Hi,
My $.02 worth.
A TR6 engine with 10:1 and an S2 cam is hardly stock.
That being said, I offer two pieces of advice:
1. dump the Weber downdrafts. If you're absolutely stuck on them, that's
okay with me. My personal opinion is that those things can't flow very
well. On the other hand, I'd love to see some dyno numbers with them.
Lots of folks use the DGV's and love them, so I could be overreacting to
the flow thing, but that J pipe between the carbs and the intake manifold
reminds me of a sink installation. Scary!
All that being said, the setup that you list would probably work fine.
If you decide to change the downdrafts, the stock Z.S. 175's are okay and
you could also use SU HS6's. If you read the comp. prep book, they were
able to get pretty good numbers with the stock carbs. I believe the key
to getting powere from the Z.S.'s or SU's is in needle selection. In that
regard, needles are somewhat easier to change on the SU's - but you can
make the SU needles fit the Z.S.'s (as described in the comp. prep manual.
2. distributor. I found on my street TR6 that without the vacuum retard,
the dizzy went to full mechanical advance at just above idle... maybe
1500 RPM's. This is not a good thing in terms of performance. I
reconnected my vac. retard, and got it to work "okay". My experience was
with Weber DCOE 40's. Getting the "proper" amount of vacuum was a pain
because the manifold only provides one "tap", but I did get it to work
okay with some creative plumbing.
You can do several things.
Get the distributor to a competent automotive shop with a distributor
machine. Get them to curve the thing for full advance at 2500-3000 RPM's
You're running pretty high compression ratio at 10:1, so don't go too
crazy on the advance thing. The comp. prep book lists 23 degrees total
advance for cranked-up TR6 engines.
Do this for mechanical advance only and dump the vaccuum retard
altogther. If you "yank the can" from the dizzy, don't forget to fill the
resultant hole in the case. Unless you only drive on dry days and never
go on any dusty roads... in other words, if your car is a "garage queen"
you don't need to fill the hole. If you need me to explain why - I may
suggest that you take up other persuits than working on your TR6.
;-)
_But_, the problem with that setup (the recurving of the stock dizzy) is
that if the curve that you come up with doesn't work with your carb/cam
setup - you're stuck having to recurve (again) to get things to work
right. This is not optimal and possibly expensive if you have to do it
many times.
So - if you get a Mallory dual point dizzy, you can change the total
advance by tweaking a screw in the housing to add/remove total advance.
Thus, if you were tuning for max. power, you could probably set the thing
once in a one hour dyno session.
If you are totally insane, you could go to a crank-trigger setup, but
that would be several times more costly than the Mallory. The Mallory
setup only costs $200 for the dizzy unit, another $50 for machine work to
install a drive-dog onto the shaft and then between $40 and $300 for an
electronic tach... as it seems to be tough to find a Mallory unit with a
tach drive right now, or at least that was my recent experience. If the
idea of points is too much for you, there are drop in magnetic trigger
units for most Mallory distributors.
Bob says: "Mallory is kewl". I'm not the only one.
Last thought - with any cam with much "overlap", the amount of vaccuum
that you get goes down... so trying to get the stock vac. retard unit to
work with "much cam" is probably a loosing proposition.
later,
rml
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