carbs

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moparmike98

moparmike98

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What's the difference between a mechanical and a vacuum secondary? Also what are your thoughts on a holley 750 ultra double pumper with edelbrock performer rpm airgap with a mopar 360 magnum crate engine unmodified in a 72 duster.
 
For a street car, you should lean toward a vacuum secondary. They only draw as much as they need.

Mechanical secondaries (double pumpers) can be difficult to tune the off line bog when stomping WOT in an automatic.
 
Vacuum opens the secondary via engine vacuum. it is adjusted in a Holley or similar architecture with a spring in a bod with a diaphragm.

Mechanical, the secondary open with with a mechanical linkage.

Double pumper means there is accelerator pump for both the primary and secondary circuits.
 
I would say for certain, use that carb and intake on that engine. The only draw back to it working well is;

Low stall converter
Numeric low gear set

Take the time to tune it and the distributor.
 
Go for it. Don't forget the 508/292 cam.
 
That's an excellent carb choice. Mechanical secondaries work great with manual transmissions and automatics with high stall torque converters.
 
As others said the back barrels of a vacuum secondary carb are opened via engine vacuum and it only has a single accelerator pump on the front circuit. A double pumper has an accelerator pump on both the front barrels and back barrels and the back barrels are opened by mechanical linkage. For most street cars a vacuum secondary works best.

That ultra double pumper is a great carb but we'd need a full run down on your setup to say if it's really right for you.

What 360 crate engine? There are a couple different HP versions
What transmission?
If auto trans what converter? (stock or high stall and if high stall how high?)
What rear gears?
Tire height (or size and I can figure it)?
Car weight with driver?
 
fishy68 said:
What 360 crate engine? There are a couple different HP versions
What transmission?
If auto trans what converter? (stock or high stall and if high stall how high?)
What rear gears?
Tire height (or size and I can figure it)?
Car weight with driver?
Click to expand...

I'm with fishy68 on this ^^^^^^^^^^.

Vacuum sec'd carbs can sometimes take some work/tweaking to get right, but when the're right, the're awesome. I'd prefer a DP whenever it's warranted, but we need to know more?
 
405hp version manual transmission unsure what one haven't figured out the gears yet. And bfgoodrich radial t/as 275-60-15 in back
 
moparmike98 said:
405hp version manual transmission unsure what one haven't figured out the gears yet. And bfgoodrich radial t/as 275-60-15 in back
Click to expand...

The double pumper should work fine with that combo. Those tires are right at 28" tall and the cam is big enough that you'll probably want a fairly low gear set such as 3.73's or lower (numerically higher)
 
Thanks guys that's going to be next on the list so thanks for the help. Right now I'm going to pick up some headers either dougs or tti steps
 
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