To stir up a hornets nest
Posted: 29 Nov 2009 01:19
Gaz, [no offence mate I just can't help it], consigning himself to
over 1200 miles of slow careful motoring, to "run in" his new
engine has got me up on one of my hobby horses.
That is the fallacy of the "traditional" running in of a new or
rebuilt modern engine. Yes, in the days of hand poured & scraped
white metal main & big end bearings which were somewhere near
round, this was essential. Even a bit later, when the machine
tolerance for pistons, & other stuff was +/- a thou, it was wise,
but today, with thin wall bearings, & good machining, if the thing
needs that type of running in, it will be run out, before it gets
there.
We mostly all now know about the running in of new cams, & followers
in our now older engines. When the rest of the engine has had that
hard type bedding in, along with the cam, it's ready to go. Just
give it time to warm the oil, before you blast it, each time you
drive it.
When I was racing, after building a new engine, we would go to some
trouble, warming the oil to temperature, in the pits, then go
racing. There was no "running in" for them. My Brabham F2 finished
every race it started, & was twice voted the most reliable racing
car in oz, by the racing mechanics club, so the treatment worked.
It was also quick. It finished second in class in its first race,
then won its class in every other race it ran. It finished 3Rd
outright in the 1967 Bathurst 100 [miles] for F1 cars.
When I sold the car, after 2 seasons, everything in the engine,
except the very expensive forged Hepolite [ex Cosworth] pistons,
which used to crack, the rings, big end bolts, & the timing chain
was original, & no wear could be measured, anywhere.
I used to laugh quietly at some of my competitors, trundling around
a practice track at low revs, running their engine in, for 50, or
even 100 miles. Of couese I never told them that this runnung in
process would be adding seconds to their lap times.
With hugh choke tubes, wild cam timing, & ignition timing usually
miles out ot low revs, these blokes put more carbon buildup in their
engines this way, than they would have with hundreds of miles of
racing. I had seen the carbon build up in an engine, after this
running in, without racing, & it was awful. It destroyed their
combustion chamber shaping, & their breathing. Carbon build up was
right through the inlet manifold, almost to the carbs, due to the
wild cam timing.
But Gaz, you are right about the revs mate.
My 7 has a similar set up to yours. The filters, & the exhaust
demanded the richer needles. It made a huge difference to the
torque, & performance from from about 2300 to 3800RPM, tapering
from there to not much if any, effect from 4250, & above. With all
this torque there is not much piont reving the stockish engine.
High com, a cam, big valves & porting may make it worth while, but
then, why own an 8.
The only reason I ever go above 4000 is to hold a gear in an
overtaking manoeuvre, or for an approaching corner, otherwise the
thing now has very satisfactory performance in this enhanced mid
range.
Hasbeen
over 1200 miles of slow careful motoring, to "run in" his new
engine has got me up on one of my hobby horses.
That is the fallacy of the "traditional" running in of a new or
rebuilt modern engine. Yes, in the days of hand poured & scraped
white metal main & big end bearings which were somewhere near
round, this was essential. Even a bit later, when the machine
tolerance for pistons, & other stuff was +/- a thou, it was wise,
but today, with thin wall bearings, & good machining, if the thing
needs that type of running in, it will be run out, before it gets
there.
We mostly all now know about the running in of new cams, & followers
in our now older engines. When the rest of the engine has had that
hard type bedding in, along with the cam, it's ready to go. Just
give it time to warm the oil, before you blast it, each time you
drive it.
When I was racing, after building a new engine, we would go to some
trouble, warming the oil to temperature, in the pits, then go
racing. There was no "running in" for them. My Brabham F2 finished
every race it started, & was twice voted the most reliable racing
car in oz, by the racing mechanics club, so the treatment worked.
It was also quick. It finished second in class in its first race,
then won its class in every other race it ran. It finished 3Rd
outright in the 1967 Bathurst 100 [miles] for F1 cars.
When I sold the car, after 2 seasons, everything in the engine,
except the very expensive forged Hepolite [ex Cosworth] pistons,
which used to crack, the rings, big end bolts, & the timing chain
was original, & no wear could be measured, anywhere.
I used to laugh quietly at some of my competitors, trundling around
a practice track at low revs, running their engine in, for 50, or
even 100 miles. Of couese I never told them that this runnung in
process would be adding seconds to their lap times.
With hugh choke tubes, wild cam timing, & ignition timing usually
miles out ot low revs, these blokes put more carbon buildup in their
engines this way, than they would have with hundreds of miles of
racing. I had seen the carbon build up in an engine, after this
running in, without racing, & it was awful. It destroyed their
combustion chamber shaping, & their breathing. Carbon build up was
right through the inlet manifold, almost to the carbs, due to the
wild cam timing.
But Gaz, you are right about the revs mate.
My 7 has a similar set up to yours. The filters, & the exhaust
demanded the richer needles. It made a huge difference to the
torque, & performance from from about 2300 to 3800RPM, tapering
from there to not much if any, effect from 4250, & above. With all
this torque there is not much piont reving the stockish engine.
High com, a cam, big valves & porting may make it worth while, but
then, why own an 8.
The only reason I ever go above 4000 is to hold a gear in an
overtaking manoeuvre, or for an approaching corner, otherwise the
thing now has very satisfactory performance in this enhanced mid
range.
Hasbeen