Edelbrock vs Holley - Vacuum or Mechanical? - Chevelle Tech
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post #1 of 17 (permalink) Old Jun 1st, 04, 8:57 AM Thread Starter
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I currently have a fairly new Edelbrock 600 CFM 4150 4 barrel with a Performer RPM manifold on my SB 350 Chevelle – just bought the car, 4 speed manual also. In cruising around, and then stomping on it a bit, I was hoping to get the rush of the back two barrels kicking in, but I don’t get that sensation. It feels like it might be a gradual opening.

I remember from my youth my friend’s 396 SS with a Holley dual pumper. The mechanical linkages for the secondaries were not initially hooked up, but when we figured out how to reconnect them…it felt like the car was powered by a jet when they kicked in...I want that feeling back!!

The Edelbrock is a what I would call a “quasi” vacuum type secondary…it has that counter weighted flipper valve, whereby the good old Holley can come with the mechanical secondaries. I see they come with vacuum secondaries, but I am worried if I buy one with vacuum instead of mechanicals I will be stuck again.

What do you think?

'72 Chevelle, 350SB, M-20, 12 bolt 3.07 pos, 600 CFM Holley 4160, Performer RPM Man., 2.02/1.6 heads, #2102 Cam, Mallory HEI, DynoMax 2.5" Ceramics
1st Velle
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post #2 of 17 (permalink) Old Jun 1st, 04, 10:19 AM
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An Edelbrock 4150? I thought that was a Holley series.

Here'a a link to Holley's technical page explaining the difference between the secondary actuating systems and the effects of each:

http://www.holley.com/HiOctn/TechSer...o/FMCTech.html
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post #3 of 17 (permalink) Old Jun 1st, 04, 10:21 AM
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You probably need to post more details about your combo, however that kick in the butt is not necessarily indicative of power, sometimes it can be because of a mismatched mechanical secondary carb. If this is a street car, stick with vacuum secondaries, you'll be much happier. And the power should come on smoothly unless the car is an auto trans and it downshifts.

Tim Shea
72 Malibu w/ZZ4, Muncie M20 and 3.73 12-bolt.
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post #4 of 17 (permalink) Old Jun 1st, 04, 12:23 PM Thread Starter
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Thanks for the feedback. My mistake also, it's an Edelbrock #1405 (600 CFM), and I am looking at a Holley #4150 (600 CFM) - List 4776 with mechanical secondaries. Street car.

I actually want to get the "kick in the pants" (as in the the downshift feeling with an automatic) instead of the power just gradualy coming up. I've been to the Holley site and read all their technical info between mech and vacuum -and it seems you could go either way.


Cast your vote, the more the better

Vacuum or Mechanical?

Many thanks.
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post #5 of 17 (permalink) Old Jun 1st, 04, 1:48 PM
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I don't think that a mechanical or a vacuum will be much different on the street if both are tuned properly. It could be that the 600 cfm carb is too small for your engine, but I don't know all the specs to your mill. I know "they" (whoever they are) say that DPs work better with stick shifts, but I'm not certain.

I think you'll be fine with a 750 cfm 4150 vacuum secondary... I only chose holley because I have experience with them. I also think a Q-jet would be a good fit for your application. They do have some large secondaries
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post #6 of 17 (permalink) Old Jun 1st, 04, 4:28 PM
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Quote:
Originally posted by Fried_Guy:
I don't think that a mechanical or a vacuum will be much different on the street if both are tuned properly.
Not trying to be a jerk, but how can your right foot possibly do a better job of providing air and fuel to your engine when it needs it then the engine can? That's the difference between a mechanical and vacuum secondary carb. With the mechanicals, they are going to open as soon as your foot goes down whether the engine needs or wants the extra air and gas or not. A vacuum secondary lets the engines vacuum signal tell it when it's time for more. Remember, we are talking street. If you drive your standard shift with the right foot planted all the time, then maybe a mechanical is not going to hurt. But then that's kinda tu\ough to do on the street. I have owned both types of carbs on street cars, and I never was able to get a mechanical carb to perform as well as vacuum. Of course that could be my lousy tuning skills (but I don't think so )

Tim Shea
72 Malibu w/ZZ4, Muncie M20 and 3.73 12-bolt.
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post #7 of 17 (permalink) Old Jun 1st, 04, 8:34 PM Thread Starter
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Thanks for the passion gentlemen in your replies. Then would you consider Edelbrock's form of secondaries on par with Holley's more traditonal vacuum secondaries? Again, the Edelbrock has that countereweighted flapper, not true vacuum.

??????
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post #8 of 17 (permalink) Old Jun 2nd, 04, 12:57 AM
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Well i can tell you from personal experience that when I switched from a 600 edelbrock to 600 holley vacuum secondary there was a big difference. Granted the edelbrock was probably a few years old and when I took it apart the floats were a bit out of adjustment but the off idle response in the holley is great. Easy to tune, I love it. Here are the 2 things I recomend if you buy a standard 600vs holley, buy the secondary metereing block and quick change vacuum set and springs of course out of summit. Basically you are turning it into a street avenger but saving about 60 bucks. With springs so easy to change you can test all you want. Trust me, when I went from the stiff spring is it came with to the lighter plain spring it made a big seat of the pants difference. Their fun little carburators. Ya you have to tune every once in a while, I always hear people complain about that, but thats why we own muscle cars, If you want a constant ****y drive buy a new p.o.s. Get the holley dude. Solved most of my problems especially with start up. By the way i have had it for a year now with no problems. Since then 3 of my buddy's changed from edelbrock to holley.
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post #9 of 17 (permalink) Old Jun 2nd, 04, 6:40 AM Thread Starter
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Thanks 70Chevelle!...that's the type of real world experience I was hoping for...plus all of the other posts. Holley it is, and I'll try the vacuum secondaries....light spring of course!
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post #10 of 17 (permalink) Old Jun 2nd, 04, 1:27 PM
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Fuel mixture is fuel mixture. If it's right, and enough, you have good power. If it's not right, and /or not enough, you have less than good power. I guarantee you that your engine does not know or care what brand or style carb is sitting on top.

ON THE STREET, you should not need a mechanical secondary carb. A PROPERLY ADJUSTED vacuum secondary (or air valve, as the case may be) carb is all you need.

In short, do some tuning of the parts you have.
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post #11 of 17 (permalink) Old Jun 2nd, 04, 1:44 PM
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I will agree with TPShea and everybody else...

With a properly tuned carb, you shouldn't feel the secondaries open, as they should do it gradually, allowing the engine to ingest the NEEDED amount of fuel/air...

I guess its your choice, but WHY spend money for another carb that will likely not increase performance of mileage, only giving you a "kick" in the pants?

I think you might also have your little "350" confused with the power of your friends SS 396...


I will strongly agree with Schurkey... For a mild street motor, I really doubt you will see a performance difference going from Edelbrock to Holley... I know several people that have switched from Holley to Edelbrock, with NO loss in performance at the track, NO loss of performance feel on the street, AND BETTER driveability... One car actually ran faster with the fresh Edelbrock versus a Pro-tuned Holley (mid-12 second car)...
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post #12 of 17 (permalink) Old Jun 2nd, 04, 2:15 PM Thread Starter
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Thanks Team for all of the input. I think I will go with the Holley with vacuum secondaries. I just don't have the confidence in that weighted flapper valve on the Edelbrock secondaries compared to a true vacuum secondary as with the Holley's.

drielly
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post #13 of 17 (permalink) Old Jun 4th, 04, 5:53 AM
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Quote:
Originally posted by 70chevelle15:
Well i can tell you from personal experience that when I switched from a 600 edelbrock to 600 holley vacuum secondary there was a big difference. Granted the edelbrock was probably a few years old and when I took it apart the floats were a bit out of adjustment but the off idle response in the holley is great. Easy to tune, I love it. Here are the 2 things I recomend if you buy a standard 600vs holley, buy the secondary metereing block and quick change vacuum set and springs of course out of summit. Basically you are turning it into a street avenger but saving about 60 bucks. With springs so easy to change you can test all you want. Trust me, when I went from the stiff spring is it came with to the lighter plain spring it made a big seat of the pants difference. Their fun little carburators. Ya you have to tune every once in a while, I always hear people complain about that, but thats why we own muscle cars, If you want a constant ****y drive buy a new p.o.s. Get the holley dude. Solved most of my problems especially with start up. By the way i have had it for a year now with no problems. Since then 3 of my buddy's changed from edelbrock to holley.
On a heavier car I've heard it's best to use the stiffersprings to prevent bog. How did you get them to work?Or was this not in your Chevelle?

'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
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post #14 of 17 (permalink) Old Jun 4th, 04, 6:27 AM
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Quote:
Originally posted by Junkyard Dawg:
On a heavier car I've heard it's best to use the stiffersprings to prevent bog. How did you get them to work?Or was this not in your Chevelle?
I run the lightest spring on my 750 3310..it has gone the fastest with that spring.My car weighs 3945 lbs. w/me,plus I have highway gears.No bog here..very,very responsive.Right out of the box too,other than the spring kit and going up to 74 primary jets.But,what works with a 454 in a heavy car might not work in a slightly lighter small block car.The purple spring is a good starting point IMHO.
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post #15 of 17 (permalink) Old Jun 4th, 04, 6:51 AM
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Gee.....and I have had just the opposite experience with the Holley being lame and the Edelbrock being a real thumper. I

The secondaries of the Edel is considered mechanical and the "flapper" butterflies open instanteously, so there is no delay! I have tested to many of these on different engines on the dyno and can tell you that mechanicals will do the job just fine.

It's tuning the carb that counts the most, so do your homework. YOu will find out that Edels are the most stable, easiest to tune, and offer the best metering (for throttle response and gas milage) because of inherent design and best of all have no gaskets below the fuel line making for a clean carb all the time. Holley double pumpers are a waste of gas most of the time and four corner idle is hard to get stable with some cams. I even have the new Demon series on my 69 Camaro ragtop....looks good but idles is unstable ....so that it's coming off.

My guess is that after spending a few bucks on a new Holley you will be just as disappointed. I would work on your Edelbrock.
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