Starting from cold my 3.8 auto engine has a pinking type noise which stops once car at full temp.
sounds as if it's coming from rear of engine
Any suggestions please


Update on this problem
have checked timing and it's fine
repaired slight crack in manifold.....noise still there
drastic action next i think...i'm going in

 

still desperate for any input/suggestions from members

 

I'm dragging this up from the depths of memory going back many years.

As far as I can recall the 3.8's would pink with poor quality fuel and this could be corrected or at least minimised by retarding the ignition. Apart from being annoying, the risk is local hot spots on the piston crown which can eventually cause failure. Our fuel quality in the UK is generally OK although I tend to steer clear of supermarket filling stations after a couple instances of poor running on a modern V8.

Even in the 60's and 70's, head distortion was an issue and skimming quite commonplace to restore a flat mating face. This, of course, increases the compression ratio and makes the potential for pinking even greater. Forty years on and your 3.8 could have been skimmed to the point where a thicker head gasket or a sandwich plate is needed to restore the correct compression ratio.

You mention a cracked manifold. Is the repair completely gas tight and the manifold mating face absolutely flat?

Graham

 

Graham
thanks for the advice will be looking into it
crack in manifold is sound
compression is down slightly so looks like may need thicker gasket
thanks again