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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