Stu_22
Member
Registered: 25th Mar 02
Location: Luton
User status: Offline
|
I guess the part of the cyclinder that the valve sits in
|
James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
Yeah the seat is a steel ring that is pressed in to the head, as thr aloy wouldn't last too long, I'll get soe mpics up soon
|
Siberia
Member
Registered: 9th Oct 03
Location: Leprechaun Land Drives : Zafira GSI
User status: Offline
|
oh... so they stop the actualy head itself from been worn...? they do a simular job that baring shells do?
fasinating
|
James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
they are they cause if you think abotu hitting a piece of alloy with a hammer, it's gonna deform very fast, now add heat?? No not good.
They serve to stop the valve from forming a recess in the head itself which is bad for airflow, and they allow leaner running, becuase you can run slightly lean and the exhaust gasses get so hot that the valve will start to wedl itself to the eat slightly, the alloys wouldn't last this long.
They also disserpate heat out of the valve.
And since lead was taken out of petrol they have had to make them even harder and the lead oxided used ot do the job.
50's-60's cars need special conversion to run unleaded fuel as th evalve seats don't survive.
|
Siberia
Member
Registered: 9th Oct 03
Location: Leprechaun Land Drives : Zafira GSI
User status: Offline
|
i'll keep asking questions 
so thats whats meant by 'getting the head work done' in older cars that ran on leaded fuel...?
|
James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
the valves are removed and hardened valve set inserts are pressed in.
Here's what a valve seat looks like. Older cars has soft seats or none at all, straight in to the ali head :eek: this is because goo dold leaded fuel froms lead oxides which are very hard and they coated the valve seats making them hard. put in unleaded and they don't last long 
(Also the ign advance need retarding and the carb tweakign, but that's not really important)
|
Stu_22
Member
Registered: 25th Mar 02
Location: Luton
User status: Offline
|
Last pic is for james - My supplier says its the best
|
James R
Member
Registered: 4th Feb 03
Location: 205GTi16/306GTi16
User status: Offline
|
Those exhaust ports will get a bit of a clean I think too, they look pretty nasty. would you care to clean up the faces of the valves so the plunger will "stick" to them? Good job btw Stu, how's the hands??
|
