Hi Guy
I would be great full if you could help me with this problem. Since re-building my engine for this season I have run into some jetting problems due to the fact that I have changed the exhaust from the end of the exhaust manifold back, and increased the size of the air filter. As this is the only change I have made I cannot think of anything else that would have made the difference.
Engine Spec:
1400 Tipo
Bore 81.1
New Standard Pistons and rings
New big end and main bearings
CR: 10:1
Standard Head
C&B 10.3 Cam
2 X 2 into 1 OD 37.5mm Exhaust Manifolds
Crank balanced
Rods lightened and balanced
Flywheel lightened and balanced with clutch pressure plate
Exhaust ID 52mm from end of exhaust manifold into George Polley AX810 race silencer
Air Filter ITG
Plugs NGK B9EGV
Ing timing 10deg BTDC
Valve Timing 112deg ATDC
Weber 40 DCNF
Venturi 28mm....ALLOWED 32mm THINK THIS IS THE BIG PART OF MY PROBLEM
Auxiliary Venturi 4.5mm
Main Jet 200mm
Air Corrector Jet 165mm
Emulsion Tube F22
Idle Jet .60mm
Pump Jet .65mm
Needle Valve 1.75mm
Starter Jet 75-F5
I have not been able to book it onto the rolling road yet should i do this before i go any further?
Gary
Jetting on Tipo 1400 Race engine
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Westfield
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Jetting on Tipo 1400 Race engine
Thank you
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Guy Croft
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Gary, try this:
Weber 40 DCNF
Venturi 28mm....ALLOWED 32mm - 28 WAY TOO SMALL go to 32mm - you can get them machined out.
Auxiliary Venturi 4.5mm OK
Main Jet 200mm - WAY TOO BIG go to 135
Air Corrector Jet 165mm - WAY TOO SMALL go to 180
Emulsion Tube F22 - probably OK
Idle Jet .60mm - TOO BIG go to 45
Pump Jet .65mm - TOO BIG go to 45
Needle Valve 1.75mm OK
Starter Jet 75-F5 - you shouldn't need to use this
beyond that YES rolling road, but be very cautious about deviating from my settings withour referring to me, because all sorts of engine things can interfere with jetting and what might look like a jetting problem (leading dyno guy to swap everything around) may be nothing to do with carb.
GC
Weber 40 DCNF
Venturi 28mm....ALLOWED 32mm - 28 WAY TOO SMALL go to 32mm - you can get them machined out.
Auxiliary Venturi 4.5mm OK
Main Jet 200mm - WAY TOO BIG go to 135
Air Corrector Jet 165mm - WAY TOO SMALL go to 180
Emulsion Tube F22 - probably OK
Idle Jet .60mm - TOO BIG go to 45
Pump Jet .65mm - TOO BIG go to 45
Needle Valve 1.75mm OK
Starter Jet 75-F5 - you shouldn't need to use this
beyond that YES rolling road, but be very cautious about deviating from my settings withour referring to me, because all sorts of engine things can interfere with jetting and what might look like a jetting problem (leading dyno guy to swap everything around) may be nothing to do with carb.
GC
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Westfield
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Guy Croft wrote:Gary, try this:
Weber 40 DCNF
Venturi 28mm....ALLOWED 32mm - 28 WAY TOO SMALL go to 32mm - you can get them machined out.
Auxiliary Venturi 4.5mm OK
Main Jet 200mm - WAY TOO BIG go to 135
Air Corrector Jet 165mm - WAY TOO SMALL go to 180
Emulsion Tube F22 - probably OK
Idle Jet .60mm - TOO BIG go to 45
Pump Jet .65mm - TOO BIG go to 45
Needle Valve 1.75mm OK
Starter Jet 75-F5 - you shouldn't need to use this
beyond that YES rolling road, but be very cautious about deviating from my settings withour referring to me, because all sorts of engine things can interfere with jetting and what might look like a jetting problem (leading dyno guy to swap everything around) may be nothing to do with carb.
GC
Guy
Thank you for your reply, Iam running a single 40 DCNF not twin, its just the main jet seems very lean and wanted to cheek with you first.
Gary
Thank you
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Guy Croft
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Westfield
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Guy
Well got on the RR today and attached results.
This is the set up I went with:
Venturi 32
Idle 45
Main 170
Air Corrector 175
Emulsion F22
Pump 65
Still running very lean at the top end power drops off at 6300rpm
Could you please give me your expert opinion.
Gary
Well got on the RR today and attached results.
This is the set up I went with:
Venturi 32
Idle 45
Main 170
Air Corrector 175
Emulsion F22
Pump 65
Still running very lean at the top end power drops off at 6300rpm
Could you please give me your expert opinion.
