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B20F wants to idle high

jnderr

jnderr

Member
Joined
Oct 18, 2007
Location
Springfield, OH
So I have a 67 amazon with a
B20F, Weber 32/36 DGV, IPD big bore kit (2130cc, 10.5:1 compression I think), KG10 cam, petronix ignition, header.

When I bought the car it had a 2 bad lobes on the cam so it was no running particularly well. I installed a KG10 cam and lifters and a few gaskets and seals.

I have not been able to get it to run quite right. I have checked the timing and it seems to have a proper amount of advance at idle 10*, it doesn't have points to the base timing is a guess, I have not tried to set it at higher RPM's because KG recommends not running it over 2500 RPM for the first 300 miles after break in.

I managed to get it to idle happily around 1000 RPM. However a little driving around and it wants to stay at 1500-1800 RPM.

I installed a weber refresh kit, the linkage is free and not bound up.

I inspected the mechanical advance and it seems to operate smoothly.

I haven't tried spraying carb cleaner around to see if it has a vacuum leak yet.

Anything else I should check?
 
Make sure the throttle arm is returning to the idle stop screw. The internal return spring isn't very strong and sometimes an additional spring is required.
 
It looks like it was installed around 2000. When I had it apart it looked like this was not the first time it had been apart. The venturis had been shimmed to keep them tight.
 
dl242gt said:
I'm sure it's OK but it's good to check that stuff. The intake/exhaust gasket is a sneaky spot if it leaks underneath.
Click to expand...

I appreciate the input believe me. After having it a part there isn't much to it, although I am tempted to upgrade to a 38 DGMS its probably a better fit for the motor. And it start with a fresh new carb.

I couldn't find torque specs for the manifold and exhaust studs, it definitely strikes me as a spot that could leak.
 
Probably something not more than about 15ft lbs or so since they are 5/16 studs. Volvo is funny with the torque specs. They will have stuff that you must strictly keep to like a main cap for example and other stuff like the manifold will be a general assumption to make the fastener safely tight for the application.

The weber is a bit small but runs well on these engines. The original SUs are bigger and make more power. Helpful with a big bore engine. There used to be a dual downdraft weber kit for Triumph TR6 which had manifold adapters that would fit the Volvo. I saw a 144 that had dual progressive webers on the B20. He had to make a hole in the hood for the carbs. I don't remember how well it ran but it must have been fun. Probably would fit under the hood better on a 122S. Lol
 
I've had the manifold leak on that very same carb set up John. They are finicky, but it should be easy to see if it's leaking.
 
jnderr said:
So I have a 67 amazon with a
B20F, Weber 32/36 DGV, IPD big bore kit (2130cc, 10.5:1 compression I think), KG10 cam, petronix ignition, header.

When I bought the car it had a 2 bad lobes on the cam so it was no running particularly well. I installed a KG10 cam and lifters and a few gaskets and seals.

I have not been able to get it to run quite right. I have checked the timing and it seems to have a proper amount of advance at idle 10*, it doesn't have points to the base timing is a guess, I have not tried to set it at higher RPM's because KG recommends not running it over 2500 RPM for the first 300 miles after break in.

I managed to get it to idle happily around 1000 RPM. However a little driving around and it wants to stay at 1500-1800 RPM.

I installed a weber refresh kit, the linkage is free and not bound up.

I inspected the mechanical advance and it seems to operate smoothly.

I haven't tried spraying carb cleaner around to see if it has a vacuum leak yet.

Anything else I should check?
Click to expand...

Lots of changes there.
Consider the distributor and maybe make another change there.
The stock B20F has a vacuum retard module on it. Applying vacuum retards the ignition timing. Your KG camshaft probably has the engine producing less vacuum at idle than the original camshaft. Less vacuum, less ignition retard, higher idle speed.
Twist the distributor to "fix" the more advanced ignition timing at low engine speeds, and you then lose ignition timing where you want it higher in the rev range.
Check it by applying 20" of vacuum with a hand pump to the vacuum retard module and see if you don't get less ignition advance at idle.
There are multiple sources of vacuum on some DGV installations, and you want to also be sure you're not getting port vacuum as your source where manifold vacuum was the original, etcetera.
Maybe an Ignition123 unit would give you easier tuning options.
 
brian smith said:
Lots of changes there.
Consider the distributor and maybe make another change there.
The stock B20F has a vacuum retard module on it. Applying vacuum retards the ignition timing. Your KG camshaft probably has the engine producing less vacuum at idle than the original camshaft. Less vacuum, less ignition retard, higher idle speed.
Twist the distributor to "fix" the more advanced ignition timing at low engine speeds, and you then lose ignition timing where you want it higher in the rev range.
Check it by applying 20" of vacuum with a hand pump to the vacuum retard module and see if you don't get less ignition advance at idle.
There are multiple sources of vacuum on some DGV installations, and you want to also be sure you're not getting port vacuum as your source where manifold vacuum was the original, etcetera.
Maybe an Ignition123 unit would give you easier tuning options.
Click to expand...

It is a mechanical advance only unit, bosch 0 231 178 007
 
The intake and exhaust should be torqued to 18-20 ftlbs. The shared holes at the top and underneath need to have the thick cast iron washers, or something really hard. Make sure the downpipe is not connected until the manifold is torqued, then do the exhaust/bellhousing clamp, then the 3 (or 2) downpipe bolts. This sequence has given me the best results as far as sealing the intake, any shifting of the exhaust can funkify the intake seal.
 
Thanks for the tips on that.

This issue might be slowly killing me :D I put a fresh gasket in there when it went all back together. Finally going to trailer it home from my in-laws to my house so I can work on it there. If I don't get a couple on nice days to drive it before it snows I'm going to be bummed.
 
cwdodson88 said:
The intake and exhaust should be torqued to 18-20 ftlbs. The shared holes at the top and underneath need to have the thick cast iron washers, or something really hard. Make sure the downpipe is not connected until the manifold is torqued, then do the exhaust/bellhousing clamp, then the 3 (or 2) downpipe bolts. This sequence has given me the best results as far as sealing the intake, any shifting of the exhaust can funkify the intake seal.
Click to expand...

I reinstalled the header and intake over the weekend with this in mind, its a massive improvement. Runs pretty good, needs a little fine tuning but its a lot better. Thanks TB!
 
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