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Duncan and Larry have nailed it.
It's completely subjective, what is expected out of the engine, HP/torque, =
what is the operating range, and depends on so many other factors, ie cam p=
rofile and phasing, port & valve sizes, CR, intake and exhaust header & pip=
e, carbs etc etc.
Also compression calculations based solely on head thickness aren't really =
accurate, valve depth and head shape vary and affect volume.
A slight lump on top of the pistons into the chamber will get the compressi=
on up without making the head too thin, and won't interfere with flame trav=
el if it's less than .050 or so and the edges are radiused/clearanced.
Another related point is that it's easy to get mechanics red-mist when sele=
cting cam profiles. BTDT, several times actually. Be realistic. A true race=
engine never operates below 4-5K RPM.
If your working with a TRactor engine, forget about the high revs, take adv=
antage of the stump-pulling (slight exaggeration) torque characteristics th=
at it has.
Glen
=20
=20
=20
-----Original Message-----
From: Duncan Charlton <duncan.charlton54@gmail.com>
To: Larry Young <cartravel@pobox.com>
Cc: Mike Piggot (new) <mikeandjudypiggott@att.net>; fot <fot@autox.team.net=
>
Sent: Sat, Oct 31, 2015 4:52 pm
Subject: Re: [Fot] Six cylinder cams
Larry=E2=80=99s comments make me wonder the precise intended purpose of the=
engine
mentioned by the original poster. =E2=80=9CTrack days=E2=80=9D might mean =
different things to
different people. Does P. J. want a good flexible power band, or does he n=
eed
an ultimate dyno horsepower figure? Does the motor have the gear set to be=
able
to take advantage of an engine with very little low-end torque? How high am=
ong
his priorities is the ability to be able to drive the car back on the trail=
er at
the end of every track weekend? Lack of sponsorship and cash prizes mean t=
hat I
must find the setup that maximizes the fun/cost ratio.
Duncan
> On Oct 31,
2015, at 1:34 PM, Larry Young <cartravel@pobox.com> wrote:
>=20
> That is an
interesting article, but only speaks to one side of the issue. I always sa=
y
that you want to pick an intake duration for an RPM range that you're willi=
ng
and able to turn. We all know what happens to a stock TR4 crank which sees
>6,000 on a regular basis. Some guys want a cam good beyond 7,000, but the=
y are
just not willing to push it that far. Nowadays I'm more of a street car guy=
, but
still like to have power. I don't believe the choices should be to do noth=
ing
or go all the way to race specs. From 1968 on Triumphs were severely detun=
ed to
pass emissions. Compression ratio and duration and hence cam overlap at TD=
C
were reduced. For example, the early TR250/6 had 193 degrees duration (mea=
sured
at 0.050), while the TR4 was about 215 and the early PI TR5/6 was 226. It s=
eems
crazy to rebuild a street car of this era to the original specs. Bumping t=
he
compression ratio by a point and increasing the duration to something like
210-215 will make the engine the way it would have been without emission
restrictions. I would not feel guilty about polluting the planet, since mo=
st of
these cars see few miles annually and most of the other pollution controls =
(e.g.
ignition retard) probably quit working years ago.
> - Larry
>=20
> On 10/29/2015
7:25 AM, Duncan Charlton wrote:
>> Cam specs and static CR are interactive.=20
This will give you a rundown if you are not already knowledgeable about thi=
s
subject:
>>=20
>>
http://www.crankshaftcoalition.com/wiki/Cam_and_compression_ratio_compatibi=
lity
>>
>> Duncan
>> (Texas)
>>=20
>>=20
>=20
>
_______________________________________________
> fot@autox.team.net
>=20
>
http://www.fot-racing.com
>=20
> Donate: http://www.team.net/donate.html
>
Archive: http://www.team.net/archive
> Forums: http://www.team.net/forums
>
http://autox.team.net/mailman/options/fot/duncan.charlton54@gmail.com
>=20
>
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Donate:
Archive: http://www.team.net/archive
Forums:
http://www.team.net/forums
http://autox.team.net/mailman/options/fot/fubog1@aol.com
=20
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<font color=3D'black' size=3D'2' face=3D'Arial, Helvetica, sans-serif'>D<fo=
nt size=3D"2">uncan and Larry have nailed it.<br>
It's completely subjective, what is expected out of the engine, HP/torque, =
what is the operating range, and depends on so many other factors, ie cam p=
rofile and phasing, port & valve sizes, CR, intake and exhaust header &=
amp; pipe, carbs etc etc.<br>
Also compression calculations based solely on head thickness aren't really =
accurate, valve depth and head shape vary and affect volume.<br>
A slight lump on top of the pistons into the chamber will get the compressi=
on up without making the head too thin, and won't interfere with flame trav=
el if it's less than .050 or so and the edges are radiused/clearanced.<br>
Another related point is that it's easy to get mechanics red-mist when sele=
cting cam profiles. BTDT, several times actually. Be realistic. A true race=
engine never operates below 4-5K RPM.<br>
If your working with a TRactor engine, forget about the high revs, take adv=
antage of the stump-pulling (slight exaggeration) torque characteristics th=
at it has.<br>
Glen<br>
</font>
<div> <br>
</div>
<div> <br>
</div>
<div> <br>
</div>
<div style=3D"font-family:arial,helvetica;font-size:10pt;color:black">-----=
Original Message-----<br>
From: Duncan Charlton <duncan.charlton54@gmail.com><br>
To: Larry Young <cartravel@pobox.com><br>
Cc: Mike Piggot (new) <mikeandjudypiggott@att.net>; fot <fot@autox=
.team.net><br>
Sent: Sat, Oct 31, 2015 4:52 pm<br>
Subject: Re: [Fot] Six cylinder cams<br>
<br>
<div id=3D"AOLMsgPart_1_cb11c7e4-f8fb-47bd-92e7-fbce53b6e55c" style=3D"marg=
in: 0px;font-family: Tahoma, Verdana, Arial, Sans-Serif;font-size: 12px;col=
or: #000;background-color: #fff;">
<pre style=3D"font-size: 9pt;"><tt>Larry=E2=80=99s comments make me wonder =
the precise intended purpose of the engine
mentioned by the original poster. =E2=80=9CTrack days=E2=80=9D might mean =
different things to
different people. Does P. J. want a good flexible power band, or does he n=
eed
an ultimate dyno horsepower figure? Does the motor have the gear set to be=
able
to take advantage of an engine with very little low-end torque? How high am=
ong
his priorities is the ability to be able to drive the car back on the trail=
er at
the end of every track weekend? Lack of sponsorship and cash prizes mean t=
hat I
must find the setup that maximizes the fun/cost ratio.
