Hey guys, I've been wrenching away on the roadrunner trying to get it running to its full potential. Had to put a new oil pan on it over the last few days discovered it had a pin hole and was leaking pretty good. But now I'm getting ready to yank the 2 4 bbl carter carbs off of it and throw a rebuild kit in them. I can tune 1 carter 4 bbl but I have no clue how to tune 2 of them. So how's it done? (I'll probably take it to a mechanic and say here tune this in for me lol.) But I'd still like to get it as good as I can.

Also I've been wondering if it's too much carburetor for the motor. Here is what I'm running: 440 with lunati 30306 cam Duration 285/295, Lift .507/.534, it has keith black pistons 10:1 compression. intake and heads are port matched and the exhaust ports are matched to the headers. 4 speed dana 3.54.... Don't know what cfm the carbs are I havent looked them up yet. Just curious if this motor is drowning its self rather than getting maximum power. The car sat for like 13 years just after the engine was rebuilt. I had to replace the gas tank and sending unit from all the rust and old gas turned to turpentine. It was running 2 fuel filters but I'm sure some of the gas made the inside of the carbs a little more than nasty.

I was trying to tune it in a bit last night. I advanced the timing just a little bit and messed with the fuel and air screws on the primary carb trying to get the smoothest idle I could out of it. I did get it running just a little better and got it to be just a little bit more responsive. But here's the problem. I took it out last night after getting all that done. I put it in 1st gear let the clutch out and had it just barely rolling. I stomped the gas pedal to the floor and opened it all the way up. It was like I turned the key off for a second and then it VERY slowly started revving up and then finally it picked up and started fish tailing all over the road. So I know this thing has gobs of power just waiting to be unlocked but it's losing probably more than half of it right after you step into it. I'm guessing the carbs are either 500's or 650's. I'll double check the numbers on them and try to find out for sure what they are. The dual 4's are cool but if it's too much for it I have no problem swapping them out for a single 4 bbl setup or maybe a 6 pack if that wouldn't be too much. I'd rather be having fun with the car than being able to say I've got a dual 4 set up lol.

 

I had a '67 GTX w/440 Commando and Tri-power.It had mechanical linkage so you could move the slide and lock it down to anything from utilizing the middle two barrel to using all three carbs and anywhere in between. If I remember correctly it had a total of 1350 cfm. and you could only roll it on with full carbs or it was too much..So if you are running two 650's I am not surprised you can't put it to the floor without bogging it out.

 

The secondary opening will need to be delayed, this can be done depending on what style of Carter carbs you have. Knowing how to adjust your accelerator pump shot will be helpful to dial it in. Give us an update when you find out what you have.

 

It is slightly delayed. The linkage rod that goes from the primary to the secondary carb has about a 2 inch slider slot in it that has to bottom out before it starts opening the secondary carb. I will definitely give you an update when I figure out what cfm I'm running. Would just go grab the numbers now and find out but I'm stuck at work. Here is a pic of the carbs and linkage. Best one I've got at the moment.

 

I would guess they are 500cfm Do you have a vacuum gauge ?
Start set the initial timing for around 15 deg BTDC and 36 total without vacuum advance connected..
adjust the mixture screws for the highest vacuum reading on the front carb- readjust the idle. then do the same with the rear trying for the same vacuum reading then work on the opening rate

 

Ok I got the numbers off he carbs to day and tried to find some info on google about them. I'm going by the numbers stamped on the bottom flange of the carbs. The secondary carb is stamped 3393sa and has B5 under that. The primary is marked c7 35645.

I didn't find anything for the primary. But the secondary I found an old ebay listing where a guy had that same carb listed with the same numbers 3393sa. He said it was an original secondary off of a 413 or 426 dual quad set up. But he didn't say the cfm. If any of you guys happen to have a way to find out by these numbers I'd appreciate it.

 

Found this: http://www.carbkits.com/catalog/details/1146

http://www.carbkits.com/catalog/se/s2

This too: http://www.hemmings.com/partslocator/carburetors.html

 

Well it makes sense that they show to be marine carbs. The guy I bought it from said that the 440 came out of a 1971 Century boat. But still don't know the cfm on them. Well judging by the fact that these are probably the original carbs that came with the motor before it had any custom work done to it... It's probably not too much carb for it.

I'm going to go ahead and put the rebuild kits in them and see what happens. Hopefully that will fix the heavy bogging at the bottom end.

I was also thinking. The cam thats in it has a power band from 3000 to 6000 if i remember right. Would that be why it bogs down? Because I'm trying to put too much into the motor before it's in its power band?

 

Found this too, but not cfm: http://www.carbguy.com/info.php

http://www.carbguy.com/info.php

I think if you measure the bores you'll find a similar one with cfm listings.