Gary
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Thank you
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Guy Croft
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Gary, hi
You are an accredited member here and a respected client of mine too but I did offer jettings which are based on exp and I did say 'be cautious about deviating from my settings without checking with me'..!
Members, there are 2 types of rolling road/dyno operator.
Type 1
.. will only work with what he sees in front of him to and go to any lengths to demonstrate a power gain. He will not undertake any analysis if the jetting or calibration looks, er 'unusual'. This is because he has no cutting-edge experience of fault-finding and he's always in a hurry. Will have been doing the job since he was 3 and will always blame the engine builder or tell you 'you won't get more than that'.
Type 2
.. has genuine experience and will stop immediately when some contemporary solution doesn't work, and say 'that's not right' - there must be something else at work here, and then try to find out what it is. He will know that if he doesn't find the cause the engine might suffer damage and he will tell you this.
I could suggest why it has been given such unusual jetting but I am not going to at this time. You need to read that thread of James Bowen
http://guy-croft.com/viewtopic.php?t=64 ... ames+bowen
from top to bottom and I strongly urge you to park that car until you have identified why it seems to need bigger main jets than I have ever used on any engine! Because if you don't - you're going to end up with a scrap motor.
GC
You are an accredited member here and a respected client of mine too but I did offer jettings which are based on exp and I did say 'be cautious about deviating from my settings without checking with me'..!
Members, there are 2 types of rolling road/dyno operator.
Type 1
.. will only work with what he sees in front of him to and go to any lengths to demonstrate a power gain. He will not undertake any analysis if the jetting or calibration looks, er 'unusual'. This is because he has no cutting-edge experience of fault-finding and he's always in a hurry. Will have been doing the job since he was 3 and will always blame the engine builder or tell you 'you won't get more than that'.
Type 2
.. has genuine experience and will stop immediately when some contemporary solution doesn't work, and say 'that's not right' - there must be something else at work here, and then try to find out what it is. He will know that if he doesn't find the cause the engine might suffer damage and he will tell you this.
I could suggest why it has been given such unusual jetting but I am not going to at this time. You need to read that thread of James Bowen
http://guy-croft.com/viewtopic.php?t=64 ... ames+bowen
from top to bottom and I strongly urge you to park that car until you have identified why it seems to need bigger main jets than I have ever used on any engine! Because if you don't - you're going to end up with a scrap motor.
GC
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Westfield
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Westfield
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Hi Guy
Read James Brown again and again I have a few questions:
Are we comparing like for like?
Single 40 DCNF v's Twin 40 DCNF's, struggling to compare two 125 main jets v's four 125 main jets surly four 125 mains flow twice as much fuel?
1400 Tipo v's 1500 X1/9
Is the X1/9 head the same as the Tipo
You talk about headers, primaries and secondary, are the headers and the primaries the same thing? My understanding of this is that the Header is the collective name for the primaries is this true?
How do you calculate the primary lenght?
Working on the exhaust manifold at the moment making it a 4 into 1 with equal length primaries but dont know how long to make it, or what id tubing to use.
On another note Guy what books have you wrote and could any of them help me out?
Gary
Read James Brown again and again I have a few questions:
Are we comparing like for like?
Single 40 DCNF v's Twin 40 DCNF's, struggling to compare two 125 main jets v's four 125 main jets surly four 125 mains flow twice as much fuel?
1400 Tipo v's 1500 X1/9
Is the X1/9 head the same as the Tipo
You talk about headers, primaries and secondary, are the headers and the primaries the same thing? My understanding of this is that the Header is the collective name for the primaries is this true?
How do you calculate the primary lenght?
Working on the exhaust manifold at the moment making it a 4 into 1 with equal length primaries but dont know how long to make it, or what id tubing to use.
On another note Guy what books have you wrote and could any of them help me out?
Gary
Thank you
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Guy Croft
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Gary, hi
Single 40 DCNF vs twin 40 DCNF: I'm struggling to compare two 125 main jets vs 4 x 125 main jets - surely 4 x 125 mains flow twice as much fuel?
Not necessarily - although they have the capability to do so... But only one cylinder at a time is actually inducting. James' engine needs 4 jets of 125 (or so) because each jet is feeding an individual cylinder. The only difference between the two setups is that the twin carb setup has superior inlet tract flow and better pressure-wave effects between ports (no interference). To keep it simple - the size of the jets depend on the airflow and other engine characteristics. Even a 2 liter 131 with a 34ADF twin choke carb with 34mm primary and secondary barrels only has 122 primary and 130 secondary main jets, 170/180 air correctors, and because the jet flows more fuel the faster the air flows thru the choke, that engine's jetting can still cope at over 120bhp and 130lbf ft torque.
