1:1 vs progressive on the street

[Cobra720]

Is there a reason why I shouldn't run my 1:1 linkage on the street vs my progressive?

I have a cobra replica that I autocross and street drive. 408w about 575/555 Solid Roller with a 5sp trans

The carb is a AED HO-Modified that John Dickey made for me. 2 linkages came with it. It's a beast on the Autocross track, very aggressive and a lot of power out of the corners at low RPM to max RPM with the 1:1.
With the progressive linkage on the street it seems a little soft, maybe tamer is the word off the clutch, but still very good. I just like the feel of the 1:1.

Am I throwing too much at the engine on the street with fuel consumption using both throttle plates and accelerators pumps for really not much to gain? or...Just run the 1:1 and don't worry about it?

[miniv8]

That might be the biggest difference, part throttle fuel economy and driveability.
It of course depends on the overall tuning of the carb, how much time has been invested in it, whether or not it will like 1:1 or progressive under light load.

The rest is just your right foot...

I am told the hottest aftermarket item right now, is digital pedal ratio tuners for drive by wire throttle.

[learner1]

I ran a 1:1 on my big block charger i had when i was younger and it's hard to go back to a progressive linkage. As far as gas mileage that's something i never kept track of back then.

[steve cowan]

I run 1:1 in my street/ strip car,I like it and don't have a problem with it,I also run front and rear power valves and square jet
Only extensive testing will tell you as it depends as usual on what you are trying to achieve.
I also think it may help with fuel distribution in a open plenum but I have no evidence to prove / disprove the theory.

[tjs44]

I have been running 2-4s since 1962.I always run progressive for street driving but set them up solid for the track.95% of them have been with AFBs.When I ran holleys I used the Ford setup progressive with the vac pods hooked together.FWIW,Tom

[Cobra720]

I can only see the use of a little more fuel as the secondary plates open earlier, although both primary and secondary open less compared to only the primary’s opening. The performance is notable (seat of the pants) feel. I also have 2 power valves and jetted accordingly. Its a real light car with 3.73 gears so it doesn’t take much pedal to get up and moving. You just need a controlled right foot Thanks for chiming in guys.

[Steve K]

I run 1:1 on my tunnel ram cars (406 and 427) with 650 eddies with no issues, even get 21 mpg (cdn) with a 660hp 427 on the highway. I just did a 350 with a dual quad vortec head with a mildly aggressive cam in an 83 GM B body with progressive linkage. This car has a 2500 rpm stall and it's a little on the sluggish side as that 2500 rpm is all done on the primary carb. As soon as it warms up here I'm going to 1:1 and see what happens. I'd rather have the primaries on both carbs working a little bit than the primaries on the rear carb work a lot...that and it seems like its running on 4 cylinders with one carb. On a TR 1:1 is the only way to go.

[tjs44]

I have NEVER run a auto with 2-4s so that is out of my knowledge.I run a factory pontiac 2-4 tunnel ram with a pair of factory 750 SD AFBs and it runs great on just the front of the rear carb.Tom

[naukkis79]

You are talking about two different things, 1:1 linkage for two carbs on top of tunnel ram or 2-4 manifold is obvious, both carbs need to be opened simultaneously for even fuel distribution. Progressive linkage for many carbs are only viable for something like sixpack where one carb is primary and two staged as secondaries.

Thread starter has two linkages for a carb, progressive which opens first primaries and secondaries come only near WOT, and 1:1 where both primaries and secondaries are opened simultaneously. To tune up carb 1:1 linkage basically makes that primary/secondary staged carb to appear as one barrel carb limiting tuning possibilities. For actual throttle response it's actually won't make any difference, progressive carb setup can also tuned to be rich everywhere and get crisp throttle response, but with staged primary/secondary setup it's also easy to tune primaries lean and secondaries rich making it possible to save gas and engine when full power isn't needed. And with two linkages it's possible to swap fast between all-rich setup and economy setup.

It's plain stupid to use engine with rich afr in streets, it will foul plugs and crap engine with soot and make cylinders to wear out rapidly as excessive fuel will wash out oil from cylinders.

