Yesterday, I pulled the heads off my to-be-a-race-engine V12. Whilst I was chuffed at the relative ease with which the heads came off, I was a bit annoyed to discover that, at some point in this engine's past, it's been run with a stray washer in one of the cyls. The result is the damage seen in the pictures below.

My question is; is the head salvageable? There's obviously quite a lot of denting, I've not measured how deep, but I'd guess the deepest is maybe 20 thou (0.5mm).

It had occurred to me I could get it properly cleaned up with some soda blasting followed by a good chemical clean; then I could TIG weld up the dents, and have the head ground flat again - obviously whilst trying to avoid getting the head hot enough to warp or otherwise deform - does anyone know what alloy Jag used for these heads?

Worst case scenario, I have a spare engine, I didn't want to start using it so soon

Any thoughts much appreciated.




A good piston...





The bad piston...





Ouch





Dings in the head





The washer that did it all.

 

Ade, looking at the head (the most limiting thing as I see it), that doesn't look too bad and odds are you can save it. I would say to use a sander or something and smooth out the edges to remove any sharp points and to make it so you don't affect the air flow in the cylinder. The other thing that I would make sure of is that the cylinder wall does not have any dings in it. The one picture that shows part of the wall appears to be good. But, that would be another show stopper. If there are dings in the cylinder wall, then you would need to bore out the cylinder to remove the scratches/dings which would then be new pistons and rings since you would want to do the same treatment to all 12 cylinders.

It would probably be best if you can get a new piston to replace the one that is dinged up. Probably not required, but I question the affect on the compression ratio for that one cylinder if you also take off the sharp edges on the piston. Shouldn't affect anything, but I would hate to take a chance.

 

I second all Thermo's recommendations, with the added proviso that you might want to take a close look at the valve seats in case one is loose, cracked or damaged.
I've seen much worse salvaged and successfully used.

Incidentally, that's gotta be one tough-assed washer!

 

Thanks for the positive replies, much appreicated!

FWIW - I am re-linering the engine anyway, with 96mm liners; so I'm also replacing all the pistons.

Valve seats - yes, that's one of the next things I need to do, is to pull all the valves out. I plan to replace them too, if necessary, given all the things I'm doing to this engine I may need larger valves anyway... so that'd answer the question about the seat too. I'm sure I'll find seat damage, the washer's dinged everything else up, I can't imagine it didn't try to escape a few times...

Does anyone know what alloy the head is made of? If I'm going to TIG fill the worst of the dents, it'd be best to use the same type of metal. I do have a knackered HE head I could shave bits off to match, if filler rods aren't available.

Cheers!
Ade.

 

What's the racer is this going into? I have a bunch of dedicated track cars, but no race jags. I have got to fix that.

 

Yes you can save the head. Take a random orbital sander and some 150 grit paper then staying inside the shiny circle take any high spot off. once done switch to 220 and finish up with 320. Always staying inside the circle.
Try not to reshape the head.
the divots will act like the divots on a golf ball and simply stabilize the fuel air flow. Welding adds risks you don’t want.
May I suggest you don’t go oversized with the piston? If you must go custom get Cosworth’s Jaguar pistons. They are lighter than most aftermarket and have some very advanced thinking in them. At least try to stay inside the stock head gasket. About 3.675 That’s (93.345 mm for the rest of the world that doesn’t use 3 barley corns from the center of the ear as a standard)
You don’t want anything to do with custom head gaskets. Trust a guy who’s been there.

 

Crumbs - it's been a while since I posted here!

Life, as it does, has rather got in the way of this project..... and I'm pretty much no further forward than last time I posted, other than having moved to a new workshop, and acquired a few more spare engines, including a couple of 6 litres (one of them actually runs!).

I did give up on the idea of expanding the bore for this iteration of the engine, although it's something I do intend to pursue at a later date, once I've got more skills at engine building. I'd also like to swap the CI liners for Nikasil coated aluminium liners, which will minimise any differential expansion issues, improve cooling, and reduce weight. I know Jaguar would have used Nikasil liners if they'd existed, back when they built the V12... and now that all ULP is ultra-low sulphur, the issues with Nikasil degrading are basically eradicated.

I actually have dibs on a set of Walkinshaw Cosworth pistons, just need to get back in touch and pay the balance for them.... I know TWR were pulling some crazy RPMs and power out of what was nearly a stock engine - I have far more latitude than they did, e.g. dry-sumping, stronger main caps, modified ignition system, external oil pump, electric water pumps, etc. I do need to get a Round Tuit though......

Thanks for your suggestions, I'll definitely try sanding the damage out, at least the high spots.

wesmc - to somewhat belatedly answer your question, it'll be an XJS V12, racing in the North West Sports Saloons Championship (currently sponsored by Ric Wood); that is, if I can ever get the damn thing built! The donor car is an extremely rusty 1977 model, I'm about one third of the way through welding the shell into some semblence of sanity... new floors, new boot floor, rebuilt windscreen surround, new/scratch-built sills, and one new (2nd hand) rear wing.

Cheers,
Ade.

 

I wouldn’t attempt to Re-engineer the liners. The stock liners work just fine and while the weight savings potential is real, the complexities of adapting the liners to work are far more complex then you’d think.
Look at a stock Jaguar liner out of the engine and you’ll start to see some of the problems. The block isn’t sand cast rather it’s die cast. It can be since there isn’t a deck on it. But the Jaguar liners provide sufficient width to give the stability needed.
nikosel liners aren’t wide enough to afford that stability. so you would need to engineer a deck.
While that is doable it would be far more complicated than you’d think.
Now you are not only doing the engineering to account for the different expansion rates between the stock liners and Nikosel you are also doing the engineering required to put a deck on a die cast block.
I honestly cannot think of any example where that has been successful.

If you want to save weight look at the stock connecting rods for one. There is a weight pad on both ends of the con rod. Remove that and you’ll save more than a pound a rod. That’s reciprocating weight that accelerates from a dead stop to over 3500ft per second back to a dead stop twice per crankshaft rotation.

I made a simple jig that allowed me to quickly do the task using a drill press.
there is even more weight to be removed. Once you eliminate the weight pads you can safely remove weight from the crankshaft
The crank weighs 78 pounds. Remove 12 pounds from the counter weights and you’ll still has a massively overbuilt crankshaft with 3 inch mains and 2.30 rods. Offset grind the crank To 2.10 and depending on the skill of your crankshaft grinder you pick up .400 more stroke and reduce the weight of your crankshaft By at least 30 pounds. By the time you recalibrate The required balance.
Instead of a stock diameter iron flywheel and pressure plate. Go to an Aluminum 7&1/4 inch triple disk. You can even still use a stock automatic ring gear And you’ve just removed another 27 pounds.
Go up to the front of the engine, and dump the stock harmonic balancer.
If you aren’t doing endurance racing you can get buy with a simple small diameter aluminum plate.
Stock the valve springs won’t float until 8300 RPM ( per factory testing) or you can buy racing valve springs for higher RPM.

The reason I’m talking about that sort of RPM is the reduced weight of the crank will allow it if you can get Kent to build their billet profile. But you will need the larger diameter lifters that are available. If you are in England Rob Beere sells them and will do the machine work required to make them work.
If here stateside it can be done with a vertical mill and a homemade jig for a lot less than round trip airfare will cost.