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Old 08-18-2021, 10:34 AM   #2
Board Member
Join Date: Oct 2011
Location: The Dalles, Oregon

Originally Posted by 1968 volvo View Post
Hi Volvo Nerds
I have a 1968 Volvo 142s with b20 engine and the suhs6 carbs. It idols at about 1300-1500rpm.
Here is the way that it acts.
-It idols high only when it warms up
-It only idols high only after you rev it
-It goes down to a reasonable rpm when in gear. (It has a BW35 transmission in it)
-It seems to be running rich but that could be the carburetors not being very well tuned

Here is what Ive tried to fix the problem
-I had the carburetors rebuilt by a gentleman by the name of Thomas Bryant (They needed to be rebuilt anyways)
-I replaced the carburetor to intake manifold gaskets
-I replaced to intake manifold to head gasket
-I removed the second set of butterfly valves in the intake manifold and plugged the holes
-I replaced all the vacuum hoses
-I replaced the one way valves for both the pcv and the brake booster
-I replaced the brake booster( I did this prior to trying to fix the rpm when I built the brakes back up)
-I made sure that the fuel pressure was in line with what the Haynes shop manual recommends by installing a fuel pressure regulator

I'm at my whits end and was wondering if anyone had other suggestions. I tried everything people recommended last time and I'm back for more.
Try resetting all fuel and air settings. Warm it up first.

loosen linkage. Back off choke and idle set screws until there is absolutely no contact. Back the chokes off an extra full turn.

Get the throttle screws to just touch the stop, then give them 1.5 turns.

Raise the jets to the bridge. make sure they are all the way flush with the bridge in the carb throat. Pull the dashpot dampers and check that the piston falls with a clink. if not, recenter the jets.

Lower the jets 12 flats (2 full turns). check that the piston falls freely to the bridge. Put the dampers back in.

Start the engine. It should idle high, so get it back in line by adjusting each carb. Use a sync tool and get the air flow correct, and idle where it should be.

Lift the front carb piston 1/8" and see what changes. If it stumbles, richen by 1 flat, if it raises the idle lean it by 1 flat, and blip the throttle after each adjustment. Do the same to the rear. Go back and fourth until lifting the piston doesnt change the idle speed.

Make sure that they are even and balanced. Make sure that all other things are correct. So valve lash, and ignition timing. Vacuum leaks are a huge problem, so check for vacuum leaks again.

If you dont have a sync tool. Go to the hardware store, and get some clear tubing (about 12 feet) a yard stick, and a couple packs of zip ties and make a manometer. Pretty easy.
Originally Posted by mikep View Post
Build it, break it, build what broke stronger, lather, rinse, repeat.

The Build Thread

Last edited by cwdodson88; 08-18-2021 at 10:39 AM..
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