[Fot] Weber help and/or advice

Tue Jan 19 06:22:06 MST 2021

Yes Tony, thank you. Lots to digest.

As far a 'look cool', there's nothing cooler than where you sit on the 
time sheet...

On 1/19/2021 5:17 AM, fubog1 wrote:
> Excellent write-up Tony!
> Glen
>
> -----Original Message-----
> From: Tony Drews via Fot <fot at autox.team.net>
> To: Alec Buchan <agb at compsnw.com>; fot at autox.team.net <fot at autox.team.net>
> Sent: Mon, Jan 18, 2021 5:20 pm
> Subject: Re: [Fot] Weber help and/or advice
>
> Alec, in my experience (also a TR-4), you can make just as much power
> with a well tuned set of SU's as with Webers.  My dad (Jack) ran SU's, I
> have Weber 42's (came with the car).  We were virtually the same speed /
> power.  Took us both a while to get there and required running on the
> Dyno to dial them in.
>
> From what I understand, the "Cannon" intake manifolds are considered
> the best.  I discovered that the 42's (which are rare as hen's teeth)
> take the same internal bits as the 40's, so I think the advantage is
> more psychological than anything over the 40's.  I ended up with the
> biggest chokes (venturi) that would fit - I think 36 mm was as big as I
> could go.  I do have a set of 45's that I keep threatening to spiff up
> and try.  I suspect that going to a 38 mm choke would be the hot ticket
> for my engine.  Depending on the build, 40's work pretty well.  Big
> bore, billet crank, hairy cam, high RPM would probably benefit from 45's.
>
> What I found on the Dyno is that there's a ton of power in just getting
> the mixture right across the rev range.  I ended up with pretty small
> air correction jets to keep it from going lean at high RPM's.  I
> probably gained around 20 HP just by tuning the carbs.
>
> From what I understand, comparing jetting from one engine build to
> another is pretty haphazard, it's best to tune it to the specific engine
> rather than just copy someone else's jetting. Also, I believe the
> emulsion tube can make quite a bit of difference, so just comparing main
> / air jet sizes if you're not running the same emulsion tube kinda
> invalidates the comparison. In my case I just used the emulsion tubes
> that came in the carb's and didn't try alternates.  I believe the big
> differences in those is more for part-throttle driveability which I
> generally ignore. If I can drive it to the grid it's fine, otherwise
> it's pretty much just wide open or closed, not a lot of part throttle.
> But other drivers may use more part throttle and so the emulsion tubes
> would be of greater importance.
>
> I love the looks of the webers, but Jack was able to get decent mixture
> control with SU's and some slighly custom needles - I think he took RB's
> and skinnied down the tips to be more of the RA needle profile there.
> He also ran 0.104" jets to get enough fuel out (stock is 0.100").  We
> would draft each other at Road America, so were pretty close in overall
> power.
>
> I'm not quite sure what kind of advice you're looking for - should I do
> it or not?  What specific setup should I get?  What carb settings should
> I start with?  None of these have cut and dried answers in my opinion.
>
> Should I do it?  Maybe, but you can also get similar results with good
> well tuned SU's.  The webers look awesome though.
>
> Which setup to get?  Partially depends on the engine build. I suspect
> you'd be happier with 40's on a decent manifold with a decent linkage.
> If you have a monster motor you'll want 45's.
>
> Starting setup?  If 40's, 36 mm chokes, possibly 150 mains with about
> 130 airs is roughly where I ended up (need to dig through the expensive
> box of brass bits to verify).  No idea what emulsion tube or accelerator
> pumps I'm running.
>
> One advantage of the webers is that they DO have accel pumps, so getting
> the engine started on a cold day without the choke is easier than with
> the SU's.
>
> I found the tuning of SU's to be more obvious than the Webers.  I used a
> couple of books and Teri Ann's website to get a good understanding of
> what I was doing with the Webers.  The big aha for me was understanding
> that the main jet affects the mixture across the entire rev range while
> the air correction affects high RPM mixture more than low RPM mixture.
> Changing the air correction does also affect lower RPM mixture so they
> need to be tweaked in combination with each other.  Getting the air
> correction small enough that it didn't lean out at high RPM but big
> enough so it didn't richen at high RPM was my key, then I tweaked the
> main jets for max power and maybe went a step richer to keep the pistons
> un-molten.
>
> Regards, Tony Drews
>
> On 1/18/2021 2:54 PM, Alec Buchan via Fot wrote:
> > It looks like I am moving up a group and in order to not maintain my
> > 'blue caboose' moniker, I am looking at converting to Webers. Moss and
> > Pierce sell a 2 x 40 DCOE kit but I've also located a 2 x 45 DCOE kit
> > (not from Moss or Pierce). looking for recommendations, if you might
> > be so kind.
> >
> > On a side note, the few of us here in the PNW are looking forward to
> > seeing all you 'front of the packers' in Portland this summer.
> >
> > Kindly,
> >
> > Alec Buchan
> > Bellingham, WA
> > '62 TR4 #5 (aka the Blue Caboose)
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