My understanding from reading Vizard is that the exhaust ports in the
head should be smaller that the exhaust manifold. They should not be
matched.
The intakes should match, but the exhaust should have a step-up in
diameter while traveling from the head to the exhaust manifold.
I would like to know why I would choose between the MSD 6A and the
Petronix.
I bought extra carbs -- I think I have 6 now :-) -- to go with the
triple carbs, but because of the whole theory of the Constant Depression
ZS carb design, I keep thinking it's just a question of how high the air
cylinders ride in triple vs dual ZS. Add more carbs and the depression
at each one is lower, and the air valve rides lower. Makes no difference
how many CD carbs you have unless the duals are not capable of supplying
sufficient volume at full throttle. Maybe the intake manifolds are so
much nicer for the triples there is an advantage there. We've discussed
this before and I'm still just as confused as ever. It would really be
nice if we had some objective data on adding the triples and doing
nothing else. Maybe it will be me. :-)
One other thing I wonder about is the richness during acceleration. If I
go to triple ZS, should I replace the air valve springs with weaker
ones, so the triple air valves rise faster than the dual (stronger
spring) ZS air valves would have risen. Said another way, since there
are now 3 carbs rather than two, would the old dual carb (strong)
springs be making the mixture too rich during acceleration by
restraining the air valve too much?
Don Malling
Richard Seaton wrote:
> I need to pick the brains of people more knowledgeable than I and that could
> be quite a large number of members!
> I'm proceeding to upgrade my stock 1969 TR6 8.5:1 CR motor, to hopefully more
> performance. I was going to do these modifications after she was rolling, but
> decided to do them now instead of working over a freshly painted car. Talked
> myself right into it.
> This is what I'm curious about, the compression will be increased to 9.25 or
> 9.5:1, three angle valve job, match intake and exhaust ports to the head,
> Petronix electronic ignition and with either and S2 cam or Piper 270 with
> triple ZS carbs. Any comments out there on what I'm getting ready to do?
> My real curiosity is the distributor. Will it need any modifications to the
> advancing springs or weights? Note the '69 has the vacuum retard and advance.
> I figured the retard would need to be eliminated. If this needs readjusting
> who can best provide this service and can it be set up by just telling whoever
> performs the work the setup of the motor?
> Thanks a bunch for any advice!!!
>
> Richard Seaton
> RSH17@msn.com
> View My restoration @ (http://groups.msn.com/Richards69TR6Restoration)
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