Carb Tuning Question

[TurboChris]

So on my 427 I'm running dual 1850 600's on a tunnel wedge. It runs good but I feel like there is improvement to be had. I want to get them generally dialed in the best I can. I'm seriously considering taking the Fairlane over to someone like Westech in SoCal to be "Dyno Tuned" on their chassis dyno.

My question is this.....

I"m looking and Quick Fuel has two products that I find interesting.

63-1QFT Quick Set Adj. Sec. Housing - makes the vacuum secondaries easily adjustable.





And  the 34-2QFT Billet Metering Plate Kit - Saw a video with Steve Brule and Richard Holdener https://www.youtube.com/watch?v=0IwoNX0PGEI





I'd like to hear opinions  / experience about using these by themselves or together before I go and spend $300 on this stuff. Good or bad.

Thanks guys

[Joe-JDC]

If you are using progressive linkage, do you have a balance vacuum tube running between the dashpots on the secondaries?  That is almost mandatory with 600vs carbs when used on 8v intake.  Joe-JDC

[TurboChris]

Yes sir. I do.

[6667fan]

If you don’t already have updated plates in secondaries, ( the type where you can swap jets out), then yes, get that kit or something equivalent.
The tunable vac pods are an upgrade but guys just changed springs forever and got it done. JMHO

[blykins]

You won't really know what it needs until you put it on a dyno.  It may be as close as you can get it, as-is.

[TurboChris]

You won't really know what it needs until you put it on a dyno.  It may be as close as you can get it, as-is.

Well, my initial plan is to get it baselined. Thinking I'd have the parts on hand so they can be installed and then keep going to finish dialing it in. Assuming they are needed of course. Install isn't that tedious. Of course the jet changes (on the jet plate) require removal of the forward carb but.... it is what it is. It won't be cheap but I suspect it there are gains to be had.

[Tommy-T]

I have used the QFT metering plate kit with good results. Just be sure that the jets don't slightly touch the float as it will on rare occasions. Once installed turn the carb upside down and you should be able to hear if the float moves freely in the float bowl. If you're cheap like me you can drill and tap the Holley metering plate with I believe 8-32 brass set screw and drill them for whatever jet size you need.
I have used the Holley quick change secondary spring kit with good results as well. Much cheaper than the QFT pods. There is a boss in the cover that you can drill to install a tube into so you can retain your balance hose between the carburetors.
I have had dyno work done at WesTec. They are a top notch shop and I'm sure that you would be happy with their work.

[pbf777]

       Just a thought: 

       My experience with most "good" dyno-tuning (vehicle on the rollers) efforts proves that this process can 'aid' in acquiring a baseline tuning result for heavy to W.O.T., but doesn't really provide well for lower throttle and transitional throttle instances, particularly considering the multitude of possible scenarios as experienced on the street.  If you really want to be able to say "those carburetors 'are' tuned to the best possible state", you'll need to jump in yourself, as even a different driver, all other variables remaining the same, can cause a need for changes in the tuning; and it's really not that complicated or difficult, but it will encompass some time.   

       Just think of it as part of the 'fun', in the experience of making your vehicle the best that it can be.   

       Scott.

[frankenfords]

I too have used the QFT billet secondary plates successfully, but one thing I had to do was fiddle with the idle fuel feed orifice sizing. On my application, the idle fuel feed orifice diameter was way too big, and made the idle circuit way too rich. I couldn't get it to run decently at anything other than WOT. Looking at the specs for the plates I was replacing (which I got from an old Holley book I have) and comparing them with the specs for the QFT plates, the idle feed sizing was way off.

The QFT plates have a screw in idle fuel feed that's basically a tiny worm screw with an even tinier hole drilled in it. I called QFT asking for either worm screws with different orifice sizes or blank worm screws, they didn't have any, so I sourced some from a RC Car supply company of all places. Then I found the appropriately sized drill bit (from Grainger) to match the orifice sizing in the original plates, and drilled the feeds in the replacement worm screws. Solved my idle and part throttle issues just like that.

My other experience with dual vacuum secondary carbs was that I needed to use the lightest spring possible (white) in both carbs to get the most out of it.

Hope this helps.

[e philpott]

They do make a bunch of different plate sizes, idle feeds and main feed sizes if you know what you need , keep fuel under 5 psi fuel pressure for side pivot bowls . I do like the vacuum secondary unit but have only used them on single four barrel carburetor applications and it is a quick easy adjustment