Progressive throttle linkage?

[ForceFed70]

Does anyone have info on where a guy can buy a kit to give progressive throttle linkage on a holley 4bbl?

I recently bought a 4bbl holley pro-jection throttle body, and with it's 1 3/4" throttle bores (900cfm) it's going to be a little touchy at part throttle unless I can figure out some sort of progressive linkage. These throttle bodies use the same linkage as a 4bbl carb as they are ment to be used as a carb to EFI replacement part.

I need to keep the throttle blades at a 1:1 ratio in order to stay away from having to stage injectors. So I need to make the whole throttle body progressive. Something so that when I have the throttle in 1/2 way the throttle blades are only open 1/4 of the way, but when I have my foot to the floor, the throttle blades open up completely.

Any ideas or suggestions?

 

[bnickel]

i thought the pro-jectio systems already had a progressive linkage. could be wrong but i swear they did.

 

[ForceFed70]

i thought the pro-jectio systems already had a progressive linkage. could be wrong but i swear they did.

According to the holley tech it's 1:1, and it sure looks 1:1 to me. He also said it's one of the "older" pro-jection units (looks brand new) and it sounds like the newer pro-jections do have progressive linkage.

That asside, it's the wrong type of "progressive". When most people talk carbs "progressive" means that the 2nd 2bbls open in a progressive mannor(later) or in the case of multiple carbs, the whole 2nd carb opens up a little later. That's NOT what I want.

When talking throttle boddies, progressive linkage usually means the single throttle blade (as most throttle bodies only have 1 maybe 2 bores) opens in a progressive manor. Basically meaning that at 1/2 throttle the plate is only open 1/4 of the way. But when the throttle is at 2/3rds the throttle plate is open 1/2 way, and when the throttle is fully depressed the plate is open fully. Due to the complexities of staging fuel injectors, THIS is what I want....to open all 4 bbls at the same time/rate, but to do so with a progressive throttle linkage.

 

[ForceFed70]

Somebody has to have some ideas!

What do you guys think of the idea I drew out below?

 

[bnickel]

that would probably work pretty well, the biggest problem i see is getting the ratio between the front and rear butterflies just right. i'd try making a simple sheetmetal prototype that you can drill different holes in to get the ratios the you can build one from aluminum. that way you can make sure they are the way you want them

 

[ForceFed70]

that would probably work pretty well, the biggest problem i see is getting the ratio between the front and rear butterflies just right. i'd try making a simple sheetmetal prototype that you can drill different holes in to get the ratios the you can build one from aluminum. that way you can make sure they are the way you want them

Don't need to worry about the front to rear ratio. The throttle body already comes with 1:1 linkage to connect the two butterflies. So I can get away with concentrating on the the main butterfly and the secondaries will take care of themselves.

I agree that it's going to take a little fooling around to get it right.

What do you think about finding a small pully and cutting it in 1/4's. Then just manipulating where the throttle shaft is located. Something like this:

 

[bnickel]

i bet that would work.

 

[mfp4073]

my mx6 has something like this....wonder if you could come up with the size you need and then dig through a junkyard for a piece to use?

 

[ForceFed70]

my mx6 has something like this....wonder if you could come up with the size you need and then dig through a junkyard for a piece to use?

Finding the size is going to be tricky. I guess I'll have to measure the cable and see how much "pull" I get. But looking at the pictures it looks pretty complicated to try and figure out exactly what size I'll need. I need a geometry expert or something to help me out with that. I have a fealing it's going to be a trail and error type thing...

Junkyard is a good idea, gotta head out there to grab a Fast Idle solenoid and a few connectors anyway, so I'll dig around and see if I can find anything that looks like it'll work.

Wish I could come up with something that's adjustable.