1400 Tipo v's 1500 X1/9 - Is the X1/9 head the same as the Tipo
Similar but the Tipo cc, ports and valve sizes may be different and it has small head bolts along the front under the plugs which the X19 doesn't.
You talk about headers, primaries and secondary, are the headers and the primaries the same thing? My understanding of this is that the Header is the collective name for the primaries is this true?
Header is a nice (easier to use) USA word for the whole ex manifold, encompassing primary and secondary pipes (if used).
How do you calculate the primary length? You cannot without software, no, not with any degree of certainty of getting it anywhere near right. Best ask someone like me, which you have.
Working on the exhaust manifold at the moment making it a 4 into 1 with equal length primaries but dont know how long to make it, or what id tubing to use.
My best knowledge says: make it between 33-36" long from head to collector, equalise the primary pipes for length, use py ID of port size plus 5mm. Tailpipe ID 1.75".
GC
Single 40 DCNF vs twin 40 DCNF: I'm struggling to compare two 125 main jets vs 4 x 125 main jets - surely 4 x 125 mains flow twice as much fuel?
Not necessarily - although they have the capability to do so... But only one cylinder at a time is actually inducting. James' engine needs 4 jets of 125 (or so) because each jet is feeding an individual cylinder. The only difference between the two setups is that the twin carb setup has superior inlet tract flow and better pressure-wave effects between ports (no interference). To keep it simple - the size of the jets depend on the airflow and other engine characteristics. Even a 2 liter 131 with a 34ADF twin choke carb with 34mm primary and secondary barrels only has 122 primary and 130 secondary main jets, 170/180 air correctors, and because the jet flows more fuel the faster the air flows thru the choke, that engine's jetting can still cope at over 120bhp and 130lbf ft torque.
1400 Tipo v's 1500 X1/9 - Is the X1/9 head the same as the Tipo
Similar but the Tipo cc, ports and valve sizes may be different and it has small head bolts along the front under the plugs which the X19 doesn't.
You talk about headers, primaries and secondary, are the headers and the primaries the same thing? My understanding of this is that the Header is the collective name for the primaries is this true?
Header is a nice (easier to use) USA word for the whole ex manifold, encompassing primary and secondary pipes (if used).
How do you calculate the primary length? You cannot without software, no, not with any degree of certainty of getting it anywhere near right. Best ask someone like me, which you have.
Working on the exhaust manifold at the moment making it a 4 into 1 with equal length primaries but dont know how long to make it, or what id tubing to use.
My best knowledge says: make it between 33-36" long from head to collector, equalise the primary pipes for length, use py ID of port size plus 5mm. Tailpipe ID 1.75".
GC
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Westfield
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Westfield
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Guy Croft
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Westfield
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Guy Croft
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Gary, hi
yes, thanks for asking that question. Here is where I would want to start:
Weber 40 DCNF
Primary Venturis 28mm....ALLOWED 32mm - 28 WAY TOO SMALL go to 32mm - you can get them machined out.
Auxiliary Venturi 4.5mm OK
Main Jet 200mm - WAY TOO BIG go to 135
Air Corrector Jet 165mm - WAY TOO SMALL go to 180
Emulsion Tube F22 - may be too lean try F24
Idle Jet .60mm - TOO BIG go to 45
Pump Jet .65mm - TOO BIG go to 45
Needle Valve 1.75mm OK
Starter Jet 75-F5 - you shouldn't need to use this
If the emulsion tube doesn't permit achievement of satisfactory operation with that kind of jetting I am unsure what to do next, assuming accurate cam timing etc. I assume the pump jets work OK on your carb?
GC
yes, thanks for asking that question. Here is where I would want to start:
Weber 40 DCNF
Primary Venturis 28mm....ALLOWED 32mm - 28 WAY TOO SMALL go to 32mm - you can get them machined out.
Auxiliary Venturi 4.5mm OK
Main Jet 200mm - WAY TOO BIG go to 135
Air Corrector Jet 165mm - WAY TOO SMALL go to 180
Emulsion Tube F22 - may be too lean try F24
Idle Jet .60mm - TOO BIG go to 45
Pump Jet .65mm - TOO BIG go to 45
Needle Valve 1.75mm OK
Starter Jet 75-F5 - you shouldn't need to use this
If the emulsion tube doesn't permit achievement of satisfactory operation with that kind of jetting I am unsure what to do next, assuming accurate cam timing etc. I assume the pump jets work OK on your carb?
GC
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