Weber Jetting sizes ?

[jtkkz]

Hello

Subject motor: 2.7 w/ E cams with Webers 40mm

What is the proper jet sizes for this set up

idle airs =
idles jets =
main jets =
emulsion tubes =
air correctors =

Thank You

[jebbach911]

Depends a lot of which venturi is in the carbs. You probably have 34mm venturis. I have a 2.7 with early "S" cams that I just went back to 32mm venturis for better low end performance for AutoX. My carbs run good with the following:

34 Venturis
145 Mains
60 idle jet
180 air corrector jet
F3 Emultion tube

[RoninLB]

me.. 2.7, E-cams, 55 idles, 135 mains, 34 vents

i suggest tuning with NGK BP5ES

Start with keeping all idles same turns, start at 2.5 turns of idles.

keep leaning all similar in 1/8 till it starts popping lean. Drive 10 miles between each 1/8 to clear things up. Weber transition should be kept in mind. It may become the leaning limits?

change plugs to NGK BP7ES and lean popping should stop.



acceleration circuit is another story

[JohnJL]

I found the same as above with F28 emulsion and 57 idles and BPR6 twin plugs were spot on. 11:1 compression.

[doc18015]

When designating ides as "55" is that equal to 0.055 drill size? What hole(s) get drilled to size a 45 to 55, for example,......the end hole on the jet or the two smaller holes on the cylinder of the jet? Simple questions for those experienced, but not so simple for me. Thanks in advance.

[doc18015]

bump

[RoninLB]

some pro wrenches around here say to just buy new PMO jets otherwise if you drill flow will be mixed up.

[2.7RACER]

doc18015,
The jets are sized metrically.
That is a 50 idle jet is 0.50mm dia.
A 60 idle is 0.60mm.
To convert to inches, 1.0mm equals 39.37 thousandths. Most folks round it off to 40 Thou.
Therefore a 50 idle (0.50mm) is equal to 20 thou.
A 60 idle (0.60mm) is equal to 24 thou.
A 45 idle (0.45mm) is equal to 18 thou.
Can you see the pattern here?
I have a set of very small drill bits for my Dremel calibrated in thousandth's.
I use the 18 thou to check my 45 idles. 18 is GO, 20 is NO GO.
Likewise mains 150 is 1.50mm, equals 60 thou.
180 air correction is 1.80mm, equals 72 thou.
I also resist drilling out the jets.
I'm fortunate to have a shop with a decent inventory about five miles away.
PMO delivers within a couple days, if I can't get them locally.
I have a small inventory, including some idles marked 45 that run as big as 55.
I always check jet sizes with the small drills, since I don't have a jet gauge.
I never believe the markings until I have checked the jets.

[jtkkz]

Thanks for all the replies...

What would be best/ideal jet sizes for street driving ?

[2.7RACER]

For a 2.7 with E cams, 32mm venturi for street use, 34mm for the track.
At sea level 135/145 main jets, 55 idles, 180 air correction, F3 emulsions.

I'm at 5500 feet. The air is thin, so I use larger air corrections (200), 140 mains, 50 idles, F3's.
I run 34m venturi's at the track although 32mm are better for street use.
The 32mm vents quit making power above 5500 RPM at this elevation with my solex cams.

I would try 135 mains first. Just for comparison get some 140's and 145's and see which is best for you. Same with idles, 50, 55 or 60's might make you happy.

It will depend on your own expectations and how you drive. You can trade power for mileage.

[doc18015]

Doug, thanks for the explanation of sizes. It may be better for accuracy to order then check for accuracy from PMO.

[jtkkz]

What do you recomend for fuel pressure? 3-4 lbs.?

[2.7RACER]

Webers and PMO's like 3.5 psi.
PMO has a simple regulator system with gauge I recommend.
It works well with the stock Porsche high pressure fuel pump used with all Porsche fuel injection systems.