carburetor choice
 

Hi

I'm sure that the carburetor choice has been also an excessively present topic in the Forum , but i ask for advises , considering my particular situation.

To improve my engine's performance , I have to keep an eye at gas price ( now oil is above 100$...) and at avoiding possible car's failures due to high power. So I have to stay quite low at HP ( now my engine is quoted at about 350hp)

I can't work on replacing the cam or other extesive engine's job , so what remains is :
-engine's timing tuning
-carburetor

Iexpect to have a better mid-throttle response and higher torque in that region as soon as I set the timing properly.

New carburetor choice : mine is an edelbrock 600cfm , 1406 , leaner than 1405.

Should I stay with this carb and possibly go for a tuning kit to work a bit on it?
Or should I go for something different?

I was just thinking to 2 choices :

-Edelbrock AVS 650cfm ( a bit more perfomance in respectto my carb and the possibility to adjust secondaries ).I don't understand a thing of this carb : the secondaries are vacuum or mechanically operated?

-Holley 650 with mechanical secondaries

I have read that Corvettes with manual shift should require mechanical secondaries...Why?So no Edelbrock?

My target is not to reach merely high power , but to have good torque and progression in the power. I don't want power to come out only when pushing hard , but always at part throttle

thanks

RE: carburetor choice
 

Here is a link to Holley's Carburetor selector guide. I ran your numbers as a 383 engine with a maximum of 6500 RPM's and I opted for mechanical secondaries.The selector does say that your 600 CFM carb is on the light side. A 700 or 750 CFM carburetor will improve performance. I have a Holley 750 on mine.

http://www.holley.com/applications/C...bSelection.asp

[sm=icon_cheers.gif]

RE: carburetor choice
 

Aldo,
If you get the kit w/ the jets, metering rods and springs, you can properly fatten up the carb you have now and make the car run quite well. I don't think that it would be worth the money to replace "ONLY" the carb for performance purposes. Then when you put "fuel economy" into the equation, that's a second reason to stay with the carb you have now. If you were going for a "performance-type" engine, I'd feel differently. Only my opinion, do the work to the one you have and stay w/ it.

RE: carburetor choice
 

You didn't say if your current carb has vacuum operated secondaries but IMO those are the best for overall performance as the secondaries open as needed, not all at once as do mechanical secondaries which are better suited for race engines.

Get your timing done first which it sounds like you've been doing with your mechanic friend. Once that's done, you can work on tuning your carb. I agree with Texas Jim re: keeping your carb and working with it if it's a vacuum secondary.

RE: carburetor choice
 

That was cool. Ran some numbers for "what if", good choices. :)

RE: carburetor choice
 

A handful of you guys really do drop some good links for great info and reference. Thanks.

RE: carburetor choice
 

thanks to everybody.

my carb has vacuum operated secondaries.
Yes I think I'll stay with my carb and tune it , when I'll understand how. I'm reading techs about here and there but I'm still understanding few about . the sparks timing setting is more scientific, carb setting seems less scientificto me

can you tell me anyway which carburetors do you ( all ) use? size and brand. just as reference...

RE: carburetor choice
 

I still/will when it's back together use the original Q-jet with some mild mods -jetting, rods, accelerator pump tweaks, air valve tweak. I know a lot of folks think they are junk but have had lots of GM cars with them and are trouble free. While there aren't as many things to adjust as a Holley, to me that's a blessing in disguise. I've worked on a friend's '66 427/450 with a Holley and there's so many tweaks that sometimes you feel like you are chasing your tail.

RE: carburetor choice
 

I usually get this backwards, but most of the time, vacuum holds the secondaries closed so that the engine only runs on the front two butterflies (barrel) on the "vacuum secondaries" carb. As the engine speeds up, vacuum decreases, and the secondaries are opened. The less vacuum there is, the more they open. On engines with "big" camshafts, there is little to no vacuum at idle, so if the carb. has vacuum secondaries, they would be open all the time, making the engine run very bad. So, mechanical secondaries are for performance engines with large camshafts, as they are operated as the throttle is mashed! :) If I get something wrong, let me know, I always get stuff about vacuum, like ported vacuum wrong (read:backwards), because I am weird.

Aldo,

Knowing what you've told me about your engine, another carb won't help much with gas milage or horsepower, I'd echo what everyone else said, the carb you have is perfect. I've used two of those Edelbrock carbs and they have been great!

RE: carburetor choice
 

On Q-jets and Holleys, you can adjust the amount of vacuum where the secondaries start to open.