I thought I would share some of my experiences with the valve repair job for the D2. I bought the truck a few weeks ago knowing of the misfire codes, and assumed the worst at the time. A compression test revealed 30 lbs. in No. 8, and the problem was apparent once the heads were off.



Obviously no coil or wire replacement is going to fix this. I can't imagine how they could continue to drive. With the heads off, and based on my experience with SB chevrolet motors, I decided to check the port matching and see if I couldn't do a minor amount of grinding and improve the flow.



When compared to the gasket, the manifolds have plenty of extra material, part of which is ground away during manufacture to give the fuel injector a clear shot at the intake valve.



The end ports on the manifold have the same amount of material. You can see the gasket outline. The injector boss is also well endowed with aluminium and could use a little weight loss to improve flow. The plan is to keep the basic shape, but remove the material that, in a perfect world, could be formed away with the original sand casting process. I'll leave the intake runners in a 80 grit finish to promote atomization and flow. It works like golf ball dimples when drawing air in under a vacuum.



Within the intake and exhaust bowls there's a sharp edge above the seat on the floor of the runner. I'll bevel that over to reduce the effect and give a smoother transition into the cylinder. Wedge heads use about 40% of the valve opening for flow, so giving it every chance to move air better at this point makes a difference.



This inside view of the exhaust bowl looking upstream from the port shows some of the roughness in casting. Compared to a small block chevy this is smooth, so hats off to Land Rover on the quality of their casting work. The heads actually are very good at flowing as-is.



On a side note, with 85K miles, I noticed the original factory cross hatch for seating the rings was still visible. There is also very little (if any) piston ring ridge on the upper side. I've noticed this before in the 4.6, and assume it is due to the hardness of the liner. Has anyone else seen this with higher miles? The dark streaks are from carbon residue after clean up. Gasket cleaner works the best.



I used a new gasket for a template. The septum is plenty thick but I'll leave most of it in place to ensure I cover the gasket between runners.



The end ports have more potential, so I'll taper the injector boss a bit and make the port as full as possible.



Final product for the head: The flash tends to make the grinding seem shallow and steep. It actually flows into the head about 3/4s of an inch.



Showing some of the bowl work on the exhaust. I polish the exhaust and keep the intake a bit rough. All this work will probably give me just a few extra cubic feet a minute at best, but every bit helps.



Front row of valves are lapped and ready for a final clean up. The replacement valve is on the left. I finished assembly this weekend and it runs great, so hopefully I'll have the chance to check the gas mileage in the next few weeks and let you know if it went up or down.

 

My engine with 110K shows no sign of wear on the liner and no ring ridge at all, I have another older block and it's the same.

 

I know this is an old post, but i'm in the middle of replacing valve springs and a valve and would like to know how your truck is running after this.

 

Working great. About 25K on the engine since refurbishing the heads. The porting seems to add a bit of power, although I don't have any sure way of knowing.

 

So it's not worth the time and effort then? I imagine that you spent at least 6-8 hours on this project.

 

It's absolutely worth the effort. Had a bad valve to swap out, might as well clean things up in there a bit.

 

I think it's worth the effort. All of my Land Rovers came to me clapped out, so going through them has given me an appreciation of the excellent workmanship present. Doing what you can to make it the best job possible builds on an already good design, and cleaning up the heads gave me a great deal of satisfaction in that regard.

 

I've ported and polished my heads and intake also. I agree that it is 100% worth the effort.

 

Im with you.