Carburetors Carb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.

I need a smaller carburetor

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Old 12-28-2010, 02:00 AM
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Re: I need a smaller carburetor

I love a good ol' rebuild qjet post. I've done several in the past and one recently about...3 months ago. Lemme know if you're curious about anything.

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Old 01-03-2011, 04:12 PM
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Re: I need a smaller carburetor

I've been looking at the edelbrock intake that is on my motor, and it actually appears to be one of those spreadbore/squarebore mixed intakes. This would be some real good news if it was, because than I wouldnt have to swap intakes, which is the biggest part of this swap.

So my question would be: since this intake doesn't have an EGR port, will this negatively effect the CC aspect of my engine?

Just searched it a bit and I would be fine without EGR, just need to locate an EGR vacuum solenoid and hook it up and the computer should be fne with it.

Last edited by bradley23150; 01-03-2011 at 04:28 PM.
Old 01-03-2011, 06:52 PM
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Re: I need a smaller carburetor

If its an 83 the computer wont even notice if the egr solenoid isnt there. Only the later ones do (I'm not sure which years though). My 85 is fine without it.
Old 01-03-2011, 08:39 PM
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Re: I need a smaller carburetor

Originally Posted by Sparkytfl
If its an 83 the computer wont even notice if the egr solenoid isnt there. Only the later ones do (I'm not sure which years though). My 85 is fine without it.

Yeah my '84 doesn't bring up any codes about it. I had to disconnect my EGR solenoid because it was making this HIDEOUS squeaking noise or clicking noise. Very annoying.
Old 01-17-2011, 04:28 PM
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Re: I need a smaller carburetor

Turns out it is a spreadbore intake. So I bolted up a stock qjet, stock throttle cable bracket and stock cc distributor and now it runs like crap. The idle is up and down, erratic, it smokes (Black smoke) and its choppy. Sounds like it has a lopey camshaft which it doesnt. I don't have a timing gun so I just did it as close as I could, but that would not cause the lopey idle and smoke. Any ideas?
Old 01-17-2011, 06:07 PM
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Re: I need a smaller carburetor

Originally Posted by bradley23150
Turns out it is a spreadbore intake. So I bolted up a stock qjet, stock throttle cable bracket and stock cc distributor and now it runs like crap. The idle is up and down, erratic, it smokes (Black smoke) and its choppy. Sounds like it has a lopey camshaft which it doesnt. I don't have a timing gun so I just did it as close as I could, but that would not cause the lopey idle and smoke. Any ideas?

If it's puffing out black smoke, then obviously its running to rich. Now this is a CCC-qjet right? So you hooked up all the connectors, right? I.E. the MCS solenoid and the TPS and such?

I would try turning the mixture screws to 2 and 1/2 turns. See what that does.
Old 01-17-2011, 06:11 PM
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Re: I need a smaller carburetor

Yes it is a CC qjet and yes I plugged the connectors in. I figured thats what black smoke meant, but I don't have the tool to turn the adjustment screws, I gotta find one.

Quick question. My last car had the same motor/trans etc... and when I turned the key on in that car the carb would make a clicking sound that would last about 3-5 seconds and then stop. This one does not do that, does that mean something is wrong?
Old 01-17-2011, 10:00 PM
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Re: I need a smaller carburetor

Originally Posted by bradley23150
Yes it is a CC qjet and yes I plugged the connectors in. I figured thats what black smoke meant, but I don't have the tool to turn the adjustment screws, I gotta find one.

Quick question. My last car had the same motor/trans etc... and when I turned the key on in that car the carb would make a clicking sound that would last about 3-5 seconds and then stop. This one does not do that, does that mean something is wrong?

BINGO! I was actually going to ask that next.

So that basically means your ECM isn't working or SOMETHING. Because, yes, you should hear the MCS clicking when you first turn the ignition to on.

Since you said you don't hear it, that means that the metering rods are out as if it was responding to a lean mixture, ergo the mixture is now very rich because nothing is controlling the solenoid for a proper mixture.

I would check to make sure the ECM has power. There should be a wire running off from the positive terminal on the battery. There's a little clip.

If you don't know what I'm talking about, I can take a picture of mine and show you what I mean.

If your ECM is connected up and running, then I would check to make sure your MCS is not hung up on something. Check to make sure it can move within the carburetor. You can check this by getting a long skinny screwdriver and poking through next to the idle airbleed on the top. I doubt the solenoid is bad.

