1987 318 Tuning with Summit Carb

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RustyRatRod said:
The hell they won't. I had a defective Quick Fuel carburetor that had an internal vacuum leak and I couldn't get it to idle come hell or high water. Sent it right on back. The next one worked fine.
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I'm not quite ready to send it back...this could (probably) is me. Haha! I'm not that familiar with Holley style carbs, though this carb is a lot different from the 4150/4160.
 
sarguy01 said:
I'm not quite ready to send it back...this could (probably) is me. Haha! I'm not that familiar with Holley style carbs, though this carb is a lot different from the 4150/4160.
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Holley used to make them. They were the 4100 series. 4110 and 4111 I believe. As I said, they were spun off the old Autolite 4100 carburetors. Summit picked them up and Holley discontinued them. I THINK Holley makes them exclusively for Summit now. Here's the Original Autolite 4100. You can see strong similarities.
AUTOLITE 4100.jpg

They were and still are pretty darn good carburetors. As you can imagine, they are not prone to leak very easily, as the main gasket is above fuel level. The Holley 4100 series was very similar, just like the Summit series you have. It's a good design. Makes for a nice street carburetor.
 
RustyRatRod said:
Holley used to make them. They were the 4100 series. 4110 and 4111 I believe. As I said, they were spun off the old Autolite 4100 carburetors. Summit picked them up and Holley discontinued them. I THINK Holley makes them exclusively for Summit now. Here's the Original Autolite 4100. You can see strong similarities.
View attachment 1716275100
They were and still are pretty darn good carburetors. As you can imagine, they are not prone to leak very easily, as the main gasket is above fuel level. The Holley 4100 series was very similar, just like the Summit series you have. It's a good design. Makes for a nice street carburetor.
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Yep
 
Can you please pull the spark plugs and show us what they look like?
 
Hysteric said:
Can you please pull the spark plugs and show us what they look like?
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It's hard to imagine the thing even runs at idle with an .046 idle feed jet. Unless it's got a .090 idle air bleed. And them I'm still not sure that would even get you a reasonable idle.
 
Newbomb Turk said:
It's hard to imagine the thing even runs at idle with an .046 idle feed jet. Unless it's got a .090 idle air bleed. And them I'm still not sure that would even get you a reasonable idle.
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It's hard to imagine it would come from summit with an IFR of that size unless some ones messed with it.
 
Newbomb Turk said:
It's hard to imagine the thing even runs at idle with an .046 idle feed jet. Unless it's got a .090 idle air bleed. And them I'm still not sure that would even get you a reasonable idle.
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They do have huge boosters. Would that have an effect on the size of the idle feed jet?
 
Newbomb Turk said:
It's hard to imagine the thing even runs at idle with an .046 idle feed jet. Unless it's got a .090 idle air bleed. And them I'm still not sure that would even get you a reasonable idle.
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I don't even see a place to change the idle feed jet. I'm changing around the air bleed.
 
Hysteric said:
It's hard to imagine it would come from summit with an IFR of that size unless some ones messed with it.
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I don't think I can change the IFR. I've read about putting wire in the IFR if they aren't a screw in type. I don't even know where the fuel enters the idle circuit.
 
sarguy01 said:
I don't think I can change the IFR. I've read about putting wire in the IFR if they aren't a screw in type. I don't even know where the fuel enters the idle circuit.
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I haven’t seen a carb like that in 10 years or so and I forgot exactly where the IFR is.

If you can get to it to drill and tap it you can change it.

Did you ever get a measurement on the idle air bleed?
 
Newbomb Turk said:
I haven’t seen a carb like that in 10 years or so and I forgot exactly where the IFR is.

If you can get to it to drill and tap it you can change it.

Did you ever get a measurement on the idle air bleed?
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I don't have a way to accurately measure. Wife and I decided to try a new bar tonight, so I didn't swap the carb back on. Tomorrow I'm headed to Carlisle. So I'm on hold.
 
sarguy01 said:
I don't have a way to accurately measure.
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Yes you do. You can buy a numbered drill bit set and if you have accurate Vernier calipers you can can verify the drill sizes and use the to check bleed and restrictor sizes.
 
Hysteric said:
Yes you do. You can buy a numbered drill bit set and if you have accurate Vernier calipers you can can verify the drill sizes and use the to check bleed and restrictor sizes.
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I can't find where the idle circuit gets fuel from and at the moment, I don't have a numbered drill set. Here's a pic of the fuel bowl. Can you see where the idle circuit is fed from?

