Jetting for 34 ICTs
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living_dead
- Posts: 109
- Joined: Mon Jan 26, 2004 12:25 pm
Jetting for 34 ICTs
I was wondering what is the best way to jet my 34 ICTs? They will be going on a 1600DP. Running most of a the time a 5,280ft sometimes a bit more. I'm clueless about jetting the carbs. Please tell me what you guys think.
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Stufenheck
- Posts: 227
- Joined: Thu Sep 20, 2001 12:01 am
LD
Couple of questions.
What emulsion tubes do you have installed?
What octane fuel are you using?
Suggest you visit the following site to learn about 34 ICT emulsion tubes and float level settings.
http://jimsvw.xenetech.com/Tech_How_To_ ... tubes.html
Jetting suggestion for 1600
between 5000 and 6500 ft.
55 idle jets
125 main fuel jets
160 main air jets
between 6600 and 9800 ft
52 idle jets
120 main fuel jets
160 main air jets
Jesse
Couple of questions.
What emulsion tubes do you have installed?
What octane fuel are you using?
Suggest you visit the following site to learn about 34 ICT emulsion tubes and float level settings.
http://jimsvw.xenetech.com/Tech_How_To_ ... tubes.html
Jetting suggestion for 1600
between 5000 and 6500 ft.
55 idle jets
125 main fuel jets
160 main air jets
between 6600 and 9800 ft
52 idle jets
120 main fuel jets
160 main air jets
Jesse
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lemorris
- Posts: 99
- Joined: Fri Nov 22, 2002 12:01 am
I'm not sure what's "best" for everybody but getting my ICTs dialed in has been a pain.
I'm currently running 130 mains with 60 idle, and I had 2 good weeks. Now I think I'm running too lean. I'm thinking about stepping down to 55 on the idle jet.
If that fails I may move up to a 1641 or 1776 and then I can start the madness all over again.
Actually I have a friend who's runnin 135 main and 60 idle in his 1641 and life is good for him.
Keep me posted, I'm insanely curious.
I'm currently running 130 mains with 60 idle, and I had 2 good weeks. Now I think I'm running too lean. I'm thinking about stepping down to 55 on the idle jet.
If that fails I may move up to a 1641 or 1776 and then I can start the madness all over again.
Actually I have a friend who's runnin 135 main and 60 idle in his 1641 and life is good for him.
Keep me posted, I'm insanely curious.
http://www.lemorris.com It's art and stuff. 
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Stufenheck
- Posts: 227
- Joined: Thu Sep 20, 2001 12:01 am
Lemorris,
Over the last 5 years been tuning on 1835 w/120 engle cam, 1.25 ratio rockers and 34 ICT's in my 64 notchback. My car has a heated O2 sensor and A/F gauge from CB performance that I use monitor air fuel ratio while driving.
Many factors will contribute to fine tuning.
1. Fuel pressure set to 3.5 LB, mechanical pumps can produce more fuel pressure if not shim correctly.
2. Set Floats even if new.
3. Synchronizing both Carbs at 3200 RPM. You be surprise how much this helps driveability.
4. Set total timing advance to 32 if using an aftermarket cam (quality timing light a must)
5. F5 Emulsion Tubes
6. Ambient Temp in engine compartment
After having done the first 4 things, and still had flat spot at 2800 RPM, Last year I came accross the site noted on earlier post. That help me finally fine tune 34 ICT's after changing to F5 emulsion tubes.
These are the jets that I'm currently using.
140 main fuel jets
170 main air jet
65 idle jets
I get 26 MPG on the freeway and 17 in town.
Jesse
Over the last 5 years been tuning on 1835 w/120 engle cam, 1.25 ratio rockers and 34 ICT's in my 64 notchback. My car has a heated O2 sensor and A/F gauge from CB performance that I use monitor air fuel ratio while driving.
Many factors will contribute to fine tuning.
