Making a center-hung Holley work off road

[Bob Barry]

To all the people who would respond "It CAN'T work off-road; do yourself a favor and get a xxxxxxxxx", in advance I'll say thanks, I'll consider that some day, but right now this is the carb I have to work with. smile.gif

Now that I've taken the plunge with the TD adapter, I'm going to be asking for some tuning advice. I've ordered and will be picking up the power valve blowout kit, the off-road needle and seat kits (dual-inlet=two kits) and the jet extension tubes with the notched float.

The question then is "what next?" Is there any magic to getting a Holley to run right off-road? Is there any recommendations or guesses at a base setting for the jets on a 750cfm vacuum-secondary carb? Any recommendations for tuning guides to get me going on this?

TIA! smile.gif

[64Trvlr]

Bob
There is nothing wrong with Holleys, I've had several on the Jeeps I've owned. And I'm running one on my Traveler now. Is there any way you can exchange the center hung float stuff you ordered for side hung floats? The side hung ones work better off road, thats what I'm running and I haven't had any problems no matter what I'm doing. If not let me know and I'll tell you what I do to make them work off road. What is the altitude where you live and off road most ( that will help with baseline jets and power valves) and what have you done with the engine and exhaust?
:cool:

[Lindel]

On a mostly stock engine, start with a base idle mix of about 1.25 turns open, and go from there, tuning with a vacuum gauge, and then road test (using backfires and driveability as your guides) to really fine tune the idle and part throttle.

You'll also want to dampen the floats, and fuel as much as possible. Holley sells a bowl insert to keep the fuel slosh down to a minimum. The center hung bowls can be made to work, it just takes a little more doing. Keep in mind that these bowls are meant to deal with extremes of acceleration, not sidehills ;)

The off road needles and seats will go a long way, as will the extended vents to making the vehicle trail worthy.

On jet sizes (not remembering Holley's numbering scheme), go conservative and start small. Is the 3310 stock? If so, use that for your base, and install progressively smaller jets, again using driveability as your guide. The secondaries will have to be done at WOT (wide open throttle), and the process will be the same. I don't think you'll have to go any bigger than the stock jet sizes, only down. You probably don't have to change the secondary vacuum spring, for off road, if you do, we can address that later.

You might want to consider a dual stage power valve, it's not necessary, but would make tuning for lower rpms a little easier. Again, go conservative, bigger isn't better here. The 3310 is already plenty big ;) .

I'll touch on the accel pump, since you can adjust that in your driveway. It's unbelievably simple. Take the throttle from it's idle setting, and basically open it up, very quickly, the quicker the better. If the engine stumbles, increase the stroke. If the engine DOESN'T stumble, decrease the stroke until it begins to, and then back off again until it doesn't.

[Lindel]

Almost forgot to mention, if you haven't already, get the secondary metering block, and toss that stupid meter plate in the trash!! It's worthless junk, and is nearly impossible to tune for.

Also, make the investment in reusable gaskets (made of nitrile, I think). You can get them in multiples, you'll want 'em. ;)

[nograin]

Here's what I know from the same carb on my 'cuda.

I find it ironic that the off-roaders find the side hungs better because the road racers don't use them - fuel starvation in the long corners.

There is a needle and seat that has a little spring loaded base. The little spring is very easy to loose :eek: and I'm not that sure how well the system works. I'm back to regular viton needle and seats now.

You can buy side hung bowls and switch them (just more money) if you choose. From what I've seen - the off-road set-up for the side hungs uses a spring on the float pivot - that would seem more effective than the spring loaded needle. (Haven't done it myself so don't know for sure.)

Meter blocks - get the whistle style vent baffles and be carefull pinning them in. You can also extend the vents upward with some fuel hose.

The rear metering block they sell to replace the plate is OK but a) no power valve provision, b) rear idle mixture is not adjustable. B) should be very small anyway - but if you are into tuning, having them is nice. A)I beleive is a problem especially on the 750 vacuum 3310s. It means you have to go about 6-8 jet sizes richer than if you had a rear power valve. Depending on the combinations, this can lead to fuel pushing forward during hard braking to a stop - then thwe motor dies. A partial fix is to run jet extensions in the back. I am right now looking for a front metering block to use on the back. I do beleive that running on a single plane manifold - which you aren't, excasserbates the problem because single planes tend to require richer settings because of their airflow characteristics.

