Got my new carb today.

OK, it aint new, but this one is close. Its the big bore (1.12) series, around 600 cfm. In my opinion, its the best street carb ever made. Back in high school, we used to make a simple bracket that turned it into mechanical secondaries. I remember basically what it looked like and I've been studying the linkage and pretty sure I got it figured out. I'll work on it this weekend. It is going on my Comet GT.

 

Them Are Neat I Got 2 Of Them

 

I have a stock manifold that went with one of them.

 

What no Holley???

 

I have one in need of a rebuild-1.12 venturi, off of a 390. Pony Carbs swears they are the best all around 4V ever made.

Seth

 

What is it?

 

If the secondarys are not mechanical, then what opens them?
I don't see a vacuum diaphram...

If they are anything like other carbs, you will mess it up by making it mechanical because there is not a secondary pump shot to bring the secondarys on.
Is this a carb with double pumps and secondary squirters?

 

It's a stock Ford 4v carb.
Off a bigger engine of course, to get the 600 cfm.
SBF versions tended to be around 400 cfm or so.

It was labeled Autolite.
Motorcraft parts came later...

 

Cool, thanks for clarifying.

I thought it looked kinda stock, but not like anything i have ever seen.

 

This is off of Pony Carb's web sight.

 

The vacuum diaphragm is mounted on the back of the 4100 carbs. You can just see the top of it in the picture.

 

As I remember, we did not have an issue. Guess I will find out when the time comes.

 

Okay.
Vacuum carbs don't open the secondarys until the secondary circuit is already in a ready state, or "on"... Therefore no pump shot is needed to cover the opening of the secondarys and 'jumpstart' the secondary circuit.

When you have mechanically opening secondarys, the secondary circuit will not be available instantly since you decide when they open. If you have no fuel to prime that circuit, you create a big 'hole' in the fuel air mix, or a huge momentary vacuum leak. This causes a short crashing in of the secondary circuit.
Most folks take their 1650 or 3310 and put a screw in the linkage to make it a mechanical secondary, then rave about how they can feel the secondarys "kick in", when they are actually feeling the bog of the 'hole' and the crashing of the engine for a moment.

I am not going to say you are wrong, I know nothing about the Autolites... you definately got me there. But if the vacuum secondary is engineered to open when the secondary circuit is flowing (or ready to flow), then forcing it cannot be a good thing.

 

Let's put it this way:
You seem to put weight in what Pony Carbs says.
eMail them a quick note asking if it helps to make this particular carb mechanical.
Can't hurt a thing.
They note that they make mods to their version.
If this is a proven pro/con, they would certainly know it.

 

That definitely rings a bell. Your probably right about that. Especially depending on where you are in the rpm range when they kick in. I always ran manuals which took it better than the automatics did. They did kick in hard. I will still make the part and see what happens. It is easily removed if I dont like it. Then again, I could just send it to Pony Carbs and let them work their magic on it. I know when the secondaries kick in on my Demon, there is no bog, it just pulls a lot harder.