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giorgio67

Valve seat infos

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Hi guys,

I'd like to know the differences from the NA Low compression engine and the HC Na/ turbo regardind the exhaust valve seat insert.

As I'm converting my engine to HC spec. I have found that the valves seat (exhaust only) are different.

It is just a question of hardness of material or what?

I want to fit the Sport 300 valves for the inlet as reported on Sj page (performance) so, I need to use the turbo/Hc seats?

Does anyone have some experience and knowledge about that?

Thanks in advance.

Regards

Giorgio

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I was always under the impression that the S300 valves were bigger still. I don


1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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I think the S300 exhaust are larger, but not certain if the inlet are, the general rule is that supercharged engines don't suffer with the same level of reduction in performance due to limited inlet valve size the way an NA car would.

But in general have to agree with Mike, if you're using S300 valves, use S300 valve seasts ,and might be worth considering A300 valve guides- if they're different.

Andy

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I have s300 valves in my head and they are indeed bigger and sodium filled to reduce heat transfer, Garry Kemp is the oracle on this, I got my cylinderhead off him it also has 3 angle valve seats and a 104 inlet cam.. He's on here so may well be worth a PM as he knows all there is to know about the 910 engine in all it's guises..

All the best

Mark


Mark MacKenzie  Elise S2 135 Sport 

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Thanks for the replays but my question is a litlte bit different.

Mine is NA engine so I don't need sodium valves, If I want to use Lotus 2.2 NA inlet valves (A912E0019F) I need to use the standard seats but for the exhaust I need to use the turbo/Na Hc seats A912E2608F.

As you can see from the parts numbers the exhaust seats are the same for the Turbo and NA HC.so my question is:

why I need to use different seats for the exhaust on the NA HC engine while on the inlet the seats are the same of the NA LC engines?

Regarding the S300 valves yes, the inlet are bigger then the standards but there are not S300 seats but again the INLET VALVE SEATS Inlet only on Turbo charged cars C912E2010F are the same as used on the NA HC engines.

sorry for my complicate message but I can't understand the reason of the differences as I think it's a question of material and not of measures.

The exhaust seats needs a more resistant material maybe?

mwmackenzie,

the s300 valves are for the inlet and are not sodium filled but the exhaust valves (B910E1383F) for the turbo are sodium filled.

The original inlet valves for the turbo engines are the same as for the NA HC.

PS:

the price for the inlet seats are 6 GBP each, the exhaust are listed at 24 GBP each....!!!

Thanks

Edited by ghe67

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I think you may have confused us with asking questions about both inlet and exhaust, all mixed together.

Can we start again?

From your first post.

You want to know the differences between NA LC exhaust valve seats and NA HC valve seats- are they just different materials?

Then for the Inlet you plan to use sport 300 inlet valves, and the s300 inlet seats are the same as the turbo cars exhaust seats.- what's the question on these?

Then there's a question at the end

The exhaust seats needs a more resistant material maybe? More resistant than what valve seats?

Have we got the questions clarified now 9and could you clarify the last one?

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Andy,

sorry for the caos...and for my bad english too.

the final question is, why exhaust seats are listed at 24 GBP and the inlet at 6?

They are in short supply or it's the material that is different?

I ask because some time ago I have bought on ebay a full set of Inlet/Exhaust seats for the 911 Lotus Sunbeam engine.

At the time I didin't know that the HC engine are fitted with different seats, as the Sunbeam was never built in HC version.

That's it,

So, I can't use these parts for my engine rebuilt....right?

Thanks again.

Cheers

Edited by ghe67

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Georgio

There are hundreds of materials available in the market for the seats. The key is to find out the hardness of the seat and try to get a valve seat material of a similar hardness. Moving from this position will determine whether the valve seat or the valve will see the most wear. Does anyone know the seat and valve material spec and/or who makes the valves and seats. If they do I might be able to get a data sheet (no promises, just depends whether or not we are doing business with them)

Regards

Ralph

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Sorry guys,

another stupid question...maybe.

It is possible to use Turbo Exhaust valves on the NA engine?

Obviously with the required different guides, collet etc...

The only differences is the diameter of the steam.

Thanks

cheers

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I would think it would be possible but the 6mm N/A exhaust valves would be better for flow. If you work out the amount of cross section area the extra 1mm takes up it does add up to quite a lot in percentage terms. On my old MG I had these special rim flow valves that had the area uder the head reduced to the max and that made the engine breathing fantastic it would rev so freely

Well thats what I think any ways lol

Buddsy


 

"Belief is the enemy of knowing" - Crrow777

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Hi Buddsy,

the normally aspirated exhaust valves are not 6 mm but 7.125 like the inlet on Na and Turbo.

The Turbo exhaust are 7.955 so they need different guides and collet.

Do you think that could be a weight issue or what?

The head diameter of all valves is the same.

Cheers

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I knew it was something like that I know thew turbo exhaust valves ar about 1 mm bigger on the stem I thought this was due to them being sodium filled to dissapate the extra heat caused by the turbo


 

"Belief is the enemy of knowing" - Crrow777

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Hi Giorio,

There are some differences in valve dia between the LC & HC. Maybe for better flow. You can ask this better on Mike Taylor from Lotusbits or his associate Simon Armstrong: [email protected]

Cheers,

Jean

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Hi Jean,

thanks for the infos.

I know that the head diameter of the turbo exhaust valves are the same as HC LC but the steam has a different diameter(7.955) so they use same seats but different guide.

I will ask to Simon more infos.

Thanks

CIAO

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