1600GT xflow, recent rebuild where:

Cylinders bored to first oversize.
New pistons & rings.
Reground crankshaft and new bearings fitted.
New valve guides and valves.

Currently full of Valvoline VR1 20w/50 oil.

How many miles should I run the engine in for?

Ta
Gary

I never exactly run mine in except I used some cheap oil for around 500 miles before changing to Valvoline just before a rolling road session

My crossflows were built with power in mind, but i used cheap mineral oil from asda for the first run and idleing, and first 50 or so miles, to make certain of any tiny bits of engine were trapped in the filter, also any water vapour that crossflows like to collect

Then for the next 300-500 miles depending on how the engine felt, i would use premium oil, and always change the filter

As for engine speeds, no harsh accelerating, and kept under 3-4k for the first 300 miles ish