five7kid

iTrader: (14)

...you gotta get the Quick Fuel adjustable secondary housing! Jegs carries it, couldn't find it on Summit's web site.

Kudos to Andy-86IROC for bringing this to our attention. If it had been mentioned on this board before, I hadn't seen it.

Mine arrived Thursday, put it on, tested adjustments driving the '57 to work Friday. Went to Bandimere that evening for Club Clash, air was terrible (9700' altitude equivilent), traction marginal (they don't spray the track down much for that event since it's all supposed to be DOT tires). First time trial, my 60' time was the best I've ever pulled! This on a "trash run" - red light, hot secondaries that stumbled after about 100', etc.

All night, though, it pulled great 60' times, even though I couldn't always get it to hook. Made it to the last round they ran (time constraints, too many cars out, shut down at midnight), last run another redlight (man, the responsiveness is so much better with the Holley than the q-jet), proceeded to run the best time ever with the Holley, and through the mufflers to boot - 15.041. Altitude was about 8600' at that point.

Am I happy? You bet! As Andy said, this is the part Holley should have used themselves.

Somebody with a SA carb - look at this post https://www.thirdgen.org/techbb2/sho...readid=107443, let us know if your carb has this type of adjustment. I know it has the quick change spring housing, but is there another adjustment there as well? Their ads say something about adjusting the secondaries with the turn of a screw.

Andy, I know what you're saying about the springs. It does seem like it could still come in sooner (I've got the needle valve at 3 turns out). I didn't like the non-squareness of the weakest Holley spring because it side-loaded the diaphragm. But, I'll do what you suggested and try another spring. As soon as I finish this post, I'm going back out to Bandimere for the Saturday ET series races (managed to get another kitchen pass).

Oh, Andy, one other thing - in the other post you asked about the check ball. I had it in the original housing, but I didn't think the QF housing had or needed one. Correct?

Damon

Holley standard (plain) springs that come inside the stock vacuum housing are VERY tight for performance use. Typically a 750 CFM VS carb won't get the secondary throttles open fully EVER on a street 350! The vacuum secondary mechanism on a Holley works TOTALLY different than a QJet.

My expereince is just the same as yours- you can put in a REDICULOUSLY light spring before you even come close to causing a stumble.

There is also a restiction built into the (stock) vacuum canister area that allows for the RATE of opeing- it's just a drilled orifice. It's function is somewhat similar to that of the vacuum break diaphragm on the side of your old QJet. It's slows the RATE of opening so the secondaries won't bog. In some cases the secondaries won't even get fully open in 1st gear since you'll be at the top of 1st too fast for it to keep up! Playing with it often yeilds EXCELLENT results in combination with a lighter spring. But don't go too far with it or it's Boggsville.

Perhaps this "screw" you are referring to serves the same fuction as the fixed orifice in a stock Holley?

You know I love QJets, but that doesn't mean I don't know how to tune a Holley!

Whatever makes your car go faster- use it!

five7kid

iTrader: (14)

Still fiddling, but it's looking better.

Made 7 passes Saturday, hard to "tune" when you get 2 time trials and then go into eliminations. But, tried the lightest Holley spring for the first TT, didn't seem to like that. Went back to their spring for the rest of the runs. Throughout the day, my 60' times were all less than 2 hundreths from each other, with air density going all over the place. Reaction times were also consistent (for me, at least). Never had that kind of consistency in those two areas before. In fact, my RT was better than my competitor's every run, which was enough to make it to the quarterfinals and into the money (slowed on me that round, lost to the season points leader).

Afterwards, I re-read the Holley spring assortment info, Quick Fuel directions, and the Holley tuning book I have. All say, "If you can feel the secondaries opening, they're opening too soon", or something to that effect. So, put it back to 1-1/2 turns for the drive home (it was delivered 2-1/2 turns out, not the 1-1/2 they guarenteed as the "factory setting", and what I assumed in my base-line) - guess what? Works even better!

Wouldn't you know, I discover this the same week I have the rear out for new gears. Won't be back together until Friday, when I'll get another two time trials before eliminations...

Damon, I know you're a q-jet guy. If I knew an inexpensive way to get rid of the gritty/rough motion in that Edelbrock 1901 AV, I'd consider using it for something. Until then, the Holley seems to be responding to me.

JRoy91RS

Thanks for the info!! I recently bought a Holley 750 cfm VS. This is my first Holley carb, so I need all the help I can get!! What is the part number on that secondary kit?

five7kid

iTrader: (14)

It's in a link in a post in the thread I link above...

Never mind. Here's the link to Jeg's page on the part http://www.jegs.com/cgi-bin/ncommerc...8&prmenbr=361.

It's gold anodized, and I have a silver carb, but with the Quick Change top on it, you can't really see that.

Blackened

I got my VS carb back on the car and dumped the 850 DP. My mileage is soooooooo much better and the power is about the same ( I cant adjust the jets in the back yet).

