All Small Six Weber 38/38 progressive jetting

[clochard68]

I just ordered a Weber 38/38 for my 200 that is currently equipped with a Weber 32/36.
The 38/38 will be modified to a progressive linkage, like in the video below.

Has anyone here done it and can give some advice on jetting?

 

[bmbm40]

That is very interesting and probably a good performance upgrade.

 

[clochard68]

Yes I hope so too. But I haven't found any info online on how to jet a progressive 38 for a six cylinder.

The standard jetting of the 38/38 is lower as what I have in my Weber 32/36 right now, so I'm struggeling what jetting I should start with.
Here is a little jetting overview:

	Standard jetting 38/38	Standard jetting 32/36	Weber 32/36 as on my engine
Main jet primary	145	140	155
Main jet secondary	145	135	160
Air corrector primary	170	165	180
Air corrector secondary	170	160	160
Emulsion tube primary	F50	?	?
Emulsion tube secondary	F50	?	?
Idle jet primary	55	55	60
Idle jet secondary	55	50	50
Pump jet	70 both barrels	50 only primary	60 only primary
Auxiliary venturies	4.0	3.5	3.5

 

[Kritas]

I'm interested and following the thread. I've been focusing on metalwork and planned on doing engine upgrades later in the project.

 

[pmuller9]

The procedure that has been documented and used many times on this forum will be the same for you.
Install an air/fuel ratio meter.
Then lock out the secondary and properly jet the primary.
Then release the secondary and jet it so the air/fuel ratio remains the same for all throttle openings and loads.

In general, idle can be rich enough for good off idle response and torque.
Cruising can be between 15 and 16.
WOT around 12.5

 

[clochard68]

Thanks Paul, I hadn't thought about jetting the primary first on it's own, but it makes totally sense!

I will try to get a decent jet kit somewhere...

 

[Frank]

Thanks Paul, I hadn't thought about jetting the primary first on it's own, but it makes totally sense!

I will try to get a decent jet kit somewhere...

I would start with the jets that are in it, then work from that baseline. May not need a jet kit.
What about the accelerator pump-shot. Does it have nozzles in both barrels? If so, did you block the now secondary barrel nozzle? How?

 

[clochard68]

Thanks for the advice Frank.

I ordered a single side accelerator pump jet that is designed for the 32/36 to put into the 38. Same size (#70) as the double side that was originally in. I have a spare #60 and #50 from the 32/36 if I need to go lower.