edelbrock 600 cfm or Holly hp series 750 cfm

[dlg423]

The local corvette mechanic here in my area tells me that I can get a lot more hp by replacing my edelbrock 1406 600 cfm carb with a holly hp series 750 cfm. I've got a GM crate vortec engine, 350 with 330 hp. Any input will be appreciated.

 

[Roy]

The Edelbrock 600 CFM is fine, especially if it runs good. Good driveability is better than the elusive higher horsepower unless you are racing. If it runs fine now, stay with the Edelbrock and enjoy your car.

 

[Scooter76]

While you may see a very slight increase in hp in the upper rpm ranges, you may loose some throttle response in the lower ranges. 600cfm is a good size for a mild street 350. Makes the engine "snappy " down low where 95% of most peoples driving is done. As always, just my opinion.

 

[Robin7TFour]

GREETINGS, isn't the stoclk q-jet a 750 cfm?



ROBIN( in the land of the confused)

 

[danny/'87]

you can get more carb info at
http://www.mortec.com/carbtip1.htm
there is a formula to use to get a proper size cfm for your application. generally a 600 cfm is a good size carb for streetable engines and double pumpers are not as good for automatics(trans) as vacuum secondaries

 

[Scooter76]

Most Qjets are rated at 750cfm. They are excellent because of the very small primaries which promotes good mixture velocity at low engine speeds,which leads to snappy throttle responce. The very large secondary side is what gives it most of it's 750cfm rating. One of the best street carbs you can run. In my statement below, I was comparing the caritristics of the two square bore carbs mentioned below. Have a good one!

 

[Flared69]

I just tuned down from a holley 750cfm to a 650cfm because of economy and rideability. It just runs smoother.

 

[Robin7TFour]

hello , hmmm he war aussie with flares now just flared> wondering.

what did you do with the 750?

robin

 

[iron cross]

Bigger, better?

In a few situations bigger is not always better And this could be one of the few times where this phrase will apply. Bigger may look good however sometimes don`t work as well as the smaller one.:L

 

[resto75]

I too went from a 750 Holley to a 600 edelbrock performer. I was having idle issues with the Holley and just replaced it as it was a older carb and probably needed rebuilding anyway. The performer cured the idle problem but the engine ran better with the Holley with more power and believe it or not better gas mileage.

I recently had a cracked head which needed to be replaced and now that that is fixed I'll try the performer awhile longer and see how it performs. The holley will be rebuilt and replaced if the performer dosen't perform.

 

[Robin7TFour]

RESTO, what kind of idle problems did you have with the holley? am curious if they're like my problems.
mine will idle fine for a while .then suddenly with no ryhme or reason starts to die out. i checked the float levels ans air screws. it is very inconsistant.
is that what you had?



ROBIN :confused

 

[texancanuc]

carb choice

i had nothing but problems with the Q-jet so when i swapped my original motor for a 300+ hp crate , the builder recommended a 600 cfm spread or square bore edelbrock. he says that will give you all the low end gusto you will need
im am also lead to beleive that edelbrock is more maintenance friendly then holley

i am hoping to post some pics soon sorry for the delay people

 

[Fishman]

750 is probably a bit large...

Someone here at the CAC posted this...

How To Calculate CFM:
Engine Size (CID) x maximum RPM / 3456 = CFM
CFM @ 100% volumetric efficiency (VE)

(Example: 350 CID x 6000 RPM = 2,100,000 / 3456 = 608 CFM)
Approximately 608 CFM would be required for this engine.

However, most Street engines are capable of achieving only about 80% VE; a modified street engine with ported heads, headers, intake and carburetor can achieve about 85% VE; a fully modified race engine can achieve 95% or greater VE. The CFM number arrived at with this formula must be factored by this percentage.


... I run about 85% VE and have a 650cfm Holley... though I could have gone with the 600cfm as well. I actually had a 750cfm on the engine at one time... the 650 is much better IMO.

 

[Robin7TFour]

FISHMAN , i used your figure and threw in my data.... i am slightly over-carbed. so how do i lower the fuel volume slightly?

ROBIN :bang

 

[Chas]

i made the switch...

took off a leaking holly and put on a Edelbrock performer 600...i have a performer manifold so it fit really good....and i love the way it runs and idles....gotta get a regulator if you change....was told most hollys have more pressure and the edelbrock only needs 5 psi....hollys are higher and if you dont regulate it , it may damage the jets.....im sure someone will have the details of that shortly...i put on a regulator and a gauge to keep an eye on it...just my opinion, good luck pal. chas

 

[Robin7TFour]

CHAS, thank you for that info. i guess i need to sell a few carbs and buy an edelbrock,

robin

 

[Chas]

i have a pic of it...

http://www.corvetteactioncenter.com/forums/attachment.php?s=&postid=304167

this is a thread i posted a pic of my carb and another of the filter i use....http://www.corvetteactioncenter.com/forums/attachment.php?s=&postid=304168

 

[Robin7TFour]

CHAS, looks very very good.


ROBIN

 

[Fishman]

FISHMAN , i used your figure and threw in my data.... i am slightly over-carbed. so how do i lower the fuel volume slightly?

ROBIN :bang

Sorry, I wouldn't be the best one to answer that... I just took the easy route and traded in my slightly used 750 to the guy that sold me the 650.

 

[resto75]

Robin I had a poor idle and had to raise the idle higher to keep it running. It was probably a tuning issue but I thought a smaller carb would be better all around. I'm still out on that issue.