Dragula

Alright five7kid.......I have generally trusted your input.....so I ordered one of these with the QuickChange top (and just for fun an accelerator pump tuning kit).
If it works as good as you say, then I will love you forever
Anyways, I have been fighting that dang bog also, works fine at part throttle, but bogs when I jab it....guess the secondaries are just "flopping" open.
So if I understand this right, it will still allow the spring to open and close as normal during acceleration, but when you jab the throttle (such as when that Acura TRIED to pass me last night) it controls the speed at which the secondary open to prevent them from "flopping" and killing the velocity of the incoming air so no fuel is pulled in, thus creating the infamous bastard named Bog?
Am I close?

five7kid

iTrader: (14)

That's close to the idea. The problem is you need air flow through the booster venturis to start pulling fuel through the circuit - that only happens as the throttle plates open. Gradual opening lets the fuel flow catch up with the air flow (the accelerator pump gives extra fuel to compensate for that lag in the primaries). The "Holley way" is to use diaphragm spring force to control how quickly it opens. The problem with that is that it also means the vacuum has to "suck" harder on the diaphragm to get it to open. Since the vacuum is created by flow through the primary and secondary venturis, more flow, (or more RPMs), is required to pull the diaphragm up if you use a stronger spring to prevent "bog".

The Quick Fuel housing simply orifices the vacuum created by the venturis, so the rate of opening is all that is affected, not the amount that the secondaries open. Result: When dialed in, the secondaries will open only as fast as fuel is pulled in, but can be opened farther at a lower RPM than they would be with a stronger spring.

By the way, Dragula, did you check your SA carb first to make sure it didn't have this type of adjustment?

Dragula

I sure did, and there is no needle valve there. There are no directions or reference to this in any of the sections or diagrams in the instruction book either. I believe what you had referred to earlier about the "adjust the secondaries with a turn of a screw" for the SA carbs was just referring to the QuickChange type secondary cover.
But either way, nope......there is definitely no needle valve like shown in the QuickFuel pictures.
Here is the SA info from the Holley web page.


Features

The first true performance carb designed specifically for the street.
No TroubleTM adjustable vacuum secondaries. Select street, high performance or fuel Economy.
No TroubleTM adjustable electric choke for cleaner, smoother warm-ups.
External No TroubleTM adjustable float with sight plug.
Gen IV No TroubleTM power valve with million mile protection.
Four vacuum ports - PCV, Power Brake, Spark and A/C or modulating.
Sintered brass, high flow fuel inlet filters located in fuel bowls.
Ford A/T kickdown.
Holley zinc castings are more stable and less susceptible to performance changes due to heat build-up, than aluminum castings.
Lifetime Limited Warranty.

JRoy91RS

Found it! Jegs P/N is 793-63-1. Holley makes one, too, but it looks a little more cumbersome 510-20-99. Couldn't find these on summit's page either, but I'll bet if you tell them that their competitor is carrying them, they would offer it to you. BTW, the link above to the jegs site doesn't work.

James

five7kid

iTrader: (14)

The Holley part would adjust the spring force, not the vacuum.

The Jegs link worked two days ago. Not sure why it isn't now, but with the p/n, you can find it on www.jegs.com.

Pony Killer

hmm. i'm not following here. What is this part your talking about, is it some sort of different quickchange spring housing or something to do with that?

A quick change spring houseing with another adjustment?

five7kid

iTrader: (14)

Don't know if you found the picture on Jegs' web site, but it looks like a "normal" Holley VS housing, but with a needle valve adjustment where it mounts to the carb. You screw the valve in to delay opening, out to let it open earlier.

The quick change cover will fit on it, that's all we were saying about that.

Andy-86IROC

Here's a pic of the housing as you receive it. It is complete with a stock replacement diaphragm, cover, and screws.

Jester

Seems like a pretty interesting idea. IMO tho, it seems kinda unnessecary. Just by changing springs you can adjust the secondaries as much as you need to...I doubt you will see any good effects from it as compared to a normal VS housing with the right spring in it.

If the secondaries were causing you bad 60' runs, then I would say you just had too light a spring in.

FWIW, once when I went to the track I decided to test out secondary springs. I tried them all in runs on the same night. I ran my best time with the stock one. Lighter isn't always better.

Andy-86IROC

And here is the one installed on my car.

Sorry five7kid, I missed your question earlier... yes you are correct that no check ball is used with the adjustable housing.

Also, when you used the lighter spring did you turn the needle valve in at all? You would need to for the lighter spring to work. Use the lightest possible spring that you can still eliminate the bog with the needle valve.

Don't worry about the side loading of the spring either, it will not affect your carb in any way. The mounting of the diaphragm is much stiffer than the spring force.

Basically you want the secondaries to follow your primaries as soon and as quickly as possible and only dampen them just enough to start fuel flow.

five7kid

iTrader: (14)

Agreed. That's why only changing the spring is not adequate. A double pumper opens both when you nail it, which is what you want when the engine can handle it. Unless you have a manual transmission or a loose converter, it typically can't handle it, thus the VS carb. And, like you said, what you're really doing is giving the fuel time to get to the boosters to meet the air that has started flowing as the throttle plates opened.

