Baseline adjustments on a Trollhole carb ('77)

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Straight to Hell

Straight to Hell

10 Year
Joined
May 20, 2013
Threads
13
Messages
18
Location
Winnipeg, Canada
My truck has a a Trollhole carb and we attempted to adjust it last week based on instructions for an Aisin. I had thought they were pretty much the same. Post adjustment it ran rich. I did some fiddling and now it's not rich anymore, but it won't hold a steady idle. Sometimes it's 750-800 sometimes it's 1100 (all in the same short commute). Now I don't know what the heck to do.
 
Make sure your accelerator cable isn't hanging up. Have a good strong return spring on the throttle linkage? Maybe try hooking your toe under the skinny pedal and pull it up when it's idling fast, see if that changes anything.
 
Pighead said:
Make sure your accelerator cable isn't hanging up. Have a good strong return spring on the throttle linkage? Maybe try hooking your toe under the skinny pedal and pull it up when it's idling fast, see if that changes anything.
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yea-take a look at the linkage too-could easily be that the little ball joints are hanging up-squirt a little Kroil in them and work them several times--if this works I would yank the whole assy and clean-relube with plain old Vaseline.
 
How do you know it is rich? If you don't have a tail pipe sniffer, it would be hard to know.

The only things that are readily adjustable are the idle speed and idle mix. If the idle speed is not consistent. it may have a sticky linkage problem.
 
Pin_Head said:
How do you know it is rich? If you don't have a tail pipe sniffer, it would be hard to know.

The only things that are readily adjustable are the idle speed and idle mix. If the idle speed is not consistent. it may have a sticky linkage problem.
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Pin head
I to have a trollhole carb that is sticking. It will only return to normal idle at 650 rpm if step and release quickly on the accelerator. Every thing else runs fine. Is there a way to lube accelerator shaft on carb? I’ve loosened all connecting cables to see if it was choke or accelerator cable that might be set to tight.

Sorry for the bumb
Btbuild
 
btbuild said:
Pin head
I to have a trollhole carb that is sticking. It will only return to normal idle at 650 rpm if step and release quickly on the accelerator. Every thing else runs fine. Is there a way to lube accelerator shaft on carb? I’ve loosened all connecting cables to see if it was choke or accelerator cable that might be set to tight.

Sorry for the bumb
Btbuild
Click to expand...

What year 40? Is there a spring on the accelerator pump to the base of the choke cable mount? If not I can send you one.

If you did the lean drop method and it won't idle smoothly check timing.
 
Hi Marshal.
(73) Here is a pick of carb.. I set timing with a vacuum gauge. It is running smooth except like I said the idle is sticky. Until I step on accelerator quickly and returns to normal idle. 650 rpm measured on my sun tach/dwell instrument. I do get a very little back fire when driving on decel. Hardly noticeable. Exhaust smells a bit rich also. I know I need a sniffer to actually measure that. All in all it runs pretty dam good except for sticky idle on return.

DB2B9430-C925-4CA2-B572-B746BB7FF4BB.webp
 
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I would start by disconnecting the accelerator linkage at the carb and trying the linkage alone. If it binds, it is a carb issue and if not, it is a linkage issue. The carb throttle shafts don't need lubrication.

You can't smell a rich mixture. If you smell gasoline vapor it is misfiring, not running rich.
 
Pin_Head said:
I would start by disconnecting the accelerator linkage at the carb and trying the linkage alone. If it binds, it is a carb issue and if not, it is a linkage issue. The carb throttle shafts don't need lubrication.

You can't smell a rich mixture. If you smell gasoline vapor it is misfiring, not running rich.
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I will unhook every thing again and double check. engine is not misfiring. could just be I need to finish exhaust from headers.
 
thebigredrocker said:
7 deg BTDC?
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Pin_Head said:
I would start by disconnecting the accelerator linkage at the carb and trying the linkage alone. If it binds, it is a carb issue and if not, it is a linkage issue. The carb throttle shafts don't need lubrication.

You can't smell a rich mixture. If you smell gasoline vapor it is misfiring, not running rich.
Click to expand...


ok unhooked linkage. same thing unless I pull throttle linkage back to original position. maybe like marshal said is there a additional return spring for throttle that is missing?

@thebigredrocker I set timing with vacuum. bb is just below window so I'm assuming 13 deg BTDC. this is where my best vacuum of about !8.5 inches.
 
Here is some more pics of my carb. I looked at sor at the non USA dizzy. It looks like they are pretty close. All I see on sor is the assembly page which does not show linkage. I hope the pics can help you guys help me.

B7AE0CE7-B8EF-44F3-BD75-0822B9CBEDA7.webp


4E56B5D4-E2FF-496B-8B70-16FCD3E9E0FE.webp
 
The spring in the middle of the first picture looks like it might be the throttle close spring, but it looks like there is no more retraction left in it, so you may have to adjust its length to get it to close all the way all the time.
 
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