164 Rumbles, Revs and Plugs

["C.M. Smith" <cmsmith@domain.elided>]

My 164L 91, 110,000 km (66,000 miles) also rumbles a little while idling
hot, but it's pretty subtle. I think it is the main bearing noise undamped
by nice heavy oil. Factory fill for the sump is fully synthetic Selenia 10W
40. I recently started using Agip 5W 50. The noise is pretty much the same.
Synthetic oil is very thin hot or cold, that's the idea. What weight of oil
are you using, BTW?

My 81 GTV6 also used to rumble noticeably when taking off after a period of
hot idling. That was definitely main bearing noise and since it occurred
from new I was unconcerned. The oil pressure at hot idle is so darn low I'm
not surprised there's not enough oil in the bearings at idle to keep them
perfectly quiet.

Bottom line ('scuse the bad pun) I wouldn't worry as long as the sound is a
muffled rumble rather than a noticeable metallic knocking, and disappears
the instant the engine starts to rev. Modern lubrication depends more on
the wedging action of the oil film than oil pressure to keep the metal
parts apart, and this wedging action increases rapidly with rpm. Think of
the bearings (if you can bear to) as flying on an ever renewing cushion of
oil riding on the crank journals, always approaching disastrous
disintegration but being saved on a split second basis by fresh oil just
pumped into the bearing gap.

The engine will often "ping" (as the English say) as you let in the clutch
gently at low rpm. The engine will stall or bog badly if you let the clutch
in smartly at low rpm. Alfa engines don't really like being driven English
style and complain when the revs get too low. Con Brio will eliminate the
brief ping to the consternation of your passengers if unfamiliar with this
style of driving. BTW, Englishmen also drive Alfas Italian style, it's the
Rollers, Daimlers, Wolsley's (mein gott, haf I forgotten 'ow to spell
"wolseley") that tolerate sedate take off ("tolerate" is perhaps
inaccurate, the mind boggles a little at a Roller being driven con brio!).

 Cars with strong personalities need to be driven according to the
nationality of the designers and builders, not the national preference of
the driver, if you want to enjoy the experience to the full. That's why
Alfa's retain their odd driving position. To the average Italian, the
driving position is perfect and not odd at all. Shift with both feet off
the floor, on all three pedals if you're going down the 'box, (the seat is
to hold you up, you don't need your heels on the floor) and shuffle the
wheel rapidly back and forth holding the wheel in both hands at the 9 and 3
or even 8 and 4 positions, if you want to feel the real magic. The arm
crossing is not common in Italy, as I understand it, (unless provoked!).
Nuvolari et al only resorted to it (while steering anyway) because the
heavy steering and big wheel of those old race cars required very rapid arm
movement from a position quite close to the wheel. I still resort to the
arm cross when turning sharply, as I am of English background and "learned"
to drive watching Stirling Moss and crew on TV and in those funny
learn-to-rally driving books.

 Pinging is not a problem, it was common before ECU's controlled high
performance engines. It was the real detonation that did the damage and the
worst type would occur at high revs, holing pistons etc, with the sounds
often masked by other engine noises. As long as the pinging is brief and at
relatively low rpm it is harmless (though still technically pre-ignition or
"detonation"). Pinging likely to cause damage is usually accompanied by
loss of power restored instantly the pinging ceases.

I still catch myself driving my 164 English style now and again, and the
car complains gracefully about the inadequate revs and throttle opening I'm
using. The 2000 rpm sounds right but I really think letting the revs drop
to below 1100 is not doing the engine any favours, Why not give that
no-torque-below-1500-rpm-short-stroke-V6 a chance and keep the revs above
1500 while letting in the clutch, you'll have much more fun and the car
will thank you for it.

 Clutches aren't sacred, they are wear items like brake pads, not permanent
fixtures like transmissions are supposed to be ( I don't wanna talk about
transmissions requiring routine replacement of say main bearings!)

As for retorquing head bolts, not necessary according to the shop manual
and my mechanic. First service at 1,000 miles the head is retorqued and
that's supposed to be it. When you replace the rear spark plugs check the
wells for oil. If the plugs coming out are wet with oil above the threads
(i.e. outside the combustion chamber) your plug well seals are crapping out
(a chronic problem due to the large valve cover casting with two separate
mating surfaces with different expansion characteristics). Check all the
front bank first before you take the intake plenum off, that way if any of
those are leaking you can buy the seals kit and do the whole job at once.
Sounds funny, but if the valve clearance check/adjustment needs doing it
should be done when you replace plugs because taking off the intake plenum
is a bit of a pain.

Michael Smith
Calgary, Alberta
Canada
91 Alfa 164L, White, original owner 

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