Summit carb help?
Thread Starter
Instructor
Joined: Jun 2018
Posts: 107
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Summit carb help?
Hi, I’m having a problem with my 74 sbc, running a sum-m08600vs carb with auto choke. The car has a summit top end kit also.
The car starts perfect, choke seems fine, and drives fine. But, usually after turning the car off then starting again whilst still hot, it idles really high, 1500rpm or so, and is pulling me down the road, and doesn’t stop this until I turn the car off.
I’ve also noticed it smells really rich when it does this. It’s like something’s stuck open.
Could it be choke problems? Or a sticking fast idle cam? Vacuum leak? Where would you start?
I bought the car with this setup, imported to the U.K. last year.
Any help would be great.
Thanks, Tim.
The car starts perfect, choke seems fine, and drives fine. But, usually after turning the car off then starting again whilst still hot, it idles really high, 1500rpm or so, and is pulling me down the road, and doesn’t stop this until I turn the car off.
I’ve also noticed it smells really rich when it does this. It’s like something’s stuck open.
Could it be choke problems? Or a sticking fast idle cam? Vacuum leak? Where would you start?
I bought the car with this setup, imported to the U.K. last year.
Any help would be great.
Thanks, Tim.
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
Go for the good first drive. Shut it off at home. Pull air filter. Take pic of choke side of car. Flip throttle once. See choke close? Take another pic. Trying to get pic of linkage on lower right side of carb. Most likely choke badly adjusted or fast idle cam (that choke engages) hanging up.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
That summit carb is a 4010 or 4011 holley. And that electric choke is kinda slow opening. https://www.ebay.com/itm/Holley-108-...AAAOSwEXtcQmsd. https://www.ebay.com/itm/Holley-108-...item1ef1e3c6f6. Get some of these. You see diff? If standard holley square bore, 1st ones. If q-jet spread bore 2nd set. These also have the holley power valve that sometimes pops, causing rich running.
Last edited by derekderek; Mar 25, 2019 at 08:09 AM.
Thread Starter
Instructor
Joined: Jun 2018
Posts: 107
Likes: 28
Hi, thanks for the reply.
The cars currently warming up, idle has dropped to normal, 700rpm, I’ll take it for a drive and try to achieve the high idle condition and then carry out the steps you’ve mentioned above.
when the car is cold, and ignition turned on, the choke does take a while to open as you say.
The cars currently warming up, idle has dropped to normal, 700rpm, I’ll take it for a drive and try to achieve the high idle condition and then carry out the steps you’ve mentioned above.
when the car is cold, and ignition turned on, the choke does take a while to open as you say.
Thread Starter
Instructor
Joined: Jun 2018
Posts: 107
Likes: 28
Hi, ok, after turning the car off, immediately after when blipping the throttle, the choke doesn’t move/close. Only after it’s cooled for a few minutes, you can see the choke closing on its own, then it closes more when blipping the throttle.
Also noticed the engine is lumpy at idle, shakes the car a little, I’m sure I used to be silky smooth.
Should the choke do anything on a warm engine on start up? As when I started the car again, the revs were high, then slowly dropped off.
Here’s a pic when warm, before touching the throttle.
Also noticed the engine is lumpy at idle, shakes the car a little, I’m sure I used to be silky smooth.
Should the choke do anything on a warm engine on start up? As when I started the car again, the revs were high, then slowly dropped off.
Here’s a pic when warm, before touching the throttle.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
The choke should NOT be doing anything on a warm engine. Look for a little line or notch on the black plastic choke cover. Loosen that cover, and turn one notch C.C.W. by using those index marks on the carb.
Next, spray a little WD40 on the fast idle cam. Work that back & forth with your fingers.
Next, follow the black GRD wire to confirm it is truly going to a good GRD. Your contact point is ok, but I see some corrosion here & there.
Next, spray a little WD40 on the fast idle cam. Work that back & forth with your fingers.
Next, follow the black GRD wire to confirm it is truly going to a good GRD. Your contact point is ok, but I see some corrosion here & there.
Last edited by HeadsU.P.; Mar 25, 2019 at 09:56 AM.
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
The problem with this electric choke, is the electric choke cools off in a couple of minutes when you shut the motor off. That's why you see the choke slowly close over a couple of minutes span. Maybe try adjusting the choke so that is most of the way open 10 or 15 minutes after shutting the engine off. Then check it in the morning when it stone cold and see if it closed enough more to actually work as a choke on a cold engine.
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watch this video on choke adjustment and in particular check where the red wire is connected, too low a voltage and the choke will not properly operate.
https://www.google.com/search?q=holl...TF-8#kpvalbx=1
https://www.google.com/search?q=holl...TF-8#kpvalbx=1
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
No, get that red wire off of that steel fuel line. The red wire is hot all the time. if it chafes it can arc to that steel fuel line. More than likely it wouldn't burn a hole in the fuel line and then light up the gasoline that come spraying out of the fuel line. But more than likely is not good enough. Get that red wire off of that steel fuel line
Last edited by derekderek; Mar 25, 2019 at 05:50 PM.