34 ICT hesitation

[67westy]

Just got my 1641 fitted with dual ICT's and the increase in power is noticeable :mrgreen: I have a slight hesitation at lower revs when moving through the gears, this seems a little worse when the engine is up to temperature. I adjusted the idle mixture again last night which seemed to improve it but it's still not quite right. Any suggestions as to what it might be, idle mixture? Jetting? I intend to get it on a rolling road once the engine is broken in but that wont be for a few months.

Jetting:
140 Main
F6 Emulsion
165 Air Correction
55 Idles

I have the balance pipe fitted and running a stock fuel pump with regulator. Need to check the pressure and make sure the regulator is working as expected. Got an SVDA dizzy, tested the vac can and it's working and timed correctly. Also fitted the anti pulse valve to the vac line.

Any suggestions welcome, the engine is fine as revs pick up and power is good. Perfectly driveable but just want it a bit smoother

 

[StuF]

Cant help you with the hesitation mate but if you do get stuck and cant resolve it take your bus to Expert Test and Tune in Lincoln.
I am taking Murphy there on Friday for a tune up and SVDA Dizzy install - has a good rep for looking after aircooled motors and knows his onions with carbs.

http://lincolnautodiagnostics.co.uk/" onclick="window.open(this.href);return false;

 

[67westy]

Cant help you with the hesitation mate but if you do get stuck and cant resolve it take your bus to Expert Test and Tune in Lincoln.
I am taking Murphy there on Friday for a tune up and SVDA Dizzy install - has a good rep for looking after aircooled motors and knows his onions with carbs.

http://lincolnautodiagnostics.co.uk/" onclick="window.open(this.href);return false;

Cheers mate, I had looked at them before but wasn't sure what aircooled experience they had so that's good to know. I also found a weber specialist at barton that I was considering. Let me know how you get on

 

[six]

Take off and plug the vac pipes from carb and block them. Take it for a run. Is the hesitation still there? Could be lack of vac signal from carbs. Check they are not blocked. I have vac from both carbs needed to pull enough signal I'm order for svda to work right.

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[gvee]

Are you sure you have the carbs balanced (both in terms of air flow and in terms of the linkage opening them evenly)?

 

[67westy]

Take off and plug the vac pipes from carb and block them. Take it for a run. Is the hesitation still there? Could be lack of vac signal from carbs. Check they are not blocked. I have vac from both carbs needed to pull enough signal I'm order for svda to work right.

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Thanks I'll give it a try. I know it's definitely working at higher revs as I've checked both connected and disconnected with a strobe, connected gives more advance.

Are you sure you have the carbs balanced (both in terms of air flow and in terms of the linkage opening them evenly)?

Pretty sure, used the Synchrometer and both are sat at 10.5 but I'll double check. Difficult to read it accurately I have to take a picture of the top as I didn't buy an elbow adaptor :lol: The linkage looks good as well but will check again, tempted to just start fresh to make sure I've got it all ok.

 

[six]

Vac from one carb can be a bit crap at low rpm where you need the vac advance. A vac gauge would help there if you have one

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[67westy]

Vac from one carb can be a bit crap at low rpm where you need the vac advance. A vac gauge would help there if you have one

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I bought one the other day actually so that gives me an excuse to use it what sort of value should I expect? I've just ordered some T-pieces just in case.

Been looking around at the airflow readings. A lot of places say they just need to be balanced but I've seen some mentions of 5-7 kg/h. Mine is around 10.5, does that seem to high? Maybe I've got the setup slightly wrong.......

 

[009]

What's your exhaust like?
I went from a standard 1600 single SOLEX to twin 34ICTs and both gave me a big flat spot around 2k rpm IIRC with the standard exhaust fitted.
However when I fitted the new Vintage Speed exhaust the flat spot disappeared and now the rev range is smooth right through (apart from being a bit lumpy from cold due lack of pre-heat)
Worth a thought?
DON

 

[67westy]

What's your exhaust like?
I went from a standard 1600 single SOLEX to twin 34ICTs and both gave me a big flat spot around 2k rpm IIRC with the standard exhaust fitted.
However when I fitted the new Vintage Speed exhaust the flat spot disappeared and now the rev range is smooth right through (apart from being a bit lumpy from cold due lack of pre-heat)
Worth a thought?
DON

Still running a stock exhaust at the moment, coffers are empty after buying the engine and carbs :lol: Exhaust is in the pipeline but it wont be until later this year or early next. The hesitation is lower down the revs for me and isn't huge, just enought to be annoying, Hopefully I'll see another improvement with the exhaust

 

[67westy]

Vac from one carb can be a bit crap at low rpm where you need the vac advance. A vac gauge would help there if you have one

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We have a winner!

