holley carbs

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Generically speaking, carbs can be lumped into 2 different categories...vacuum secondary or double pumper. Vacuum secondary carbs are when the secondary throttles are operating by a vacuum signal. They can be identified by a vacuum pod on the carburator. Double pumper carbs are when both primary and secondary throttles are mechanical driven. There are no vacuum pods on these carbs and can also be identified by accelerator pumps on both he primary and secondary side of the carb. There's more to it but that's it in a nutshell.
 
Good explaination.

When you look at a double pumper, for the most part, you can see a picture of them at Summit racing, they look like a naked carb, nothing really on them. Just linkage on the drivers side, fuel lines on the passenger side. No round tilted dash pot for the secondary operation.

The twin squirters are seen looking into it, but the pumps can be seen from the outside of the carb, down low, underneath at the corner on the fuel bowls.

That is it for Holleys.

Note that all Carters are mechanical in secondary operation. There secondarys can be held back from opening when it is to cold. Choke linkage disables there operation. But once warmed up, they'll open like a Holley double pumper. The air door above them, weighted or spring loaded is not so much a vacuum operation as it is more of a air velocity operation. And thats what puts the Carters into a vacuum operation type catogory. (Humm sp?)

It's the same idea working on a different angle. You can make a Carter operate ethier way. It just takes work to do it.
 
On the carter the secondaries won't pull fuel until the air door is open. The throttle plates (the ones in the bottom of the carb) are what is mechanical. Ya can't make a Carter a full mechanical secondary carb. The closest you can come to that would be (on an AVS) to remove all tension from the air valve spring or (on an AFB) break down the carb, remove the air valve assembly and remove weight from, or entirely remove the counterweight(s)
 
The previuos people summed up the difference between vacuum and mechanical secondaries pretty well but there are some other important differences:

4150 vs. 4160 series carbs.

Almost all Holleys have a primary metering block with 2 jets, one for each primary barrel plus a power valve that adds additional fuel when the manifold vacuum drops below a certain value. There will also be two idle mixture screws that (obviously) control fuel added at idle. Again, there is one for each barrel.

The 4160 style carbs use a metering plate (not to be confused with a metering block) that has pre-drilled holes that meter fuel into the secondary barrels once the throttle valves starts to open.

The 4150 style carbs use a metering block with interchangeable jets. Some Holleys use a power valve in the secondary metering block and some don't. Those that don't stagger the jets with jet sizes being about 6 sizes larger in the rear metering block vs. the front.

There are also single and dual feed, center pivot and side pivot floats, with or without choke towers, mechanical or electrical chokes, four and two idle circuit carbs and those with interchangeable air bleeds.

Any questions? :)
 
I don't think he'll EVER ask another question:toothy10:
 
68 Sedan said:
Ya can't make a Carter a full mechanical secondary carb. The closest you can come to that would be (on an AVS) to remove all tension from the air valve spring or (on an AFB) break down the carb, remove the air valve assembly and remove weight from, or entirely remove the counterweight(s)
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The throttle plate opertaion can allways be made to operate. You just need to remove or modify, aka cut off a tang, in order for the secondarys to allways open up.

Do not remove the counter weighted secondary door and reassemble the carb without it. Just incase you misread/understand what 68 means. Just remove enuff weight till it stays open. (Not a great idea IMO, but if your car can handle it, then by all means........)

As far as getting a secondary squirter to work, check out this shot of a modified AFB.

Note the secondary squirters and the adjustable rod set up.
Owner of the carb told me the rod was modified to a long slope rather than a step rod. Then straightened and threaded with jam nut, locking nut.

He didn't say how he ran the plumbing for the secondary squirter, but I poked around a few carbs I have. I think it easier to run it external rather than through the carb.

No word on the air horn.

ABF metering2.jpg
 
The web site for Holley is Holley.com. There is a lot of useful technical info there.
I worked at Holley in Detroit for 10 years during the late 70's. Man, I missed the good years by 10 plus years. I used to hear some perty good stories from some of the older engineers. I would eat lunch with Zora Duntov in the caferteria when he was doing intake manifold design there after he retired from GM. I would bug him about my '69 'vette...:pirat:
 
1BADGTS said:
The web site for Holley is Holley.com. There is a lot of useful technical info there.
I worked at Holley in Detroit for 10 years during the late 70's. Man, I missed the good years by 10 plus years. I used to hear some perty good stories from some of the older engineers. I would eat lunch with Zora Duntov in the caferteria when he was doing intake manifold design there after he retired from GM. I would bug him about my '69 'vette...:pirat:
Click to expand...

Pretty cool! Even though I consider Zora the enemy, I would have loved to pump that guy for info. BTW, when I was in HS a friend of mine's aunt had a red '69 vette. She was absolutely beautiful and so was her car. :) IIRC, it was a 396 but that was a long time ago.

