Fuel System: 164: - adjusting strombergs

woodturner-fran · Sep 2nd, 2007, 20:37

Hi all,

So due to lumpy tickover issues etc, I decided to give the twin strombergs a bit of TLC. Went through the set up as per the haynes manual (I know

) and the two pistons don't seem to be balanced. When you rev the engine, the front carb seems to put through a lot more fuel than the rear one too.

So, I was going to take apart the carbs and clean them out (the pistons do look pretty dirty). Is there an adjustment for the piston height through the top of the damper pot? And I'm thinking of buying some kind of recon kit for it, or at least replace the diaphragms. Whats the current wisdom on doing this?

Fran

pookie · Sep 2nd, 2007, 20:48

The mixture on some Stromberg carbs is adjusted down inside the pistons with I think, a 3mm allen key in a special tool to stop the piston assembly turning. If the piston turns during adjustment the diaphragms will tear.
The difference in height is probably down to worn diaphagms, or one carb is working harder than the other due to possibly maladjustment.

Pookie

Pigeon · Sep 2nd, 2007, 23:15

If there are no holes in the diaphragms then difference in height is down to imbalance of the actuation of the butterflies. This is adjusted by loosening the locknuts on the rods connecting the throttle spindle arm to the cranks on the carbs and twiddling the rods in the ball ends. It's a bit of a pain because very small amounts of twiddle make a significant difference and they tend to move when you do the locknuts back up.

Clan · Sep 3rd, 2007, 09:55

Fuel mixture adjustment is done by pressing the jet up or down in the lower housing . The Jet is a tight press fit in the housing ,
This is done with 3 Volvo special tools . One to press the jet down, one to press the jet up and the third is a stepped spacer to set the jets both in the same position for a basic stating point where you will measure the CO and press both jets up or down a very small amount to get the CO about 3% .
It is almost impossible to do this without the correct tools as hitting the jet with a drift may close up the calibrated jet or even break the carb body and also there is no way of determining how far the jet has moved in relation to the second jet in the other carb . Some of the longer established Volvo Dealers will still have these tools hanging up on the boards but whether they would have the staff with any knowledge of how to use them is debatable !

The big brass screw on the outside of the carb near the temperature compensator is an air bleed for fine tuning the CO but in practice makes very little difference .

woodturner-fran · Sep 4th, 2007, 01:04

I'm hoping to strip the carbs down tomorrow night and have a look. I can get all the parts locally so at least I know that stuff is available.

Thanks for the info so far - I will report back soon.

Fran

Sep 2nd, 2007, 20:37	#1
woodturner-fran Junior Member Last Online: Jul 8th, 2014 23:46 Join Date: Jun 2007 Location: Kildare	adjusting strombergs Hi all, So due to lumpy tickover issues etc, I decided to give the twin strombergs a bit of TLC. Went through the set up as per the haynes manual (I know ) and the two pistons don't seem to be balanced. When you rev the engine, the front carb seems to put through a lot more fuel than the rear one too. So, I was going to take apart the carbs and clean them out (the pistons do look pretty dirty). Is there an adjustment for the piston height through the top of the damper pot? And I'm thinking of buying some kind of recon kit for it, or at least replace the diaphragms. Whats the current wisdom on doing this? Fran

Sep 2nd, 2007, 20:48	#2
pookie Premier Member Last Online: Apr 2nd, 2021 21:13 Join Date: May 2006 Location: Stockport	The mixture on some Stromberg carbs is adjusted down inside the pistons with I think, a 3mm allen key in a special tool to stop the piston assembly turning. If the piston turns during adjustment the diaphragms will tear. The difference in height is probably down to worn diaphagms, or one carb is working harder than the other due to possibly maladjustment. Pookie __________________ Growing old disgracefully

Sep 2nd, 2007, 23:15	#3
Pigeon Volvo-loving biker Last Online: Feb 3rd, 2019 05:24 Join Date: Sep 2006 Location: All alone in the crazy city	If there are no holes in the diaphragms then difference in height is down to imbalance of the actuation of the butterflies. This is adjusted by loosening the locknuts on the rods connecting the throttle spindle arm to the cranks on the carbs and twiddling the rods in the ball ends. It's a bit of a pain because very small amounts of twiddle make a significant difference and they tend to move when you do the locknuts back up. __________________ Pigeon's Nest Be kind to pigeons

Sep 3rd, 2007, 09:55	#4
Clan Experienced Member Last Online: Yesterday 23:35 Join Date: Jun 2007 Location: L/H side	Fuel mixture adjustment is done by pressing the jet up or down in the lower housing . The Jet is a tight press fit in the housing , This is done with 3 Volvo special tools . One to press the jet down, one to press the jet up and the third is a stepped spacer to set the jets both in the same position for a basic stating point where you will measure the CO and press both jets up or down a very small amount to get the CO about 3% . It is almost impossible to do this without the correct tools as hitting the jet with a drift may close up the calibrated jet or even break the carb body and also there is no way of determining how far the jet has moved in relation to the second jet in the other carb . Some of the longer established Volvo Dealers will still have these tools hanging up on the boards but whether they would have the staff with any knowledge of how to use them is debatable ! The big brass screw on the outside of the carb near the temperature compensator is an air bleed for fine tuning the CO but in practice makes very little difference .

Sep 4th, 2007, 01:04	#5
woodturner-fran Junior Member Last Online: Jul 8th, 2014 23:46 Join Date: Jun 2007 Location: Kildare	I'm hoping to strip the carbs down tomorrow night and have a look. I can get all the parts locally so at least I know that stuff is available. Thanks for the info so far - I will report back soon. Fran

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