Vac signal from single carb (click to see the video):



Vac signal from both carbs (click to see the video):




Drives much better now, cheers for all the input! I think I can still tweak the setup now but it's certainly better.

 

[six]

My Brazilian bosch svda begins to move with 5 inch hg. It's fully open at 12 inch hg at best my ich pulls 11in hg.

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[gvee]

Good work Adam!

Might have to do the same on mine (I haven't noticed a hesitation since resetting, but my setup is very similar to yours so I might get an improvement too!)

Silly question time: did both of your carbs have vac ports already? Did you just throw a T-piece between them and the dizzy? Got any pictures of the install?

 

[67westy]

Good work Adam!

Might have to do the same on mine (I haven't noticed a hesitation since resetting, but my setup is very similar to yours so I might get an improvement too!)

Silly question time: did both of your carbs have vac ports already? Did you just throw a T-piece between them and the dizzy? Got any pictures of the install?

Yup both had the vac ports, I had blocked the RHS one. Basically run both carbs to the T-piece. Between T-piece and dizzy I have an anti pulse valve. I'll get you some pics tonight, at the moment it's a temporary install made up of bits I could find in the garage, robbed most the parts from my vacuum tester :lol:

I think I'm going to re-run single and dual tests with the anti pulse valve removed to see what (if any) difference it makes.

Are you at stanford hall? My T pieces might have arrived by then if you want one, will only be there in the morning though. Can bring the gauge as well to check before you replumb stuff

 

[six]

Drop the apv and use a reducer close to the vac can. Does the same as a apv for nearly zero money I.e. dampens the fluctuations and smooths things out. I notice that the vac is smoother with it over a apv

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[67westy]

Drop the apv and use a reducer close to the vac can. Does the same as a apv for nearly zero money I.e. dampens the fluctuations and smooths things out. I notice that the vac is smoother with it over a apv

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Cheers for the tip

Good work Adam!

Might have to do the same on mine (I haven't noticed a hesitation since resetting, but my setup is very similar to yours so I might get an improvement too!)

Silly question time: did both of your carbs have vac ports already? Did you just throw a T-piece between them and the dizzy? Got any pictures of the install?

Here's a pic for what it's worth, I'll be redoing it a bit neater when the parts arrive:

 

[K@rlos]

Vac from one carb can be a bit crap at low rpm where you need the vac advance. A vac gauge would help there if you have one

Sent from my SM-N910F using Tapatalk

I bought one the other day actually so that gives me an excuse to use it what sort of value should I expect? I've just ordered some T-pieces just in case.

Been looking around at the airflow readings. A lot of places say they just need to be balanced but I've seen some mentions of 5-7 kg/h. Mine is around 10.5, does that seem to high? Maybe I've got the setup slightly wrong.......

The flow reading seems a bit high to me tbh :? Any twin carbs I do I set for 6, I'd suggest upping the idle jets and bring the kg/h down. The richer idle circuit should get rid of the hesitation.

 

[Padwah]

I've just rejetted and setup the 34 ICTs on my van this weekend, I went for the following jets based on the recommendation of Laurie Pettit/Mucky Green and its now running much better than when fitted with the jets they were supplied with:

150 Main
F6 Emulsion
170 Air Correction
55 Idles

I've got the speed screw 1 1/2 turns in and the idle mixture screw 1 1/2 turns out and the van idles at 900rpm which gives a reading of 5kg/h on the air flow meter on both carbs. I'm not an expert and just followed the setup guide here: http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm" onclick="window.open(this.href);return false; and Punnets setup guide on the Just Kampers forum here: http://www.justkampers.com/forum/viewtopic.php?f=15&t=169891" onclick="window.open(this.href);return false; but at least you have a comparison.

On a side note, is your fuel regulator mounted correctly? The instructions say they should be mounted horizontally which I took to mean that the regulator should be flat so I've mounted mine on an L shaped bracket on the fan housing and mounted it there, similar to Pottinger on this this thread: http://forum.earlybay.com/viewtopic.php?f=4&t=41882" onclick="window.open(this.href);return false;

 

[67westy]

Thanks for the input guys! I had occssional popping when coming off the throttle on the way to Stanford hall yesterday so I'm going to try setting it up again and get that air flow down a bit. I will be getting it on a rolling road once I get 500 miles on the engine so that should sort the jetting out.

Good point on the fuel regulator, will get that changed! I still need to check the pressure as well

 

[Padwah]

Popping in the exhaust coming off throttle is usually an air leak in the exhaust, check your gaskets and that your exhaust is done up nice and tight.