Any questions, just ask away.
Old 01-17-2011, 10:40 PM
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Re: I need a smaller carburetor

Do you mean an inline fuse coming off of the battery?

There are multiple connections that arent hooked up under the hood, and I JUST realized there was a ground that was in the same area as the carburetor plugs that was not hooked up, I will ground it tomorrow. I still have the carburetor from my old car, so I can also plug it in and just turn on the key and if that carb clicks, than the solenoid is bad in my current carb.

I'll post back tomorrow, thanks for the tips!
Old 01-18-2011, 03:55 PM
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Re: I need a smaller carburetor

Allright, I hooked up that ground and checked it with my multimeter to make sure I got power, and I do. Turned the key on in hopes that I would hear that elusive "click" but it was silent. So I grabbed my other carburetor and just rested it on the motor and plugged it in, still no clicks, which told me that the carb was probably not the problem. I checked the connector that you told me about and it had a good 12 volts on it as well. Then I figured check the simlest possible thing that could have happened, so I pulled the ECM fuse and it was blown. I replaced it, turned the key on, and "click, click, click..." yay! It still smokes but it doesnt look as thick any more. I borrowed my friends timing gun and I am going to set the timing to 6* BTDC which is what the sticker under the hood told me to do, and I will try to find one of those wierd screwdrivers so I can attempt to dial in the idle mixture screws. Thats the plan anyway, do you think I am headed in the right direction?
Old 01-18-2011, 04:43 PM
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Re: I need a smaller carburetor

Originally Posted by bradley23150
Allright, I hooked up that ground and checked it with my multimeter to make sure I got power, and I do. Turned the key on in hopes that I would hear that elusive "click" but it was silent. So I grabbed my other carburetor and just rested it on the motor and plugged it in, still no clicks, which told me that the carb was probably not the problem. I checked the connector that you told me about and it had a good 12 volts on it as well. Then I figured check the simlest possible thing that could have happened, so I pulled the ECM fuse and it was blown. I replaced it, turned the key on, and "click, click, click..." yay! It still smokes but it doesnt look as thick any more. I borrowed my friends timing gun and I am going to set the timing to 6* BTDC which is what the sticker under the hood told me to do, and I will try to find one of those wierd screwdrivers so I can attempt to dial in the idle mixture screws. Thats the plan anyway, do you think I am headed in the right direction?

Good, GOOD to hear! I'm just sorta curious as to why the fuse was blown. Well, it works now, so that's what matters.

As for you, YES. You are heading in the right direction.

So as for your mixture screws, I personally bought one of those long bendable adjusters with the weird bar shaped head. BUT, if you have a deep 1/4 socket, you MIGHT be able to squeak by with like a 9 or 10 mm. Something like that.

Remember, 2 and 1/2 full turns on the idle mixture screws and start out with 4 full turns on the idle air bleed. Then try and get into closed loop and check your dwell.

Let me know how you go.
Old 01-18-2011, 05:01 PM
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Re: I need a smaller carburetor

Do you mean to tighten them all the way in, and then go 2.5 turns out, and start there? And whats the other screw? Is it the one on the top of the choke/air horn, if so its still covered by a little piece of metal. I will work on her a bit more tomorrow and try a small socket.

Thanks!
Old 01-18-2011, 08:12 PM
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Re: I need a smaller carburetor

Originally Posted by bradley23150
Do you mean to tighten them all the way in, and then go 2.5 turns out, and start there? And whats the other screw? Is it the one on the top of the choke/air horn, if so its still covered by a little piece of metal. I will work on her a bit more tomorrow and try a small socket.

Thanks!

Yes...and yes.

Tighten them all the way in, but do it ever so that the needle is firmly seated. Don't overdo it.

But yeah, underneath the metal cover is the idle air bleed. If you're prying it off, be careful not to lose that in the intake! :X
Old 01-18-2011, 08:17 PM
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Re: I need a smaller carburetor

Yeah, I thought thats what you meant, just making sure. I know not to over-tighten them lol. Why would I need to adjust the air bleed screw?
Old 01-18-2011, 08:47 PM
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Re: I need a smaller carburetor

Originally Posted by bradley23150
Yeah, I thought thats what you meant, just making sure. I know not to over-tighten them lol. Why would I need to adjust the air bleed screw?

Have you taken off the air horn on your carb? It might not be intuitive at first, but the MCS solenoid hits the air bleed valve which helps suck in more fuel when idling. I have a picture somewhere that SORTA explained it in a rebuild kit.