1. Fuel pressure set to 3.5 LB, mechanical pumps can produce more fuel pressure if not shim correctly.
2. Set Floats even if new.
3. Synchronizing both Carbs at 3200 RPM. You be surprise how much this helps driveability.
4. Set total timing advance to 32 if using an aftermarket cam (quality timing light a must)
5. F5 Emulsion Tubes
6. Ambient Temp in engine compartment
After having done the first 4 things, and still had flat spot at 2800 RPM, Last year I came accross the site noted on earlier post. That help me finally fine tune 34 ICT's after changing to F5 emulsion tubes.
These are the jets that I'm currently using.
140 main fuel jets
170 main air jet
65 idle jets
I get 26 MPG on the freeway and 17 in town.
Jesse
-
Stufenheck
- Posts: 227
- Joined: Thu Sep 20, 2001 12:01 am
In applications of sea level to 5000 feet here is what Weber's suggested jetting for 34 ICT.
http://www.racetep.com/weber/34_ICT.pdf
CB Performance website has jetting information that you may try. Use the link below, once there select Weber Jetting Chart, then scroll down to ICT.
http://www.cbperformance.com/carbs.asp
Here are two links for Manuals on Weber Carburetors
The CB Weber Tech Manual has a good section on the operation of ICT?s pages 110 to 114.
http://www.cbperformance.com/catalog.asp?ProductID=4
http://www.fetchbook.info/showImage.do? ... 0895863774
HP books Weber Carburetors is a great manual to help understand carburetors circuits and emulsion tubes. There are charts to help selection venturies and jets base on engine displacement and maximum RPM. Includes Altitude Compensation Table for main fuel jets for ranges at 5000-6500, 6600-9800 and 9800 - 13000 ft. Main jets that range from 2.00 to 1.25 at sea level - 5000ft are reduce in size by .05, see example below.
Elevation (ft) [Main Jet]
0-5000 [130]
5000-6500 [125]
6600-9800 [120]
9800-13000 [115]
Jesse
http://www.racetep.com/weber/34_ICT.pdf
CB Performance website has jetting information that you may try. Use the link below, once there select Weber Jetting Chart, then scroll down to ICT.
http://www.cbperformance.com/carbs.asp
Here are two links for Manuals on Weber Carburetors
The CB Weber Tech Manual has a good section on the operation of ICT?s pages 110 to 114.
http://www.cbperformance.com/catalog.asp?ProductID=4
http://www.fetchbook.info/showImage.do? ... 0895863774
HP books Weber Carburetors is a great manual to help understand carburetors circuits and emulsion tubes. There are charts to help selection venturies and jets base on engine displacement and maximum RPM. Includes Altitude Compensation Table for main fuel jets for ranges at 5000-6500, 6600-9800 and 9800 - 13000 ft. Main jets that range from 2.00 to 1.25 at sea level - 5000ft are reduce in size by .05, see example below.
Elevation (ft) [Main Jet]
0-5000 [130]
5000-6500 [125]
6600-9800 [120]
9800-13000 [115]
Jesse
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Stufenheck
- Posts: 227
- Joined: Thu Sep 20, 2001 12:01 am
Everyone just notice that the site I noted on my first reply is down. However I did capture the information last year and have just converted to jpg. If you go to the following photo album you see what I was trying to convey.
http://f2.pg.photos.yahoo.com/ph/stufen ... /my_photos
Jesse
http://f2.pg.photos.yahoo.com/ph/stufen ... /my_photos
Jesse
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Humanure
- Posts: 2
- Joined: Mon Mar 15, 2004 9:00 am
Whenever I come across a link that is dead, I copy the link, paste it here: http://www.archive.org/web/web.php and most of the times I find what I am looking for. They archive around 30 billion, I repeat, billion pages from as far back as 1996. Great tool. Thanks Stufen for all the links and info!
