Two quick questions about this:
1) Which head is "better" (ie: breathes better), the early or the late?
As I understand it, the early and late head share the same exhaust
ports, but the intakes changed. The early head (which I have on my 71)
has different intake port spacing than the late head (which is the head
that was used on all years for PI cars). Just wondering which head is
preferable...
2) I have also heard that the later style intake manifold is better,
due to longer and straighter runners. I understand that a straighter
runner is preferable, but why is longer better? I have heard that a
longer runner produces more low-RPM power, a short runner provides more
high-RPM power. Is this correct, or have I got it backwards?
Thanks!
Tim Holbrook
1971 TR6
T
--- "Robert M. Lang" <lang@isis.mit.edu> wrote:
> Date: Sun, 5 Jan 2003 09:54:59 -0500 (EST)
> From: "Robert M. Lang" <lang@isis.mit.edu>
> To: Richard Seaton <rsh17@msn.com>
> CC: Doug Dwyer <dougdwyer@earthlink.net>,
> Web_disscusion List
> <6pack@autox.team.net>
> Subject: Re: More early-vs-late stuff: instruments
>
> On Sat, 4 Jan 2003, Richard Seaton wrote:
>
> > Doug,
>
> Hi,
>
> Just trying to fill in some blanks...
>
> > There was a cam difference in about '73, to a milder cam.
>
> The change was in 72, around CC75000.
>
> > Exhaust manifold change to two 3 into 1.
>
> This change was with CF1 ('73).
>
> > Narrow spacing on the head. I think this is only on '69 TR6's, but
> I'm not
> > sure.
>
> This change was for 72 also. Figure CC75000. Note: this change
> brought the
> "PI" head to fed. spec. cars.
>
> > Sometime the intake was changed to a straighter flow to the head,
> I'm not sure
> > when this took place.
>
> CC75000.
>
> > "long" crank for '69's and TR250's, This long area is the machined
> part that
> > connects to the flywheel. There for the flywheels are different
> too.
>
> I'm not sure when this change occurred, but it was before CC50000 for
> sure.
>
> > Prettier bumpers on the pre-74 or 73.
>
> I agree.
>
> > Brass bushing in the earlier transmissions, not sure when they
> changed to
> > steel.
>
> Supposedly they changed for CF12500, but I've had several boxes apart
> that
> were above this number that used brass. The latest TR6's def. had the
> steel bushings (75 and 76)
>
> > A type O/D (2nd, 3rd & 4th) for early 6's, J type o/d (3rd & 4th).
>
> Yep.
>
> > Trailing arm brackets changed One notch inner and two notch outer
> for up to
> > CC61570. 3 notch inner and 2 notch outer from CC61571.
>
> It's good to know this.
>
> > A few distributor and carb changes.
>
> Almost every year is slightly different!
>
> > alternator changes
>
> Early cars had the Lucas ACR17, that later cars have the Lucas ACR18
>
> > water pump pulley differences
>
> Early cars have narrow belts and single pulleys. They switched to 1/2
> belts, not sure when, but figure CF1. The later cars with air pumps
> (75
> and 76) have a double pulley water pump for the air pump.
>
> > Sorry I can't give you the commission #'s when the changes
> occurred, but you
> > can look in the Moss or TFR catalogues for that.
>
> But don't take the catalogue information for granted! Some of the
> info is
> very valuable and some is almost completely wrong! Use the catalogs
> as
> guidelines but be prepared to order other stuff than what you think
> you
> have.
>
> Welcome to the world of owning 40 year-old-cars! Quirky ones at that.
>
> > I think the only performance differences are the camshaft, intake
> and
> > exhaust manifold changes. This is what you are really wanting to
> know isn't
> > it?
>
> There are internal engine changes too. Like diff con rods, the valves
> and
> valve springs. There's lots of little changes even durnig a
> production
> year!
>
> > Not to mention the 1969 TR6's just look better than the latter
> ones!!!! LOL
> > I'm sure I'm setting myself up for feedback on this one!
>
> I'd tend to agree with this, but some of have later cars and are
> quite
> comfortable with the appearance...
>
> If we're looking for recommendations, my preference is 72. It's the
> last
> of the early chassis (a-type O/D, basic suspension stuff) but has the
> later engine (with early rods!) so its got better performance
> potential.
> IMHO, if you want a driver that also can double for autocross, etc.,
> then
> the '72 is just about ideal (if it is all original).
>
> > Richard Seaton
> > '69 TR6 CC27413L(O)
>
> But I like all TR6's and I even like TR6 inpsired cars (like
> TVR2500's).
>
> Good luck deciding.
> rml
>
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