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Discussion Starter #61 (Edited)
Mark, what does your Buick run @ altitude?

I don't know where this quote came from yet " The Edelbrock #1910 is 850 cfm, larger than any Rochester model ever produced, and is fully capable of handling the needs of up to a 500 hp "fire breather". "

Maybe, but at 600hp, they fall flat on thier azzes unless they are HEAVILY prepped. Takes a bit more than simple tuning it would seem.

Meaning the larger 800+cfm Qjet runs ok, but the instant WOT of the Holley , it cannot replicate. It "FEELS LIKE" a stock 360 HP car with 3.73/s with the Qjet on. With the Holley, a WHOLE LOT MORE!

So, long story short. I now know what the engine builder meant by questioning my choice of a Qjet. The MJ467 's power level is above what a Qjet can support without some modifications,. It's like taking headers off and putting manifolds on. Night and day. And even Marks' race Qjet was off 22-24 HP from the 850 on the dyno.

So Eric, I don't expect to be able to light them up at will, at any speed. However, it would be nice to be able to make the power to overcome the tires once in a while. The idle was high , like 1050 rpm. All I've done is drain the fuel. Finding an appropriate shipping box is the hard part!


Maybe the sign I need to heed is that my old race 850 runs exceptionally well on the MJ467, like it BELONGS there. All that with one very minor tweak, a little more gap in the primary squirter arm. Even at low rpm it behaves surprisingly well. One small flat spot and this engine produces better vacuum than the 427, . if I swapped out the 085 PV for a 105 PV, that mid throttle stumble would likely disappear as well. The engine just wants that big 850 atop and eats every cfm of it up! Its like an old pair of hunting boots, fits perfect.

And now I need a "tailor" to get the Qjet close to fitting. But it wont be as "sexy" as the DP. Cant be,

My pay grade allows me to replace the diaphram on my leaf blower carb is all. Which worked out mint unlike my Qjet foray!
 

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Discussion Starter #64 (Edited)
Well, "STOCK APPEARING" means he is running a hidden electric pump, no power piston and other mods. So I know it can be done, Mark's "Buford" carb was set up to run 11's. It BANGS it nice. But it sure as heck isnt economical>Much akin to, if not WORSE than, the big pig HOLLEY double pumper at normal around town driving.

So I'm not looking for a drag carb here that gets 9 mpg at speed. I hope Eric can make Tom's big QJ RUN AS SMOOTHLY as the big pig holley does. Right now, the race Holley is nearly flawless just "puttin' 'round town". Again, one PV change, and it would be utterly flawless imho.

Both Qjets have ALOT of work to be done before they have the drivability of the Holley. Goofy result I know. The SBC carb is way off in driveability( much too lean) . The BBC truck carb, better. Odd, I know, but utterly true.

PS I ran the big pig race 850 for years on the 427 with a vacuum gauge ( still attached), so it was been tweaked on rather a bit by me. Its not "out of the box". Freckle too much carb for a 427, ( although not at 7200 rpms where the 750 pulled near 5" Hg) . Not too much for this beast though, even at 1800 rpms in 4h gear. Its freaky smooth.

HONESTLY, I might just suck up the 13 mpg highway cruise as my old race Holley mates with the MJ467 like it was MADE for it.( ps this with no vacuum advance and other tricks for more efficient cruise). Yet I would like to have at least one Qjet that can work well enough on the MJ467.

Mark's ORDERS to not race with a Qjet on, are spot on.
 

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Gene, if you don't mind my input,if you had a 515 HP MJ build,Qjet would be perfect. Bolt it on and forget about it.
600 HP. with a Qjet .Not so much..stick with the 850 for street and strip.
I would not be willing to give up any of those ponies,on or off the strip.
 

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Lot of talk about the 850 cfm 1910 carb in this thread. Can anyone tell me where they are getting the extra 50 CFM compared to a common large primary 1980s truck carb that is 800 cfm per Doug Roe? Had 'em both side by side and I sure can't find it. Seems like marketing BS to me.

Also... on that article above... not sure how anyone can talk about common rod / jet combinations without mentioning air bleeds. Some of the dual main bleed carbs in the 70s had 0.125 main bleeds and 76-77 jets and ~0.044"-0.049" metering rods to run right on a smogged up 305.
 

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Cliff pointed out the differences of the 1910 in his book but I can't remember where he thought the extra 50 cfm come from. If that friend of mine would ever give the book back.
Wonder if they flowed it at 1.55 vs. 1.5 or something.
I was thinking no mention of air bleeds either.
 

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How about using a fella who actually designed the Qjet as the rebuilder?
Tom Toal. Ontario NY . Tom was on the original Qjet desgn team. I just dropped off Harold Bettes Qjet that I cant seem to get to run, and Tom Mobley's which "flapped on and off".

Anyway, if anyone needs a Qjet redone I;d recommend Tom. I met up with him when I first got the Chevelle 20 years ago. Now I am FINALLY getting around to putting a proper Qjet on top. We'll see how gifted he still in a week or so when I bolt one on.

Just putting that out there, FYI.
Curious Gene, how can you make a recommendation when you have not installed or run the carb? Shouldn't you defer until you have the performance results you would expect with this builder? I fully think all will go well, but then again you seem to have run into less than satisfactory results before?

SMI did my LS5 OE carb about 5 years ago, quick turn around and snappy performance.
 
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Lot of talk about the 850 cfm 1910 carb in this thread. Can anyone tell me where they are getting the extra 50 CFM compared to a common large primary 1980s truck carb that is 800 cfm per Doug Roe? Had 'em both side by side and I sure can't find it. Seems like marketing BS to me.

