Progressive linkage vs straight linkage on a 2x2 manifold
 

I am planning to upgrade my flathead and run dual Holly 94's on a slingshot manifold. My motor is pretty much stock with some high compression heads and a set of headers. Eventually I plan to upgrade the cam but for now am starting with the intake manifold. My question is when setting up the manifold, are there any thoughts on running progressive or straight linkage?

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Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

With two carbs you need straight linkage and make sure carbs are synchronized.

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

I agree. Progressive linkage may give you better throttle response and possibly better fuel economy, depending on you're driving style.

Sal

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

It would be just like a 4 barrel with mechanically operated secondaries.

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

Yep
Progressive

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

I have a slingshot as well and used straight linkage. It works good, however, I like the response you received and curious to try progressive as well.
On a side not, you will notice one of the manifold mounting bolts on the left side does not allow a hex head bolt. I used an allen head on mine. Just a heads up. Please let us know which way you decide and how you like it.

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

Thanks for all the replies. I will keep you posted. I'm leaning towards trying both as for a nominal investment I can convert to a progressive linkage.


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Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

With progressive linkage brings up another question. Does the secondary carb need any modification in this application? In my tri-power setup the outer carbs are modified with no mixture control and heavier butterflies to avoid leaking fuel caused by engine vacuum.


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Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

I think I answered my own question. Here is a write up I found about The Holley 94 Secondary carb.

CARB BASE-HOLLEY 94 Secondary Base Assembly-w/Spring This is what you need to make your outside carbs work right. This base our new alum base reamed and fitted with a new throttle shaft-- and fitted with our new 12 degree throttle plates that give you a great seal with no sticking in the bores.Throttle plates are lapped to bore. This base is an exact reproduction of the original early holley 94-2100 base. These bases are used on the outside carbs on a 3x2 setup and on the outside carbs on a six deuce setup when running progressive linkage. They can also be used in any other location where you dont need or want an idle circuit such as the secondary carb on a dual setup running progressive linkage. These bases dont have any idle circuits And come with our new torsion return springs and carb arms. These eliminate the need for any throttle return springs and work much better. Due to the 12 degree plates --you dont need any throttle stop screws or hardware on your carb.

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Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

Would be fun to try both setups . . . why the heck not! You'll probably need to buy a 3x2 progressive linkage and only use one "side" of it. Can't say that I've ever done it -but worth a try.

Can't see much of an issue with having idle mixture screws in both - you can still tune the idle . . . with one, with both, doesn't really matter. Once you get "off idle", then the main jets will come into play.

In my mind, the engine will only need a certain amount of air/fuel to go a certain speed - so can't really imagine that a progressive linkage setup has much to gain. As these carbs have really small throttle plates - don't think there is any real performance issue with having BOTH of them coming in at the same rate. BUT - will be interesting to see what happens in your "real world" testing.

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

the two 94's will have to jetted down from the stock jets, no matter how you configure them. on the new strombergs we went from the stock 45 to 35 and syncronized them, worked out great

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

Bursonaw, who makes that carb base? just curious.

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

The cab base I found at Vintage Speed. http://vintagespeed.com/

I think that speedway might have them as well.


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Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

I used a couple of those carb bases on my yblock w/tripower. I worked forever trying to make 70yr carb bases seal at idle without success. Installing those fixed my vacuum leak at idle. Well worth the $$$.

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

Two 94's on his setup, I'd start with stock jets and play from there. Probably need the power valves playing with, 5.5 or such. May find all's well with stock jets and power valves.

45 down to 35!!!! Damn! That's a massive difference! you certainly wouldn't need that massive drop in numbers for 94's
Martin.

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

Me - would throw a straight linkage on it, sync the carbs with a UniSyn, jet them to match the engine and it's fuel needs and drive it . . . you'll probably not improve on that in my mind. :)

D

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

You may find those air cleaners to be restricting.

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

I run dual 94's with straight linkage. My engine is stock with mild Howard cam. As mentioned"Unisync" them. I was advised by "CharlieNY" to block off the PV"S and am very satisfied with the set-up.

Re: Progressive linkage vs straight linkage on a 2x2 manifold
 

What size main jets you got in there?
Martin.