progressive jet sizes

[Gunthner]

I have a progressive carb on a 1.8 litre engine in my bus. Runs okay, but I feel it can run better. Here are the jet sizes that I have on the carb that came with the bus:

primary idle 50, secondary idle 45; primary main 135, secondary main 140; primary correction jet 180, secondary correction jet 170.

For those with a progressive carb on a 1.8 litre engine that runs good, do you know what jets and combination of jets you have? Any suggestions on jet sizes other than getting rid of the progressive?

[Marc]

Here's how Redline jets the proggy for a 1600:
Carb Type PN 32/36 DFEV 22680.070
Main Venturi 26/27
Aux. Vent. 4.5/4.5
Main Jet 135/140
Emulsion Tube F6/F6
Air Correc. 170/180
Idle Jet 45/50
Pump Jet 65
Pump Bleed 40
Needle Valve 200
Float Level 38.5/46.5

You've got the same jets but the idles and airs have been reversed; you might want to first try switching the airs around to see what happens (theoretically it should make the primary fatter and secondary leaner esp. at the top end)...it won't be a big change, but it'd be interesting to see if you can tell the difference.
Usually the biggest challenge is in overcoming hesitation on acceleration (due to the outsized intake runners and lack of preheat) without going so rich that your mileage gets blown to heck.

[Gunthner]

Looking at the Redline jet specs, I see a couple of differences. Both the idle jets and air correction jets are reversed. Since it will only be a matter of switching them, I will see what happens when I switch them.

On another progressive spec sheet, it had the following 'original' jet settings:

idle 60/50
main 137/140
air correction 165/160

Guess we will see if runs any different after I first switch jets, and then will mess with changing jet sizes.

[metropoj]

Where is it you feel it could run better ? Idle, Accelleration, top end ? There is the inherent flat spot in progressives, search through the threads on tht one, as it's been covered a lot and the inherent problems with long intake manifolds .....

[wildthings]

I jet the progressive on my Type IV 1800 very different from the way it came, I no longer have any flat spot or over enrichment at high speeds. Don't know if it would work for you or others as I run a homemade two runner manifold that best resembles one off a stock 1600 Type 1 dual port, I also have some manifold heat, but not as much as I would like. The air velocity though my manifold is much higher than yours so I may get less fuel drop out. I usually get about 24 mpg and have excellent power.

Primary main jet 115
Primary air corrector jet 155
Idle jet biggest available from Weber
!!! Power valve is plugged !!!
Emulsion tube has most of the holes towards the bottom, I have no code# for it
Accelerator pump shooter 45 or 50
Secondaries are as they came out of the box

I have no idea how similar or different my vacuum signiture might be to yours. I would guess that if you wanted to try going this route you might end up being one (main) jet size richer to account for the manifold differences. [/b]

[metropoj]

Wildthings, I would LOVE to see what you've done here, as I can only picture the manifold and the picture is pretty fuzzy

perhaps post a pic on the Samba if you could and let us see the link please ? We appreeciate your input .... Your design may help out some people with the problems ....

[Peter]

60 primary/50secondary/air,fuel mixture screw set at 1:3/4 too 2 turns out...for a highway driver the plugs run a tan/brown color and around town just a very small amount of richness...that is why I went from 2 turns too sightly less(1:3/4)

primary idle 50, secondary idle 45; primary main 135, secondary main 140; primary correction jet 180, secondary correction jet 170.

For those with a progressive carb on a 1.8 litre engine that runs good, do you know what jets and combination of jets you have? Any suggestions on jet sizes other than getting rid of the progressive?[/quote]

[Peter]

I used to have the flat spot also until I set both the idle and timing at 850RPM... ss

Where is it you feel it could run better ? Idle, Accelleration, top end ? There is the inherent flat spot in progressives, search through the threads on tht one, as it's been covered a lot and the inherent problems with long intake manifolds .....

[Gunthner]

Thanks for all of the information. I plan on playing with some of the combinations this weekend. Peter, I too would like to see what kind of manifold engineering you came up with. Also, what kind of distributor do you have?

[Gunthner]

Sorry Wildthings, you're the one with home built manifold, my apologies. What distributor are you running on your engine? And I too would like to take a look at it; sounds intriguing.

[wildthings]

I don't know the part #, but it is just a Bosch vacuum/centrifugal distributor. Might be stock, might not. It was on the bus when I bought it and still does good, though it looks like a rust bucket inside anymore.

I will try to take some pictures of my manifold for you, but I'm not sure if you will be able to see anything of value from them.

[Gunthner]

Wildthings, from what I have read on this site. stock progressives don't have enough suck to affect a vac distributor. Did you drill out your port?

[wildthings]

Drilling out the port would not affect the vacuum available, just the rate at which it would travel into the hose towards the vacuum can. All you would be accomplishing by drilling out the orifice would be to lessen its designed dampening affect, and I don't think you would gain anything by doing it.

Your progressive carb set up has long large diameter runners with a very large total internal air volume, this tends to slow and weaken the vacuum signal to the carb and causes response problems, this may be what you are thinking of.