Sorry, Lindel, I don't like the nitrile rubber gaskets - they like to go funny and leak. My preference is for Holley or Barry Grant gaskets with a very light coat of vaseline, wd-40 or the like to remove most of the adhesives effectiveness.

The only fuel control kits I've seen for the bowls seem to require another spacer (making the bowl bigger) but do come with the fuel cell type honeycomb which seems like a good idea. My questions are whether you have to extend the bowls, is there room, and how will that effect heat soak?

I would just guess that the front jets would be betweem 69-74 and the backs from 75-80. (if you have backs). Start with what they give you, and go rich if you have any doubts.

Good luck.

[Bob Barry]

Thanks for all the quick advice!!! smile.gif

For specs, I've got a factory 360 4bbl, stock except for an Edelbrock Performer Cam/Lifters/Spring/Chain. Stock converter, 3.54 gears.

For conditions, I'm at sea-level, and the off-roading is mainly forest roads, climbing up and down rocky trails, so a lot of quick bumping, blipping the throttle, lots of rocking motion, jostling, etc. Good smooth throttle-response is a must, as is fuel-control- it's really easy to stall out if the jets get uncovered.

As far as side-hung vs. center-hung, the bowls on there now are center-hung; I didn't know there was a way to switch them to side-hung, as I thought that was the characteristic of the single-feed carb with the fuel transfer tube. I'll try to make these work, and switch if possible and necessary (I've only used this carb on my Olds 455 and 403, where forward motion is the only forces it really has to deal with... smile.gif ).

Lindel, you're right, I've got the secondary metering plate setup. Will the secondaries really come into play enough off-road (bumping over things on rocky hillclimbs with my QT in LO) to merit swapping to a rear plate with jets? This is not rock-crawling up vertical faces (though I wish!), so very little full-throttle 4000+rpm situations.

The 3310 is stock; 68's in the primaries, IIRC (this may be wrong); I'll check when I install the extension tubes. It's got the 6.5" single-stage power valve.

Now even Holley has these plates with dial-a-jet settings on it; I imagine they're expensive, but maybe worthwhile for on-the-spot tuning? Anybody have any first-hand experience with these setups?

For the extended vent, a loop of rubber line from one vent to the other, with an opening sliced in the top? I've seen that before, but never had occasion to use it.

[ August 09, 2001: Message edited by: Bob Barry ]

[Lindel]

I've seen the vent's setup that way, too. You have to remember that I was using my Holley's in go fast situations, so setup in my case was a little different (I was using the 3310 on a 289, believe it or not!).

You'll be able to make the center hung bowls work, and for less money than new bowls.

The reason I said start from base and go lean is you're over carbureted for a 360, by a huge amount.

I doubt that you'll ever need the secondaries on the trails, but I can garantee you will want them on the road you take to get to the trail!!

The secondary metering block vs. metering plate for the tuneability, nothing more, and you will have to tune your WOT settings, or you'll be wasting a LOT of gas at WOT.

You don't need a power valve for the secondary metering block becuase you're already past the point that the power valve would do anything!! The power valve is for the transition from idle, or near idle to WOT conditions only! It operates in conjunction with the accelerator pump to make a smooth transition from idle to WOT.

Personally, I wouldn't get the dial-a-jet, or the gimmicks that allow any jet changes from the outside of the bowl. The reason is that Holley's are "maintenance intensive", and you'd be adding to the complexity. The reason Holley's work as well as they do, and are as popular as they are, is they're fairly simple.

On the gaskets, the nitrile will work fine if you don't over-tighten them. If you spray them with silicone lube, they'll last that much longer.

On the issue of heat, since that's always a concern with FSJ's, the bigger extensions for the fuel bowls, and the foam inserts that come with them, is more fuel in the bowl is a good thing, since it will take longer to heat, and as a rule will stay cooler. Especially if you use a phenolic spacer to slow down heat transfer (Moroso makes one that will work well for $30)

[Veepster]

the vent system you mentioned BobBarry is the way to go...simple and easy...

metering plates...........leave it and don't worry about it...not worth the hassle to change out...

power valve......this can ONLY be adjusted with a vacuum guage...THERE IS NO OTHER WAY!...

accel pump...the pump cams come in many different sizes(the color tells you what it is) and if you do not have any transition problems don't worry about it...I have a chart that I can forward to you that will give you tons of info on pump cams

idle setup.....before you start this you need to make sure the throttle plates are in the correct position....there is a 'window' of adjustment for the idle speed screws, and you need to stay in it.....the throttle plates cover a transition slot in the throat, if you open the blades too much with the idle speed set screw it uncovers too much of the transtion slot and therefore will render your idle set screw useless....so what you do is set the blades in the correct position then play with the idle speed screw to verify how much you can change it before you are out of 'the window'.....usually a turn in each direction....

