Non-stock valves, has anyone? 90 SE.

[Loc-Nar]

After a timing belt disaster I'm in the process of replacing all the valves and having some head work done. The shop I've taken the head to seems to be fairly experienced with this type of thing, pile of Healey heads or something there which seem to be if not an exact match very close. They also handle racing rework of heads for other cars, especially Corvettes (sodium valves).

It was suggested that I ditch the sodium exhaust valves and replace them with inconel for cost and durability reasons. They say rarely do they reccomend sodium replacements and float at higher RPM's won't be an issue.

Has anyone used inconel or stainless exhaust valves, should I be worried about it?

Steve

[Vulcan Grey]

The sodium valves weren't chosen because they were more expensive... So why replace them with something else because they are cheaper?

The sodium filled exhaust valves were used to extract heat and move it up to the stems where it could be cooled by the water jacket.

For the same reason, Lotus used silicon-bronze valve guides for the exhaust. Silicon-Bronze conducts heat 2x faster than steel.

Inconel is only about as conductive as stainless steel 21-4N (which some use as valve material).

The Lotus 910 in your SE was specifically built for the extra heat of a turbo, most other engine aren't.

Inconel will probably handle the heat, but will it be able to get rid of the heat?

I would be definitely worried that any machining that they might do might be done incorrectly. Unfortunately for me a machine shop that worked on my Lotus head, accidentally machined a taper into the head to block surface. Since the Lotus head does not have very many flat surfaces on it, it is easy to get it fixtured incorrectly. It is very important that the cams remain parallel to the head surface on the combustion side. If the head is already warped it will be very difficult for them to indicate off of that surface, and nearly impossible to find any other surface to use...

[Loc-Nar]

I do hope the machining is done well, they were reccomended by JAE and there were several of these heads there in various stages of rework. They have to weld/cut the mating surface due to the coin slot cut in the head right where the sleeve meets the head. The sodium valves break off easily.

I've talked to the shop a copule of times and yes, the sodium valves were chosen for a reason. Over time metallurgy changes though, and from what I am reading regarding other performance cars people are putting the inconel valves in instead of the OEM sodium valves, frequently high boost 400+hp 4 bangers. Not because they are (much) cheaper, but they are better suited for these high heat (1700F) applications, stronger, less wear on the guides, etc. I am going to just call Lotus on this, see what they say. I imagine it will be "not tested-your own risk", but maybe they have tried it. Cheaper does not necessarily mean worse, it could just be technology marching on.

Other than that they say "no wear on the guides whatsoever", "looks brand new even for a 40K mile engine".

I have been busy trying to wrestle the engine out of the car. It is straightforward, but little things are annoying. I am sure anyone that has removed the engine can relate. The hoses all turn to dust when you pull on them!

[stormy69]

i would be comfortable with the inconel, thats what ford used in the 2.3 turbo for years. sodium filled is great but there is a history of failure (not on lotus that i know of tho) for that type of valve.

Edited July 28, 2009 by James 95s4

[wookiecj]

To digress slightly on your post, one of the first things that we look at on any vehicle that we do any work on, is the hoses. They do disintegrate/split etc and if there is anything wrong with any of them they are strongly recommended as an item to be changed. The cheap ones we do as a matter of course... the expensive ones are referred to the owner for a decision. Unfortunately hose changes are a fact of Esprit ownership. Water leaks can wreck a motor, even small fuel leaks can mean a roadside BBQ and vacuum leaks can mean performance issues.

[Loc-Nar]

I'm getting back to this project after a bit of downtime. I did go with the custom made inconel valves. The shop pretty much insisted on it. Need piston(s), liner(s). As far as the hoses I am replacing them all, inspecting the fuel tanks, etc. As I get more into it more updates.

[Bibs]

Speak to Mike Taylor at Lotusbits re pistons/liners, he should be able to help.

[Artie]

Steve,

If you are replacing the stock pistons and rods, JAE has an awesome set of JE pistons and Saenz rods that are almost sacrilige to button up inside the engine. I installed this rotating assembly last year when I rebuilt my engine! Pricey for pistons and rods, but far cheaper than stockers!

Art

[Loc-Nar]

Thanks Art, I'll ask about those. I got the engine out yesterday and the cause was teeth missing from the timing belt.

[Artie]

They are very pretty pieces! See!: