[DeTomaso] Webers - update

[jderyke at aol.com]

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