Best baseline jet setup for Ford Kent 1700

[John Lehnen]

Any recommendations for chokes, mains and corrections for a 1990 Ford Kent crossflow 1700?

[John Lehnen]

The Caterham Seven Super Sprint  is equipped with dual Weber DCOE 40's

 

[MV8]

What parts do you have now? I would expect to see something close to the following for a standard or mild tune: 4.5 aux venturi, 33-34 venturi, F11 or F16 emulsion tube, 115-135 main jet, 160-190 air corrector, 40-43F9 slow jet, 35 pump jet, with a 7.5-8.5mm float level.

[John Lehnen]

Aux 4.5, 32 Venturi, Emulsion F16, Main Jet 130, Air Correction 180, Slow Jet 50F8 Pump Jet 35 and floats 8

[MV8]

Sounds like a good start. If after tuning, if fully closed butterflies still results in a too high idle rpm with 12deg advance, you might consider F9 smaller air bleed idle jets. You can check if the idle jetting is correct after tuning by raising the engine 300 rpm with the idle speed adjustment screw, then turning the mix screw in or out slowly to to see if it increases rpm (remember where you started). IN for more rpm=rich/idle jet too big, OUT= too lean. No rpm increase from turning the mix screw either way at 300rpm above idle means the idle jetting is correct.

Edited September 2, 2023 by MV8

[John Lehnen]

Thanks very much.

[IamScotticus]

When I can ill get you my DCOE's. But I imagine you may be a little different for 1700.

 

There are a lot of variables that affect the proper tune.

Altitude, ignition, air cleaners,   driving style, etc.

 

 

 

[John Lehnen]

Thanks.  Elevation: 320 ft above sea level; Ignition: Lucas electronic; Air Cleaners: K&N 56-1350; Driving style: aggressive road and rallying.  I have found an interesting calculator on-line that gives recommendations for all the variables.

[John Lehnen]

Calculator is here... https://www.carbparts.eu/calc

 

[IamScotticus]

That's a good calculator. 

Remember that Weber part numbers aren't always sequential.  For example,  if an air corrector is 165 and decreasing the size for enriching is desired, the corrector number may not be 164.  Or  it may.  Weber was known for numbering parts in the haphazard order they were created.

Just something to watch.

 

Consider using an AFR you can watch throughout the driving range.  Useful to indicate any air leaks.

https://www.innovatemotorsports.com/mtx-al-wideband-air-fuel-ratio-gauge.html

There are cheaper AFRs, but this one is much cooler and fits the standard 53mm hole.

 

Edited September 3, 2023 by IamScotticus

[MV8]

I'd lean toward the "flexibility" parts button versus the "power" button.  It reduces the choke size recommendation for better drive ability off-idle, better, economy, and emission. FWIW, my suggestions were not from a calculator.

[John Lehnen]

Good advice - Thanks.

[John Lehnen]

13 hours ago, IamScotticus said:

That's a good calculator. 

Remember that Weber part numbers aren't always sequential.  For example,  if an air corrector is 165 and decreasing the size for enriching is desired, the corrector number may not be 164.  Or  it may.  Weber was known for numbering parts in the haphazard order they were created.

Just something to watch.

 

Consider using an AFR you can watch throughout the driving range.  Useful to indicate any air leaks.

https://www.innovatemotorsports.com/mtx-al-wideband-air-fuel-ratio-gauge.html

There are cheaper AFRs, but this one is much cooler and fits the standard 53mm hole.

 

Thanks

[IamScotticus]

See this from Tony Weale's excellent 7 Bible

 

[John Lehnen]

It's great when things work out...  The 1700 S/Sprint is exactly what I had decided for Test 1.  I ordered the 45F9's earlier today from Pegasus!

Thanks for the chart...

J

[IamScotticus]

I have to renig on my 151 numbers, I never got into my 151s.  I got into my (was a) 32DFM.  I can get my 151s numbers in a while, but I suspect they will be the same as Tony's chart.

Edited September 4, 2023 by IamScotticus