A mate has a MK1 MR2 which he's running in the MR2 challenge this year, and has had a blueprinted engine built for it. His question, how long should he run it in for?
My knowledge of running in engines always dictated 500 miles of no more than 1/4 throttle & 3000rpm, then change the oil and start gradually increasing revs/throttle up to 1000 miles. No I understand that modern engines take far less running in, but a MK1 MR2 isn't really 'modern', so any advice offered will be gratefully received.
Ta!

He really needs to speak to his engine builder / supplier.

I know you may of wanted a definitive answer and maybe others may be bold enough to give you exact details but it does depend on what bits he has got and that responsibility can only be left down to the man that built it.

HTH.

bout 5 mins till its warm and then rag it, then everything beds in as it should

if you dont rag it the rings wont bed in etc then do an oil change

Have a read up on the internet. There are a few schools of thought on running in new engines alot of people seem to say thrash it now instead of being gentle.

Once hot a trip around the M25, lots of different revs and loads, its important to give WOT to snap the rings into the bores for a few seconds then completely off the loud pedal to allow the rings to relax and oil to lubricate the bores.

Don't let it idle, revs above 2000.