'Breaking-in' new camshafts

[David Morris]

Hi All,

I often enjoy YouTube videos featuring restoring and rebuilding classic US vehicles. There are UK equivalents, but they seem to concentrate on just getting cars running, not actually driving them for considerable distances? These US cars usually date from the mid-1960s and into the late 1980s. and invariably are V8s. The engines usually have flat tappets, as do our Jowett engines.

The presenter’s comment routinely on the need to use oil that has a high zinc content, to prevent high tappet wear, and sometimes use a zinc additive to strengthen normal engine oil.

On more high-performance vehicles, the camshaft is often changed for added power output. What attracted my attention is when a new camshaft is installed, not only is a special running-in oil or paste applied to the tappets and the new camshaft, but a strict ‘breaking-in’ routine is followed for the new camshaft.

The newly rebuilt engine is run up to heat and continuously kept running for 20 mins at around 2500rpm. The engine oil is then drained and replaced, including a fresh filter. This is apparently to eliminate oil contamination with metal particles from the initial wearing-in process.
With the increasingly high cost of new camshafts, do we mandate such a strict breaking-in routine for our camshafts? Are they sold with such a warning label?

The routine I have outlined for a new camshaft sounds similar to that required for an engine rebuilt with the well-renowned NZ head gaskets? Which, in my experience, need attention to check correct torque settings on a regular basis, throughout their life, as the gaskets and the rest of the engine ages. I have found engines fitted with these excellent head gaskets, where subsequently the engines have almost ‘finger-tight’ head nuts and unfortunately subsequent head gasket failures.

All the best,

David

[Forumadmin]

I agree with all that you say David.
The change of oil after rebuild also allows you to search for any unwanted particles that may indicate a problem.
There has been discussion on JT about zinc before. viewtopic.php?t=6280
As for running in, then that used to be the mantra for a new car well into the 1970s but manufacturing tolerances improved greatly so it is now not normally done. But revving the guts out of a new engine, especially with cold oil, is not what I would recommend, but try telling that to the new generation, who will take their new Porsche from the forecourt and see if it can do 0 to 60 in 3 secs.