Quick carb hook up question

[saxart]

I'm in the process of converting my truck from a 2bbl carb to a 4bbl carb as part of a crate engine swap. The question mark comes when hooking up the carb linkage. Got a rebuilt Quadrajet from National Carb, and an original cast iron intake from a local engine rebuilder.

The question is, how is the original throttle linkage hooked up, and where does the throttle return spring attach? The engine has a thermostat housing with a spring hook on it at the front of the engine, but it seems the spring should attach and pull to the rear of the engine.

Here's what things look like right now.



Any thoughts are appreciated.

[geunther]

Factory setup. But 72s had a cable for the 4bbl versus the solid linkage. And the return spring went back to the mounting tab for the cable.

[FirstOwner69]

Here are 2 pictures of my original '69 350 engine. The thing circled with yellow in the 2nd pic is the kick-down switch used with a TH400 transmission. The thing circled with blue is the bracket that depresses the switch. They were circled for a previous thread. You should be able to see the tab on the coil bracket for attaching the spring. If you have a TH350, the kick-down is a different setup.

[HO455]

Your new carb is off a newer vehicle that came with a throttle cable not a rod. You can convert the existing throttle by drilling the plate (probably have to remove the post where the cable hooked up), or obtain the correct base plate for the carb, or convert to a cable throttle gas pedal. The cable throttle conversion is popular, but will require a trip to the wrecking yard. For a restoration get the correct base plate is your only option. Drilling the plate is fastest, but be careful with your layout to ensure the geometry is correct. Otherwise you may not get full range of throttle or make the throttle extremely touchy. Maybe someone with a correct carb could supply you with the measurement from the center of the throttle shaft to the center of the hole for the rod. Take a compass and make an arc on the plate at that dimension. Then all you would have to decide is where to place the hole on the arc. The other thing to consider if you drill is where the pedal sits at idle. Too high will be a pain.

[saxart]

Thanks for all of the thoughts. I forgot to mention, this is a manual trans (SM465). I'll try removing the post that's there for the cable-throttle and see how that works for the solid linkage I have.

What type of bracket should a manual trans have at the back of the engine (no coil...HEI) for the throttle return spring?

Thanks

[Coley]

My set up is pretty much identical to Guenthers. The only difference is that I've added one more throttle return spring just in case the original lets go...allowing the engine to run/rev up.
Which of the trucks used the 'rod' instead of the 'cable'?....TH400 trucks or? pre-71' or?

Coley

[FirstOwner69]

Originally Posted by Coley

My set up is pretty much identical to Guenthers. The only difference is that I've added one more throttle return spring just in case the original lets go...allowing the engine to run/rev up.
Which of the trucks used the 'rod' instead of the 'cable'?....TH400 trucks or? pre-71' or?

Coley

Pre-71s used the rod regardless of transmission.

[yuccales]

You could saw off the rod where the line is, weld a thick washer to it. That way you can use the posts on your carb, till you get a cable set up.

[rockyrivermark]

I would drill that carb plate and put a drift pin threw the rod.

[saxart]

Finally having a chance to get back to this so I thought I would tap into our collective knowledge again.

If you compare this picture to the pic I posted in the original post at the top, you'll see that I removed the cable "lug" from the throttle arm.



I was hoping that the arm would fit the remaining hole, but it's too small. After doing a little research, I was hoping this would work, so I ordered one:

http://67-72chevytrucks.com/vboard/s...ad.php?t=70868

...but it didn't fit either the carb throttle or the throttle linkage of the truck. Does anybody know if there is a bushing that will fix this? The throttle linkage is 1/4" wide, and the hole in the carb throttle is just shy of 3/8". If you do a google search for "throttle bushings" you of course many hits for throttle plate shaft repair bushings, which this is not.

Again, any assistance is greatly appreciated.

[AussieinNC]

Make a short bushing from 5/16 ID metal fuel line and slip it over the rod...it only needs to be about 3/8 inch long...

The metal fuel pipe should just fit into the hole in the throttle plate...

Secure rod with cotter pin or hair pin clip...make sure the rod does not bind on that other pin...

[Coley]

I'm not sure what auto parts (chain) stores you have in your area (Napa or?)....but any major chain will carry bushing material for that arrangement.
Often they will have bushing material available in small drawer/cases and you can simply choose the I.D (inside diameter) and O.D (outside diameter) that you need.
Similar bushings are used in the door pin/hinge arrangements as well....just larger. Some are straight hollow bushings...and some have a handy 'flange' on one end.
It looks like you need the following;
Bronze (Oilite or equivalent) bushing
Flange type is acceptable
1/4" I.D
3/8" O.D
length....can be cut if necessary.

The advantage of using actual bushing 'material' (ie: oil impregnated bronze) is that it will always rotate nicely and will not bind....which is not a good thing for a throttle arrangement.

my two bits.
Coley