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Old 09-22-2016, 02:13 PM   #1
AnthonyG
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Default Question on throttle stroke

I have been enjoying my '35 and never really noticed since installing an Edelbrock 4 barrel that the stock pedal / throttle mech. doesn't allow enough stroke to fully open the 4 barrel. Probably only opens the secondaries 1/2 way. I never beat the car up so haven't really had an issue. Anyone else notice this. I am using the stock mech. and throttle rod. Thinking the stroke is what it is so thinking to resolve would need to change the diam. of the rotation ( reduce the moment arm to get more pivot ) where it connects to the carb throttle pivot?
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Old 09-22-2016, 02:18 PM   #2
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Default Re: Question on throttle stroke

You need to add a spring to force the throttle open.
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Old 09-22-2016, 02:19 PM   #3
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Default Re: Question on throttle stroke

^^ That sounds like not a very good idea.
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Old 09-22-2016, 02:40 PM   #4
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Default Re: Question on throttle stroke

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Originally Posted by 39topless View Post
You need to add a spring to force the throttle open.
Let me second the response to that dumb idea! DD


THAT SOUNDS LIKE NOT A VERY GOOD IDEA ! ! !
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Old 09-22-2016, 02:42 PM   #5
AnthonyG
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Default Re: Question on throttle stroke

Where / how would the spring go? Not sure what that arrangement would look like? If your pulling my chain for a laugh that's cool, if not need more detail??
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Old 09-22-2016, 02:48 PM   #6
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Default Re: Question on throttle stroke

Tony.......Post a CLOSER picture of how the throttle rod attaches to your carburetor's butterfly linkage. That attachment point needs to be CLOSER to the throttle SHAFT. In other words, the distance needs to be SHORTENED. DD

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Old 09-22-2016, 03:19 PM   #7
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Default Re: Question on throttle stroke

From what I can see in the above picture, it looks like the throttle attachment point at the carb needs to be move toward the front of the engine. It looks like the linkage is attached to the rear of the butterfly shaft. I'll bet the carb is rotated on the manifold from it's intended position in order to use the original linkage.
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Old 09-22-2016, 03:24 PM   #8
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Default Re: Question on throttle stroke

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Originally Posted by 40cpe View Post
From what I can see in the above picture, it looks like the throttle attachment point at the carb needs to be move toward the front of the engine. It looks like the linkage is attached to the rear of the butterfly shaft. I'll bet the carb is rotated on the manifold from it's intended position in order to use the original linkage.
You're probably correct in that the carb has been turned 180. That's why it APPEARS that the linkage throttle rod is now attached BELOW, rather than above the shaft. We need BETTER pic of linkage attach point. DD
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Old 09-22-2016, 03:29 PM   #9
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Default Re: Question on throttle stroke

see next
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Last edited by AnthonyG; 09-22-2016 at 03:40 PM.
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Old 09-22-2016, 03:30 PM   #10
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Default Re: Question on throttle stroke

You need to attach the stock throttle rod on the WCFB throttle lever closer to the axis (throttle shaft) so there is less distance needed to open the throttle to true WOT. (wide open throttle). Chances are the original carb (97) took less distance to open all of the way. Or change the stock linkage to aftermarket cable linkage.

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Old 09-22-2016, 03:31 PM   #11
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Default Re: Question on throttle stroke

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Originally Posted by AnthonyG View Post
Img_0692.jpg
That ain't gonna work. Post it in your "flatty" album and I'll bring it to the front. DD
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Old 09-22-2016, 03:36 PM   #12
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Default Re: Question on throttle stroke

Sorry having problem downloading pic
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Old 09-22-2016, 03:48 PM   #13
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Default Re: Question on throttle stroke

If you'll remove that stud at the bottom, then drill a new hole just above it, as close to the BOTTOM of that bend, re-install the linkage to it and you'll be pretty darn close to good. DD

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Old 09-22-2016, 04:01 PM   #14
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Default Re: Question on throttle stroke

