Carburetor wizard…or someone that knows more then me

[Cheapsunglasses]

Hello everyone, I have a 4327s Carter on my 68 GTX low performance 440. I get great 13:1 afr idling. Acceleration it’s 11:1-12:1. But cruising is 10:1, I don’t know much about tuning carbs, but I do know 10:1 is little rich. I pulled #3 and #8 plug out to confirm it, here’s what they look like

The carburetor is a 3 step rod carb, it has .089 jets in the primary, I guess I should have looked at the secondary jets while I had it apart lol. And it has .065x.062x.053 metering rods.

Suggestions are greatly appreciated! And let me know if I need to give more information!

 

[pnora]

What plugs?

 

[Don Frelier]

I think the three step rods had taller jets. If someone changed them to a standard style then you may be running on the smaller steps. I would suggest using 2 step rods and jets from a matching strip kit.

 

[Cheapsunglasses]

What plugs?

I have 440 source aluminum heads on it, and the plugs are ngk r zfr6f 11g

 

[Cheapsunglasses]

I think the three step rods had taller jets. If someone changed them to a standard style then you may be running on the smaller steps. I would suggest using 2 step rods and jets from a matching strip kit.

I’ve read some afbs have 2 steps and some had 3 steps

I’ve found through an avs/afb 3 step rods are hard to come by and you use edelbrock 2 steps, would the edelbrock 1407 be a matching carb?

 

[Cheapsunglasses]

*This one being a 3 step

 

[pnora]

 

[pnora]

THE CARBURETOR SHOP / Carter AFB tips

 

[Cheapsunglasses]

View attachment 1303405

Well that’s interesting and informative, thanks. I thought the way to tell was 2 step has flat caps, and 3 step has bump ups, I also think I read on this forum it had 3 steps

 

[Don Frelier]

Yes the domed caps were for 3 step rods.
I made my own flat caps for an AFB with a little stainless, tin snips and a file.
I did some math on the jet size and rod dimensions you listed.
If anything I would expect it to be on the lean side. (It's pretty close to the standard competition series 625 cfm stock setup)
Maybe something else is wrong? Float level? Ignition timing?

 

[RJRENTON]

Hello everyone, I have a 4327s Carter on my 68 GTX low performance 440. I get great 13:1 afr idling. Acceleration it’s 11:1-12:1. But cruising is 10:1, I don’t know much about tuning carbs, but I do know 10:1 is little rich. I pulled #3 and #8 plug out to confirm it, here’s what they look like

The carburetor is a 3 step rod carb, it has .089 jets in the primary, I guess I should have looked at the secondary jets while I had it apart lol. And it has .065x.062x.053 metering rods.

Suggestions are greatly appreciated! And let me know if I need to give more information!

View attachment 1303401

View attachment 1303404

The plugs you show in your examples are 3/4" reach plugs. Someone has installed aluminum heads which almost always use 3/4" reach plugs. The standard heads on a 440 are iron, #906, and use 3/8" reach plugs. Perhaps the cam and other engine components have been changed......something appears to be "non-stock". Just my opinion of course.
BOB RENTON

 

[Cheapsunglasses]

The plugs you show in your examples are 3/4" reach plugs. Someone has installed aluminum heads which almost always use 3/4" reach plugs. The standard heads on a 440 are iron, #906, and use 3/8" reach plugs. Perhaps the cam and other engine components have been changed......something appears to be "non-stock". Just my opinion of course.
BOB RENTON

Did you not read what I posted? I changed to 440 source heads, everything else other than the intake is bone stock

 

[Cheapsunglasses]

Yes the domed caps were for 3 step rods.
I made my own flat caps for an AFB with a little stainless, tin snips and a file.
I did some math on the jet size and rod dimensions you listed.
If anything I would expect it to be on the lean side. (It's pretty close to the standard competition series 625 cfm stock setup)
Maybe something else is wrong? Float level? Ignition timing?

How can my engine be running lean, when the spark plugs are black, or do you mean the edelbrock 1407 would be on the lean side?

 

[Don Frelier]

How can my engine be running lean, when the spark plugs are black, or do you mean the edelbrock 1407 would be on the lean side?

I didn't say it was running lean, the jet size and rod combination you listed should be on the lean side.

 

[Cheapsunglasses]

I didn't say it was running lean, the jet size and rod combination you listed should be on the lean side.

Ah, that makes sense, thanks! I’ll look up what the spec is suppose to be on the float level, and I’ll see what mine is after work

 

[Cheapsunglasses]

Yes the domed caps were for 3 step rods.
I made my own flat caps for an AFB with a little stainless, tin snips and a file.
I did some math on the jet size and rod dimensions you listed.
If anything I would expect it to be on the lean side. (It's pretty close to the standard competition series 625 cfm stock setup)
Maybe something else is wrong? Float level? Ignition timing?

I reread what you wrote. I’m sorry I read it wrong the first time

 

[RJRENTON]

Did you not read what I posted? I changed to 440 source heads, everything else other than the intake is bone stock

SORRY....I just missed that info.....I was looking at the plugs...
BOB RENTON

 

[Cheapsunglasses]

SORRY....I just missed that info.....I was looking at the plugs...
BOB RENTON

Well I guess I’m wrong there too lol, it’s a stock low performance 440, with magnum manifolds. The engine came out of 40,000 mile 69 new port, original owner had it garage kept and it was a Sunday driver. Guy died, wrecker came to get it off the property, wrecker didn’t strap it down and off the wrecker it fell! Got the engine for $500, and it’s living happily in my car, well sorta happy

 

[66Satellite47]

THE CARBURETOR SHOP / Carter AFB tips

I think this explains why I was never successful at rebuilding Carter AVS or Thermoquad carbs. I remain a Holley guy.

 

[Geoff 2]

The plugs are too cold. Should be a NGK 5. Low speed cruise is controlled by the idle cct, not the met rods.
If the engine is modified in any way [ different cam, intake, headers etc ], it can change the transfer slot running position which will alter the delicate low speed balance.
Stupid question: have you made sure the choke is fully 'off'?