I had to look up my old notes on this because I posted a similar query to
the list two years ago. Some research and information from other listers
like Barney showed me that the subject of cam selections was quite complex.
For one, if you go with too high a lift on the cam, you will also have to
upgrade your valve springs to take advantage of power past 6000 rpm. Plus,
you may need to index the cam timing. These requirements come into play at
or around the 270 cam point I think (although I am far from an expert on
the subject).
From my query, I found another lister had gotten a mild street cam from
Lawrie (also on the list). I ended up also going that route because -
1. Lawrie is on the list
2. The price was right
3. Lawrie was also very helpful in providing personal technical advice on
setting up the cam.
It is a 265 degree cam with .283 lobe height and 108 degrees lobe center.
Actually it was a regrind so I sent him my old one in exchange. It looks
like it is very similar to Piper's BP255 with a power increase of 8 bhp.
Power band is 1000-6000 rpms.
I had attempted to go with a fast road cam in my 71BGT many years ago but
the Isky cam failed in less than 10k miles so I had to put a stock one in.
So I was a bit paranoid from that experience. However, in that case, I
never really noticed any performance gain before the lobe failure.
So far, this cam has worked out well. Its still early as I only have about
800 miles on the engine with this mild road cam and +.060 pistons. But its
quite peppy, even though it won't blow the doors off any of these modern
rice rockets. I'm not sure what the compression ratio is but it is at least
9:1, maybe more. The pistons were not dished like the low compression ones
but still had a slight depression. How else can I determine the compression
ratio? I bought them from mechspec in the UK.
David Councill
67 BGT
72 B
At 04:41 PM 4/25/2004 -0700, John Di Fede wrote:
>I wrote:
>
>
> >I am currently rebuilding my 1973 MGB engine and would like some advice
> regarding upgraded cam choices and >any recommendations or personal
> experience with a particular cam.
>
> >I will be installing this cam into a MGB engine with a +.020 overbore
> and a ported cylinder head (based on Peter >Burgess "Power Tuning MGB"
> suggestions) with 1.625 inlet valves, peco exhaust, K&N filters and HIF
> carbs (but I >have a Weber 45 DCOE and cannon manifold sitting on
> a >shelf in my garage)
>
>Regarding the engine's compression.....
>
>I've just measured the combustion chamber cc'c and estimate that the
>compression ratio on this engine will be AT LEAST 9:1.
>
>
>I've also found the Piper website in the UK where they claim their Fast
>Road cam #BP270 will produce a 12 BHP gain. Cam Stats = 276 duration,
>intake/exhaust lift .405", overlap 62, @ 1500-6500 rpm power band.
>
>This cam (or a variant of it) also was highly recommended by Peter Burgess.
>
>My MG is not a racer. I like to think of it as a modified street car. I
>am looking for more all around performance, while retaining a reasonable idle.
>
>Any thoughts or comments experiences regarding this Piper cam in an
>otherwise stock MGB ??
>
>Here is the link to
>Piper. http://www.pipercams.co.uk/NewPiperWeb/redesign/PiperCamFrames.html
>
>Select "Austin Rover B Series MGA MGB"
>
>CAUTION: This link may take a while to load depending on your download speed.
>
>
>As always, Thanks!
>
>John
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