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19 January 2001 |
This is another of those subjects that crops up
on the message board frequently. I am constantly surprised by the number of
engine builders - or people who charge other folk for building engines at any
rate - that never hand out such an information sheet. It seems pretty daft to
me that having taken a wad of money off of a customer for an engine you've
lovingly put together, you'd want to help that person get the very best out of
the engine. And the running/breaking in procedure is absolutely crucial. It at
least ensures no damage is incurred when the engine first bursts into life.
A collection of the usual suspects have
explained their own methods on the board, along with various others - many of
which probably work just as well for them, a few which are down-right dubious.
Following is a sheet I administer with every customer engine I build. Most of
it is pure common sense, but then that's what tends to get most folk into
trouble in the first place! I've been using this procedure for some 15 years
now without any problems reported whatsoever. And believe me - when a customer
pays out the sort of money it takes to have an engine built, they'll be banging
on the door at the slightest hiccup! With that in mind - I'm sure this will
work for most.
Running in New Engines - the
Mintec method.
Install engine. It is absolutely imperative
that the cooling system is more than sufficient to deal with any temperatures
likely to be produced by the engine. More power means more heat to be
dissipated. A standard radiator is very unlikely to be able to cope with a
reasonable power increase over standard.
Do not fill cooling system yet. Set clutch throw-out and free-play take
up. Double-check all connections electrical, oil, fuel and cooling system. Put
in engine oil – use a cheap multi-grade mineral oil. DO NOT use either semi or
full synthetic oils. They will stop the rings from bedding in. Remove spark
plugs, and spin engine over in bursts of a few seconds at a time to pick up oil
pressure and prevent starter motor damage. DO NOT start engine until oil
pressure picks up.
Once oil pressure is showing, check ignition
timing statically. Set to figure advised by distributor maker, or if no figures
available, set at around 6-8 degrees BTDC. Re-fit sparkplugs
and start engine. DO NOT allow to idle under
1,500rpm at start-up - 2,000rpm is preferable. Allow engine to run until
cylinder head is warm to the touch, then switch off and allow to cool completely. Fill cooling system and re-start. 2,000 rpm should be maintained for the first
ten minutes of running, irrespective of use, to prevent cam/follower damage,
and help bed same in. After this period, reduce idle to 1,500rpm on race units,
1,200rpm on road units until engine is run in. After this, race units should
not be allowed to idle at under 1,200rpm as valve train damage and premature
wear can occur from erratic low speed running, and the water pump is very
in-efficient at low revs. Road units, aim for 900rpm as a minimum. All that
trying to get the idle down to 600 rpm like uncle Joe used to on his old banger
is nonsense - that was Ok when cams barely had lobes!
Run engine in using part throttle and low loads
only, and keep rpm down to no more than 60% of rpm limit. Use the gearbox. DO
NOT put engine under unnecessary loads (i.e. going up hills in top gear just
using the throttle to maintain progress). Although the bulk of the engine
requires little running in because of accurate building and tolerances
employed, the more miles you can achieve the better the ring seal will be. 500
miles is enough. During running in, make sure the engine does not run hot, too
lean or too rich. Both will cause premature piston/ring failure. Temperatures
over 95 degrees C (203 degrees F) are unacceptable. If this occurs, re-set
static ignition timing to 2 or 3 degrees BTDC, re-check carburettor/fuelling
settings, and re-check cooling system capability.
Once the running-in period is complete,
re-torque cylinder head nuts – 50lb ft for the nine main 3/8”AF nuts, 25lb ft
for 5/16”AF rocker post nuts and end two 3/8”AF nuts. Re-set valve clearances
(see below for settings). Where roller tip rockers are used, DO NOT push feeler blades through from front as standard. The
roller tip acts like a panel roller and will draw the blade through
irrespective of gap size – even if there isn’t one. The feeler blade must be
wiped sideways from one side to the other.
Finally re-check all connections, and then have
the unit set up on a rolling road. As soon as it’s finished, and whilst still
hot, ask the rolling road operator to check the ignition timing at, say 2,000
or 2,500 rpm using the TDC pointer/mark on the timing cover/crank pulley. The actual
reading is irrelevant, just a reference point. Make a note of this, and check
it periodically in the future. It will also serve to re-set it in the event of
ignition component changes/engine re-builds for whatever reason in the future.
Carry out periodic compression tests – they can help forewarn of possible
trouble. Always do them immediately after competitive use or when engine’s hot,
with throttle wide open.
Running without an air filter will cause
premature wear to valves, guides, seats, pistons, and rings.
RECOMMENDED VALVE CLEARANCE:
NOTES:
In this end section I add obviously the valve
clearances I'll recommend for the cam and usage, plus anything particularly
relevant to the individual's engine. I believe you simply cannot have enough information,
but also realise too much would just swap the recipient. Hence this is short,
to the point, and covers all those items that cause hassle when starting an
engine for the first time.