Ford Forums banner

Dubbelpumper Or Secondry Vacuum

2K views 17 replies 12 participants last post by  xdclevo 
#1 ·
Good day all!! This is a wonderfull forum and I visit/read often. I am new and are from South Africa. The V8 era is long past in this country with only manufacturers BMW, Daimler Chrysler having V8's in some models. I bought a Fairmont GT 351C 4V Auto not so long ago and would like a bit more oomph without having to strip engine or heads. Someone advised a performer inlet manifold with 750cfm carbie. This is not a daily driver, I use it for my enjoyment and the occasional drag 4 or 5 times a year. I need to know:
1) Which manifld in Performer range: Performer or Performer RPM II
2) Which Holley carb 750with sec or mech vacuum or 750 dubbelpumper
3) Which eloctronic ignition and coil is suitable for this combination
Can someone provide the correct part no.s for me.
Any advise is happily received
Cheers vir eers (Cheers for now)
Daanp
 
#2 ·
daanp said:
I need to know:
1) Which manifld in Performer range: Performer or Performer RPM II
2) Which Holley carb 750with sec or mech vacuum or 750 dubbelpumper
3) Which eloctronic ignition and coil is suitable for this combination
Can someone provide the correct part no.s for me.
Any advise is happily received
Cheers vir eers (Cheers for now)
Daanp
1: I'd probably recommend using a Weiand Xcelerator, which I feel is a bit better of an intake manifold than the Performer for a 4V application. An Edelbrock Torker is a good choice, too. (Provide more engine/chassis details for a better recommendation.)

2: I'd recommend a Holley 750 double pumper with a 4V engine.

3: I use MSD exclusively, but the Accel and Mallory parts are also worthwhile, especially if you want a vacuum advance part.

Most of the part numbers are available from jegs.com or summit.com for any part that is still in production. Use ebay for sourcing parts that are no longer in production.

:davis:
 
#3 ·
I had a 750 vac secondary on mine, back then it made 270 rear wheel hp, i changed to a 750 double pumper and it went down to 265hp (this was 10 mins later)
But and it is a BIG BUT, i made a genuine 30 hp from start to top of the power curve more than the vacuum secondary until it tappered off 5 hp lower.
It completely changed the car, and was exactly what i was after.
Go the double pumper if you are racing it.
 
#4 ·
OK more questions... If I go for the Weiand Xclrtr option how will height affect the bonnet and shaker setup. This is a ausie 1972 Falcon XYGt which SA import a few of back then. I woukd like to keep the existing shaker setup if possible, even if I have to mount the shaker on top of bonnet. The car is FMX auto with 2.75diff. How will fuel consumption be affected with such a change? Thx for advice.
Daanp
 
#5 ·
Brenx uses a Weiand plus a spacer on his XB, he had to cut a hole in the bonnet for the air filter, i dont know if the XY is much different, someone here will know.
You need to change your diff centre to at least 3.5 if you want to drag (4.11 would be even better).
I also recomend the 750 double pumper and a good set of 4 into 1 extractors, with 2-1/2 inch twin pipes.
 
#7 ·
As for intake manifolds.i,m not aware of a performer rpm manifold for the clevo.The performer works to around 5500 rpm then power tapers off.If your intention is to rev hard as 4v.s like to do than you may want to consider something rather than the weiand excellerator.Whilst the 2v version is a great piece,the same cannot be said about its 4v counterpart.About the best dual plane 4v piece on the market comes from Blue Thunder from the US.I would prefer the Torker over the xcellerator (4v) anyday.alternativley look at other offerings from Parker,TFC or Active .
 
#8 ·
Race-double pumper
Fuel consumption-Vacuum secondary.
With a double pumper the secondaries are vitually always open, and hence will use double the fuel.
With the sec vacuum, the secondaries only open when there is sufficient vacuum created by the engine, and hence only using the two primaries, alot of the time.
 
#12 ·
TICK4D said:
Race-double pumper
Fuel consumption-Vacuum secondary.
With a double pumper the secondaries are vitually always open, and hence will use double the fuel.
With the sec vacuum, the secondaries only open when there is sufficient vacuum created by the engine, and hence only using the two primaries, alot of the time.
A little OT, but I thought that Vac Secs operated from lack of vacuum, not supply of it. :idk:

And fitting a DP does not in anyway mean double the fuel.

I have more than halved the fuel consumption of my 351 by fitting a DP.
 
#14 ·
If you are running a Standard Stall Converter and 2.75:1 Diff, I would not be running a Single Plane Manifold.
 
#15 ·
vac secondaries are progressively opened in relation to air velocity through the primarys (done via a venturi). rate is controlled via a spring and a groove in the check valve (that little ball that always rolls under the bench when you pop the secondary canister open).

Fuel consumption is more related to jetting and your right foot.

id go a DP for outright performance

What gears / stall and cam??
 
#16 ·
TTNOS8 said:
A little OT, but I thought that Vac Secs operated from lack of vacuum, not supply of it. :idk:

And fitting a DP does not in anyway mean double the fuel.

I have more than halved the fuel consumption of my 351 by fitting a DP.
OK lets look at it from another angle! If I use a 750 with mechanical secondry I may adjust it to operate similar to a DP. Right? What then is the real benefit of a DP. Every potensial dragster say, "If I can only fit a DP to my car" I will increase my ET by "X"seconds. Is this true or not? Isnt it perhaps a case of bigger is better or of what my mate fit to his car or just general talk we overhear?
 
#17 ·
Mech secondary and DP are the same thing.

DP's give fuel dependant on throttle position, where as a vac secondary gives it according to engine demand. A DP can be beneficial helping fuel the car past a potential soft spot.

Probably over simplifying things, but thats roughly it..
 
#18 ·
daanp said:
OK lets look at it from another angle! If I use a 750 with mechanical secondry I may adjust it to operate similar to a DP. Right? What then is the real benefit of a DP. Every potensial dragster say, "If I can only fit a DP to my car" I will increase my ET by "X"seconds. Is this true or not? Isnt it perhaps a case of bigger is better or of what my mate fit to his car or just general talk we overhear?
If you are talking about making a vac secondry into a DP, it is usually not recomended. If you have a double pumper, you require a "double pump shot" of fuel from the excellerator pumps. It needs this beacause in one hit you have the capeability of flowing 750 cfm. If it is a real vac secondary, when you crack the throttle, you will only be capeable of flowing 375 cfm, so it only needs a single shot of fuel from the acc pumps. Also, a DP has secondry jets and some have 4 corner idle adjustments. So best off keeping the carby how it was made.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top