[DeTomaso] Webers - update

[wkooiman at earthlink.net]

1)  I thought about that.  It might also be this cam/compression combo.  11:1, big solid cam, 3" straight through exhaust.  They all contribute to the sound.  Although, I still have a small amount of smoke from the driver's side, plus #8 is pulling less air.

2)  Got it covered.  In fact, I don't think I've even seen foam air filters for Webers in a long time.  Most are tea-strainers or the K/N style.

3)  I'll look for it.  I've gotten most of my advice from cobracountry.com and this list.

4)  I have a very nice fuel pressure regulator, but I haven't adjusted the pressure yet.

5)  Yes.  That's part of the fun.

6)  Maybe I lucked out and got close with the out-of-the-box jets.  I know it's rich, but probably not by much.  It starts right up, even when cold - a sure sign of too rich.  Of course, cold in Houston is still 60-70 degrees this time of year.  With the old cam - CompCams 282S, it got about 15mpg - down from 19mpg on a Holley.


-----Original Message-----
>From: jderyke at aol.com
>Sent: Dec 22, 2009 2:19 PM
>To: wkooiman at earthlink.net, detomaso at realbig.com
>Subject: Re: [DeTomaso] Webers - update
>
>A half-dozen tips that may come in handy:
>1- Funny noises from Webers may just be the I.R. pulses you aren't used to. 
>Read your plugs during a nice hard run and rejet the mains accordingly for 
>larger venturis. 
>
>2- Do NOT use any type of foam air cleaners on Webers! The pulses in the IR 
>manifolds carry fuel up as well as down, the foam soaks it up and with the 
>slightest pop, you'll have a carb fire. Worse, in a carb fire, the aux 
>venturis that stick up are die-cast zinc and melt at low temperatures. The molten 
>metal runs down the intake into the cylinder and in the next engine cycle, 
>a piston contacts the now-solid metal and cracks its top ring land. I had to 
>overhaul an engine due to this! Webers do not have true chokes; instead 
>they have a fuel- enrichment circuit, so its real easy to go lean during 
>warm-ups & get pops or backfires.
>
>3- The absolute best Weber tuning book is Bob Tomlinson's 'Weber Tech 
>Manual' for VW & Porsche engines. Next is Haynes 'Weber Carburetors owners 
>workshop manual'. 
>
>4- Do not use cheap fuel pressure regulators on a set of Webers; they will 
>run lean if you do. A stock Ford mechanical fuel pump works just fine on 
>four hungry carbs without regulation. 
>
>5- In a Weber there are five (5) separate tuning circuits and they all 
>interact with each other to some extent. Each barrel has 5 jets and two air 
>bleeds plus an emulsion tube and venturi; all are tuneable, and if you get 
>really good at it or do it on a dyno, you may find some cylinders take slightly 
>different jets even when airflows are perfectly balanced. The last time I 
>checked, the cheapest jets were around $5 each and its really easy to 
>accumulate hundreds of dollars in no-longer-needed jets. So to tune Webers, I solder 
>up the jets and hand-drill them with metric drills until the tune is close, 
>then I buy new jets only in the size the drilling indicates. One cannot 
>drill jets and get the same fuel flow that a correctly bored & honed jet gives 
>but this gets you close and cuts down on buying jets during the initial 
>tuning phase. MSC in New York <www.mscdirect.com> sells metric drills cheap on a 
>onesy-twosy basis by mail-order.
>
>6- The most common problem with Webers is either no power and 20 mpg or 
>lots of power and 12 mpg, all due to poor tuning. You'll know you're close when 
>the engine response is different on cool cloudy days vs warm sunny days.... 
>Good luck, Will- J Deryke 
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