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Author Topic: choke???  (Read 440 times)

Anthony Prescott

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choke???
« on: September 18, 2010, 11:33:41 AM »

why is it needed? i know what it does, but why does it need to do it?
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Brian

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choke???
« Reply #1 on: September 18, 2010, 01:14:36 PM »

It's to supply more fuel for the cold mornings, and therefore a cold motor, and for a faster warm up of the motor. 




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choke???
« Reply #2 on: September 18, 2010, 05:02:18 PM »

Due to poor flow characteristics of stock ports, ported heads and intakes don't require chokes, EFI engines don't require them because the fuel is injected right at the valve back itself, so it is difficult to have fuel stick to everything prior to the combustion chamber itself.
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Steve

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choke???
« Reply #3 on: September 18, 2010, 06:32:13 PM »

Quote from: dana44
Due to poor flow characteristics of stock ports, ported heads and intakes don't require chokes, EFI engines don't require them because the fuel is injected right at the valve back itself, so it is difficult to have fuel stick to everything prior to the combustion chamber itself.


 
Yup!
 
 
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Rich

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choke???
« Reply #4 on: September 19, 2010, 07:46:11 AM »

 I have a manual choke and almost NEVER have to use it,  unless it's really cold outside (30F) and then only for about 20-30 seconds. My heads flow well, plus it's warm here all the time.
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choke???
« Reply #5 on: September 19, 2010, 04:40:29 PM »

After I port heads and intake, the choke is removed permanently, tends to flood very quickly with ported heads, warmed up and not jerky within a minute and a block down the road. Pretty wonderful considering I had a 352 Ford truck that had to have the choke on no matter what the outside temp was for the first ten minutes at least.
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Steve

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choke???
« Reply #6 on: September 19, 2010, 07:23:35 PM »

Polaraco tends to load up with the ported heads and the EFI for the first few minutes in closed loop.  Once it goes into the next step it's fine
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Rich

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choke???
« Reply #7 on: September 19, 2010, 09:39:29 PM »

 It might do that if the intake ports are too smooth - they like a bit of roughness to keep the fuel mixed with the air.  I only polish the exhaust ports and leave the intakes with the roughness left by the carbide burr-seems to work well. 
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Rich

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choke???
« Reply #8 on: September 19, 2010, 09:44:14 PM »


Quote from: dana44
After I port heads and intake, the choke is removed permanently, tends to flood very quickly with ported heads, warmed up and not jerky within a minute and a block down the road. Pretty wonderful considering I had a 352 Ford truck that had to have the choke on no matter what the outside temp was for the first ten minutes at least.

 I never thought to correlate the two together (porting/ no need for a choke), but you're right -my will flood in a heartbeat too if I use the choke when it's not really cold - and all this time I thought my idle mixture was just too rich.
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choke???
« Reply #9 on: September 20, 2010, 06:34:49 AM »

Took me about a week to figure it out, 30 years ago.
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Steve

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choke???
« Reply #10 on: September 20, 2010, 06:35:43 AM »

Quote from: krautmaster
 It might do that if the intake ports are too smooth - they like a bit of roughness to keep the fuel mixed with the air.  I only polish the exhaust ports and leave the intakes with the roughness left by the carbide burr-seems to work well. 


 
That's what I did as well.  You got it right
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choke???
« Reply #11 on: September 20, 2010, 09:22:17 AM »

The carbide burr surface may reduce the top end flow by 2-4cfm (based on all tests done on a flow bench comparison), but it helps keep the fuel suspended so much better than stock or polished for the street. I don't know of anyone that could tell the difference on the street, except the fact bottom end is a little bit better and chances are good you would never take a set of ported heads to their limit on the street to begin with. It is more about efficiency than racing it isn't even funny. On top of that, take a set of polished and a set of burr cut ported heads off an engine after street driving for years and you will notice a definite difference in the cleanliness of the ports, look like they have a break-in run on them compared to polished intakes that have definite smooth dirty spots in the port curves, it really is amazing.
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