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pigsmith@... wrote:

Yesterday I went to look at an anvil and ended up as a spectator to a

conversation about engines. I vaguely understand about "porting" and the
reasons for putting in shorter connecting rods, but in doing so, the
air/fuel mix above the piston doesn't get compressed as much. I thought
the ideal was to get the most volume squeezed into the smallest space
before igniting it? Or am I confusing myself with some basic jet engine
theory from way back? Is the point of increasing the volume of air/fuel
mixture the whole point, period (not the squeezing)? Did I just answer
my own question(s)?

Well, the point of porting IS to get more air/fuel in the cylinder.
Why they would put shorted con rods I have no idea, unless they were
having detonation problems (and then that is still a screwy way of
getting around the problem).
Did you get the anvil?

-Mitch Utsey

Yup, I got the anvil..
To get back to the short connecting rods-- their reasoning was that in
doing so the crank takes less time to make a complete revolution,
there's less weight to pull while doing so, and with boring out the
cylinders and putting in a nice snappy cam, the idea was to get more
"hit" out of the engine.
But I'm confused about the compression part. Enlarging the volume of air
seems counterproductive to the reasons for shortening the rods: yeah
sure, the crank goes around quicker, but the compression is reduced
because the rods are shorter....?
JL

Howdy,
This is partly a test to post to the new address, but mainly to ask a question:
Yesterday I went to look at an anvil and ended up as a spectator to a conversation about engines. I vaguely understand about "porting" and the reasons for putting in shorter connecting rods, but in doing so, the air/fuel mix above the piston doesn't get compressed as much. I thought the ideal was to get the most volume squeezed into the smallest space before igniting it? Or am I confusing myself with some basic jet engine theory from way back? Is the point of increasing the volume of air/fuel mixture the whole point, period (not the squeezing)? Did I just answer my own question(s)?
Straighten me out on this, please.
PS. When I asked the guys in yesterday's conversation the question about the compression, they got a glazed distant look about them. Makes me think they don't quite understand everything they know about this stuff, either.
JL

pigsmith@... wrote:

Yesterday I went to look at an anvil and ended up as a spectator to a conversation about engines. I vaguely understand about "porting" and the reasons for putting in shorter connecting rods, but in doing so, the air/fuel mix above the piston doesn't get compressed as much. I thought the ideal was to get the most volume squeezed into the smallest space before igniting it? Or am I confusing myself with some basic jet engine theory from way back? Is the point of increasing the volume of air/fuel mixture the whole point, period (not the squeezing)? Did I just answer my own question(s)?

Well, the point of porting IS to get more air/fuel in the cylinder. Why they would put shorted con rods I have no idea, unless they were having detonation problems (and then that is still a screwy way of getting around the problem).
Did you get the anvil?

--

-Mitch Utsey

I'm just worried about being nekkid
and neck deep in the Nile while some
Egyptian sails by Saying, " Hey,
where's all your stuff?"

-David Mandeville

Did Roman Medics refer to IV's as 4's?

What do little birdies see when they are knocked unconscious?

Think Globally, act tactically

I'm by no means an expert on building a motor, but I believe JL's
explanation is correct. It would reduce compression, but only if you
reused the same pistons. If you put in shorter conn rods, it allows the
motor to twist higher RPM's due to JL's reasons. Add after-market domed
pistons or ones where the wrist pin is lower in the piston or some combo of
both these traits, and compression is kept at the same level or near it,
(could even be higher with the right combination). The benefit is only
found at higher RPM's, good for go fast machines, but normally not much use
for Jeeps where Torque and Grunt gets ya more. This is my rudimentary
understanding of motors from years of hot rod and street rod mags, feel
free to inform me I'm way off base :^)

Jack Starcher
Lewis Center, Ohio
'46 CJ2A
---------------------- Forwarded by Jack Starcher/COH/ColumbiaGas on
10/16/98 08:02 AM ---------------------------


pigsmith@... on 10/15/98 09:17:54 PM

Please respond to WillysTech@... @ INTERNET



To: WillysTech@... @ INTERNET

cc:



Subject: [WillysTech] Re: More air on top?




From: "J. Loving" <pigsmith@...>

pigsmith@... wrote:

Yesterday I went to look at an anvil and ended up as a spectator to a

conversation about engines. I vaguely understand about "porting" and the
reasons for putting in shorter connecting rods, but in doing so, the
air/fuel mix above the piston doesn't get compressed as much. I thought
the ideal was to get the most volume squeezed into the smallest space
before igniting it? Or am I confusing myself with some basic jet engine
theory from way back? Is the point of increasing the volume of air/fuel
mixture the whole point, period (not the squeezing)? Did I just answer
my own question(s)?

Well, the point of porting IS to get more air/fuel in the cylinder.
Why they would put shorted con rods I have no idea, unless they were
having detonation problems (and then that is still a screwy way of
getting around the problem).
Did you get the anvil?

-Mitch Utsey

Yup, I got the anvil..
To get back to the short connecting rods-- their reasoning was that in
doing so the crank takes less time to make a complete revolution,
there's less weight to pull while doing so, and with boring out the
cylinders and putting in a nice snappy cam, the idea was to get more
"hit" out of the engine.
But I'm confused about the compression part. Enlarging the volume of air
seems counterproductive to the reasons for shortening the rods: yeah
sure, the crank goes around quicker, but the compression is reduced
because the rods are shorter....?
JL


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