PS. Yes I know I dug up an old post, it was pulled up in my search query
PS. Yes I know I dug up an old post, it was pulled up in my search query
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Leiif
- Posts: 67
- Joined: Thu Oct 10, 2013 12:00 pm
Re:
I know this is an old thread but I am working on tuning my dual ICTs on a fresh rebuilt 1800 in my Bus. I put a Scat C25 cam in and static balanced things, other than that it is pretty much stock. I did switch to F5 emulsion tubes but it still stumbles off idle. Currently running 140 mains, 60 idles and 160 air corrections. The engine runs far better with this than the F78, 130, 52, 160 set-up it had. Any insight appreciated.Stufenheck wrote:Lemorris,
Over the last 5 years been tuning on 1835 w/120 engle cam, 1.25 ratio rockers and 34 ICT's in my 64 notchback. My car has a heated O2 sensor and A/F gauge from CB performance that I use monitor air fuel ratio while driving.
Many factors will contribute to fine tuning.
1. Fuel pressure set to 3.5 LB, mechanical pumps can produce more fuel pressure if not shim correctly.
2. Set Floats even if new.
3. Synchronizing both Carbs at 3200 RPM. You be surprise how much this helps driveability.
4. Set total timing advance to 32 if using an aftermarket cam (quality timing light a must)
5. F5 Emulsion Tubes
6. Ambient Temp in engine compartment
After having done the first 4 things, and still had flat spot at 2800 RPM, Last year I came accross the site noted on earlier post. That help me finally fine tune 34 ICT's after changing to F5 emulsion tubes.
These are the jets that I'm currently using.
140 main fuel jets
170 main air jet
65 idle jets
I get 26 MPG on the freeway and 17 in town.
Jesse
-
Leiif
- Posts: 67
- Joined: Thu Oct 10, 2013 12:00 pm
Re: Jetting for 34 ICTs
Ordered rebuild kits and got recommended jets from Pierce Manifolds. Still not right as I am in 3 1/2 on the speed screw. The mixture is at 2 1/2 plus a little. Not sure if the mixture even matters with the speed screw so far in.
Right now running 60 idles, 140 mains and 160 air with F5 emulsion tubes. The pump exhaust are stamped 40. Still has a slight hesitation on acceleration and the speed screws are too far in.
Seems most people say out on the speed screws but what I am reading it is the number of turns "in" from first contact that we should be counting. The mixture screw is measured "out" from contact.
With my present set-up any one know what should be changed next or how to proceed?
UPDATE - Carbs won't idle with the speed screws at 1 1/2 . I double checked and reset all the linkage, adjusted dwell, adjusted timing and reset the screws to baseline settings of - mix 2 out, speed 1 1/2 in. The engine won't idle with those settings. It runs well enough everywhere but idle. I did have a vacuum leak all the way up at the brake booster. All the hoses to that line have now been changed.
Besides the above numbers I also have the 50 pump jet. Runs smooth and strong, just can't take foot off the pedal all the way. Gets all the way down to about 300 RPM before it dies. I can get it to idle but my speed screws have to be in 3 to 3 1/2 or so. I tried the mix screw at 4 out, 3 out, 2 1/2 out and 2. Not much difference for any of those with the speed screws at 1 1/2.
I see others running bigger mains. Do the main jets affect the idle circuit?
Right now running 60 idles, 140 mains and 160 air with F5 emulsion tubes. The pump exhaust are stamped 40. Still has a slight hesitation on acceleration and the speed screws are too far in.
Seems most people say out on the speed screws but what I am reading it is the number of turns "in" from first contact that we should be counting. The mixture screw is measured "out" from contact.
With my present set-up any one know what should be changed next or how to proceed?
UPDATE - Carbs won't idle with the speed screws at 1 1/2 . I double checked and reset all the linkage, adjusted dwell, adjusted timing and reset the screws to baseline settings of - mix 2 out, speed 1 1/2 in. The engine won't idle with those settings. It runs well enough everywhere but idle. I did have a vacuum leak all the way up at the brake booster. All the hoses to that line have now been changed.
Besides the above numbers I also have the 50 pump jet. Runs smooth and strong, just can't take foot off the pedal all the way. Gets all the way down to about 300 RPM before it dies. I can get it to idle but my speed screws have to be in 3 to 3 1/2 or so. I tried the mix screw at 4 out, 3 out, 2 1/2 out and 2. Not much difference for any of those with the speed screws at 1 1/2.
I see others running bigger mains. Do the main jets affect the idle circuit?