to have a new seat pressed in. I doubt that can be done without removing the engine.

[stevieturbo]

The valve isn't showing any sign of damage and looks pretty straight.
I take your point about the valve seat though. On the pic you can clearly see that the debris has caused some distortion to the head where it hit, around where the valve seat is inserted. Even though the valve seat itself doesn't look affected, it's quite close and must have been quite a bang.

Hopefully as you’ve suggested, some light lapping of the valve might just work, but I won’t know until it’s reassembled.
Obviously if it does leak, it’s a much bigger job to have a new seat pressed in. I doubt that can be done without removing the engine.

You will know when you lap the valve if things clean up ok

You will know after lapping the valve and testing if the chamber/port is sealed ok.

No need to wait til it's assembled.

And if the seat needs replaced, it is of course a head off and machine shop job.

You might be better giving the head to a reputable machine shop and having them check it out incl all the valves.

[scudderfish]

If you're North London area, pop your head over to these people https://maps.app.goo.gl/k23YHpr3FUiakze66 They've done various bits on my V8 over the years. It's a few blokes in a shed with big machines and so many engine parts on shelves.