asking on here as i know you gents have a collective of experience with high revving k-series. Just rebuilding my cylinder head and on putting the valves back in i noticed one of the valve spring retainers sat “higher” on the valve stem than the others. so took it back out. teh collets were sitting further down inside the retainer and the retainer looks to have some very light cracks and deformation around where the collets sit… i.e. it has opened out a wee touch allowing the collets to slide down.
the head is standard valved (hi-port non-vvc, non VHPD) and sprung item, with hydraulic lifters and standard cams. she regularly see’s 8000rpm in bursts tho she never holds over 7500rpm sustained.
are the rest of the retainers likely to fail under this sort of load, given normal springs, normal valves and a mild cam or should i be looking to replace the retainers? decided to pull and inspect the rest of the retainers again and they look a-ok
What you have experienced is called ‘pull through’ and is caused by a poor fit between the collets and the inside taper of the cap. The absolute strength of the cap is not the problem here, it is more likely to be a damaged collet or poorly formed cap, if the taper doesn’t fit correctly around the collets and ‘lock’ then there will be movement in the joint and this will cause erosion of the mating surface until eventually the collets will start to pull through. There is a point at which the cap rises far enough for the follower to operate on the cap rather than the valve stem, this dislocates the cap from the collets with each valve opening and accelerates the erosion. Valve drop occurs quickly after this. VHPD caps with the support rings removed will do the job or steel caps.
add a decent set of cam’s and pullys Phil and thats a 4 figure sum. on a 50quid engine the minis just a fun toy mate, she owes me little and makes me smile! dont want to fall into the trap of spending a fortune on it as i’ll jsut get annoyed when i push to hard and she brakes.