SmartSelect_20240712_191917_Gallery.jpg
 
If you look at the the centre electrode or the spark plug gap does the centre electrode look clean like the bottom photo I posted or does it look black like the rest of the plug?
 
sarguy01 said:
Black. All 8 look the same.
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Check your ignition and the voltage the alternator is putting out. When the ignition doesn't get enough voltage to fire the plug correctly it can present as an overly rich condition when in facts its just not enough ignition energy to fire the plug correctly.

I once changed the the pulley size on my alternator to stop throwing the fan belt at the top of the track and when I fired it up the tune was different and the data logger was now telling me it was rich so I pulled the plugs and yep they looked rich but I hadn't changed a jet which means the AFR didn't change but the combustion did. I checked the voltage the alternator was putting out and it had now dropped to 13.5v instead of its regular 14v + at idle.

What gap size does your ignition system require?
 
I agree with others: the idle jets seem to be huge. Can see no reason for them being that large for a carb designed to go on a relatively stock engine. Is 0.046" a misprint & they are actually 0.036" [ more like it ]?

You see the booster pic in post #25? The 1/4" diam brass tube? The small tube inside the tube [ visible in the pic ] is the idle jet [ fuel ] . You need to get some numbered drills, use as a go-no-go gauge & see if they are 046. If so, you should reduce the area to about 0.032". You do some calculations to find a piece of wire that will reduce the area. Since at this stage you are trying to clean up the idle, you should be able, for a short test, to scrunch up a length that will sit inside the 1/4" tube & poke one end of the wire into the jet. If the problem is solved, then a more permanent fix is pretty easy.
 
Bewy said:
I agree with others: the idle jets seem to be huge. Can see no reason for them being that large for a carb designed to go on a relatively stock engine. Is 0.046" a misprint & they are actually 0.036" [ more like it ]?

You see the booster pic in post #25? The 1/4" diam brass tube? The small tube inside the tube [ visible in the pic ] is the idle jet [ fuel ] . You need to get some numbered drills, use as a go-no-go gauge & see if they are 046. If so, you should reduce the area to about 0.032". You do some calculations to find a piece of wire that will reduce the area. Since at this stage you are trying to clean up the idle, you should be able, for a short test, to scrunch up a length that will sit inside the 1/4" tube & poke one end of the wire into the jet. If the problem is solved, then a more permanent fix is pretty easy.
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If you're correct and that's them, they sure look big, don't they?
 
Bewy said:
I agree with others: the idle jets seem to be huge. Can see no reason for them being that large for a carb designed to go on a relatively stock engine. Is 0.046" a misprint & they are actually 0.036" [ more like it ]?

You see the booster pic in post #25? The 1/4" diam brass tube? The small tube inside the tube [ visible in the pic ] is the idle jet [ fuel ] . You need to get some numbered drills, use as a go-no-go gauge & see if they are 046. If so, you should reduce the area to about 0.032". You do some calculations to find a piece of wire that will reduce the area. Since at this stage you are trying to clean up the idle, you should be able, for a short test, to scrunch up a length that will sit inside the 1/4" tube & poke one end of the wire into the jet. If the problem is solved, then a more permanent fix is pretty easy.
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The .046 is the two circled brass jets in post 25. I can change those out. Those allow air in and mix with the fuel from the idle circuit. I had intially put in smaller diameter ones in thinking it would make it leaner, but I had it backwards. Bigger air bleeds should lean out the mix.

I'll get some numbered bits and check the inner brass tubes. No clue what their diameter is. From what I'm researching, it's better to not mess with the air bleeds and only change the fuel being delivered to the idle system. So like you said, I'll measure the tubes and maybe throw in some wire to restrict fuel delivery to the idle system. And go back to .043 air bleeds.
 
Hysteric said:
Check your ignition and the voltage the alternator is putting out. When the ignition doesn't get enough voltage to fire the plug correctly it can present as an overly rich condition when in facts its just not enough ignition energy to fire the plug correctly.

I once changed the the pulley size on my alternator to stop throwing the fan belt at the top of the track and when I fired it up the tune was different and the data logger was now telling me it was rich so I pulled the plugs and yep they looked rich but I hadn't changed a jet which means the AFR didn't change but the combustion did. I checked the voltage the alternator was putting out and it had now dropped to 13.5v instead of its regular 14v + at idle.

What gap size does your ignition system require?
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I've got the Proform Orange box, so .035 is the gap I'm using.

Agree, as I'm sitting here chatting with my Dad on the way to Carlisle, I'm wondering if weak spark is part of my issue. I'll check the charging system voltage and my grounds on the Orange box. That's if I don't end up finding a deal on an MSD or similar today. I've heard mixed reviews on the reliability of new Orange boxes.
 
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