Running in

[hirstydg]

Hi All

Just finished the rebuild of my 3.8 FHC and hoping to enjoy it over the summer. The handbook states that the engine should be restricted to 2500 rpm for the 1st 1000 miles and 3000 rpm till 2000 miles. This is quite restrictive especially when I will probably only be driving about 1500 miles per year, so it would take me 18 months to run in the engine. I have also read comments to the effect that driving as gently as that can lead to poor bedding in of piston rings and heavy oil consumption later. My engine has been rebored with new pistons, reground crank, new crank bearings and new oil pump. Also new valves and guides. Engine is filled with Penrite running in oil (how long should I leave that in for?). So should I restrict myself to 54 mph for the first 1000 miles? And obviously straining in too high a gear to be avoided. I'd greatly appreciate your thoughts on this.

Thanks

David

[pmansson]

You certainly don?t want to coast along the motorway for hours and hours, below 2500. Some uphill work, some Engine braking going downhill, some acceleration, some motorway and so on. Ideally between 2000 and 2500 and touching 3000 at brief moments long Before those 2000 miles. Testing the torque at low revs is not good.
Hope this helps.
The rules were written in the 50s when Engine oils were different. My BMW Engines from the early 70s, after a full rebuild, can be used flat out pretty much the first day....

Peder

[abowie]

Everyone will have a different opinion. AFAIK modern ring materials pretty much obviate the need for the traditional "running in" process.
I was advised to avoid high revs for a while and so didn't go over 3500 for the first 1000 miles or so but with nearly 3000 miles on the engine now I'll happily pull 4500 rpm in first and second.
WRT changing the oil my personal approach is to do a change very early on on the principle that if there is a rogue bit of swarf in there, or just some fine particulate matter, I want to take it out ASAP. Then another change at a couple of 100 miles. Oil is cheap, engines are not.

[hirstydg]

Many thanks, that is sound advice. Part throttle and varied driving with 3000 rpm rev limit till 1000 miles seems good. I have done one oil and filter change already after only static running of the engine and intend to do a second change from the running in oil to Penrite classic 20/50 at about 400 miles. Does that seem about the right interval?

David

[SEJohnson95]

Richard's 4.2 was run in with a 2500 rpm rev limit and the oil was changed after 500 miles. She barely uses any oil now. Hope this helps :)

[malcolm]

An old friend of mine, who was also a specialist Jag mechanicv in the 60's, owned a 3.8 back then. His views on running in even then were similar to above. he felt more harm was done by people slavishly folowing rev limitations rather then driving sensibly, although obnviously this didn't mean revving too high either. He advocated first oil change early, and simply avoiding "stressing" the engine by, for example, trying to climb hills in too high a gear (sometimes by people trying to keep under that rev limit) or using to much throttle from low speed. He felt that for those with no "feel", a simple accelerator peddle restriction could be effective - made them change down early on hills, and stopped over demanding the engine from low revs. He also suggested avoiding constant speed driving. His cars were always the smoothest you'd ever drive. Incidentally, he ended up winning the Essoflow championship in 1974 in, if my memory is correct, a V8 ford falcon. He also owned and raced BUY 12 for a while. (Mark 2)

[Mark Gordon]

I can only echo what has generally been said already. After my rebuild, I limited revs to 2500 for the first 300 miles with no full throttle accelerations. Changed the oil at 300 miles, then gradually increased the throttle pressure and increased the rev limit to 3000 rpm for the next 200 miles. After that, it was fully broken in and I drove it without concerns to rev or throttle limits. After 1500 miles following the first oil change, I finally had to add one quart of oil.
A friend went through a professional rebuild and babied his engine for I think a thousand miles or so and he had a heavy oil burning problem because the rings weren't properly bedded. He changed the oil and started driving it like he stole it and the rings bedded and the oil burning problem went away. Just anecdotal but these two cases support others' experiences.

[andrewh]

Last engine I rebuilt was a Rover V8 and it had new rings but the bores were just honed. I was told not to pussy it too much and it was suggested to me that it was good to drive it up a hill in a slightly high gear to bed the rings. I do t mean to labour it , but to make the engine work without over revving it. I did this a bit for limited periods and the engine is really good now. I think the golden rule is not to be frightened of it or you will glaze the bores, but also not to race it without fear.