Weber tuning questions

[JCF]

I have a 2.2 liter - 901/05 engine that had the pistons and cylinders changed to 2.2 Mahles, original heads fly cut to fit .Original Solex cams.

I was running the Webers with :

venturis 30mm
main jets 125
main air bleeds 180
idle jets 55
idle air bleeds 110

Ran well but the power would run out around 5000 rpm.
I was told that I could go to 32 venturis with 130 mains but then read a PMO Tech Report that stated " After extensive testing and customer feedback, we've changed the jetting for smaller stock motors: 2.0, 2.2T, E, and 2.4T. We now use;

venturis 30mm
main jets 130
main air bleeds 180
idle jets 50
idle air bleeds 110
"

I changed my main jets and idle jets as recommended and now my car is running poorly.
Between 3000 and 4000 or at steady throttle I am getting a lot of bogging and hesitation and the inside of the tail pipe is getting fairly heavy dark residue.
As long as I am feeding it gas it is ok and seems better over 4200 rpms with noticable power increase at the top end.
Around town though it is brutal.

Timing and rest check out ok.

Before I start switching jets and stuff again - any recomendations as to which direction to go ?
Weber Tech manuals I am reading seem to indicate that 55 idle jets might work better ?
What would happen if I went with the 32 venturis with either 50 or 55 jets ?

Sorry this is so long. I feel kind of stupid - since it wasn't broke but I tried to fix it and now it is broke.
I was just trying to get some more top end hp.
Asking too much ?

Thanks;
John

[2.7RACER]

John,
Look at the specs for your 901/5 ports and valves. Intake and Exhaust ports 32mm.
Intake valves 39mm, ex valves 35mm,
This compares to a 2.2 liter "S" 911/02 with 36 and 35 mm ports and 46mm intake valves with 40 mm exhaust valves.
The 2.2 "S" engine makes 180 hp at 6500 rpm.
The 2.2 "E" engine cammed like your engine with smaller ports 46 and 40mm valves makes 155 hp at 6200 rpm.
Your original head ports and valves are restricting flow at high rpm's.
You need to enlarge the ports and valve sizes to make that engine breath.
Then you can install bigger venturi's and corresponding jets to take advantage.
You may need to enlarge the exhaust system to take full advantage.
Your engine needs to breath to perform at high rpm's.

[Jim_Brown]

John

Have you verified that your fuel pressure is at 3.5 psi and the flow is OK?

Have you set your float/ fuel levels with the PMO fuel level tool while the engine is running?

Also, where did you see that PMO bulletin? I wonder if it is a recent change. The recommendation on their website for small stock engines is 30 venturi, 125 mains, 180 air correct, 110 idle air bleed, 50 idle jets.

http://www.pmocarb.com/bulletins.htm

I have their recommended jetting on a 2.0T (except I have 55 idle jets because that is what was in there) and it runs well.

Good Luck,
Jim

[JCF]

Thanks guys.

Just got back from a drive - it's cool here today and wanted to see if it would run any differently.
It was a bit better after warming up.
Def. seems faster - but that may be wishful as it should feel quicker with more torque rather than hp . No ?

Yes fuel flow is ok - 0.7cc
Haven't checked the pressure but was fine before I started messing with the carbs.
Yeah, the S spec heads are on the wish list.
So you think I should just accept the way it was until then and go back to the orig set up ?

That PMO report was in the March Panorama, pg 117.
From what I understand it is because of the ethanol now used in the gasoline.


Thanks again

[JCF]

Problem solved.

Left the 130 mains in and switched back to the 55 idle jets.
Runs great .