650 Spreadbore Double Pumper?

[LR1970]

Can someone please explain to me how a 650 Spread bore Double Pumper works? Does the smaller primaries open before the secondaries?

Sorry but I'm new to this.

 

[rumblefish360]

Wow yea! You are new to this. OK, here we go....

The carb works as any other carb does. Primary side opens first to a certain degree. The exact amount I am insure of. But let's just say at approx. 50% of the primary side opening, the linkage of the carb starts to open the secondary side.
By the time your at full throttle, both sides of the carb are fully open.

The carbs linkage is set up in this manor to allow easy driving on just the primary side. The only carb where both side open up at the same time is the Holley dominator with 1:1 linkage. This is a all out drag racing carb.

I suggest two books. One for Holley and one for Carter carbs. The carbs are a little different from each other.

 

[Cranky]

You can also get other Holley carbs where the linkage opens all 4 barrels together besides the Dominator and have seen them on boats too. Haven't had much experience with the spread bore Holleys but what little I did have wasn't very good but the 4150 series have treated me well.

 

[LR1970]

Thanks, I was always under the impression that double pumpers opened together. When I saw a speadbore DP I was a bit confussed.

 

[rumblefish360]

Double pumper is a ref to the carb having a pump shot ability on both primary and secondary sides of the carb. You'll find them on mechanical secondary carbs from Holley. Not vacuum secondary carbs IIRC.

 

[WP29440SE]

Thanks, I was always under the impression that double pumpers opened together. When I saw a speadbore DP I was a bit confussed.

spread bore , is referring to the base plate bolt pattern where it bolts to the intake. some carbs are spread bore, some are square bore , and some are universal. most aftermarket intakes will accept both.

 

[Meep-Meep]

The Holley's that open all four barrels at once (really 5 deg of primary before secondaries kick in) is the center squirter. The popular one is the 660 CFM list 4223.