[yak]

i am rebuilding a brand new 6709 holley carb . just rebuilding because its been sitting 25 years probably- has 65 primaries and i forget the secondarys- it is a spread bore double pumper carb with 650 primarys and 850 or maybe 750 secondarys. engine is a full roller 400 stroked to 455 with around a .535 lift cam, 4 gear and 3.23 , 1975 455ho trans am, would 72 primary and 82 secondary jets be a good start?
just bought it couple weeks ago and the rochester on it is screwy....thanks

[DevoBuzz]

I think so. Im running 73/80 on my combo in my sig.

[74Grandville]

that is an interesting carb with a small primary. i would leave the 65 to start and run a secondary jet around 78-80. holley shows that carb having a 76 secondary from the factory. you'll need an air fuel meter to really dial it in.

[Tom Vaught]

Originally Posted by yak

i am rebuilding a brand new 6709 holley carb . just rebuilding because its been sitting 25 years probably- has 65 primaries and i forget the secondarys- it is a spread bore double pumper carb with 650 primarys and 850 or maybe 750 secondarys. engine is a full roller 400 stroked to 455 with around a .535 lift cam, 4 gear and 3.23 , 1975 455ho trans am, would 72 primary and 82 secondary jets be a good start?
just bought it couple weeks ago and the rochester on it is screwy....thanks

You actually have a very unique Holley carb there yak.

It is a 4150 Double Pumper Carb, not a 4165 or 4175 Spreadbore carb.

It was designed for Ford Vehicles (trying to get better gas mileage on the 428 cid engine)
so they used a 650 cfm 4150 Primary Throttle Blade and a 850 4150 Secondary Throttle Blade. So your question about using a 72 Primary Jet and a 82 Secondary Jet is pretty close for a first attempt with the carb. For the Ford to run they needed at least a 68 jet in the Primary.

I would put 6.5 Power Valves in it starting out. Should have decent idle vacuum on a 455 engine.

Nice Score there.

Tom V.

[72LuxuryLeMansLa.]

Originally Posted by Tom Vaught

You actually have a very unique Holley carb there yak.

It is a 4150 Double Pumper Carb, not a 4165 or 4175 Spreadbore carb.

It was designed for Ford Vehicles (trying to get better gas mileage on the 428 cid engine)
so they used a 650 cfm 4150 Primary Throttle Blade and a 850 4150 Secondary Throttle Blade. So your question about using a 72 Primary Jet and a 82 Secondary Jet is pretty close for a first attempt with the carb. For the Ford to run they needed at least a 68 jet in the Primary.

I would put 6.5 Power Valves in it starting out. Should have decent idle vacuum on a 455 engine.

Nice Score there.

Tom V.

What would you know about Holley Carbs?

[tom s]

So Tom,it takes the 4150 bolt pattern and not the spread bore?Tom

[Formula jg]

As an option you can tune the primary side by disconnecting the secondaries then do all your testing like tip-in, throttle crowding, very low speed cruise (like driving in a parking lot type speed), neighbourhood speed cruise and partial throttle stab just no WOT testing (you can do that after you've nailed down the primary side).

[74Grandville]

Originally Posted by Tom Vaught

It is a 4150 Double Pumper Carb.

It was designed for Ford Vehicles (trying to get better gas mileage on the 428 cid engine)
so they used a 650 cfm 4150 Primary Throttle Blade and a 850 4150 Secondary Throttle Blade. .

Looking at the holley specs though the venturi on both primary and secondary are smaller than a normal 650/850. Ventries are almost like a 550/750 that is why I was thinking the smaller jets.

Holley states it's 750cfm carb. it's almost like a 950 type carb with the small venturi and large baseplate.

[Tom Vaught]

Originally Posted by tom s

So Tom,it takes the 4150 bolt pattern and not the spread bore?Tom

Correct. 4150 bolt pattern.

Kind of a Hybrid carb that was supposed to allow some of the features of the spread bore carbs for the guys with 4150 type intake manifolds. Not many sold.
A Pair on a dual quad intake (Inline not turned sideways) would work pretty good.
Holley sold a bunch of them for the 406 and 427 dual quad intake manifold guys.
Still rated 750 cfm but not equal throttle plate size like a normal 750 DP.

Tom V.