But basically as the solenoid goes up and down, the adjustment on the airbleed simply adjust how much the air valve opens up. It really just fine tunes your mixture when you're idling in closed loop.

On mine I think it runs about...5-6 turns out. Ideally the closer to 4 turns out on the airbleed the better governed by the mixture screws. The more you turn down the idle air bleed the richer the mixture gets.

I basically don't run any PCV to get the best readings from my O2...and because I don't want to ruin the sensor itself. I'm still debating on whether PCV is really all that necessary. Personally I don't think so. I pull good vacuum at idle too. like 20 inches at 550 rpms.
Old 01-19-2011, 01:36 PM
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Re: I need a smaller carburetor

The carb I am using is one that has never been rebuilt, it still has the rivets on the choke housing. It does however have the idle adjustment screws drilled. Today I unplugged the plug from the distributor and set the timing at ~6*BTDC, but I couldnt find a socket that would work for the idle screws, I have to find one of those screwdrivers to get those adjusted correctly.
Old 01-19-2011, 04:56 PM
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Re: I need a smaller carburetor

Originally Posted by bradley23150
The carb I am using is one that has never been rebuilt, it still has the rivets on the choke housing. It does however have the idle adjustment screws drilled. Today I unplugged the plug from the distributor and set the timing at ~6*BTDC, but I couldnt find a socket that would work for the idle screws, I have to find one of those screwdrivers to get those adjusted correctly.

The deep socket is not going to be a perfect fit. But it sorta worked for me.

If you adjusted your idle mixture screws properly, there is still a chance that the MCS solenoid is out of whack. Meaning that the throw is over 1.208 inches (something like that, I don't remember off the top of my head). But I highly doubt the rich stop screw would be messed up on the MCS.
Old 01-19-2011, 06:06 PM
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Re: I need a smaller carburetor

Yeah the deep sockets didnt really work at all for me, I will try and grab one of those tools tomorrow, autozone should have them, right?

I didn't tough the idle screws yet, I tested my sockets on another carb had to see if any would work.
Old 01-19-2011, 06:08 PM
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Re: I need a smaller carburetor

Is this the tool that I need?

http://www.autozone.com/autozone/acc...questid=374097
Old 01-19-2011, 06:14 PM
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Re: I need a smaller carburetor

Originally Posted by bradley23150

It is...but those are the wrong adapters. The connector on the screw is really just a rectangle. None of those shapes looked to be like the one.
Old 01-19-2011, 06:17 PM
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Re: I need a smaller carburetor

The adapter all the way to the right they call it a "double-D bit" I was thinking would work, as the screw is a rectangle with rounded ends resembling 2 letter D's.... Thats what I figured anyway?
Old 01-19-2011, 06:30 PM
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Re: I need a smaller carburetor

I know the one they sell at advance auto works. That one probably works too. And if you have more time than money like I do, you can make a tool by taking a bolt and cutting a notch into the end with a file.

I'm also pretty sure you'll want to back them out more than 2.5 times. My official manual for 1985 calls for 3 3/8 and I usually need to back them out to closer to 4 to get the air bleed into a better range of adjustment. I imagine the 83 wont be too different.
Old 01-19-2011, 07:15 PM
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Re: I need a smaller carburetor

Thanks for the advice, and I certainly have alot more time than I do money, lol. I have plenty of bolts laying around so I will have to try that if that tool wont work for me. I will see what range of turns suits me best, I guess.
Old 01-19-2011, 07:19 PM
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Re: I need a smaller carburetor

Originally Posted by Sparkytfl
I know the one they sell at advance auto works. That one probably works too. And if you have more time than money like I do, you can make a tool by taking a bolt and cutting a notch into the end with a file.

