Hi Wayne,
Earlier today, you asked about engine balancing.
I'm the owner of a major balancing workshop here in Holland, Europe.
Though we mainly balance all sorts of rotors for industrial customers,
we also get a lot of automotive crankshafts for balancing.
This is mainly done for three groups of customers:
1. Importers/ distributors of new cars.
Every now and then, a proud owner is confronted with vibration
problems in a new car and the supplier then asks us to investigate and
rectify this.
[No, I'm not gonna tell you which makes... :-) ]
2. For racing and rallying.
Crankshafts are often modified from standard and this may upset the mass
distribution.
3. For classic cars (that is, over here, anything older than, say, 15 years).
We get a lot of classic car owners as visiting customers and a few years ago
one of them asked me to hold a lecture about balancing for a local car club
(of historic
Volvo owners), which I did.
When preparing this lecture, I've gathered some statistical info on the last
100 crankshafts we had balanced.
It was found that, statistically, the clutch assemblies have the largest
unbalances.
This can be explained when you know how clutches are rebuilt.
Generally a workshop disassembles a batch of clutches of a certain type and,
after repairing the constituent parts, they reassemble them 'at random'.
Most repair workshops do not rebalance these clutches afterwards.
I've been at several ones of them!
Flywheels can only get a 'new' unbalance when material (mass) is removed
(e.g. for racing) or when resurfacing (skimming) is not done correctly.
When crankshafts are reground, the 'new' axis of rotation (i.e. after grinding)
should coincide with the 'old' axis of rotation (before grinding). (=main
journals)
Even an error as small as 0.02 mm (.001 in) is enough to upset mass
distribution and will cause unbalances.
After having balanced thousands of crankshafts, it is also possible to say
something
about which makes are more likely to have unbalance than others:
- Porsche, BMW, Alfa Romeo and Volkswagen Golf (Rabbit) GTI crankshafts
are almost always flawless.
- Triumph and MG crankshafts, especially those from the 70s, are
among the WORST!
I have the following possible explanations for this last phenomenon:
1. The Seventies were NOT a great era in British motoring history.
2. These now so cherished classic cars were, at one time, just cheap old
bangers (clunkers ?) where repairs just had to be made cheaply and
cheerfully.
3. Many (most?) TRs and MGs we now have over here have been (re-)imported
from the USA.
I hope I don't insult anyone but it is my sincere opinion that
engineering standards (at least as far as automotive repair/maintenance
is concerned) in the USA are not at a very high level.
This very personal opinion is, a.o., based upon carefully looking at
ex-USA MG's when I was looking for a B to buy for myself.
So, Wayne, in my opinion it is certainly recommended that you have the
crankshaft
balanced now that your engine is still apart.
By the way, just to give you an indication, we charge a flat rate, including
taxes,
of (about, US) $ 120 for balancing a (4-cyl. in-line engine's) crankshaft, where
flywheel, pulley and clutch assembly are also balanced (at first, individually,
later also in combination with the crankshaft).
This, however, does _not_ include the balancing of pistons and conrods, as
most owners prefer to do this themselves to save money (because in this country,
we have to charge about $50/hr for labour costs because of high taxation
to finance our excellent social security system. This is also the reason why
premium fuel, as required for most MGs, costs over $5 /U.S. gallon here).
Concluding:
- I would recommend that you have the crankshaft checked for unbalance locally
as we found that MG crankshafts often do have relatively large unbalances.
- If you want to save money I strongly recommend that you have,
at least, the clutch assembly checked for unbalance (cheaper) OR you should
verify that the workshop that it comes from _does_ balance.
- Also check the mass of the conrods! I have seen sets where one conrod
was 35 g (1.2 oz) heavier than the other three!
Obviously the conrods of two different engines had been combined.
(YES, this was on an engine of a USA-reimported car!)
BTW I found in literature that it was common practice to balance automotive
crankshafts as early as 1924! (Alfred P. Sloane, My years with General Motors).
Hope this has been of some interest to you!
WARNING: The usual disclaimers do NOT apply, as I make a living out of
balancing!
Bert Palte
working at Vortex Balanceertechniek BV, Soest, Holland.
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