Larry,
I fitted a "285" cam to my UK spec 1500 (twin SUs)
The figures are:
Power band 2200 - 6800
Vale timing 34-76 58-34
Duration 290deg, 272 deg
Valve lift 0.44"
Now I don't know what half of that means, but I can tell you that it
runs and pulls better than it used to with the standard cam. It ticks
over at 800 rpm, and pulls smoothly. It will run in 3rd gear on
tickover, foot off the gas pedal without snatching.
As you will know, I have an o/d gearbox fitted so I did not want to
loose low down torque as most of my motoring is done between 3500 and
4500 rpm.
Only engine mods are LCB manifold, K & Ns, polished and ported head
(DIY job, following an old Triumph tuning guide) and skimmed head to
raise the compresion a bit. (can't remember the calculations now, but
did work them out once)
I also got the crank micropolished and flywheel lightened and then
balanced as a unit.
I am pleased enough with it. It drives nicely but is noisy. Lots of
mechanical noise, but I think it is all getting a bit "loose" now at
105,000.
My 1275, with equivalent mods, runs and revs much more smoothly, and
just generally fells a happier motor!
Guy
----- Original Message -----
From "Larry Macy" <macy at bblmail.psycha.upenn.edu>
To: "Spridgets" <spridgets@autox.team.net>; "MG List"
<mgs@autox.team.net>
Sent: 27 October 2000 01:50
Subject: Cams re deux
> OK I got a question. As most of you know I am in the process of
doing a
> rebuild on a 1500 Midget engine. I have been thinking about putting
a cam
> in the engine, for a bit more performance. I have run into some
> questions I have no idea about. All of the rebuilds I have ever done
have
> been stock. Whether it was a 7490 cu. in. Waukesha, a D-9
Caterpillar
> diesel, or the 1500 that is now coming apart on me, it was always
stock.
>
> I am getting a lot of info on cams that I do not know how to
interpret. I
> am looking for a mild street cam. I understand that for the most
part a
> cam shifts the powerband, while adding a bit more ponies. (at least
I
> think that is what I understand).
>
> There seems to be 3 relevant things on a cam, but I don't quite get
what
> they mean, or how they relate to performance. Now bear with me.
>
> We have duration, which is how long the valves are open.
> We have lift, which is how far the valves open.
> We have cam lobe lift, which I don't know what the hell it means.
>
> For instance I have an Kent cam that has
> 295 duration
> .382 in lift & .378 exh lift
> .261 cam lift.
> Power range 2500 - 6500
>
> An APT cam that has:
> 278 duration
> .256 lobe lift
> 231 cam duration @ .050 lift
> Power range 2000 - 6500
>
> And Ted Schumacher that will grind a cam for me, but I forget the
exact
> specs.
>
> And Elgin Cams, Which Mike G posted the other day, but I don't have
handy.
>
> I know that all that stuff is supposed to make the engine breath
better,
> but what the hell does it all mean??
>
> I know that the longer the duration the longer the valves stay open,
I
> know that the greater the lift the more fuel/air charge gets into
the
> cylinder. I know that if the lift gets too much you need stronger
> springs. I know that there is such a thing as valve overlap that is
> supposed to make the charge mix a bit better. (for those of that
don't
> know, that is when both valves are open at the same time, one
closing and
> the other opening, I think it happens on the intake stoke when the
> exhaust valve is not quite closed and the intake is beginning to
open,
> but I forget a lot of the theory as to why that is a good thing).
>
> Ok put it in simple layman's terms for me. I want a cam that will
give me
> a bit more oomph, but that I can tolerate in a car that is still a
daily
> driver. I do spend a bit of time at stop lights so the less "lumpy"
idle
> the better. What cam do I choose, and why should I choose that one,
or
> should I stay with the stock one??
>
> I am going with the 9:1 pistons, balancing, and debating lightening
the
> flywheel. I do not want a race car, I want a daily driver with a bit
more
> oomph. I have a Weber DGV (water coke) and headers. Someday I will
do the
> dual SU's but not today.
>
> Remember this is a street car, not a race car.
>
> Help
>
> Thanks
>
> Larry
>
> BTW I think my sig line really fits here ;-)
>
> Larry Macy
> 78 Midget
>
> Keep your top down and your chin up.
>
> Larry B. Macy, Ph.D.
> macy@bblmail.psycha.upenn.edu
> System Manager/Administrator
> Neuropsychiatry Section
> Department of Psychiatry
> University of Pennsylvania
> 3400 Spruce St. - 10 Gates
> Philadelphia, PA 19104
>
> Ask a question and you're a fool for three minutes; do not ask a
> question and you're a fool for the rest of your life.
>
>
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