$.02...
some of the power could be related to cam timing
(+/-4 degrees will kill ya', which is less than one tooth
position on the cam gears.
Both adjustable cam gears, and/or offset keys are avail.
to alter the valve timing.
What's you vac. at an idle like?
Above 21? 15-18?
I have to admit from experience when I switched back
to dual SU's from my Weber DGV downdraft, a power loss
although mild, was noticeable. In my case it could have been
that the Weber DGV had been rejetted on the rich side
(The PO did alot of highway cruisng as a daily driver)
ymmv
Paul Tegler
Twin 73' MGB GTs YB and OB
YB born 8/72 (Primrose Yellow) Yellow BGT
OB born 1/73 (Blaze Red) Orange BGT
email: wizardz@amdyne.net
http://www.amdyne.net/~ptegler/mgmain.htm
-----Original Message-----
From: Matt Milkevitch <milkm@mail.vt.edu>
To: mgs@autox.team.net <mgs@autox.team.net>
Date: Wednesday, March 10, 1999 2:48 PM
Subject: Compression test- - -opinions needed (long)
>Fellow Listers,
>
> Approximately 1 year ago, I completed a full rebuild on
>of the engine in my '74 BGT. I completely redid everything, to
>include 8.7:1 pistons, mild camshaft (Piper BP 270), unleaded
>conversion, and so forth. In addition, I also redid my SU HIF4
>carbs, replacing a Weber I had previously used. Also, I am running a
>cannon header, Lucas 45D4 (Eurospec), and Peco exhaust.
>
> My problem since completion has been lack of power.
>Given my modifications, I was looking for an engine that would pull
>well, but it remains something of a dog. Granted, what I'm saying is
>very subjective...and I was reminded by a friend that these cars
>weren't all that fast to begin with. Sensing some type of internal
>engine problem, I took it to a local MG shop and had them check it.
>They performed a leak down test, and said that I was losing
>compression badly, and that they could hear the air leaking through
>the oil dipstick hole. This indicated to them that the rings weren't
>holding up. In addition, a compression test indicated that all
>figures were hovering around the 130 psi mark.
>
> Since that time, I've done a few adjustments (mixture,
>timing etc) and have seen some small improvements. I also performed
>another compression test giving the following figures:
>
> Cyl 1 = 140
> Cyl 2 = 135
> Cyl 3 = 145
> Cyl 4 = 141
>
> Precision here is relatively good, and the difference
>in these figures and earlier ones probably can be attributed to
>difference in compression testers. One more note: oil consumption
>is about nil, and oil pressure is very good (45 at idle, around 70-75
>at 60 mph).
>
>
> My question to the group: opinions on these
>figures/data?? Does anyone have a "ballpark" idea on the ideal
>compression of an MGB 18V engine with 8.7:1 pistons?? Right now, I'm
>contemplating a teardown and putting new rings on, and would like to
>get the collective wisdom of the group.
>
>
> Thanks for any advice,
>
>
> Matt Milkevitch
> '74 BGT
>Matthew Milkevitch
>Graduate Student, Ph.D. Candidate
>Dr. Karen J. Brewer(Chem), Advisor
>Dr. Brenda W. Shirley(Biol), Co-Advisor
>Va. Tech
>Blacksburg, VA 24061
>(540) 231-4708
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