New car doubts

[johnnynumfiv]

Be careful with that 3.8, they like to blow head gaskets.

[hightower99]

So we bought a Peugeot 407 ST Sport pack V6. Of course i had to kidnap it and go for some twisties ..

My question is .. Why should you wait a certain amount of time, or better yet, a couple of thousand kms till you can rev new cars really hard?

sorry I got carried away and never gave a good answer to the question!!!

well running in the engine is mostly (80-90%) about the piston rings. from the factory they do not seal around the total 360 degrees of the cylinder. to make sure they do you should understand that it is not the spring tension of the rings that hold against the pressure of combustion.... it is the gasses from combustion that holds them. as the gas expands it hits the rings and gets between them and the piston and pushes the rings against the cylinder walls. To get the rings to press hard enough that they warp and match the shape of the cylinder you will need to get some good pressure in there... so run your motor hard! The last 10-20% of running in is to knock off any burrs or sharp edges in the engine. This is why it is important to change (if not flush out) your oil after the first 50 miles!!! because all the little bits of metal that get knocked off go into the oil and if the contaminated oil runs through your engine too long it will breakdown and deposite the metal bits in places they shouldn't be. there is no need to "bed in" bearings and there is no need to "harden" metal surfaces as niegther of these things happen and if they do something was really wrong in the first place.

I hope that is a suitable answer if you have any more specific questions I will be happy to answer.

Engine designer and tester
Stewart a.k.a. Hightower99

[hightower99]

Be careful with that 3.8, they like to blow head gaskets.

yeah I know that is why when it happened to my dad's car I switched mine out with nice fat copper ones with high carbon steel inner piston seal rings!!!