13 replies to this topic

[BaronVonchesto]

Hey all.

 

Considering rebuilding my head in the not too distant future. I'm unsure if my head has unleaded seats, so I figured I'd put new ones in anyway.  I can find exhaust valve seats for my 998 A+, but not inlet ones.

 

Is there such a thing as a replacement inlet valve seat? Or you're stuck with whats on your head?

 

I sent a question to minispares, but got a reply saying there's no such thing as inlet valve seats.

[Retroman]

Its only the exhaust that needs the hard inserts

 

The exhaust valve gets a lot hotter than the inlet and even the valve itself can burn.

 

Some turbo exhaust valves are sodium filled to help carry heat away from the valve head to the guide

[Spider]

As Retroman has said in your case, but if due to wear, you find you need Inlet Seat, yes, they are available.

[nicklouse]

yes you can have replacement seats on the inlet as well as the exhaust. but there is little point. just lap them in o have them recut if needed.

[Retroman]

When they are machined they need an interference fit of about 0.0045"

 

And need cooling with liquid nitrogen to get them in

 

If not they can fall out, which is not nice

[nicklouse]

When they are machined they need an interference fit of about 0.0045"

 

And need cooling with liquid nitrogen to get them in

 

If not they can fall out, which is not nice

had that happen on one of my builds. trashed one Omega piston. gained an Ashtray.

[Pigeonto]

The factory unleaded heads had all 8 done. I can't actually say they all did but my one certainly has

[Retroman]

We had one too, it was early days of unleaded, batting down the 3rd lane after an SR Nova

 

Just got a massive rattle, and were lucky the seat was still round the valve

[Turbo Phil]

As above, it's only really required on the exhaust side. It is possible to insert the inlet side but there's little point.
I've never seen a factory head with inserts on all the valves. Though I guess anything's possible knowing BL/Rover.

Phil.

[ACDodd]

The standard factory A+ 998 head has inlet valve seat inserts as well as the exhaust.

Ac

[Pigeonto]

Aha, there we go. They must have dabbled with the 1275 too. 1992 my one with all 8 done

[BaronVonchesto]

The standard factory A+ 998 head has inlet valve seat inserts as well as the exhaust.

Ac

is it ever necessary to change these to hardened seats and if yes where can I get them?

[ACDodd]

No, not necessary.

Ac

[Turbo Phil]

The standard factory A+ 998 head has inlet valve seat inserts as well as the exhaust.

Ac

 

Not doubting your wisdom AC, but there must be a exception to this rule, as I've had factory unleaded 998 heads with ex inserts only before.

Phil.