You're absolutley right, the Holley site has just about everything anyone would need to know including theory, list # pdf, and tuning help. I cut my teeth on Holleys as a young hot rodder in the early 80's and I just haven't found a reason to run any other carb. Shoot, I'm even running a list 4777 double pumper on my 5000# truck which is not supposed to work at all and the response after tuning is phenomenal. Zero bog and plants me right in the seat IMMEDIATELY off idle. I bought the carb used and of course, the throttle shaft bores were worn so I replaced it with a Quick Fuel base plate.

I think Holleys get a bad name due to people getting a used carb with blown power valves, bad needles and seats, unscrupulous drilling by a previous owner and just plain bad tuning. A little reading goes a long way.

Holleys have been around since before my late father was born and he was born in 1921. I'm proud to have a Holley ex-employee on this site and I hope everyone else feels the same way. Have a beer on me my friend and I hope to meet you someday to hear the stories from the Holley plant. :cheers:
 
ok thanks, that cleared up alot, now im looking at buying a 650 double pumper and right now just have a used 600 holley with vacum secondaries on my 360 to see how i like the holleys. I like the 600 with v/secondaries alot better than my AFB. What is the advantage to running mechanical secondaries against vacum secondaries? would this be a good rout to go?(buy the 650 DP?)
 
thanson_mopar said:
What is the advantage to running mechanical secondaries against vacum secondaries? would this be a good rout to go?(buy the 650 DP?)
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The advantage would be secondarys NOW! when you want them.

For a performance engine/car, yes, it is the way to go.

Theres one little tiny catch to the DP though. You'll need to be able to use the extra cfm's when you want them and that could cause a problem if the set up is not ready for them.

You'll have to tune the carb just so. To much throttle opening to early will cause a bog and the race.

Things that favor the use of a DP are;

A lighter car
Steep gears
High stall
Manual trans cars DP's.
A slightly smaller CFM needed for the cars engine is the way to go for a street car of mild performance. (This will keep velocity up when all barrels are opened to early vs a larger carb that will kill velocity and performance.)
Of hand, I don't remember your engine size and specs, but a 650 will work well on most everything small block, OE, cid.

Your foot can control most problems, but then again, the foot gets you into most problems. He he he.
 
rumblefish360 said:
The advantage would be secondarys NOW! when you want them.

For a performance engine/car, yes, it is the way to go.

Theres one little tiny catch to the DP though. You'll need to be able to use the extra cfm's when you want them and that could cause a problem if the set up is not ready for them.

You'll have to tune the carb just so. To much throttle opening to early will cause a bog and the race.

Things that favor the use of a DP are;

A lighter car
Steep gears
High stall
Manual trans cars DP's.
A slightly smaller CFM needed for the cars engine is the way to go for a street car of mild performance. (This will keep velocity up when all barrels are opened to early vs a larger carb that will kill velocity and performance.)
Of hand, I don't remember your engine size and specs, but a 650 will work well on most everything small block, OE, cid.

Your foot can control most problems, but then again, the foot gets you into most problems. He he he.
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ok, well my engine is a 360 with ported J heads that have the 2.02 intake valves, it is a manual trans. runs aprox mid 13s right now but the carb on it right now needs some tuning(should just be slight float adjustmetn). I believe a 650 should be perfect size and if adjusted properly my car should run low 13s, possibly high 12's. am i on the right track here?
 
Low 13's should be esay enuff. Alot is also in the suspension and so on.......
 
I ran a 750 dp with 4 corner idle on my 360 and it picked up 2 1/10s over the carter based eddie I had on there
 
Tate, theres not enuff info for a real recomendation, but I'd do a 750 to start with period.
If the cam is a bit radical, the like Daredevil has/had, the 4 corner idle system unit I'd look at.
 
Not enough carb on a 360 with decent heads.

340+ inch mopars tend to like more carb than you may think or the calculators spit out.
 
also what is four corner idle?
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A 4 corner idle system is two more idle circuts in the secondary side.
http://holley.com/0-80535-1.asp

ok, well i should look for a 750 DP then?
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Tate, would you send me a pm listing every detail of the engine. Your questions are good IF I knew what I was working on. I have no clue except what you have provided.

On a dead stock 360 smog engine I'd use a 750 all the way up to when I had my 10.5-1 360 with RPM heads and intake, super comp headers w/ 3 inch exhaust and a whopper of a cam, 4 spd w/ 4.10's.

A regular 4150 750 will do the trick on most any med. to large OE sized small block. Even better when built up.
 
I ran a 650 DP on my Duster 340, never ran out of carb. It took a bit of twiddling to get it tuned spot-on, but once there, it was in the sweet spot!
 
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