Choke Setting Issues or ??
Thread Starter
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Tuned
Joined: Jun 2006
Posts: 363
Likes: 3
From: Graham WA
Choke Setting Issues or ??
I have a 1986 460 engine in my truck, stock except for an after market Holly 4160 600 cfm carb. Manual 4spd.
The engine starts up fine. I start down the road and reach a stop sign in about 2-3 minutes. At that point the fuel system seems to lean out too much (like the choke comes off too soon). You then have to rev the engine up to pull away from a stop for the next 2-3 miles. I've tried several different choke adjustment settings with the same result.
Once the engine is at full temperature, all is well.
Is this the carb/choke or is something else going on like maybe a temperature activated vacuum switch in the emissins system or something else?
Tired of just living with this issue! I'm about to go buy a manual choke kit.
Opinions please!
Tom
The engine starts up fine. I start down the road and reach a stop sign in about 2-3 minutes. At that point the fuel system seems to lean out too much (like the choke comes off too soon). You then have to rev the engine up to pull away from a stop for the next 2-3 miles. I've tried several different choke adjustment settings with the same result.
Once the engine is at full temperature, all is well.
Is this the carb/choke or is something else going on like maybe a temperature activated vacuum switch in the emissins system or something else?
Tired of just living with this issue! I'm about to go buy a manual choke kit.
Opinions please!
Tom
Laughing Gas
Joined: Apr 2003
Posts: 837
Likes: 2
From: Minnesota
Sounds like carb/choke to me, but then I'm not an expert on this type of thing. Every 460 I've had warms up pretty quick. It almost sounds like the choke is warming up faster than the engine ???
I'm thinking a couple things.
Not enough choke initially so it opens too far too fast ...
What thermostat are you running? Engine heating up slower than the choke heater opens the choke plate.
????
I'm thinking a couple things.
Not enough choke initially so it opens too far too fast ...
What thermostat are you running? Engine heating up slower than the choke heater opens the choke plate.
????
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Another thought is that the stock 4180 uses a 7.5V choke element.
Perhaps it's not opening soon enough?
Did you find a 12V source in 'Run' to power your 12V choke element on the 4160, or use the one from your old carb?
Perhaps it's not opening soon enough?
Did you find a 12V source in 'Run' to power your 12V choke element on the 4160, or use the one from your old carb?
Thread Starter
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Tuned
Joined: Jun 2006
Posts: 363
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From: Graham WA
Choke or ??
I appreciate the responses. I really think the choke is opening too soon. I have not smelled excessive raw fuel in the exhaust like you would expect if the choke was staying on too long. The issue mimmics, a vacuum leak. But if it were a vacuum leak it would still act up once it reaches operating temperature, which is not the case. As far as the thermostat the warm up time seems reasonable, not like an engine with a thermostat stuck open.
I will very systematically adjust choke to stay on longer and longer and see if I can make this big boy happy. Otherwise I'm going to a manual choke or work in a voltage regulator circuit of sorts to force the choke to open more slowly. Don't know what else it could be. I wonder if Holly or someone else makes chokes of different duration bi-metal spring? I really don't like a manual choke because of forgetting to push it off at consequently burning fuel unnecessarily. But I hate the bucking bronco warm ups even more and it isn't likely good to run lean like that.
I will very systematically adjust choke to stay on longer and longer and see if I can make this big boy happy. Otherwise I'm going to a manual choke or work in a voltage regulator circuit of sorts to force the choke to open more slowly. Don't know what else it could be. I wonder if Holly or someone else makes chokes of different duration bi-metal spring? I really don't like a manual choke because of forgetting to push it off at consequently burning fuel unnecessarily. But I hate the bucking bronco warm ups even more and it isn't likely good to run lean like that.
Thread Starter
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Tuned
Joined: Jun 2006
Posts: 363
Likes: 3
From: Graham WA
12v or ?
You have a good point there and I am going to check your theory out before going farther.
I have several vehicles (too many actually), and I have made a hobby of sorts out of bringing the old ones back to life......ummmm.......problem with that is repairs and issues seem to bump into one another in my mind and it's hard to remember everything you have done and to which car....haha. Hell to get some age on the old body and mind, Eh.
The point is, I seem to remember hooking it up straight from the battery when I first replaced the carb. Right away, I had this same choke issue and I investigated and found yes, the stock carb choke works off a lower voltage. I then had to repair the original choke wire in the harness (it was dead) and that is what the choke is currently fed by. But, it's certainly a good suggestion and I'm going to measure that voltage and see what it is currently.
If I connect to a 12v wire, what about when the engine starts and the voltage jumps to 13v+? Won't that accelerate the choke open function even more?
Are you suggesting I find a constant 12v somewhere to connect to for the choke? Or, are you thinking it is currently running off a 13v+ wire?
Tom
Last edited by E30tdf; Sep 28, 2009 at 06:25 PM. Reason: clarity
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
I really meant a battery voltage wire that is hot in Run...
The difference between 12 & 13.7V is negligible.
The difference between 7.5 & 12 is considerable.
Like I said you could always use your old choke that was meant for the resistance wire (used to excite the alternator) if you don't want to hack the harness.
It only came to my attention when I swapped to a 3G alternator and had to purchase a 12V choke to keep it from coming off too soon.
The difference between 12 & 13.7V is negligible.
The difference between 7.5 & 12 is considerable.
Like I said you could always use your old choke that was meant for the resistance wire (used to excite the alternator) if you don't want to hack the harness.
It only came to my attention when I swapped to a 3G alternator and had to purchase a 12V choke to keep it from coming off too soon.
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Tuned
Joined: Jun 2006
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From: Graham WA
Good Idea
I didn't think about that. Swap in the choke from the original carb. Dang, sometimes I go about making a fix harder than it needs to be.
I'm leaving on a flight to Minneapolis tomorrow morning, but I"m going to give that a try when I get back (next week).
Thanks!
I'm leaving on a flight to Minneapolis tomorrow morning, but I"m going to give that a try when I get back (next week).
Thanks!
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Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
You need to set the choke back to spec and start over. If nothing else, go out in the morning when the engine is totally cold. Loosen the choke heater cover and back it off until the choke valve opens, then roate the heater until the choke butterfly valve is just closed against the choke air horn. Tighten the screws and see what happens.
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Tuned
Joined: Jun 2006
Posts: 363
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From: Graham WA
Turns out the issue is a intermitent disconnect/break in the harness somewhere. Sometimes I have voltage to the choke and sometimes not. So as ArdWrknTrk suggested the choke is likely opening too slow (opens only after sufficient engine temperature is reached to heat the choke externally). It sure did not seem that way to me based on my experience with chokes, but no other explaination has viability. Once I track down the wiring issue or choose another source for power, it will likely work much better.
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Tuned
Joined: Jun 2006
Posts: 363
Likes: 3
From: Graham WA
Changed Source for Choke DC Feed
What I ultimately did was patch into the power feed to the wiper motor since that is 12v and is only hot when in "run" mode. I need to tweak the adjustment a bit more but it is 80% better now. It apears my connector or wiring coming from the alternator is bad (measured only 6 volts when it worked at all).