I wouuld suggest picking up a Holley book if you do not have one......SA Designs sells a few different ones, the info in them is incredible!!!

[JOECOOL]

Mr. Gasket makes some nifty fuel bowl o-ring gaskets, the round ones that go on the fuel bowl bolt holes. These are made of teflon and can be used over and over again. They are only 5-9 bucks from PAW this is in my opinion the biggest PITA about tuning Holleys.
Also on the adptor you use to mount the Holley on the stock manifold?
which one is that?
Before you mont it turn the carb upside down and mount the adaptor on the carb without a gasket to check that all those passages on the base of the carb are covered up. I went through a couple because they didnt. I ended up using a generic black plastic regular four hole holley spacer when I mounted my holley on my 360 with a stock 4bbl manifold.

[Lindel]

The one from Moroso is a plain 4 hole phenolic adapter, 1/2" thick. I got it mainly to isolate my Edelbrock 1406 from a hot intake manifold. Even still, I'm having a minor perculation issue with the high heat (ambient and under-hood combined).

[JOECOOL]

Yea that spacer is what I used but it was 1" thick to keep the carb cooler: Here a picture of my holley on the stock intake setup:
http://home.earthlink.net/~zzjoecool/wsnAA3C.html

[ August 09, 2001: Message edited by: RudyC ]

[Bob Barry]

<BLOCKQUOTE>quote:</font><HR>Originally posted by RudyC:
Also on the adptor you use to mount the Holley on the stock manifold?
which one is that?
Before you mont it turn the carb upside down and mount the adaptor on the carb without a gasket to check that all those passages on the base of the carb are covered up. I went through a couple because they didnt. I ended up using a generic black plastic regular four hole holley spacer when I mounted my holley on my 360 with a stock 4bbl manifold.<HR></BLOCKQUOTE>

I'm using the TD Performance (I think that's what TransDapt is called these days) TDP-2199 spacer for adapting a squarebore to the Motorcraft spreadbore pattern. I thought about hogging out a stock 4-hole squarebore spacer to mate with the spreadbore pattern, but the Motorcraft primaries are much smaller and the centers for the secondaries are in a way different location, so whatever I did there would be a "step" in the throttle-bore.

Plus, the Motorcraft secondaries extend out so far that only about 1/8" of the spacer would overlap the sealing ridge on the manifold.

If I could find an aluminum or plastic blank, I would have scribed the different carb gaskets on either side and used a drill and die-grinder to make my own, but I don't know of a source for "uncut" adapters. I suppose somewhere in the US you can walk into a place and ask for a 12"x12"x1" thick slab of aluminum with true faces, but not around here.

I'd love to find a factory squarebore 4-bbl AMC intake, but they are just not in the yards around here. No such thing as a "pick-a-part" anywhere near here, and all the other yards have crushed their pre-'85 stuff LONG ago.

[nograin]

There's got to be some more off road tricks for that carb. Especially to keep the float from bouncing around etc.

Hey, Were Is JeepBob?
Calling Jeep Bob.

Bob Barry,
You mentioned a transfer tube. I've only seen transfer tubes on side hung bowls, not center hung. There also was a nose inlet "lemans" bowl that I am not really familiar with.

Power valves are actuated by low manifold pressure, same as your old motocraft smile.gif and that is pretty much deep throttle territory.

My warning about the secondary block needing a powervalve obviously doesn't apply if you stay with the plate.

Hey Veepster. Do your accel pump cam charts show relation to throttle position? The one in the HP Books (also a good Holley Book) only has the total output of each cam.

Bob,
For your altitude, and 60 deg F, the H & H pocket dyno shows 68 Front jets on a 750 and 74 on a 780. The book was published in 1974 soooo, I'm guessing the 780 refers to the old version of the 3310 vac secondary carb, but am not sure. I'ld start with your 68s and if you get any ping at all (WOT) then jump up 4 if not 6 sizes. Best thing to do is make on of those homemade air fuel meters with an O2 sensor. Then there would be no questions as to whats up.
See Bob2000 website for details plus the old posts here. He also explains why not to worry about changing jets when moving a carb from on motor to another. It may or may not be neccessary.

[jeepbob]

I have been out thrashing on my CJ to get it ready to go to Silver Lake.