Yep, need to drill another hole to remount 1/4" ball closer to center of butterfly throttle shaft, not a lot of room to do so. Scicala, if I went to an aftermarket cable still would have the same stroke unless I lengthen the rod attached to the pedal pivot assy at firewall or eliminate stock pedal assy all together and went with a universal street rod pedal assy. Really don't wanna go that route.
Thx guys,
Will report back
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Old 09-22-2016, 04:05 PM   #15
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Default Re: Question on throttle stroke

^^ will work, but might make the throttle "touchy". I would fab a small piece of metal to bolt to the present stud hole and extend forward of the present tab. Envision a circle around the throttle shaft and drill a hole slightly forward and above the present stud hole to mount the linkage. Fab the new piece to lay next to the bend in the present carb tab to prevent it moving.

But I usually do things the hard way.

Edit: before doing my suggestion, unhook your linkage at the carb and be sure it will extend farther forward to connect to the new stud location..
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Old 09-22-2016, 04:14 PM   #16
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Default Re: Question on throttle stroke

Tony................WAIT...STOP! I just noticed that you NOW have that carburetor mounted on top of that goofy riser again, like you did once before. That's MOST of your problem. Look at the angle on your throttle rod. Your throttle spoon (gas pedal) is spending most of it's travel pulling your carburetor's butterfly shaft DOWNWARD, rather than REARward. Hell, get rid of that goofy riser and get that throttle linkage rod more LEVEL, like real cars. Re-drilling and re-mounting that stud like previously suggested WILL NOT fix your situstion. Get that rod LEVEL! DD

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Old 09-22-2016, 04:31 PM   #17
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Default Re: Question on throttle stroke

Good catch, Coopman.
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Old 09-22-2016, 11:12 PM   #18
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Default Re: Question on throttle stroke

Personally I would cut the arm off the right side of the linkage (leaving enough for the spring to bear against), then weld it on the left side (extending it slightly), and finally turn the carb around to way it is intended to be run.

Shortening the length of the carb arm will make it a lot more sensitive to the angle the linkage rod pushes from and harder to set-up to eliminate the chance of over-centering.
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Old 09-23-2016, 01:42 AM   #19
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Default Re: Question on throttle stroke

It may not simply be a matter of the ball being closer to the shaft. There is a geometry issue here. The lever on the carb assumes a straight pull to the rear. Lets say the shaft rotates 80 degrees. With throttle closed the pivot ball will be at 40 degrees forward. At wide open the ball will be 40 degrees back. at half throttle the the ball will be straight down and the angle between the rod and the lever will be 90 degrees.

Because of your high rise spacer setup your throttle rod is approaching at an angle of 45 degrees. The angle between the rod and the lever is 90 degrees at idle. you pull back and the lever gets to a position where you can't pull any more.

Make a new lever, or bolt something on to the existing lever. Move the ball forward so at half throttle the angle between the rod is 90 degrees. make sure the distance of the ball from the shaft is correct to give full stroke. It may need to go slightly nearer the shaft but my hunch is that it will be ok at the current radius.

The other option is to construct a relay lever or bellcrank to keep the link and the new link horizontal.

It is a bad idea to have throttle linkages running at steep angles, because if the engine rises in it's mounts due to torque reaction, it can cause the throttle to go more open or more closed and cause a kangarooing action while driving down the road.

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Old 09-23-2016, 08:35 AM   #20
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Default Re: Question on throttle stroke

I modified a ss braided throttle cable to snap on the ball on top of firewall pivot and used one of the rear carb mounting bolts to secure cable on level pull plain approx 8 " behind butterfly throttle shaft. Seems to open all the way now. Will test today. As Mart and V8Coopman indicated it most likely was the steep angle due to hi- rise messing up the geometry. PS V8Coopman, I like the "goofy" hi-rise setup, eyes of the beholder you know and a lot more torque. also gives me a good platform for running multiple carb setup which would normally have interference with alternator setup.I do thank you for picking up the geometry issue, it was a good call
Thx to all for the good advise and ideas.
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Last edited by AnthonyG; 09-23-2016 at 08:46 AM. Reason: clarify
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