1971 Lightning oil leak from behind tappet block

GlennA65 · 30 November, 2023, 18:33:13

Hi. I have taken the head off my A65 to track down an oil leak from behind the tappet block on the barrels. I have poured petrol into the head bolt holes to see what happens and found that it goes straight through the centre bolt hole and emerges exactly where the oil is coming from.
So I suspect oil is getting past the head bolt and washer and running out from behind the tappet block. This is somewhat of a relief as I feared I may have a porous barrel.
I thought I might re assemble it all with some silicone under the washer/bolt head but before I do I would like to ask you guys if this is a known issue and is there a genius hack to sort it out?

Many thanks in advance

Cheers Glenn. Might see you at Kempton this Saturday!

DAVE BRADY · 30 November, 2023, 18:50:42

Hi,

Never had this problem myself but is it possible that the bolt is not tightening fully down in its threaded hole. Clean the thread in the crank case to make sure it toques down properly. Also is the face that the washer sits on perfectly flat? Over the years the surface can get a bit dished especially if the wrong washer has been used. Also check that the bolt is the right length.
If all looks fine then a bit of silicon will not do any harm but make sure that there is no surplus to get in to the engine and potentially block oil ways.

Dave.

Gup holland · 30 November, 2023, 18:54:16

Hello Glenn, I had something like that. But through a bolthole in front of the head , near exhaust. When I used a torch I could see a tiny hole what came out of the fins of the head. I used a copper washer under the washer of the headbolt.
This stopped the leakage, this was 20 years ago and is still oiltight.

Gr gup

GlennA65 · 30 November, 2023, 23:00:13

Quote from: DAVE BRADY on 30 November, 2023, 18:50:42
Hi,

Never had this problem myself but is it possible that the bolt is not tightening fully down in its threaded hole. Clean the thread in the crank case to make sure it toques down properly. Also is the face that the washer sits on perfectly flat? Over the years the surface can get a bit dished especially if the wrong washer has been used. Also check that the bolt is the right length.
If all looks fine then a bit of silicon will not do any harm but make sure that there is no surplus to get in to the engine and potentially block oil ways.

Dave.

Thanks Dave, It is possible the bolt wasn't seating properly I guess. It is a new bolt and a new, correctly thick washer but I did not specifically check it seated correctly. Good point, I will be double certain when I put it back together. Many thanks

GlennA65 · 30 November, 2023, 23:12:26

Quote from: Gup holland on 30 November, 2023, 18:54:16
Hello Glenn, I had something like that. But through a bolthole in front of the head , near exhaust. When I used a torch I could see a tiny hole what came out of the fins of the head. I used a copper washer under the washer of the headbolt.
This stopped the leakage, this was 20 years ago and is still oiltight.

Gr gup

This is interesting Gup. Many thanks. I had it in the back of my head that there had been a comment somewhere in this forum about a copper washer but I couldn't find it again. Perhaps it was you that mentioned this before. It occurred to me that the washer might mess with the Torque settings but I guess the head gasket is copper so perhaps not. The other possible issue is that there isn't much metal for the washer to seat on where the bolt fits in (see picture). Think I might give it a go though.
Thanks again.

DAVE BRADY · 01 December, 2023, 08:55:28

Hi Glen,

I can see how there would be bit of a leak with the 'over tidying' of the casting. The head bolt seats can get a bit out of shape over the years and I refaced mine to get a good surface for the washer to sit on.
You will probably get away with some silicon but ideally dressing the surface would be better.

Dave.

GlennA65 · 01 December, 2023, 11:15:58

Quote from: DAVE BRADY on 01 December, 2023, 08:55:28
Hi Glen,

I can see how there would be bit of a leak with the 'over tidying' of the casting. The head bolt seats can get a bit out of shape over the years and I refaced mine to get a good surface for the washer to sit on.
You will probably get away with some silicon but ideally dressing the surface would be better.

Dave.

Thanks again Dave. Yeah mine has 2 really thin knife edges and when I looked carefully at the picture the right hand narrowing actually has a notch in it which would easily be enough to create the oil leak. Yours has a lot more for the washer to sit on. Hard to imagine how this head would not have leaked from day 1! So I have a tower drill, I will need to get the correct tool to face that off. What would that be called? Think I will also employ the copper washer partly to make up for the material removed.

Thanks for the suggestions guys, much appreciated. Deffinitely getting there!! Cheers Glenn

GlennA65 · 01 December, 2023, 11:17:35

A milling tool maybe?

DAVE BRADY · 01 December, 2023, 11:32:27

Hi Glen,

I believe it is called an end mill. I found a 3/4" one with a 1/2' shaft to fit my pillar drill. I set the head on the pillar drill using a bolt of the correct size to line it up and secured it to prevent movement and then put the cutter in. The material removed to restore the surface is not that much and with yours just enough to establish a full circle to eliminate the nicks that let the oil through. Rather than buy one for a one off job you could borrow mine. Where about are you?

Dave.

GlennA65 · 01 December, 2023, 11:41:05

That would be amazing Dave! I'm in London. It would need to fit in a 13mm chuck though.

Thanks for the generous offer. Cheers Glenn

DAVE BRADY · 01 December, 2023, 12:56:11

Hi,

OK, PM your address and I will post it early next week.

Dave.

GlennA65 · 10 December, 2023, 17:57:34

So here is the newly machined face for the centre head bolt. pretty pleased with it, many thanks for the loan of the end mill Dave.
I reckon with the addition of a nicely annealed copper washer we should be oil tight now. Time will tell. I'll post an update when I get it all running again. got a few other jobs to do first.
Thanks for all of your ideas.
Cheers Glenn

DAVE BRADY · 10 December, 2023, 19:42:40

Hi,

Good job. After a few hundred miles re torque the head and the head gasket and the copper washer will then last for ever or at least until the head needs to come off again.

Dave.

GlennA65 · 11 December, 2023, 14:48:55

Yeah I will re-torque as you suggest. Whenever I've done that on my Triumph nothing seems to happen. I have to over torque it to get it to move and then the torque seems to be as it was before. But, I'll definitely do it just incase.
Cheers Glenn

DAVE BRADY · 11 December, 2023, 16:10:09

Hi Glenn,

I just get the torque wrench to klick as usual to confirm that all bolts are still as they should be. I have heard it suggested that the bolts should be backed off a bit and then torqued again but I never do this rather just confirm that they are all correct.

Dave.