Hi eddie,
These engines (definitely 1098's anyway) have no rear main seal on the
crankshaft. Oil is retained in the engine by utilising the vaccuum you're
describing (as well as by a 'thread' on the crank end that 'turns' the oil
back into the engine).The sealed oil cap maintains this negative pressure.
Andy
sprite mkIIA
>From: "Eddie Sheffield" <esheffield@prizmail.com>
>Reply-To: "Eddie Sheffield" <esheffield@prizmail.com>
>To: "Spridgets" <spridgets@autox.team.net>
>Subject: More carb/engine curiosities (longish)
>Date: Tue, 27 Feb 2001 18:06:01 -0500
>
>First, thanks to everyone who responded to my SU carb questions a week or
>so
>ago. Unfortunately I'm still having problems, but have some new "evidence"
>that may be relavant, but I can't really interpret what it means.
>
>I have carbs from a 1967, but the rest is 1971 (I think, I can't swear to
>the intake manifold.) I did one small mod on the intake manifold, though.
>The connector coming out the top center (usually a right angle bend) was
>broken off, plus there is no air pump, etc. (it was de-smogged when I got
>it). So since I was installing the 1967 carbs I thought I'd as closely as
>possible duplicate the 1967 emissions stuff - PCV mounted on the intake
>with
>a connection to the oil separator on the timing cover. I'm assuming the
>dizzy is 1971 and should be driven off the intake manifold rather than the
>carb. So I basically have what looks like page 318 of Bentley. Ideally
>should be what's on page 320.
>
>(Looking closer at those pages just now, I think I may be getting to the
>root of my problems)
>
>Anyway, I discovered that if I take the oil filler cap off while running it
>speeds up noticably. Disconnect the hose from the oil separator and it
>really speeds up. Unhook the PCV from the manifold and it runs like a bat
>out of he##. One think I JUST noticed in Bentley is that the 1967 used a
>FILTERED oil filler cap, while the 1971 used a SEALED one. The connection
>that would normally go to the carbon canister is open, btw. So it seems
>that
>I have some kind of severe back pressure/vacuum thing going on in the
>crankcase. Also discovered the sudden appearance of a oil puddle under the
>car that wasn't there before. That's notable because I had been impressed
>that it didn't have any major leaks before, and didn't notice it on
>Saturday
>when I last ran it for a little while.
>
>I do now have some 1972 vintage carbs that have the correct connections for
>the crankcase ventilation and a carbon canister, so I believe I'll go ahead
>and put them on ASAP and see what that does.
>
>Couple of questions:
>
>1) I remember reading somewhere (might have been in Vizard - haven't read
>it
>all, just skimmed it a bit and hoping to really use it in the future) about
>how crankcase pressures can cause problems if not handle properly. Can
>someone explain why? And did what changed in the 1275s between 1967 and
>1971
>that would cause such differences in the crankcase pressures?
>
>2) Does anyone have one of those Y connectors that goes between the carbs
>and connects to the oil separator? The carbs I bought didn't come with
>that.
>VB has it, Moss doesn't appear to. Rather send a few bucks to a list member
>than to VB.
>
>I have to admit, these A-series engines seem a little touchier than the
>(older) American iron I've dealt with in the past. Not a slam, just an
>observation. I just need to get used to the differences. Certainly newer
>engines are touchier than the older. When they work, they're great. But let
>one little sensor go out...
>
>Eddie
>1971 Midget (under pressure)
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