I'm also pretty sure you'll want to back them out more than 2.5 times. My official manual for 1985 calls for 3 3/8 and I usually need to back them out to closer to 4 to get the air bleed into a better range of adjustment. I imagine the 83 wont be too different.
3 and 3/8 could be for a 350 rather than a 305. But its specific to the carb itself on which engine.
Old 01-19-2011, 07:24 PM
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Re: I need a smaller carburetor

I dont know if it matters but this carburetor is not off of a thirdgen, its from a caprice. I don't remember what year, though but it is identical to a third gen unit.
Old 01-19-2011, 08:49 PM
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Re: I need a smaller carburetor

Originally Posted by bradley23150
I dont know if it matters but this carburetor is not off of a thirdgen, its from a caprice. I don't remember what year, though but it is identical to a third gen unit.
That's fine. I'm guessing the caprice was a 305, right? And if not, you can adjust for such.
Old 01-19-2011, 08:55 PM
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Re: I need a smaller carburetor

Yes, its was a 305.
Old 01-20-2011, 02:03 PM
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Re: I need a smaller carburetor

Originally Posted by RocketyMan
3 and 3/8 could be for a 350 rather than a 305. But its specific to the carb itself on which engine.
No, only 305s that year. My book also lists like ten different e4me "list numbers" (yes I'm using the holley term) which have slightly varying adjustments for choke angles and other things. Half say 3 3/8, the other half say "3 with additional adjustments on-vehicle". Seems those ones are all carbs with rear vacuum break. The book is weird, it lists all sorts of gm crap that doesnt even apply to these cars. If I wanted to know where the rpo sticker on a 6000 was, I wouldnt be looking in the firebird book.

But that doesnt really matter. Bradley needs a dwell meter. It's really the only way to get this right. If the idle air can be adjusted to get the dwell right with the front screws at 2.5, then its fine. If the idle air is bottomed out and the dwell still isnt high enough (I'm betting it'll be close), then the front screws need to be backed out another turn.

For my own, before my 350 swap, it was front screws at 3 3/8, and idle air was about two turns from bottomed.
Old 01-21-2011, 02:09 PM
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Re: I need a smaller carburetor

Well I got the tool from advanced auto, its a different brand but its the same thing and it works if anyone was wondering. Buuuut.... I tried adjusting the screws and no matter where the screw was the motor didnt seem to change. I even tightened the screws down all the way and nothing..... This is my daily driver and I can't have it down for too long so I had to put the holley/MSD parts back on it and it runs just how it did before, so I think that rochester may need a rebuild?

Also-
If I saw a couple sparks come out of my alternator, thats bad right? lol
Old 01-21-2011, 02:37 PM
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Re: I need a smaller carburetor

For the time being, is this the right bracket for my carb to fix my transmission tv cable?

http://www.summitracing.com/parts/SUM-700202/
Old 01-22-2011, 04:43 PM
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Re: I need a smaller carburetor

Whhhaaat? I didnt know summit sold a generic one, I couldve saved myself ten bucks. Yeah thats the right thing if its a 4150 or 4160. That plus you need the bracket that holds the cables in place in the right starting positions.

Changing those front idle screws will have very little effect. It's a many part system, the carb compensates for where those and the idle air bleed are by adjusting the dwell. You mostly just set them to the right starting position so things wont be of at higher throttle positions.
Old 01-22-2011, 06:13 PM
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Re: I need a smaller carburetor

It has this bracket on it:

http://www.summitracing.com/parts/HLY-20-95/
Old 01-22-2011, 06:23 PM
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Re: I need a smaller carburetor

Originally Posted by Sparkytfl
No, only 305s that year. My book also lists like ten different e4me "list numbers" (yes I'm using the holley term) which have slightly varying adjustments for choke angles and other things. Half say 3 3/8, the other half say "3 with additional adjustments on-vehicle". Seems those ones are all carbs with rear vacuum break. The book is weird, it lists all sorts of gm crap that doesnt even apply to these cars. If I wanted to know where the rpo sticker on a 6000 was, I wouldnt be looking in the firebird book.

But that doesnt really matter. Bradley needs a dwell meter. It's really the only way to get this right. If the idle air can be adjusted to get the dwell right with the front screws at 2.5, then its fine. If the idle air is bottomed out and the dwell still isnt high enough (I'm betting it'll be close), then the front screws need to be backed out another turn.

For my own, before my 350 swap, it was front screws at 3 3/8, and idle air was about two turns from bottomed.
Yeah..you know what. You're right. It's really what the dwell says it is.

I can't remember where I read that the best adjustment for 50% dwell is when you get REAL close to 4 turns out on the idle air bleed. Meaning wherever the idle mixture screws are set. ....seems almost arbitrary ???


Originally Posted by bradley23150
Well I got the tool from advanced auto, its a different brand but its the same thing and it works if anyone was wondering. Buuuut.... I tried adjusting the screws and no matter where the screw was the motor didnt seem to change. I even tightened the screws down all the way and nothing..... This is my daily driver and I can't have it down for too long so I had to put the holley/MSD parts back on it and it runs just how it did before, so I think that rochester may need a rebuild?