[yak]

Definitely an oddball carb. Have to turn idle screws wrong way to lean out and bowl and plate gaskets in a trick kit dont fit

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[Formulas]

Its like my 7010 carb except mine is vacuum secondary .. I swapped another front float bowl on mine .. tried to convert it to lower transfer slot/ifr. metering by removing the imulsion/down tube then installing a drilled set screw in the plate face now it doesnt get enough fuel at all near closed throttle.. will have to play some more with it

[Tom Vaught]

Great pictures, especially the throttle blades picture showing the special Number "107" Primary Blades and the Number "180" Secondary Blades.
As many know, spread bores used the larger Dominator type 2.0" rear blades vs the 180 blades used on the 850 cfm carbs.

So that picture just proved my point and posts that you have the special small primary large secondary '4150 style carb vs a true Spread Bore 4165/4175 style carb.

Tom V.

But there will always be doubters to any post made.

[PAUL K]

Interesting that it uses the anti-pullover style accelerator pump nozzles.

[Formulas]

#7010

[Bruce Meyer]

Originally Posted by PAUL K

Interesting that it uses the anti-pullover style accelerator pump nozzles.

Also interesting is it looks like it has large (REO) accelerator pumps on both ends.

[Tom Vaught]

Take another look Bruce, had be confused too for a minute.

The carb has bee played with. It has a 50 cc pump housing with a 30cc arm on the front and a 30cc pump housing on the rear. 50cc pump housing has the recessed screws in the housing. 30cc housing has the exposed screws. 30 cc pump arm will have the black hex on the plunger head and the spring is attached to the lever.. 50 CC pump would use the larger spring housing pump arm.

That being said, some of the "Ford Carbs" were Emission 750s with the reverse idle system (screw controls air and not fuel/air mixture) fixed fuel orifice in the idle circuit.

Tom V.

[yak]

Originally Posted by Tom Vaught

Take another look Bruce, had be confused too for a minute.

The carb has bee played with. It has a 50 cc pump housing with a 30cc arm on the front and a 30cc pump housing on the rear. 50cc pump housing has the recessed screws in the housing. 30cc housing has the exposed screws. 30 cc pump arm will have the black hex on the plunger head and the spring is attached to the lever.. 50 CC pump would use the larger spring housing pump arm.

That being said, some of the "Ford Carbs" were Emission 750s with the reverse idle system (screw controls air and not fuel/air mixture) fixed fuel orifice in the idle circuit.

Tom V.

Although it's possible the carb has been messed with I think it's pretty unlikely. Guy bought it new and put in on a 318 used it for a day then bought a smaller cfm one. Sat in the box from the replacement carb in his shop until he told me to take it.

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[yak]

Originally Posted by PAUL K

Interesting that it uses the anti-pullover style accelerator pump nozzles.

Never even noticed they were different. Any advantage to these? Never seen them before

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[Tom Vaught]

Originally Posted by yak

Never even noticed they were different. Any advantage to these? Never seen them before

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Would someone please stop sending the massively oversize pictures to the threads.
It just royally screws up the discussion in most cases. In this case because the picture was 100 times larger it made it very easy to see the numbers on the throttle blades.

That being said, you get a small primary on a larger engine like a 428 engine you can generated enough "pull" on the shooter discharge holes to cause them to "pull-over".
So the "Pull-Over" shooters were installed for that application vs the normal shooters.
Put a regular shooter on the carb and probably will have shooter pull over issues at given speeds.

Some carbs actually have a bleed hole in the accelerator pump circuit passage to help in that area when using a normal shooter. More than one way to fix an issue. But a hole leaks fuel baack into the bowl too vs going to the engine.

Tom V.

[Tom Vaught]

Originally Posted by yak

Never even noticed they were different. Any advantage to these? Never seen them before

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Would someone please stop sending the massively oversize pictures to the threads.
It just royally screws up the discussion in most cases. In this case because the picture was 100 times larger it made it very easy to see the numbers on the throttle blades.

That being said, you get a small primary on a larger engine like a 428 engine you can generated enough "pull" on the shooter discharge holes to cause them to "pull-over".
So the "Pull-Over" shooters were installed for that application vs the normal shooters.
Put a regular shooter on the carb and probably will have shooter pull over issues at given speeds.

Some carbs actually have a bleed hole in the accelerator pump circuit passage to help in that area when using a normal shooter. More than one way to fix an issue.
But a hole leaks fuel back into the bowl too vs going to the engine.

Tom V.