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supercoach24 Offline
#1 Posted : Monday, 3 February 2020 3:50:42 PM(UTC)

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Hi guys looking for some help and info about automatic choke duration on a Stromberg 2 barrel fitted to a 69 HT 253 V8.

Nowhere in the workshop manuals will it state how long the choke must stay on, all it says is it is dependant of atmospheric temperature.
I am looking for peoples advice/opinion about choke duration especially mine.

Going by the temp gauge should the choke be switching off after the needle has passed the first marker on the temp gauge or should the choke stay on longer until needle reaches halfway?

My choke is staying on until the engine reaches its normal temp which is just past 180F. I feel the choke is staying on longer than it should. Is this too long for a 25 degree day?


I am also having other issues with the auto choke, as soon as I blip the throttle after start up whether it be 2 sec or 30 sec, the fast idle cam drops from 1st step (1500rpm) to 3rs step (900rpm) car stalls as cant maintain revs. It misses 2nd step completely on the fast idles cam. I have bent arms and made changes, but nothing fixs the issues. Have also replaced the thermos spring inside the housing and that has done nothing. I am also noticing a lot of black soot type on the ground from the exhaust, which indicates a lot of fuel being unburnt properly.

My engine is not happy and shaking at high rpm during start up, but once warm seems to perform ok.

So I am in a spot of bother and don’t know where to go from here, I am just wanting to learn so I am able to fix it myself in the future.

Any stromberg/Holden guru located in Adelaide that might be able to help me tune everything up

Edited by user Monday, 3 February 2020 3:52:08 PM(UTC)  | Reason: Not specified

Smitty2 Offline
#2 Posted : Monday, 3 February 2020 9:33:00 PM(UTC)

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.... auto chokes (all of them ínc leccy ones)
work off heat ... and except electric ones (which work off a heated coil)
they work/react to engine temps AND atmospheric temps

A choke may not kick in at all on a 42° hot summers day
but will stay on longer than usual if the air temp.. and
engine temp is -10°.

the íssues' you state are normal.... Holden say that to reduce choke enhanced
higher idle speeds, you blip the throttle and the carb should drop one or
2 steps off the fast idle cam.

Regarding the black soot and unhappy idle, that sounds like the engine
is 'overchoked'....so yes you need a carb place/expert to look at it
It may be something as simple as the choke valve/flap wrongly adjusted

Edited by user Monday, 3 February 2020 9:33:58 PM(UTC)  | Reason: Not specified

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Dr Terry Offline
#3 Posted : Wednesday, 5 February 2020 7:35:13 AM(UTC)
Dr Terry

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Setting up auto chokes is almost a 'black art'.

There are several things to consider. One of the most important is the choke pull-off diaphragm setting, which from your description sounds like it's not quite right.

I'd ask around & find an old school carby dude. He'll need a few cold mornings to get it right, but a good one will sort it out.

Dr Terry
If at first you don't succeed, just call it Version 1.0
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