[Holdon]

Have got a 680cfm vac sec on the way from Quickfuel. Spoke to a well known speed shop this week and they recommended around the 700cfm size and also told me the victor jnr is way too big for my 195 heads. So looks like im going to be changing to a performer rpm air gap at some stage also.

[Overdriv]

I have an Edelbrock 750 on a 406 in a 3400# S10. I have a 700R4 trans, 2800RPM stall, 456:1 rear with 32X18.5X15 MT Sportsmans on the rear.

Running about 2100RPM at 60MPH I have gotten 16MPG with the AC on, driving very easy.

I like the Edelbrock carbs for the street. They are very easy to change calibration. But, if I were going to race, I'd use a double pumper of some sort.

Everyone has their favorite carb and a story why they don't like another brand, each to his own and good luck with what ever you decide on.

[Holdon]

Well guys I have got my 680 quickfuel on and running. Sort of happy and sort of not at the same time. Have gained a bit of response but maybe not as much as I thought I would from my old 830cfm dp pro systems carb. I had trouble with initial start up, it just didnt want to fire, and still doesnt when it's been sitting for a while, plus the first day I had it out on the road I found it started missing after idling around for a little while, maybe a bit rich on the idle circuit im guessing. I backed the electric choke setting off to nothing so it stays open, could that be effecting the bad starting? My first day on the road with this carb involved a fair bit of low speed work in town and on parade and it seemed to use more fuel than my old carb, really not what I expected. I wound the idle screws in half a turn each and the idle seemed to improve and the missing after idling around also seemed to dissapear. My 830cfm dp was running 76s or 78s from memory on the primaries and the new carb has 68s yet it seems to be using more fuel around town. Maybe the idle circuit is just way too rich? A mate has a electronic fuel ratio meter that screws into the exhaust so I asked if i could borrow that to test it under real driving conditions, how good are these tools?

[35hotrod]

Just ran across this thread, wish I'd seen it sooner. I have Pro Systems 780 dp on my sbc 350 with AFR 195's, 236* dur @ .050, .535 lift hydraulic roller. Previously had Holley 750 vac sec and Speed Demon 750 annular booster carbs on Rpm Air Gap manifold. The Pro Systems carb gets better mileage than the other two, not huge but noticeable. However the difference in response and "clean" carburetion is enormous. No more rich idle or funky off idle response. No bog, just instant, quick response. This was out of the box performance, only required a slight idle speed adjustment, set to 700 - 750 rpm. My advice would have been to change the Victor Jr. to a good high rise dual plane manifold and keep your foot out of the secondaries. Might be tough to get fuel economy with 249* @ .050. As said earlier, if you're punching it all the time vacuum secondaries won't save much fuel. AFA over carbing, David Vizard did some testing with a 1250 cfm carb on a 350 sbc and came up with some interesting results.

[Holdon]

Geez not the news I wanted to hear. It was a performance shop that told me the carb was too big, but he did also recommend a manifold change. To be honest Im getting real sick of so called 'experts' giving me the wrong advice, sounds like he was on the money with the manifold change advice but the carb may have been oh as it was. Oh well I have got this QFS 680 on there now so guess I will just have to make it work. Am thinking a bit smaller cam and Weiand Stealth manifold might be on the cards some time in the future though. Do love the sound I get with this cam though

[NWayne]

My Pro Systems 4150 780dp has been the best carb I've ever owned. It was great right out of the box. Idle was almost spot on, just backed it down a liitle. I'm running it on a sbc 350 with Brodix ik200 heads, 225/230 540/540 hydraulic roller cam, and a Edelbrock e-force supercharger. The throttle response is unreal with this carb. No bogs no complaints, love it.

[35hotrod]

Hey Holdon, I'm sure you'll get it sorted. I considered a Quickfuel carb before I discovered Pro Systems and am sure the QF is a quality piece. My basic advice for carb tuning is to only make one change at a time. Good luck to you!

[SDLuck]

Do you have a vacuum advance on the distributor? This will help gas mileage

[Holdon]

My cam is too big to run a vacuum advance.

[SDLuck]

How much vacuum does it have and how much initial timing and total?

[Holdon]

Originally Posted by SDLuck

How much vacuum does it have and how much initial timing and total?

I havent had a vacuum gauge on it yet so not sure how much it has. My distributor needs the advance curve altered cause after setting timing at 36 degrees total it ended up with 22 degrees at idle. I have heard since then that these AFR heads behave better with about 30 - 32 degrees total anyway so might try that.

[duaneh]

I have a quick fuel 780 ssvac. sec. carb on a modified 350. Absolutly perfect out of the box. Buy *** you will have no regrets!!