Charley & Peggy Robinson had this to say:
>Hi Max,
>
> See below.
>
>Max Heim wrote:
>>
>> Charley, I think you are misconstruing the "bedding in" part. That occurs
>> after the engine is started, when you run it at a constant RPM for a
>> certain period of time,
>
> Not really, Max. In the earlier thread, it was averred that the
>engine needed to be started immediately, to get the oil to it sooner,
>otherwise extended cranking before starting would do-in the cam. This
>was based on one (1) cam grinder's pronouncement.
>
...and you disagree with the cam grinder on this? Anyway, the oil
starvation aspect would be averted by the Twist method, as you pointed
out, and I previously concurred. But you still need to start the engine
sometime, and when you do, you still want it to run well, and stay
running. Even with oil pressure up, extended cranking without starting
would be bad for the cam, as would starting and stopping, stumbling,
lugging, and missing.
>> you want to get it running at this RPM ASAP, and not be cranking and
>> cranking trying to start the engine (as could happen with a first-time
>> startup with a new carburetor of a different type), and then fussing
>> getting it to run correctly.
>
> Aw shux, Max, after my first one 40 years ago, I haven't built an
>engine that didn't fire right up as soon as I tried to start it.
>Frankly, it's a matter of pride with me. It means I did everything
>right. If the mechanic covered all the bases, it should fire right up.
>
So, you think that buying a brand-new Weber, and manifold, and hooking it
up to a just-rebuilt engine, it should fire up first time, and run
properly at all engine speeds (avoiding all the problems I mentioned)?
Sure, that would be nice, but the point was, how can you guarantee it? It
has nothing to do with the engine prep (granting you did everything
right), and everything to do with the *untested* carb setup. But maybe
you are a Weber expert and do not find this a daunting prospect.
Otherwise, I stand by the recommendation to use the carbs that were
running previously, in order to avoid any anxiety on this score.
> So I think it was sage advice not to swap
>> carburetors while the engine is being rebuilt with a new cam, even if the
>> long-term plan is to change to a Weber.
>
> I wouldn't put the Weber on it either, but it has nothing to do with
>the cam. If the carb works it should fire right up. If it doesn't,
>someone didn't take steps to ensure that it would.
>
And what would those steps be, that is what I am asking? Hard to jet a
carb, or adjust the choke, on a non-operating engine...
>> Twist's description of starting up a new engine is perfectly correct as
>> far as it goes, but it doesn't go so far as to describe the process of
>> bedding in a new cam.
>
> Twist's tip was aimed at not putting running loads on the engine until
>it had oil under pressure, so that no sliding surfaces would gall.
>Sliding surfaces include the cam and lifters.
>
Yes, yes, we all know that. And we agree it is the thing to do. But it is
not what we are talking about, as it does not (even potentially) involve
the carburetors.
> Max, this "process" is not unique to bedding in a cam. Any mechanic
>is going to run a newly rebuilt engine in for a half-hour or more at a
>couple of KRPM. Meanwhile the engine will be checked for leaks,
>overheating, noises, etc, etc. No big deal. Might even tip a brew to
>celebrate. ;^)
>
Hmmm, perhaps. I have never rebuilt an engine without installing a new
cam, so I can't comment. But I do know that the cam manufacturer's
instructions include a specific bedding-in period. And, of course, the
celebratory brew goes without saying...
> Cheers,
>
> CR
>
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.
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