First off I will say that a 750 is way too much carb for a 360. The biggest thing needed for any kind of offroading is throttle responce and the 750 is just too big to allow that. Throttle responce is crisper if the air flow velocity is kept high and with the size of the throttle plates on a 750 it is not possible. I would trade it to some kid for a 600 with vac secondaries and side hung floats and some cash. The side hung floats do use a dampening spring to work off road better.
To make the holley power valve work the best, drive with a vac gauge hooked up to find your crusing vac and get a power valve that is about 4" lower (if your crusing vac is 10" then get a #6 power valve). Vent whistles are not reccomended for offroad use, not totally sure why, but have read 3 different articles saying this. There is a vent screen that IMO works well and while I have not needed to do it, after the vent tubes are extended, K&N makes a small filter that can go over the tube and this makes it hard for fuel to get out. Run your float levels a little lower than the openings. Everyone else has pretty well covered the acc pump adjustments, but the Holley Tric kits do have a larger squirter that also helps.
The secondary spring should be changed and for your motor with a 600, I would use a light spring unless mileage is a concern, then I would go up 1 step. Have someone follow you, and go lighter until there is black smoke under heavey acceleration, then go back 1 step. This sounds like a hack way to set the opening point, but it is much less expensive than a dyno and much safer and easier on equipment than holding the brakes and standing on the gas.
Tune the idle circut with a vac gauge unless you have an O2 sensor and gauge or a sniffer this is the most accurate way.
An interesting concept that I just read about is to put an O2 sensor in and tune the carb using the rich/lean meter. This way you know you got it right.

[64Trvlr]

JeepBob
That's a much better idea than the one I gave him. And with the smaller carb the throttle response is going to be great. That's the best way to go.
:cool:

[Bob Barry]

OK, in no particular order:

Veep: I'd like to see that pump cam chart, as the four cams I've got are differentiated by color, but nothing else.

Lindel: A two-stage power valve from a 2150 screws right into the block, so I might try that (I've got a few extras around); otherwise I'll keep the stock 6.5".

Rudy: I've picked I'm going to get a set of reuseable gaskets, at least so I don't have to scrape gaskets any more. :(

Nograin: I looked, and the stock jets are 72's, so it looks like I might just stock up on a set of jets.

Thanks for all the advice; I'll report back the results.

[Veepster]

yes the chart I have shows total output and relation to throttle position and also the differences in the 2 mounting holes......I will scan and post.....I think there is about 6-10 different pump cams..

I have been using thr float whistle for a long time!!...it works for me....

also to help with offroading.....if you have adjustable fuel pressure decrease it to about 3 pounds, it wil help from blowing the needle open

[Bob Barry]

Well, guys, it works off-road!!!

I got the TD Performance adapter late yesterday (Friday), so I put it on that night, but didn't want to tune it and wake the neighbors. Besides, the rear vacuum fitting interferes directly with the Holley's PCV port, so I had to run out this morning (Saturday) and buy a pipe-plug for that hole.

I installed it with #68 jets in the primaries and the stock metering plate in the back. It has the off-road seats, the jet extension tubes, and a loop of 1/4" fuel-line connecting the bowl-vents, with an opening slit at the top of the loop. I've still got the "whistle"-type vent baffle, which I'll install when I can find the time.

The bottom of my carb is a little odd, so I couldn't install the powervalve anti-blowout kit; there are TWO passages to the power-valve vacuum chamber, a big and a little one, and the big one seems to have threads in it. The small passage opens into a cast-in channel, whereas the kit presumes it opens at the flat base portion of the carb. This is a bummer, because I've already popped back through the carb a couple times, and don't want to put a good power-valve in there and start tuning that system until the check-ball is installed. The current power-valve still seems to be working, though; does every pop-back through the carb cause the power-valve diaphram to rip?

I was able to scavenge the electric choke mini-harness from the '79 2-bbl Limited I parted, and tie it into the factory oil-pressure sensor to keep the choke from getting voltage until the engine is running.

All I did this morning was adjust the floats and adjust idle-speed. That's because I was leaving at 11:00 to go test out the carb.

RESULTS: Fantastic. That is, fantastic as measured by the amount of attention I had to pay to the carb, which was none, because it didn't studder, stumble, stall, flood, or do anything but run and run and run, no matter what angle I ran it at, how little or much throttle I gave it, how long I let it sit idling while spotting my wheeling-pal through the trail, etc.

