will I see a difference in replacing my Edelbrock 600 cfm carb with a holley 650 with vaccum secondaries?

 

Probably not a tremendous amount of difference.

 

Your wallet will be smaller.

 

I've always heard Holley's were temperamental with those power valves blowing from a good backfire. I originally planned on putting a holley on, but ended up getting an Edelbrock. A guy at work swore by them and had always had good mileage with them. I probably drive mine less than 200 miles a year so mileage wouldn't make a difference to me. I know they're not as easy to tune as an edelbrock.

 

Yes you will notice a difference, no there not harder to tune. I guess your just going to have to put it one an see for yourself. Fuel mileage depends more on your ability to tune and the weight of your foot although I have better results with Holleys.

 

If you're really after is a milege improvement and are willing to tune your combination then a Q-JET will work the best. Other than that stay with the Edelbrock and tune it. it can be fine tuned to a sharpe edge. just takes effort and knowledge.
Yes the holley can be tuned too. but you'll have spent big money needlessly for a new holley carb to replace the edelbrock and be no further ahead.

 

Doesn't sound like mileage is an issue.
Not as easy, as in needing to drain fuel in order to change gets or power valve, perhaps. More tuneability makes up for that.

I wouldn't go with a vacuum secondary carb, though. Why do you think that is the thing to do?

Power valve blow-outs are a thing of the past with PV check valves.

 

I always thought mechanical secondaries worked better with a 5spd

 

If your only driving 200 miles a year, bolt on a Holley DP and make those 200 miles enjoyable and quick

Very easy to tune, but you will give up mpg for smp (smiles per hour)

Both carbs can be tuned for application but Holey gets it done really easy. We've tried 3 Edelbrocks in our camp over the years and all I can say is they make great paper weights.

 

What "difference" are you looking for?

What do you want your Edelbrock to do, that it's not doing now?

 

I'd just like to go faster. I don't mind the edelbrock. Just wanna go faster. I know my heads are my limiting factor and I'm keeping an eye open for some other heads.

 

Just about everything else on your car is much more of a factor as to how much horsepower you're making than the carb.
The heads are good example. Exhaust and camshaft and intake manifold are some others.

At your present power level a 600cfm carb is not holding you back. A 650 is not going to make any more power. A 750 will make a bit more but not worth the $$$ at this point.

You can fine tune the edelbrock by sharpening up the jetting and get more power. You'd see much more power just by switching to a RPM intake manifold from the performer, than switching carbs.
Porting the cylinder heads and installing larger valves will get you about 25 or so HP. Shaving the heads to increase the compression ratio will get you torque and power all the way from idle to Max rpm.

Tell me some details of your present combination an I'll suggest some changes.
Intake , heads, headers, exhaust. rear gear ratio. camshaft grind compression ratio etc.

 

I have a Holley Street dominator intake. It's power band is similar to the performer. I have a comp 270 h-10 cam. Edelbrock 1405. I'm using untouched 416 heads. I didn't want to pay the money to have larger valves put in if I was considering different heads. I was looking at aftermarket 58cc heads. I can't find them in my summit magazine and I can't find the catalog that they're in. I don't mind the compression and having to run airplane fuel or octane boost. It doesn't knock and it runs good. I'm also running flowtech heads and I'm using a holley mechanical pump the I believe is 80 or 90 gph. Would a performer RPM hurt me or help me with that cam's powerband? I believe it was from 1800-5200 rpm