Choke question

[sogood]

The mechanical choke on my engine didn't seem to be opening the choke plate fully and despite replacing the choke it still only opens the plate part way. There is still plenty of movement in the plate after the engine has warmed up to operating temperature ( showing about 115 degrees on the gauge) . Can I just bend the connecting rod from the choke spring to the choke mechanism to take up the slack and provide better opening of the plate ? Thanks in advance.

 

[Bondo]

Ayuh,.... Which carb,..??

 

[sogood]

Sorry, Rochester Quadrajet.

 

[Scott Danforth]

what are you working on, and do you have it adjusted correctly

 

[sogood]

what are you working on, and do you have it adjusted correctly

That's my question. Can I adjust it "mechanically"? It's a Rochester Quadrajet carb on a Mercruiser 5.7 with a mechanical (spring operated) choke. I just want to know if it's ok to adjust/ bend the offset in the rod from the choke spring to the choke mechanism on the carb to take up the bit of slack? Regarding the operating temp mentioned ( 115 degrees) showing on the gauge , this is on idle on muffs and I recently replaced the thermostat. I imagine it would run hotter under load.

 

[Scott Danforth]

115 degrees is still a cold motor. get an IR thermometer and check. 140 degrees minimum. did you assemble the spacer sleeve and thermostat correctly in the housing?

loosten the 3 screws securing the choke. turn the choke in the housing right or left to adjust the choke. no need to bend rods

 

[Lou C]

I bet you have the well style or divorced choke. It needs normal engine temp to heat the exhaust crossover and 115* won't cut it. Yes you can bend tHe rod to adjust it. On mine when the temp gauge says 160 the manifold right under the spring is about 100-115*, it will open all the way then. Be sure to clean the Choke LINKAGE...
Your main problem is an engine running too cold

 

[sogood]

115 degrees is still a cold motor. get an IR thermometer and check. 140 degrees minimum. did you assemble the spacer sleeve and thermostat correctly in the housing?

loosten the 3 screws securing the choke. turn the choke in the housing right or left to adjust the choke. no need to bend rods

I think you're possibly thinking of a different choke set up. Mine is mounted on top of the block, starboard side, below the carb and is held in place with one screw. I refitted the new thermostat exactly as per the old one and as per instructions. What's the best recommended temp stat to use in my case? Ireland has a temperate climate with no huge variations and I'm using it in salt water.

 

[sogood]

Thanks Lou. I think you may well be right.

 

[Lou C]

Well or divorced choke is what you got

 

[Scott Danforth]

agree with Lou. a divorced choke requires the motor to be warm (140 min, 160 preferred). get an IR thermometer to check and not the dash gauge which is a suggestion at best.

 

[Bondo]

I think you're possibly thinking of a different choke set up. Mine is mounted on top of the block, starboard side, below the carb and is held in place with one screw.

Ayuh,..... Scott was talkin' 'bout an Electric choke adjustment,....

Lou is talkin' 'bout the divorced choke, which uses a choke spring mounted in the choke stove in the Intake Manifold, not the Block,....

The choke stove is a little pocket in or on top of the exhaust cross-over passage that runs under the carb to help warm things up, 'n prevent carb icing,....

Yer carb could also be converted to an electric choke, say if ya had an intake manifold problem, 'n yer replacement manifold didn't have a spot for the choke element/ coil,...
They're both 'bout the same bi-metal spring, 1 uses motor heat to pull off, the other is an electric heater,....

 

[QBhoy]

Take the cover off and rotate it to disconnect it. Just pump the throttle to start when cold.
That carb is well known for the autochoke to fail.

 

[Lou C]

No Title

Ahh nope, the Q-Jet came with a divorced choke for marine use, they can be converted to an electric choke if you want to use a Q-Jet on a Vortec manifold that does not have an exhaust crossover. For auto applications, they used the divorced choke, the exhaust heated air choke, and later on the electric choke. We had the well or divorced choke on our '72 Chev Impala 350 with the 2 bbl Rochester, we had the exhaust heated air choke on the '75 Olds Delta 88 with the 4bbl Rochester Q-Jet, and my old '88 4.3 has the divorced choke with the Q-Jet. In the pic, the choke spring is inside the tin cover right above the breather hose in the valve cover. The exhaust crossover inside the Pre-Vortec intake manifold heats the area right under the spring to open the choke. It is actually more accurate than an electric choke in some ways because it is responding to actual engine temp, not a timer/electric heater. But if your engine runs too cool they will not open all the way which is not good because the engine will be running too rich all the time.

 

[sogood]

Thanks for all the inputs folks. If I want the engine to warm up more should I then use a 160 degree stat as opposed to a 140 which I think I put I to it. Also, would anyone have a ball park idea of how long it should take for the engine to get up to full operating temperature when idling on muff? I know there are many variables but any thoughts welcome. Thanks again.

 

[Lou C]

Well most will say to keep the 140 'stat in salt water but I have used a 160 in salt with no ill effects all these years as the OMC had no option of a 140. It will take a while for it to completely warm up on the muffs, as long as 20 min depending on the temp of the water in your home and the outside air temp. Make sure to clean the choke linkage and the choke shaft were it passes through the air horn (ie top of the carb) with carb cleaner. It does not take much in the way of deposits to make a choke stick. Every year when we did a tune up on our old school cars, cleaning the carb linkages and choke shaft was part of it....