Also-
If I saw a couple sparks come out of my alternator, thats bad right? lol

Umm..that shouldn't be right. I don't see how a car can run if you screw the idle mixture screws all the way in.

AND yes...if you see sparks out your alternator, that's def BAD! lol. Yikes...
Old 01-22-2011, 08:15 PM
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Re: I need a smaller carburetor

The idle air bleed meters how much air is introduced into the emulsion, and the idle screws meter how much emulsion is allowed into the engine. They both have a significant effect.

If the engine is running with the idle mixture screws closed, then fuel is coming from somewhere else. The idle speed setting can have the throttle open enough to expose too much of the idle transfer ports, the choke can be closed exposing the mains to vacuum and making them discharge, or the fuel level in the bowl can be too high making it drip from the mains.
Old 01-31-2011, 04:53 PM
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Re: I need a smaller carburetor

Well that TV cable adjustment bracket did nothing, still habe the really early shifting problem... I tried to adjust the cable like the guy at the speed shop told me to do, but I cant get the button pressed in far enough it seems. It feels like my finger will break before the button gets pressed in far enough... Any idea?
Old 01-31-2011, 07:30 PM
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You only have to press it far enough for the housing to move in the fitting. Pull it back a little, let go of the button, take the throttle to wide open. It's set.
Old 01-31-2011, 07:42 PM
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Re: I need a smaller carburetor

The guy at the speed shop told me to press in the button, bring the linkage to WOT, let go of the button, and bring the linkage back to idle.

Is what your saying is that I am supposed to just press the button, pull the tv cable out of the housing a little, let go of the button, and then bring it to WOT and I am done??
Old 01-31-2011, 07:51 PM
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Re: I need a smaller carburetor

No, press the button, push the housing all the way back towards the bracket, let go of the button, open the throttle to WOT.
Old 01-31-2011, 08:30 PM
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Re: I need a smaller carburetor

I guess if I knew how the cable/housing worked I would understand what you mean. I will try that tomorrow, thanks!
Old 01-31-2011, 08:38 PM
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Re: I need a smaller carburetor

You might have to spray a lot of wd40 all around and squeeze the button with pliers to get it moving and loosened up a bit. Mine was stuck pretty well too.

Grab the sleeving part of the cable behind the housing, if you're holding the button tight enough you should be able to move that in and out and it'll make a zipping noise. You'll want it pulled all the way back (away from the carb). Then step on the gas pedal hard enough that you'll almost worry the cable is going to snap. It'll suddenly jump into position.

Oh and make a mental note of how far it'll travel in each direction. Make sure that it actually moved, and that it didnt move all the way and you still have some adjustment room left.

Last edited by Sparkytfl; 01-31-2011 at 08:44 PM.
Old 01-31-2011, 09:16 PM
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Re: I need a smaller carburetor

Okay, I got the cable to slide backwards into the housing, slid it all the way back, and then jammed the gas pedal into the floor, and the cable didnt move:

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So what I did was I slid it all the way back the opposite direction and then slowly slid it away from the carb to where the metal stopper on the end just bumped up against the plastic mounting point:



Does it look right? The cable housing does not slide at all when I let go of the button no matter where the throttle is..
Old 01-31-2011, 09:31 PM
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Re: I need a smaller carburetor

No it needs to be tighter than that. If you were able to floor it without the cable getting tight enough to adjust, it means either your cable is stretched a bit, or your one-size-fits-most bracket holds the housing a bit too close to the carb. I think what I'd try would be shortening the cable, maybe with something like this http://ep.yimg.com/ca/I/cvfsupplyco-store_2108_10722610 long enough to see if that works.
Old 01-31-2011, 09:31 PM
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Re: I need a smaller carburetor

That bracket isn't for a 700R4, it's for older transmissions with convential kickdown cables.
Old 01-31-2011, 09:40 PM
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Re: I need a smaller carburetor

Ugh one thing after another with this car...

Which bracket isnt for an r4? I bought the adapter for the linkage today and it is definitely for a 700r4.
Old 02-01-2011, 12:41 PM
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Re: I need a smaller carburetor

When I go on summit and select throttle cable bracket, 4150, and 700r4, thats the bracket that comes up, the 20-95 which he says he has. Going to the holley site, it shows me this http://www.holley.com/20-95.asp which confirms thats the right one. Unless somethings more complicated than that.
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