Need info on what the best oil is to use whilst running in the LET after rebuild, and approx. how many miles to do with this oil before a change to the usual 10w40 semi-syn?
Best oil for run in?
Need info on what the best oil is to use whilst running in the LET after rebuild, and approx. how many miles to do with this oil before a change to the usual 10w40 semi-syn?
the same stuff you plan to use in it, then 500 miles later, drain it...
15W-40 Pure Mineral, Synthetics won't allow rings etc to bed in properly. 500 miles ish as above. I'd run fully synth in it as the running oil myself though, turbo's just cook any mineral in the semi, and turn it to water in my experience.
i'll await a lot of flak heading in from a certain forum here, but i think that with the sort of materials & tolerances that these engines were designed & built with, i think that running in is only used these days to make sure the cheque has cleared....
we run big diesel stuff, when it gets rebuilt, or even when new, it gets put straight to work.. we buy stihl saws & honda engined plant, and it gets used straight away at full power.....ok, we give stuff an early 1st service, but apart from that, it works for a living. and production car engines arwe the same, what is the gm service interval on a LET, 4500miles on 10w40 multigrade????.
a rebuild does allow for more chance of contamination & swarf than a new build (engine plants are like operating theatres) so 500miles to clean everything up should be enough. then just service it as per the book.
I was also under the 'impression' that it needed to be run in with mineral oil for a short period but wasn't 100% sure. I have been thinking about using fully syn oil (going on various things I've read) when the oil is changed but haven't really seen any fully syn 10w40 around on the high street so unaware of what to go for.
Do I need to cycle between different driving conditions or just drive sensibly and slowly for the first few hundred miles?
There's still an element of running in, take new bearings out of an engine after it's been run for the first time and they will have concentric marks around them where the higher spots on the crank/cams etc has polished them, but the days of taking high spots off of bearings etc are long gone as you say. Running in regime at work is about 2 hours on the dyno, then it's up to making full power for its power run/dyno session or carb setup/mapping, rings are bedded in etc, then we send it away with the customer with mineral in and tell them not to thrash it until it's on its running oil after 500 miles or so (and we tend to take cards more than cheques)
Reason for the mineral is that while it does protect the engine from metal on metal contact it's not perfect so it does allow a little wearing to get all the right clearances etc between all the mating parts.
A lot of race teams will do 2 10 minute runs at 7k rpm to run it in though, but imo that's just risking something that isn't happy yet snagging and wrecking an engine and is often done because they've done it so many times before without problems when they don't have time to do a proper running in.
A rebuild should never ever have any swarf in it either if done properly. More than half the time is spent cleaning, rather than building. A proper race engine, should be so clean inside that you'd eat your dinner off it before it sees oil.
Avoid high RPM, but do do a lot of full throttle/engine braking, pushes the rings out onto the bores under their actual operating conditions, so they wear a little better to their purpose.Originally Posted by Nova_Tek
the moment an engine is up to running temperature after a build or rebuild, 99.99% of the running in is done.
i was told by a bloke who used to work in detroit that they used to build the engines with oiled bearings/shells etc, but dry rings. yank engines are usually good for about 600000miles
its not like we are playing with xflows that need a decoke every 20000miles here
Actually we do, a lot of single seaters still run crossflows, and pre crossflows evenWe've got a Ford Kent sectioned in 'reception' too.
It does take a bit more than running temp to run them in, I've seen a new rebuild that was taken for it's power run a bit earlier than it liked and the power was slowly increasing as the rings bedded in.
30-40 miles of 'running in' for the rings.... after that its pretty pointless and if you havent got the gas seal right then, then you have screwed the bottom end imho.
Treat hear mean keep her keen. use something thick and chewy then change to 10/40 semi synth. Jobs an orange root vegetable.
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