Best compromise is to use progressive linkage, keep primary lean but use big shot from accelerator pump, pretty crisp throttle response is still achieved. With big plenum intakes it's still a quite bit slower response than with rich everywhere tune.

[steve cowan]

Is there a reason why I shouldn't run my 1:1 linkage on the street vs my progressive?

I have a cobra replica that I autocross and street drive. 408w about 575/555 Solid Roller with a 5sp trans

The carb is a AED HO-Modified that John Dickey made for me. 2 linkages came with it. It's a beast on the Autocross track, very aggressive and a lot of power out of the corners at low RPM to max RPM with the 1:1.
With the progressive linkage on the street it seems a little soft, maybe tamer is the word off the clutch, but still very good. I just like the feel of the 1:1.

Am I throwing too much at the engine on the street with fuel consumption using both throttle plates and accelerators pumps for really not much to gain? or...Just run the 1:1 and don't worry about it?

Sounds like you have done some testing and I have said i use the 1:1 linkage on a single carb open plenum small block for a few years and it has taken some work as in a nice fuel curve,I understand on the dyno, results would maybe vary depending upon application.

[Cobra720]

You are talking about two different things, 1:1 linkage for two carbs on top of tunnel ram or 2-4 manifold is obvious, both carbs need to be opened simultaneously for even fuel distribution. Progressive linkage for many carbs are only viable for something like sixpack where one carb is primary and two staged as secondaries.

Thread starter has two linkages for a carb, progressive which opens first primaries and secondaries come only near WOT, and 1:1 where both primaries and secondaries are opened simultaneously. To tune up carb 1:1 linkage basically makes that primary/secondary staged carb to appear as one barrel carb limiting tuning possibilities. For actual throttle response it's actually won't make any difference, progressive carb setup can also tuned to be rich everywhere and get crisp throttle response, but with staged primary/secondary setup it's also easy to tune primaries lean and secondaries rich making it possible to save gas and engine when full power isn't needed. And with two linkages it's possible to swap fast between all-rich setup and economy setup.

It's plain stupid to use engine with rich afr in streets, it will foul plugs and crap engine with soot and make cylinders to wear out rapidly as excessive fuel will wash out oil from cylinders.

Best compromise is to use progressive linkage, keep primary lean but use big shot from accelerator pump, pretty crisp throttle response is still achieved. With big plenum intakes it's still a quite bit slower response than with rich everywhere tune.

This is something I was worried about and the reason for the post. [ Excessive fuel from the secondary pump for not much gain on the street]. (3rd paragraph)

I think you provided me with a reasonable answer in your last paragraph.

I'll stick with 1:1 for competition because it's smooth and aggressively powerful and use the progressive for leaner street driving and have the quick sec. opening providing a richer mix with power.

It only takes a minute to change between the two.

[Robban 54]

1614930247928-2050233454.jpg

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Have been driving like this for a few years love it.
SBC383 with Edelbrock 435hp Top-End Kit TH350 10in 2400stall converter Jaguar rear axle 3.07 Quaife limited slip differential.
Cruising 60 mph 2500rpm vacuum 15-16 inch on low speed circuit afr 14,0-15,0.
Ignition locked 30 degrees plus 15 degrees vacuum.
Carb 950 HP Pro System.
100% sure 1-1 linkage easy to change 30 seconds 2 m3 screws.

[ClassAct]

1614930247928-2050233454.jpg1614930362924293385840.jpg1614930428195-1413487516.jpg

Have been driving like this for a few years love it.
SBC383 with Edelbrock 435hp Top-End Kit TH350 10in 2400stall converter Jaguar rear axle 3.07 Quaife limited slip differential.
Cruising 60 mph 2500rpm vacuum 15-16 inch on low speed circuit afr 14,0-15,0.
Ignition locked 30 degrees plus 15 degrees vacuum.
Carb 950 HP Pro System.
100% sure 1-1 linkage easy to change 30 seconds 2 m3 screws.

Did you make or buy those linkage pieces that change the throttle ratio??

[Robban 54]

1614954043892913849131.jpg

The screwed-on sheet metal piece made to get 100% 1to1.