There is a momentary flat-spot when transitioning from idle or cruise to acceleration with partial-throttle; it holds back for a second, then catches right back up. Might this be an accelerator pump cam deal to tune this spot out?

What I really need is a set of true-duals to complement the upgraded intake setup. Already I can tell that this carb is making more power than the 4350; usually swapping from something like a Qjet to a Holley doesn't net you much performance improvement, if any.

Thanks again for all the posts; now that it's working on the truck, I'll just be into fine-tuning it.

[64Trvlr]

Bob
Glad to hear all went well with your test. Try adjusting the accelerator pump before you change cams. How new is the carb?
:cool:

[Bob Barry]

<BLOCKQUOTE>quote:</font><HR>Originally posted by 64Trvlr:
Bob
Glad to hear all went well with your test. Try adjusting the accelerator pump before you change cams. How new is the carb?
:cool:<HR></BLOCKQUOTE>

I'll try adjusting it; what's the SOP for that adjustment? (I gotta get a book on this stuff, rather than bugging people on the list with every little question) Literally the only thing I was able to adjust before I was scheduled to hit the trail was the float-level.

The carb itself is pretty old; I must have bought it in 1983 or so (and then I bought it as a Holley rebuild), but I've only run it for a total of two years since then. It's a 3310-2. Are you thinking its design may preclude the easy installation of that Power-valve saver? That'd stink. :(

[JOECOOL]

Well I don't sweat he powervalve saver too much.Once its all dialed in you shouldn't have any more back fire to worry about. The bigger hole may be for a screw.
The stumble does sound like an accel pump ajustment is needed.
I just close up the spring loaded screw on the lever till it just has some free play and then get rid of the free play. I hope that sounds right.
What I liked best about the holley (other than the newfound power)was that it totally got rid of that cold morning stumble that I could never get rid of with the motorcraft carb. Just fire it up and wait a few seconds and drive. It was like my wifes fuel injected Caravan.

[Lindel]

The adj procedure is buried in amongst this thread somewhere around the beginning. ;)

On the secondary metering block, there's no place to put a power valve, so that's not an issue! There's the blank for one, if it's going to be a primary metering block, at the beginning of the casting process, but if it's slated to be a secondary metering block, nothing is done to the power valve fitting. It's left as a machined in blank.

Glad it's working so well, Bob. Let me know if there's anything else you need!! smile.gif

[Veepster]

accel pump adjustments.......there is only one adjustment that should be made to the linkage.....and that is to verify there is no bind at full throttle....there is supposed to be .015-.020 clearance between the pump arm and the accel pump diaphram at WOT.....I would verify that before any changes....

[Veepster]

No grain and Bob Barry..

I e-mailed you the pump cam chart...I was in a hurry so I hope it is OK......let me know!...If anybody else wants it send me an e-mail at bart@teamgodspeed.com

[Bob Barry]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Veepster:
No grain and Bob Barry..

I e-mailed you the pump cam chart...I was in a hurry so I hope it is OK......let me know!...If anybody else wants it send me an e-mail at bart@teamgodspeed.com<HR></BLOCKQUOTE>

It came through fine over here; thanks!!!

I'll let you know how the tuning goes.

[nograin]

Sorry Veep! Meant to e-mail you right back, I stared at it for a while doing some mental gymnastics. It was 1 am here and I guess the synapse that was saying e-mail you back a BIG Thanks must of misfired.

Thats second chart was real helpful. It shows that me that I can extend my shot, and even though the total volume is down, the amount from off idle could be the same using another cam. I like :D

[Bob Barry]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Bob Barry:
Well, guys, it works off-road!!!
[snip]
There is a momentary flat-spot when transitioning from idle or cruise to acceleration with partial-throttle; it holds back for a second, then catches right back up. Might this be an accelerator pump cam deal to tune this spot out?<HR></BLOCKQUOTE>

Well, I finally got around to tuning this flat-spot; actually, once I changed the power-valve to a two-stage unit, the flat spot turned into a serious bog, the kind that stalls out your truck when you're pulling out into traffic quickly.

It's no surprise, as a Holley model 3310 750cfm carb is too much carb for this motor, even though it's a vacuum-secondary carb. The engine does not pull enough air for the main circuits to start drawing fuel soon enough, so there is a huge transition window that I had to cover with tuning the carb.

The truck would idle fine, and once past that spot was hunky-dory, but the transition from the idle circuit to the mains was leaving a huge lean spot that would pop back through the carb and stall out if I didn't feather it.