I haven't had a chance to do any more tweaking since Saturday. Have the rear out for new gears, so it's pretty hard to do full-throttle testing in that condition...

Andy-86IROC

Hi Jester, I understand what you are saying but I can guarantee that this part made my car significantly faster in first and second gear. My car is fast enough through first that the secondaries just wouldn't open, even with the lightest spring. Removeing the check ball allowed me to play with my power but I was in bog city. Experimenting with springs would only change when they started to open, not how fast they opened.

When I put this part on and drove the car I knew right away it was a BIG improvement. I've had it long enough now to have it dialed in pretty well and I can say that I have never experienced a more responsive VS carb. I've owned several 600s and this is my second 750.

The only issue I have now is that if I'm turning high RPM at a light throttle, 3500-4000 on interstate, and then punch it, I still get a noticeable bog. I'm running secondary jet extensions so this may be partly to blame for that.


five7kid, what gears are you getting? This is a big block your working with right?

five7kid

iTrader: (14)

I've had 3.08 gears, 24.75" tires up to last weekend. 3.73's went in this week, no runs yet (SSM lift bars just arrived this morning). The plan is to get it running again tomorrow (have the day off), and out to the track tomorrow afternoon.

Yes, this is a 401 big block (4.124" x 3.76"), stock oval port small chamber heads with the mods in the sig.

Dragula

Just put mine on yesterday morning........after a few runs to get the screw set right, I picked up about .3-.4 second consistently!!!! I recommend this for everyone!!!!

five7kid

iTrader: (14)

Well, I can't say exactly how much it helped me, because I threw the gear change into the mix before I got it set correctly. I do know that this Friday evening and Saturday were a bracket racer's worst nightmare - the changes I made to the car, plus constantly changing atmospheric and wind conditions - ugh!

Friday night: I had to most consistent 60' times I've ever seen with the Holley and certainly more consistent than the q-jet. When everybody was slowing, I was maintaining. By 11 p.m. Friday, the winds had died down, I'd been hitting the brakes at the top end to keep from breaking out, so hadn't made a full pass in eliminations (hey, I was dialing based on what I had run). Last race, against this 3-sec faster car, I miss-judged his closing speed, didn't back off, broke out - 1st sub-15 second time slip in my life (give me a break, we're at altitude).

Saturday, weather again all over the place. 1st time trial in morning, get my second 14-second time slip. 2nd time trial against a 30-mph head wind, weather's gotten hot and humid, so was slower again. I'm not used to running in the afternoon, but still manage a first round win - again backing off at the top end. 2nd round, against a 2-sec slower car, mis-judged my closing speed, didn't back off soon enough, broke out - best time ever in the car.

I'm not attributing all the improvement to this one piece, but having it made tuning sooooo much easier!

JRoy91RS

Dragula,

That is one awesome setup you have on your IROC.


:hail: :hail: :hail:

If I had the budget, I would be doing the same to my RS. Do you have any times yet? Just curious if you've gotten that stroker to hook up.

James

BadSS

I didn't have to use this mod very often when tuning in a carb, and never saw any miracles from it,,,,, but as far as this adjustment on the vacuum secondary diaphram housing goes,, there is a "DIY" mod that is very simple and easy to do.

Tools and materials - drill or dremel, 1/8" bit, 1/16" bit, 8-32 tap, a Holley idle mixture screw, and teflon tape.

Take off the original housing, make sure you are level and straight and drill from the back side out to the front with a 1/8" bit. Now from the check ball area with a 1/16" bit, drill at an angle towards the back in line with the vacuum port below. Don't mar up the check ball area. The idea is to enlarge the hole below into a little larger and kinda like a slotted opening. Drill with little pressue so you can feel when it opens to the vacuum passage below. Now, use a 8-32 tap, on the hole you made to the outside with the 1/8" bit. Again make sure you tap level and straight. Do not tap all the way through. Tap only as deep as it is required for the idle mixture screw to totally block the opening. You can test this by blowing through the check ball hole with the idle mixture screw in as far as you have tapped it. Keep tapping the opening and testing until it seals totally. I always used a couple wraps of teflon tape about 1/2 way up the screw to make a tight seal while testing. For the worry warts, once you've determined the best setting for your car, you can use loc-tite to set the screw. Your final results will look just like the picture posted previously with an idle mixture screw as the adjustment or set screw.

Dragula

JRoy, the buildup was funded over about 4 years.....lots of waiting.
Hook up? No way, I have to pedal the thing until about the middle of 2nd gear and it chirps third when the ol 700r4 hits it at 6500 RPM
Still in the tuning stages right now, so far with crappy traction I am only managing 13's......but when its tuned, with a good day with good conditions (Texas is HOT........air temp about 100 deg with road temp about 160) and something other than 235/60/15 tires, I think 12's are attainable.
I am ditching the RPM AirGap manifold......don't like it, the QC of the manifold was atrocious and it had such huge core shift that I couldn't even port match the darn thing.
I'm thinking about a Weiand Stealth........haven't heard bad things about them yet.