Duncan
> On Oct 31,
2015, at 1:34 PM, Larry Young <<a removedlink__e913380f-5d6b-40df-854c-1=
947be360e2c__href=3D"mailto:cartravel@pobox.com";>cartravel@pobox.com</a>>=
; wrote:
>=20
> That is an
interesting article, but only speaks to one side of the issue. I always sa=
y
that you want to pick an intake duration for an RPM range that you're willi=
ng
and able to turn. We all know what happens to a stock TR4 crank which sees
>6,000 on a regular basis. Some guys want a cam good beyond 7,000, but =
they are
just not willing to push it that far. Nowadays I'm more of a street car guy=
, but
still like to have power. I don't believe the choices should be to do noth=
ing
or go all the way to race specs. From 1968 on Triumphs were severely detun=
ed to
pass emissions. Compression ratio and duration and hence cam overlap at TD=
C
were reduced. For example, the early TR250/6 had 193 degrees duration (mea=
sured
at 0.050), while the TR4 was about 215 and the early PI TR5/6 was 226. It s=
eems
crazy to rebuild a street car of this era to the original specs. Bumping t=
he
compression ratio by a point and increasing the duration to something like
210-215 will make the engine the way it would have been without emission
restrictions. I would not feel guilty about polluting the planet, since mo=
st of
these cars see few miles annually and most of the other pollution controls =
(e.g.
ignition retard) probably quit working years ago.
> - Larry
>=20
> On 10/29/2015
7:25 AM, Duncan Charlton wrote:
>> Cam specs and static CR are interactive.=20
This will give you a rundown if you are not already knowledgeable about thi=
s
subject:
>>=20
>>
<a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"http://www.cr=
ankshaftcoalition.com/wiki/Cam_and_compression_ratio_compatibility" target=
=3D"_blank">http://www.crankshaftcoalition.com/wiki/Cam_and_compression_rat=
io_compatibility</a>
>>
>> Duncan
>> (Texas)
>>=20
>>=20
>=20
>
_______________________________________________
> <a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"mailto:f=
ot@autox.team.net">fot@autox.team.net</a>
>=20
>
<a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"http://www.fo=
t-racing.com" target=3D"_blank">http://www.fot-racing.com</a>
>=20
> Donate: <a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"=
te.html</a>
>
Archive: <a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"http=
://www.team.net/archive" target=3D"_blank">http://www.team.net/archive</a>
> Forums: <a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"=
http://www.team.net/forums"; target=3D"_blank">http://www.team.net/forums</a=
>
>
<a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"http://autox.=
team.net/mailman/options/fot/duncan.charlton54@gmail.com" target=3D"_blank"=
>http://autox.team.net/mailman/options/fot/duncan.charlton54@gmail.com</a>
>=20
>
_______________________________________________
<a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"mailto:fot@au=
tox.team.net">fot@autox.team.net</a>
<a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"http://www.fo=
t-racing.com" target=3D"_blank">http://www.fot-racing.com</a>
Donate:
<a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"http://www.te=
am.net/donate.html" target=3D"_blank">http://www.team.net/donate.html</a>
Archive: <a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"http=
://www.team.net/archive" target=3D"_blank">http://www.team.net/archive</a>
Forums:
<a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"http://www.te=
am.net/forums" target=3D"_blank">http://www.team.net/forums</a>
<a removedlink__e913380f-5d6b-40df-854c-1947be360e2c__href=3D"http://autox.=
team.net/mailman/options/fot/fubog1@aol.com" target=3D"_blank">http://autox=
.team.net/mailman/options/fot/fubog1@aol.com</a>
</tt></pre>
</div>
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_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Archive: http://www.team.net/archive
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