Thread: Which head gasket for TD5

Strangy, to measure valve/crown clearance you need to know the piston protrusion. All gasket thickness are based on this initial factor.
Machining the face of the head may or may not alter the requirement for next thickness and therefore it must be measured to maintain the correct CR in the engine also.
Quite often head machining will also involve valve seat recutting which then increases the valve/crown clearance resulting in the use of the original or lesser thickness gasket.
Using a thicker gasket for just any old reason will alter the CR of the engine quite marginally.
The only time the whole gasket thickness needs to be considered is in the event of any bottom end work as you said, but you still need to maintain OE tolerance valve/crown.

As alloy heads on diesels generally have a minimum machining limit based on the surface hardness of the face, this is generally less than the overall critical value required to cause valve contact with the piston.
Also, increasing the gap with a thicker gasket will allow a higher carbon buildup on the crown of the piston which will eventually result in face contact. Being a direct injection, all combustion is done in the combustion bowl. Increased gap causes a burn above the bowl surface which also reduces power and increases EGT's.
The clearances must be kept as close to original tolerance as possible.

As for TRS, I would take what they say with a pinch of salt. They aren't engine builders and definitely not diesel certified. They sell "stuff" and that's about it.

As for cam clearances, don't know how you came about the info but it makes absolutely no difference to the timing chain etc etc particularly with an 8thou facing.
I've worked on everything from KT50's, Wartsila V16's right down to lowly Toyota L series and have never seen an instance or supplied components where this results in incorrect cam timing.

Cheers

Andrew

can i just say that you should never ever machine a td5 head as it has been heat treated so if you face it you will lose that if you think it is warped have that shop chick it but i would doubt it and to say 12or 3 hole gaskit should be replaced with a 3 hole is silly if it had a 1 refit a 1 thank you

Strangy, to measure valve/crown clearance you need to know the piston protrusion. All gasket thickness are based on this initial factor.
Machining the face of the head may or may not alter the requirement for next thickness and therefore it must be measured to maintain the correct CR in the engine also.
Quite often head machining will also involve valve seat recutting which then increases the valve/crown clearance resulting in the use of the original or lesser thickness gasket.
Using a thicker gasket for just any old reason will alter the CR of the engine quite marginally.
The only time the whole gasket thickness needs to be considered is in the event of any bottom end work as you said, but you still need to maintain OE tolerance valve/crown.

No arguement here

As alloy heads on diesels generally have a minimum machining limit based on the surface hardness of the face, this is generally less than the overall critical value required to cause valve contact with the piston.
Also, increasing the gap with a thicker gasket will allow a higher carbon buildup on the crown of the piston which will eventually result in face contact. Being a direct injection, all combustion is done in the combustion bowl. Increased gap causes a burn above the bowl surface which also reduces power and increases EGT's.
The clearances must be kept as close to original tolerance as possible.

Also agreed.

As for cam clearances, don't know how you came about the info but it makes absolutely no difference to the timing chain etc etc particularly with an 8thou facing.
I've worked on everything from KT50's, Wartsila V16's right down to lowly Toyota L series and have never seen an instance or supplied components where this results in incorrect cam timing.

I didnt come across this info it is simple maths considered by most engine builders and engineers, that applies when you reduce or increase the centres of 2 or more shafts driven by a fixed pitch system IE Chain or tooth belt you will alter the synchnosation of these shafts as there is no adjustment on the load side and you require futher travel in the adjustment system and a means of synchronising these shafts again. I m not advocating that the timing will never be right. I am pointing out that this should be consideration in the entire job. I dont want to get into a contest over engine building experience and i am sure there are many with much more than myself and the technical explanations could become very indepth beyond the scope of the original post. however a number of mine and competitors comp motors with o/head cams require adjustable cam gears to get the timing correct after machining. (before considering performance cams etc) and again you and many here know the huge number of factors influencing and affecting the overall outcome.

LR have slotted the gear for the assurance of correct timing which will allow for most adjustments and they weren't designing it for others to modify. All who have machined their head have gone against LR recommendations so evaluation of any potential problems and solutions is appropriate by each indivisual. My post/s point out this is now a factor to be considered not that it is the sole factor for number of holes in gasket choice.

And yeah you are also correct with TRS, I didnt base my gasket choice on their say so






Cheers

Thanks for everyones input, i know all too well about the clearance a CR ratio change etc with different thickness gaskets, would ussually replace same for same however reading the forum there are differing opinions, i am a mechanic however have never worked on a td5 into much depth as far as the engine goes, i will be getting the head machined just to remove any marks from the fire rings, all alloy heads are hardened in some sort of way and i have never had problems in the past with alloy heads on diesals and machining, so i dont see what the go is with that, if i blows up those people are welcome to give me the "i told you so".

Originally Posted by RRV80

... i will be getting the head machined just to remove any marks from the fire rings, all alloy heads are hardened in some sort of way and i have never had problems in the past with alloy heads on diesals and machining, so i dont see what the go is with that, if i blows up those people are welcome to give me the "i told you so".

I think the "face hardening" of LR diesel heads is a myth!

I had mine hardness tested on a number of surfaces prior to machining, and the face is no harder than any other part of the head. The only thing to be aware of if the valve to face depth. Machine away!

Interestingly.. Due to work constraints I had TRS re-assemble my TD5...

They had to order in a 1 hole Gasket as I had a 1 hole from new.

Commonly they only see 2 or 3, hadnt seen a 1..

The head was skimmed 0.008" and is running a 1 hole again

Hardness testing seemed to confirm awabbits comments too...

Originally Posted by Tombie2

Hardness testing seemed to confirm awabbits comments too...

Wouldn't it be interesting to have multi surfaces of an unused head hardness tested!

DL

strange comments here about hardness of aluminium heads, The process involves specialized 'heat treatment' of the alloy, followed by an annealing process, various patents and methods are used by the industry.

As some one commented, 'don't machine the heads'?? mentioning the 'heat treatment', and assuming this somehow only affects the surface. The treatment used by almost all vehicle manufactured heads treats the alloy head as a complete unit and therefore can be machined faced, as done at the factory prior to engine assembly. Machined 'after' any hardness heat treatment.
Maybe getting confused with nikasil plated type cylinder liners as used in high performance engine cylinder bores, which do away with the need for steel liners, as it can be plated direct to aluminium. these cylinders cannot be rebored or machined without re plating.

This process is very costly and I don't know of any cylinder head manufacturer's that would even consider such a thing.

Machining an alloy diesel/petrol head from a landrover, or any vehicle, does not affect the hardness of the material, the limit of tolerance is to keep other factors, clearances etc. within limits, as mentioned several times here.

Cheers.