[Fot] FW: TR6 Cannon Intake Manifold

[John Styduhar]

Iskenderian racing valve spring kit for the TR-2-3-4 shows a seat pressure
of 100 lbs.

On Wed, Sep 16, 2015 at 6:38 AM, MadMarx <tr4racing at googlemail.com> wrote:

> Marcel,
>
>
>
> I use 55 kg seat pressure.
>
>
>
> Cheers
>
> Chris
>
>
>
> *Von:* Fot [mailto:fot-bounces at autox.team.net] *Im Auftrag von *Marcel
> Van Mulders
> *Gesendet:* Mittwoch, 16. September 2015 12:22
> *An:* 'Michael Porter'
> *Cc:* fot at autox.team.net
> *Betreff:* Re: [Fot] FW: TR6 Cannon Intake Manifold
>
>
>
>
>
>
> Thanks Keith and Michael. About valve springs and seat pressure : it's a question about
>
> keeping the valve train parts together but also to avoid that the valves
> bounce off the seats after (the first) landing. I suppose this valve bounce
> is not so clearly reflected in the power  dropping at high revs, . On
> youtube are very interesting high speed cam video's on valve bounce, spring
> surge...
> ------------------------------
>
> *Van:* Michael Porter [mailto:mdporter at dfn.com <mdporter at dfn.com>]
> *Verzonden:* woensdag 16 september 2015 10:57
> *Aan:* Van Mulders Marcel
> *Onderwerp:* Re: [Fot] FW: TR6 Cannon Intake Manifold
>
> On 9/16/2015 2:18 AM, Van Mulders Marcel wrote:
>
> Thanks to the Fot members for their reactions : most are warnings that
> triple 45 Webers may be too big on a TR6 engine. But it is a race engine
> (2720cc) and the owner has already bought 3 good secondhand 45 Webers with
> identical progression holes : 36mm main venturi's seem  to be a reasonable
> starting point in this case? If necessary, he can go down to 34mm in 45
> Webers.
>
>  I've seen TR6 racecars with 45 Webers and I wonder if the Cannon
> manifold, with 40mm diameter bores on the carburetor side, can be reamed to
> 45mm?
>
> Another question : the valve seat pressure on my TR4A racecar is 35 kgs/77
> lbs. I've also a cylinderhead with only 25 kgs/55lbs seat pressure. The
> springs on both cylinderheads are 5.25kg/mm (290lbs/").
>
> Do you think 25kgs seat pressure is enough?
>
>
>
>
> On fitting 45s to the 40DCOE manifold, yes, I think there's enough meat to
> match the manifold to the carburetor exit.  It would mean increasing the
> radius by 2.5mm (~ 0.100"), but I wouldn't do it until 45mm soft mounts can
> be obtained--if only 40mm are available, then it's a waste of time and
> money.  I would recommend that the shop doing the machining find a suitable
> diameter end mill with a 10-15 deg. taper, just to minimize the finish work
> required and to make a smooth transition to the smaller manifold bore.
>
> I don't actually understand the complaints about 45DCOEs being too big for
> a moderately-sized six-cylinder.  For all-around use on the street, 40s
> would be more than enough, but on the track, 45s are fine.  In fact, I
> recall 45s with 38mm main venturis being used commonly, but mostly on
> engines tuned to 7200 rpm or so.  The advantage of Webers is that they have
> lots of spares to tune to carburetor to the application, although the
> expense of having such spares on hand for tuning is rarely part of the
> equation.
>
> As for valve seat pressures, they're not as important as having just
> enough spring pressure to keep the follower tracking the cam profile.  For
> normally-aspirated engines, anyway (seat pressures become more of an issue
> with supercharged engines, when too much boost can push a valve off its
> seat if the static spring pressure is too low).  The lower the combined
> weight of the valve train, the lower the spring pressure required.  The
> steeper the ramps on the cam, the greater the spring pressure required to
> overcome the acceleration of the valve train parts.  So, it's kind of a
> balancing act, and one that can usually only be handled on the dyno, while
> looking for power drops at high rpm due to valve float.
>
>
> Cheers.
>
> --
>
>
>
>
>
> Michael Porter
>
> Roswell, NM
>
>
>
>
>
> Never let anyone drive you crazy when you know it's within walking distance....
>
>
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