The first thought, after browsing the 'net for Holley tuning tips (which there are a LOT of, btw), was to go up in shooter size. I installed the biggest shooter that came in the Holley Trick-kit (a necessary resource for any Holley tuning), a #37, which was significantly bigger than the stock #25. Unfortunately, the bog was still there, as bad as ever.

So I installed a blue accelerator-pump cam on the #1 screw setting. Still the big bog.

Next was ignition timing. With the distributor plugged, I set it to 15º advanced. This helped a bit, but didn't solve the problem completely either. The bog was serious; when I tried to crack the throttle by hand, I could sense this big "void" in the plenum that called for more fuel.

I know that scientifically I'm supposed to try one change at a time so I could evaluate it for improvement, but since the existing combination was so far out of whack I decided to try a completely different combination all at once: I moved up from #68 to #70 main jets, went with a 6.5" single-stage power valve, and set the blue acclerator-pump cam at the #2 hole.

That did the trick; now I can punch it from a dead stop, and it pulls smooth and hard. My driveway is an incline, so I pulsed the throttle going up it, and it would pull, then drop when I backed off, and drop its idle real low but not ever stall. It might be running a little rich, though, so I might try to take some fuel out.

Now I can start backtracking to see if any of the changes weren't necessary or optimal. I did try the blue cam back on the #1 screw hole, and a bit of hesitation came back so it looks like hole #2 is the winner. I'll try a smaller accelerator-pump shooter next, maybe a #31, and see if the bog starts to creep back in.

I'm also thinking of trying an 8.5" power-valve or higher, since this truck idles in drive with 15" of vacuum; I'll have to check it at cruise. If that power-valve can kick in earlier, then maybe I can take some fuel out of the main jets and run those a bit smaller.

Any particular pointers for further fine-tuning the transition? I know there's a half-dozen ways to cover up that gap in the fuel-curve, and my tuning has, but I'm quite sure it's far from optimal.

I'm just happy I don't have to fear for my life when I'm pulling out into traffic. smile.gif

[jeepbob]

Bob,
I am not a big fan of the 2 stage power valve as it tends never quite work like you think they should. I would try to find your crusing vac then drop back to a valve that is about 4" lower that that. If the power valve opens to early then you are useing it instead of the main jets to get the fuel you need. The power valve should only open when the main jets can not supply enough fuel like when under mid to heavy acceleration or pulling a heavy load. If you have a bid bog you may want to go with a heavier spring in the secondaries so they do not open as soon and the motor can handle the extra air. The 360 should be more than enough motor to overwhelm the primaries but not the primaries and secondaries together so tuning the secondary spring becomes important.

[Bob Barry]

JeepBob,

I think the secondaries are working pretty well. I used to (and still do) tune the opening of the secondaries on my Qjets by "ear"; they have a distinctive "moan" when they start to open. On this Holley, the "moan" doesn't really start until I start to build speed. It's running the stock secondary spring, which is pretty heavy, IIRC.

I'll have to run the vacuum-gauge into the cabin and see what I'm cruising at. Power was good once it was up and running, even when it was bogging at transition, so the power valve was not WAY off to begin with.

It's good to hear from someone else that the two-stage valves aren't all they're cracked u to be. I wonder if a Motorcraft 2150 might run better with a single-stage valve than with the two-stage valve they came with? (they are exact interchanges). Maybe some of this tuning practice can translate over to my 2150 as well.

[jeepbob]

The "moan" you hear with Q/jets and other carbs is the air rushing thru the "flapper" plates on the top of the secondaries. Q/jets and Carter Thermoquads are famous for this. The reason for the moan is that the flappers must actually be sucked open by the motor. The throttle plates may be wide open in the secondaries but until there is enough vac to open the flappers there is no flow. This is the inheirent design flaw that I do not like as it will create a bog by lowering the air speed thru the venturies so you may not be able to draw enough fuel to stop the bog. The holleys work by just cracking the throttle plates as needed and this helps keep the air speed up. You may still need a heavier spring in the secondaries. With my 600, I find that a light spring works well. It is still possible that you are not (like you stated) getting enough air speed thru the primaries to get enough fuel to prevent a bog and a power valve that opens sooner would help cure that. It would prolly also let you go back to smaller jets.
BTW I am glad to see some one else using a Holley off road with success (besides me) as I believe that they are mainly misunderstood so every one just blames the the carb.

[64Trvlr]

I'm running a Holley on mine and it works great. Good to see I'm not he only one here using one.
:cool: