In another thread, brainsboy stated: These carbs (Edelbrocks) are great for someone who wants to bolt a carb on and go. They are what I call plug and play carbs. As for performance I have never liked them. The secondary system although advertised as mechanical has top throttle plates that are based on draw, or air demand. I have seen many guys think they are at full throttle but the truth is that the primarys are still doing 80% of the work. The secondarys can be adjusted for this by their counter weights. You can drill out weight to make them lighter. If you need heavier ones then you have to replace them with a different part number. Its kind of a pain and their isnt much information on these procedures. For what its worth in almost all cases you can pick up quicker times and more power by switching to a holly. With that being said they still make for a great daily driver street carb. I know my ignorance is showing, but how DO you tell when (if) the secondaries open and to what degree?
With the Edelbrock carbs you could try running without the air filter in place (not recommended) and see how far the "air flow plate" is opening.....
I hate to say it but that is not neccisarily a bad thing. If you are just slamming the secondarys open just to dump more fuel in there then you can easily end up running too rich. This is why the vacuum secondary carbs both holley and carter/edelbrock are preferred to run on the street over the double pumpers. But for most parts if you open an edelbrock to WOT with the car in neutral in your driveway the vacuum secondarys probably will not open unless you like to continuously rev your car at high rpm's in the driveway because neither the carburetor or the motor is not requiring the extra fuel or extra air. Anything more than what you need is just wasting fuel.
Aren't these air flow plates at the bottom of the carb? How can you get in a position to see what's happening w/o sitting on the engine (mine doesn't have a chair and that sounds particularly problematic if it only occurs going down the road). Seriously, how can I tell what's happening. I have an idea that I'm not getting much out of the secondaries. I didn't see a whole lot of difference from the original 2 bbl.
I should have added that it really doesn't matter as long as the air flow valve is properly calibrated for air fuel ratio - if it doesn't open all the way its because the engine can't use the extra air and fuel.
When you say calibrated, do you mean the lean adjustment I did when it was installed ot the jets that are built into it? (See, my ignorance is showing.) I get the feeling from the way my machine is performing that it dumps too much fuel in the very early stages and then not fully openning at the top.
That fuel is metered by your needles and jets, you can have too weak of springs and the needles will stay fully seated at the bottom causing a lean condition in the carb because of the vacuum pressure. Then when the vacuum changes sufficently enough the needles shoot all the way to the top of the chamber and create a rich condition. Another problem is you might have the wrong needle and jet size. The option for this is to buy a strip kit and change the jets and needles as needed. Alot of people just throw an edelbrock on a car and leave it without tuning it, or even adjusting the needles and jets for altitude, then they throw an Holley carb on and have to get someone to tune it in for it to even run and then of course it runs better and in turn edelbrock gets a bad rap because people dont take the time to learn about them. P.S. thank you Paul for clarifying your statement a little bit.
I guess I need to have some sort of "ruler" to be able to tell what is happenning compared to what should happen. Does the strip kit you mention have a way to tell other than changing parts and driving it to see? (My seat of the pants meter is probably not very accurate).
A A/f meter would be a hugh help in tuning it. But, like paul said if it doesnt need it it wont open the secondaries.
The plates are the butterflies on the top of the carb. The open according to air flow. If they dont open all the way you dont need the air flow. Assuming they are working correctly and nothing is binding up. You may not see much improvement over a 2 barrel on a stock engine. Nothing else has changed to increase the air flow. Cam,heads,exhaust,etc. You can go and bolt on a 650 double pumper Holley and I guarantee it will go slower than the Edelbrock on a stock motor.
If the secondaries are working right you won't feel them open. try disabling them and drive the car. See if it feels different. You can also use a twisty etc on the linkage to see if they are opening...
+1 if you look in your carburetor manual you will find a quick procedure on how to calculate the rod and jet sizes if you dont have it you can download it here http://www.edelbrock.com/automotive_new/mc/carbs_acc/carbs_access_main.shtml Also one thing I should ask is where is the vacuum advance on your distributor attached too, the manifold or one of the ports on the carb? The reason I am asking is because one of the ports on the front of the Edelbrock is metered just like the plastic valve that was on the vacuum line originally, the other port is a continuous vacuum. If you have removed the plastic valve from the vacuum line and attached the line to the continuous vacuum port then you can be advancing your distributor too soon, causing a performance loss.
It has a cam that gives a lumpy idle and headers, but stock heads. The vacuum line is hooked to the metered port of the carb.
I have used both carbs over the years and this is my meager experience with them. I think that the Edelbrocks are easier for the normal person to calibrate to their engines IF they study the manual and follow what it says to do using the trick kit that Edelbrock sells. That kit usually costs around $40 in addition to the carb. An Edelbrock usually runs pretty good out of the box on a near stock engine. Edelbrocks have more tuning options for the common person. On a Holley you need to have much more understanding to figure out the air bleeds and immulsion cicuits, drill the air bleeds or change them out on the nicer carbs etc. For all out performance a Holley will walk all over an Edelbrock in most casses. I think if someone bothered to look if Edelbrock still runs a race car my money says it has a Holley on it. lol People think a Holley needs adjusting every week but I don't have that problem. I am using a Holley 1850-600 vacuum sec. carb on my 460 F100 that I had on the 351w when it was in the truck. Runs like a clock but the 460 is milder than the Windsor was. Tried a 3310-750 and it was slower and less responsive. Sorry for the book, here alone as usual and thought I would add my 50 cents. lol clint
