I was always under the impression that, for street use, one should enlarge
the intake valves and leave the exhaust valves alone. Generally speaking,
or so I have been led to believe, the recommended approach for improving the
performance of four cylinder LBC engines is (in order of incremental cost
versus incremental power increase):
1. Carburation
2. Increased Compression Ratio
3. New cam (greater overlap/dwell)
4. Bigger inlet valves/port and polish
5. Revised exhaust manifold/free flow exhaust system
Depending upon the cost of new carburettors, maybe #1, 2 and 3 will be in a
slightly different order. However, I have never seen a recommendation to
increase exhaust valve size before doing any of the other things.
-----Original Message-----
From: Chris Lillja <Chris_Lillja@pupress.princeton.edu>
To: John Middlesworth <jape@email.unc.edu>; triumphs@autox.team.net
<triumphs@autox.team.net>
Date: Monday, February 22, 1999 9:41 AM
Subject: Re: Larger valves in TR3A
>
>John,
>
>I installed the Moss valves in my 4A. I measured both them carefully
against
>the stock and basically, the intakes are the same size (maybe .01"
>larger) while the exhausts are a good bit larger (like .1"). This seems
like
>a good thing for a street engine.
>
>This matches my porting philosophy. I go nuts on the exhausts and pretty
>much leave the intakes alone (street use remember).
>
>The old dear seemed to pick up some torque on the bottom and suddenly it
wanted
>to pull right past red line... One cylinder was pretty tired when I started
>(just 90psi).
>
>I was mainly interested in the fact that they are high quality stainless
>valves. I put in hard seats too. Seem to work great. Most old valves can be
>reused so it's kind of overkill. I'm running about 10/1 compression on
>unleaded gas so I figured I needed all the help I can get.
>
>Yep. May be illegal in some classes.
>Christopher M.Lillja
>Marketing Associate
>Princeton University Press
>Fax:609 258 6305
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