Weber Carbs still spitting even after recent rebuild.

[bobm]

New to 911's and just got back 66 2.0 from shop. Top end rebuild, chains, tensioners. Carbs gone thru by Ariz expert along with dizzy. Less then 50 miles on motor.
Reason for rebuild was low compression on two cylinders, and popping thru carbs. Sent carbs in for rebuild but popping did't go away when reinstalled so went for rebuild.
Current issue is still spitting thru # 3 &4 carbs, somtimes you can also hear popping thru exhaust, idles smooth but pops between 1500 & 2800 rpm. Above 3000 OK. When driving you can feel stuttering between the 15-28 rpm range and bogs down in 5th in that RPM range, pulls smooth above 3000.
Shop said they had running good but started this on way home. They want me to put 500 - 800 miles on then bring back for oil change and adjustment.
A little hard to drive with all the popping.
If all is rebuilt why the spitting, any ideas for what to do or will this just get better with time.
Thanks for any ideas
Bob
Nor Cal
# 304014

[lemonlib]

dis you check the main jets .. on 3, 4? three things...too small on the main jets, air leak on the stacks, or cloged on 3 or 4.. do they hunt when you lean them out? do they reponces ? spit back means too much fuel..sound like the secondary circuit works fine...

lemon

[lemonlib]

seem contradictory....spit back is too much fuel....but pops means lean outs...some times even on rebuilts when dirty fuel gets in the system this happenns..

[bobm]

Hi Thanks for the info.
I may be using the wrong term " popping or spitting". I put on a syn tool (idle 8-9 rpm) on each stack and all cyl's are at 5. When I rev up to 15-28 it moves up to 10+. Most cyl's run smooth but when 3-4 make the pop sound the syn tool jumps way up. I did lean out at idle and both cyl's (3-4) would stumble then I backed out to smooth, so I did get a reaction. I have not checked the jet's as carb's were benched tested when rebuilt, BUT the carbs did sit a while motor was rebuilt. Also when carbs were rebuilt they were jetted for 2.0. Shop bought 2.0 rings then found out motor had been upgraded to 2.2 so re-ringed at 2.2. Heads (valves/guides) redone but no jet adjustment made to carbs as they were finished first. Mechanic said he checked floats and had to replace one and then did adjust everything until he was happy. When I left shop it ran pretty well then on the way home it got rough at th 15-28 rpm. Should jets be changed for the now 2.2 PC's. Other cy's 1,2,5,6 seem to operate well.
Thanks for your assistance.
Bob
Bob

[1QuickS]

STE reading of 5 at idle is good, I typically see 4.5 when I set them up.

The spitting (or "sniffing") up through the intakes is due to lean mixture. Since the spitting occurs near the end of effectiveness of the progression circuit and the mains seem fine (you can run to redline without issue) then I guess there is a partial blocking of the idle jets on #3 and #4 that restricts fuel flow at maximum demand but supplies adequate fuel during lower RPM operation. This blockage could occur during your drive home as debris left in the carbs after cleaning would be flushed through the galleries and then take up new residence in your idle jets, these idle jets have the smallest orifices in the entirety of the Webers; probably .55mm in diameter for your 2.2.

[lemonlib]

Try cleaning out the idle and main jets...it drove me crazy once....I just got in new carbs and they won't response..turns out I had a small debree from the tank that got past the filter...only other thing I could think off is that float level was not set right..thus the spit back

Lemon

[1QuickS]

Another item to check; emulsion tubes can get a little debris on them and cause the issue...I experienced this myself from a small bit of paper towel stuck to one of the orifices.

[lemonlib]

Lame question...but is your fuel filter fairly new..? Cause what happens is when you have a engine out . Filter dries out...and the particles fall off the filter material...and then when it's all hooked up...it gets past the filter ...right into the carbs..been here done that...

Lemon

[lemonlib]

Another thing to check...we assume that3 and 4 going to be lean...so if you pull the plugs it's going to be white..but are the others are the same?....if they are all white then the carbs are jetted wrong ..remember you car is now a 2.2...not a 2.0 no more...


2 cents
Lemon

[bobm]

Good thoughts Guy's.
I will check.
Ideas on which jets would be correct for a now 2.2 Motor.
Bob