5 replies to this topic

[mini-geek]

The head is a minisport stg 3 head that has don about 5000 miles I have striped it down for my re build and have noticed some pitting on the exhaust valve.

whats the cause of this and what should I do?

Here is a picture of my valve

[R1minimagic]

Hi, is that the only valve and position that was pitted? if so, could be debris or i have known Minisport to have very bad quality parts in the past with micro pitting in new parts so could be erosion..

[mini-geek]

they are all pretty much the same as this but the inlets are ok.

[R1minimagic]

What about the build of your engine, what CR and what fuel and oil have you been using? Is it unleaded head?

[alicetheauto]

Are you using an additive/ lead substitute? Could be the valve micro-welding to the seat through lack of lead.

[mini-geek]

no it's an unleaded head atleast it's ment to be

IIRC it was running 9.5:1 CR (what ever a standard 1275 with 21.5cc head would run) and i was using normal 95 octain fuel. and I was using comma 20-50 oil and prior to that semi sinthetic 10-40