Valve seat material for LPG.
Posted: July 12th, 2013, 8:42 pm
Hello Guy I hope you're well, I wonder if you can help with a question related to valve seat materials suitable for LPG use in a turbocharged engine?
Basically I have been tasked with the job of exhaust seat insert removal and replacement on an Audi 20 valve head, its a job I have undertaken before and so the process is not entirely new to me.
This has become necessary due to the exhaust valves being replaced with client supplied inconel items as the stock two piece items tend to suffer from the heads coming off them at high-ish mileages.
The client wants to use these inconel items, however I found out a while back that the seat inserts in the head are 27mm diameter at their outer periphery whereas the stock valves are 28mm, in other words they overhang the seat insert with the seat placement being somewhat inboard towards the stem.
The two photos show the lack of a contact area when lapped together and their poor locations.
The new inconel items have a 2.0mm wide contact area and are also 28mm diameter but its contact area is located at the outboard edge of the valve meaning any seat is going to be far too thin, indeed I've heard of people just dropping these items in and using them, I can only imagine theyre going to run into seat life problems before too long, so with that in mind I have to put in larger inserts of 28.50mm to accomodate the valve correctly.
The question is what insert material would you recommend for the application?
Sintered, copper alloy, stellite?
Any help you can offer as ever gratefully appreciated.
Tony.
Basically I have been tasked with the job of exhaust seat insert removal and replacement on an Audi 20 valve head, its a job I have undertaken before and so the process is not entirely new to me.
This has become necessary due to the exhaust valves being replaced with client supplied inconel items as the stock two piece items tend to suffer from the heads coming off them at high-ish mileages.
The client wants to use these inconel items, however I found out a while back that the seat inserts in the head are 27mm diameter at their outer periphery whereas the stock valves are 28mm, in other words they overhang the seat insert with the seat placement being somewhat inboard towards the stem.
The two photos show the lack of a contact area when lapped together and their poor locations.
The new inconel items have a 2.0mm wide contact area and are also 28mm diameter but its contact area is located at the outboard edge of the valve meaning any seat is going to be far too thin, indeed I've heard of people just dropping these items in and using them, I can only imagine theyre going to run into seat life problems before too long, so with that in mind I have to put in larger inserts of 28.50mm to accomodate the valve correctly.
The question is what insert material would you recommend for the application?
Sintered, copper alloy, stellite?
Any help you can offer as ever gratefully appreciated.
Tony.