by Ae92typeX » Mon Nov 28, 2005 12:16 am
prevents valve seat recession/vsr since the introduction of lead free petrol.
Basically, older cars dont have a solid insert into their heads- the valves just go straight into the cast head. Through high temp/ non lubed running without lead the valves can stick/microweld which causes them to recess into the head more. This can damage the head beyond repair, cause leaking and sticking valves/burnt valves etc
All alloy head cars have inserts, but on older models many are still not solid enough to prevent vsr
When you mod them to run on unleaded they put a solid insert into the head to stop this happening.
Ive seen quite afew old 4's which have suffered badly from vsr, not many bigger lower reving old engines though (6's & 8's).
In all the cars Ive run with valve addiditive Ive found no noticable running difference, but have taken off the head on several and seen no noticable wear in ones running it.
Theres quite afew different options on the market, valvemaster being one of the more expensive options.
In this mini I have now Ive been running moreys upper cylinder lubricant. Had the head off a while ago and the valves were still mint, un carboned and non recessed. ~$20 a bottle and treats 650L of fuel.