five7kid

iTrader: (14)

In my experience - NOT!

Just thought I'd spend a few minutes on my observations over the past 10 years or so messing with street and strip carbs. Since you'll often hear things like, "Doesn't matter what kind of carb you get, as long as it's the right size for your engine." Or, "Get the one that is easiest for you to tune." etc., I thought it worthwhile to share some of my "insights".

Now, I realize there are different levels of skill out there, and I'm taking that into consideration. Every time I forget that, I am reminded by a bud at the track who has my high school drool car, a 1968 Camaro 327 4-speed, which he bought new (he's a few years older than me). He'll come up holding his time slip, and ask questions like, "Now, when you guys talk about hundredths and thousandths of a second, were is that on my time slip?" Forget even talking jets and squirters with him. He's a great guy, but this stuff is simply over his head.

Anyway, I'm sure I've said things over the years that I wouldn't say now, such as, a Holley 750 vacuum secondary is a pretty good carb. But, I'm still learning, so even what I'm saying now may look pretty stupid in another 10 years. In the past decade, I've had a few factory q-jets (Monte Carlo, pickup, CC 3rd gen), a couple of Edelbrock q-jets (still running one on the '84 full size van 350, the 1901 that I ran on the 396 was a piece of junk), Holleys in various configurations and modifications, and even a F*rd progressive 2bbl. I cut my teeth on a whole bunch more types of carb starting about 35 years ago as well. I'd have to say that the modified Holley currently on the 396 and the '86 CC q-jet currently (but not for long) on the Camaro are the best carbs for their purposes that I've ever had.

The biggest eye-openers I've had are these:

1) Not gaining any performance going from Edelbrock q-jet to Holley 750 VS on the 396 (although consistency did improve slightly).

2) The 2 tenths I gained in the 1/4 mile with the '57 when switching from 750 VS Holley to 650 DP Holley.

3) The difference it made with the '86 CC q-jet rebuilding and properly installing air tubes, and later a simple, dumb thing as new mount gasket.

4) Gaining 2 tenths and 3 MPH when switching from rejetted/air bleed changes Holley/Proform running E85, to the Quick Fuel Technologies E85 metering blocks.

5) No performance improvement going from CC q-jet to Holley 6210 spreadbore double pumper on the Camaro. I expected similar results as #2.

Also, I've seen what happens when other people have made changes, particularly going from Edelbrock to Holley or Demon. The only person I have heard about getting better performance from Edelbrock was a guy with a '65 Impala 396 dual-quad - and to this day I'm convinced he didn't know what he was doing with the Demon.

It's Item #4 that really prompted me to sit down and write this. I was hoping to improve idle quality with those metering blocks, which they did, but I never expected that kind of horsepower improvement. I know we get a lot of people talking about Holley tuning problems; mostly those involve worn-out carbs, or someone who is making changes that they don't understand and are leaving out details out of ignorance that would help us get them on the right track. But, the problems I hear people asking about on Performer carbs convince me that those carbs are simply of inferior design, and the tweaking necessary to get them to work on our kinds of cars just isn't possible, or at least reasonable, on them. Things such as air bleeds, emulsion tubes, transition slots, idle restictors, do make a big difference in how the carb works, and although most of us don't having access to the equipment necessary to fine tweak these things, having them properly designed - or at all adjustable - is a big deal.

Well, I could go on, but I'm sure others will have things to add. One thing I am convinced is that my opinions are not biased because I'm using the parts I champion. Rather, I champion the parts I do because I am no Ben Franklin fool.

So, flame away. Or, whatever. . .

Damon

No flame here.... at least your experience with QJets is consistent with mine. I'll put a properly tuned QJet up against ANY other VS carb on the market. And maybe a few double pumpers, too. VERY flexible carbs with tons of airflow potential for peak power but still good metering capabilities even at low airflows. I also believe their secondary design is lightyears ahead of a Holley VS in terms of how fast it can get truly wide open without bogging- air valves over the bores beats vacuum diaphragms opening the secondary throttles hands-down in my book. A QJet can be truly wide open at very modest RPMs without any bogs or fuel metering problems where a Holley VS, even with a light spring in the vacuum chamber, often takes a LOT more RPMs before the throttles are wide open. No proof, but that's my guess on why they work so well.

#4 doesn't surprise me if the original metering blocks you were using were for a carb running gasoline. E85 requires a MUCH richer mix than gasoline. So much more that the metering block passages themselves become restrictions- not just the jets.

Bigseth

iTrader: (11)

Good info, Im building a 383 for my camaro, It will have 64cc chamber 190cc runner alum heads, cc503 cam (224/230 dur, 536/544 lift w/ 1.6 rockers), flattop 2 valve relief pistons, hooker 2210 longtubes.
What do you think I should run for a carb? I plan on making this thing as streetable as possible and I was looking at the street avenger 770 cause I can get it below cost from work ($275). I do have the option for quick fuels as well but they are $400. It is a T5 car. Not trying to jack a thread but you seem like the person to ask.

Thanks
Seth

xpndbl3

iTrader: (5)

i like the proform 750 or the quick fuel(same thing). Skip the avenger anything, all a marketing ploy to rid your wallet of money. 750 double pumper also would work well.

Tobias05

five7kid

iTrader: (14)

Well, QFT does use the Proform main body, and Proform gives you the QFT phone # with their product information, but that's about where the sameness ends. I got the Proform metering blocks because I couldn't find a source at the time for the QFT E85 blocks, and when I called QFT to get the parts to make them into E85 blocks, I got completely stonewalled. QFT wanted me to buy a set of their metering blocks.

That means I have a set of Proform billet metering blocks that aren't being used. . .

Can't argue with that. I will say, however, that QFT makes an adjustable VS housing for Holleys that does it the "right" way, IMO. You meter the vacuum signal, rather than adjust opening by the spring force. Allows the secondaries to fully open while allowing you to tune out the initial opening bog.

loneroad

iTrader: (3)

whats wrong with the avengers?

Apeiron

Nothing, you can just get the exact same thing without the "Avenger" name for a lot less money.

Travis&camaro

So Whats the same Carb as a street advenger 770? I dont know if i should buy a qjet or the street advenger 770 I have about the same set up as the guy with the 383 but mine just a 350 with biger heads?

loneroad

iTrader: (3)

ive been running edelbrocks for years. This is my first holley and im trying to learn everything I can along the way.The first thing I have found out that it can get expensive buying all the tuning kits.

five7kid

iTrader: (14)

A universal 750 vacuum secondary will do the job as well as an Avenger. You'll give up one vacuum port, see-through fuel bowl site plugs, and quick-change secondary diaphragm spring cover.

jeffcj

iTrader: (3)

Nice post! Great info based on real world experience...

five7kid

iTrader: (14)

Let me say a little more about that. I did jet up, and the main passages are more than big enough to handle the E85. When I put on the Proform billet blocks, which are the same basic thing as the QFT E85 blocks, it didn't make a difference in performance. What seems to have made a difference with the E85 blocks is the emulsion restrictors that were modified. Idle restrictors are also opened up more, but that shouldn't be a big contributor to WOT power.