4 barrel carb swap (finally!)

[MattH]

Decided to get on and do this, remove the ultra reliable 2 barrel and put on the NOS Carter AFB and Offenhauser 360 manifold, both of which I bought at the Great Leighs Hot Rod show in 1994.

I also have a 4 barrel Holley which I know nothing about except it was running on a 340.
Was going to fit the Holley but the carb studs fouled the fuel bowls and the Bananarama! the sides of the inlet bore, so clearly this Holley is far too big for the Offy manifold and probably for a stock internals 318.

See separate thread on "what is it?" to try and ID this big carb.

So I've got the 2 barrel and manifold off quite easily, the found the Offy manifold doesn't have recesses for the dowels which secure the gaskets and keep things in place. Drill time
Seems Ok, and manifold on, so that nice clean inside of engine doesnt get mucked up.

Will need to remove some bolts tomorrow as I forgot the cable and kickdown bracket.

Tomorrow will be starting to connect bits up and see if things line up. i do hope so as I want it back on the road by the 27th to take to the A602's RWYB at Santa Pod to see if it actually makes it any better than last year with the 2 barrel.

So the carb on the right is what I'm opting to fit, not sure what it is but it says Carter AFB on it and fits the inlet.
Advice very much appreciated on what to do with the choke, which looks to be electric. Any one know or do I just ditch it and convert to a manual choke cable??
It seems the second set of butterflies doesnt open when the choke flap is shut.

[MattH]

Has anyone experience of the electric choke?

It looks like it just warms up with current from an igntion feed and takes the choke off, so a simple earth lead and fused live feed from the ignition.

Or should I just take it off?

Bear in mind its a road car, used quite alot and has been reliable up to now.

[Pete]

You can wire it up to a switchable power supply and then earth - do NOT use any of the feeds to the Ballast as a source.

They are adjustable, but in my opinion they can go in the bin and keep the old MSD units company....

Not a fan of AFB design generic Carbs at all. Not enough pump shot.

With a holley is is 4 or 5 pumps from cold and off you go without a choke....

[MattH]

So it is fitted, choke wired open rather than using the electrics.
Started first time but I cant get the kickdown linkage right.
Original 2 barrel slotted bar seemed too short, as the lever was going over centre and dropping down, made a longer one but still doesnt seem right.

Questions
1 - are the slotted bars that links the throttle lever to the top of the kick down linkage available in different lengths to suit different carbs?
2 - Am i correct that adjustment is:- hold carb on Wide Open Throttle, then push kickdown lever fully back towards bulkhead, and the slotted bar should hold the two at that location with the back edge of the slot, meaning the throttle lever can go forwards (closing throttle) even if the kickdown lever doesnt return as quickly?

[Adam]

Matt, there are 2 types of kickdown linkage. Earlier ones are 3 piece. They're adjustable (threaded) on the slotted throttle rod, and on the vertical rod that goes down to the trans rod. You align them by putting a 3/16 (I think) drill bit through holes in the bracket.

Later ones are one piece, with just a threaded adjustment on the slotted throttle rod. They can be tricky to adjust for applications other than the intended. Basically you want the kickdown lever on the trans to be (almost) turned as far as it will go at full throttle, i.e. allowing full throttle to be attained, whilst still allowing the throttle to close to the idle stop (obviously!). I recall I had to elongate the slot on my old Satellite to get that range without it hitting the firewall.

I'm sure you know that there should be a spring to keep the slotted rod forwards against the throttle lever, so that it acts on the trans kickdown lever as soon as you push the throttle. As you say, the slot is there to allow the throttle to close unimpeded.

Not sure I've explained this very well, but hope it helps! I do have a spare one piece linkage if you need it.

[MattH]

Adam, mine seems a bit different to what you describe. It has a slotted rod though.
I may have solved it by making this longer one.
Also threaded the throttle cable so the kickdown linkage doesnt push against the cable when moving backwards. Cable was pushing the linkage forward and it was going over centre and dropping down.
I now have Wide Open Throttle with the linkage set to its back stop.
Not sure where I may be missing a spring though?
The kickdown linkage springs forward on its own, possibly from the trans.

Pictures have explanations. I await any comments on what might look wrong. I did look at James' Demon last night but he has a cable shift so slightly different set up.

[Adam]

The slotted rod needs to be held forward against the throttle lever with a spring, so that it acts on the trans kickdown lever as soon as you touch the throttle (see pic - I know it's a Holley, but the principle's the same). You may need to adjust the linkage (or make a longer rod!) to maintain full throttle movement.

DSC08146.JPG (93.95 KiB) Viewed 2242 times

[MattH]

The slotted rod needs to be held forward against the throttle lever with a spring, so that it acts on the trans kickdown lever as soon as you touch the throttle (see pic - I know it's a Holley, but the principle's the same). You may need to adjust the linkage (or make a longer rod!) to maintain full throttle movement.

DSC08146.JPG

I just saw James Demon in the petrol station and he said the same. So it looks like I need to make another rod with a slot that starts further towards the front of the car, and get a spring to hold the two together.
This picture is very helpful Adam, thank you.

[MattH]

So it seems to work. I got anew pair of throttle springs from USAutomotive as well as a carb spacer to raise the air filter base away from the carb.
The kickdown rod now has tension pulling it towards the front and the throttle closes properly and ticks over.
It got me to the MMA meet and back, seems to go OK but lack of thermostat means its slow to warm up and bogs slightly, not helped by the electric choke wired off.

I'll be going to Brooklands Sunday for the Motor Sport day, so that will be a good test, but thanks to the advice I am happy to drive it now.

Maybe that spreadbore Holley will be the next step now Ive got a bit of a clue what I'm doing?

[Super Sloth]

I had to buy a threaded extension for my throttle linkage for the 4 barrel swap.
You do need to make sure you get the transmission linkage set up right. This tells the box what line pressure it needs to make and if it's not setup correctly you'll kill the gearbox.
It needs to be setup such that when the throttle is all the way back the trans linkage is also all the way back. When you push the linkage back you should make it click into "kickdown". You can then set the upper section with the drill bit as Adam desdcribed and then adjust the the linkage at the vertical adjuster.
I'm making the assumption that my A body linkage matches what you have and invariably ma mopar likes to throw in different combinations to confuse us all!

[Blue]

That's it in a nutshell. When you change to an aftermarket carb and/or intake you usually have to modify the throttle cable bracket and the length of the first part to the kickdown linkage to achieve the above.

[MattH]

Well it got us to Brooklands and back, seems to use more fuel possibly and maybe a bit more mid range torque. It is also a cow to start and keep running until warm. I suspect I need to get the choke working.

I can see why I left the 2 barrel on for so long, it just worked!

[Pete]

They are great as long as it does not have "Edelbrock" written on it.....We call those "Idlesh1tes" at work....

[Super Sloth]

It might be a bit oversized or need a bit of setting up? You will have to catch and hold it on the pedal if you've just wired the choke to the stop.
It shouldn't be consuming more fuel if you're driving it in the same way as when it had the 2 barrel and it's set up properly. Mind you, if you're using the extra power it offers, then that'll happen anyway. Take the lead weights out of your shoes!

[MattH]

It does need seeting up, its a Carter not an Edelbrock but I know most swear by Holleys.
The choke is just wired open, I can probably wire up the electric choke to help it run better from cold. Just time at the moment!