Also... on that article above... not sure how anyone can talk about common rod / jet combinations without mentioning air bleeds. Some of the dual main bleed carbs in the 70s had 0.125 main bleeds and 76-77 jets and ~0.044"-0.049" metering rods to run right on a smogged up 305.
The difference in the cfm rating from 800 to 850 is the amount of opening of the secondary air flap. The full-open angle of the air flap is 1.270", as measured from the leading edge of the flaps to the rear of opening in the casting. The flaps also have two additional holes and two small tabs to help with air distribution into the secondaries.
Ruggles book has the specs of the 1910 and the M4M (75 and later) carbs. The 1910 has .070" upper air bleeds and 52M primary metering rods.
The accelerator pump is also modified with stiffer springs and has a bigger shot.
IMHO if you aren't starting with a M4M or an edelbrock carb, you probably won't achieve maximum results.
 

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Some interesting stuff from Cliff Ruggles forum :
The idle fuel is controlled by how the idle system is set-up. In theory it really wouldn't matter if the power piston was up or down as the starting point for the idle fuel is at the tiny hole in the bottom of the idle tubes at the bottom of the carburetor.

On very early units the upper idle bleeds were tiny and there to break the siphon effect as the fuel bowl would drain empty after shut-down.

Tiny bleeds didn't require very big idle tubes either. As emission standards tightened we started to see the factory come in with much larger idle bleeds to add more air to the fuel that made it to the idle mixture screws and transfer slots.

As they continued to increase air supply to the idle system most Q-jets were no longer able to function well when the user installed them on engines that made poor vacuum at idle speed.

This very quickly gave the Q-jet a bad reputation as a "high performance" carburetor even though the rest of the design is excellent for high performance work.

Between the HOPELESS 1965-66 (and some 67 models) plunger type bypass fuel valves, the early poorly designed hinge pin float arrangement, and leaning them up for emissions, Q-jet got an early bad reputation for high performance work.

Some specific models had a good reputation for high performance, the Chevy 7029207's for example were, and still are sought after by folks who race in Stock and Super Stock Classes. In reality the 207's are no different anyplace compared to the "grocery getter" and truck carbs from the same period, they just had really good idle calibrations and work well with "hefty" camshafts and lower vacuum at idle speed.

Not really trying to put a history lesson up here, but in reality the 1976 and later APT models are far superior to any of the early and highly coveted "high performance" factory Q-jets. They have an excellent float/hinge pin set-up, APT, convert to electric choke, and most are bigger CFM.

Edelbrock even patterned their "famous" 1910 850 cfm units from 1980-81 Chevy truck carburetors. They gave them a little more idle fuel, .149" fuel inlet seat, Marine length accl pump, larger primary jets, increased the open angle of the secondary airflaps, and added a couple of holes and "goofy" notches/bent tabs to the flaps.

They called them "850" cfm models and they were and are very popular to this day. As good as the 1910's are, they are identical to most 1979-86 truck SMAB Q-jets just have a few simple mods made to them.......Cliff
 

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The difference in the cfm rating from 800 to 850 is the amount of opening of the secondary air flap. The full-open angle of the air flap is 1.270", as measured from the leading edge of the flaps to the rear of opening in the casting.
I must have some 850's laying around then. :)
 

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I must have some 850's laying around then. :)
Yeah, all you have to do is shorten the secondary air valve stop. Make sure the flap reaches vertical.
This is on the carbs with 1/8" bigger primaries - M4M's and edelbrocks
 

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Discussion Starter #73
Thumper, I used Tom years ago. He is NOT a performance guru. Hence the carb is going to Eric for one last tweak.

I dont give recommendations lightly.

From Chris mr 4 speed: "Gene, if you don't mind my input,if you had a 515 HP MJ build,Qjet would be perfect. Bolt it on and forget about it.
600 HP. with a Qjet .Not so much..stick with the 850 for street and strip.
I would not be willing to give up any of those ponies,on or off the strip."

Oh, absolutely. The Holley is like nitrous as compared to the Qjets. Mark warned me on this, he knew. This beast is well beyond their "natural" limits. I simply had no idea how much "night and day" there would be. I'll have Eric tweak the Qjet once more, but that's it.

Maybe he'll get it to one or two plugs wires off, now its like three to four!
 

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Discussion Starter #75 (Edited)
The "pretty one" I have ( which is WAY far from supporting the MJ467) is one of the early of the late. The big benefit according to Mr Toal is the extended float.

mr 4 speed, I havent figured out how the new quote thingy works, but FOR SURE! .. chasin' my tail in circles like a flea-ridden hound....bucking the "Chevlle godz" who INSIST if you have one of the best BBC builders EVER build you a special BBC, DAMMIT LET IT BREATHE!

and now I have the tune for "Let It Be" in my head.... singin' words of wisdom... LET IT BREATHE... LET IT BREATHE..., let it breathe... Let IT BREATHE!! "

WORSE yet with them fancy dancy whiteazz 2" primary pipes, which MJ assured me were NOT too big. Yup. Particularly with a big Holley on the other end!

This BEAST could use a Dominator by Chevelle godz rules! At least that's what I think Eric said. :)

Sorry for all the grief I 've caused Mr Jones, Mr Mobley, Mr Bettes.....this is NOT your typical 454. Not even close. Where a Qjet might support some airflow, it truly mucks up the "port torque" characteristics of the higher HP MJ mills. ( unless you build it race style, of course) Must be the extreme velocity raging thru this beast that simply sucks a Qjet dry.

Mark, what the heck did you do to these heads!? :eek: ( I know its the complete system that does it, but cast iron oval port SHAZZAM man!)
 

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Discussion Starter #76
PS, didnt I read in the Roe book that going full vertical on the blades wasn't optimal, or was that the air valves? The "pretty carb" i have goes full vertical. The ugly truck carb goes to 15 degrees off or so, what I would deem stock. Way more rip with the big ugly than the little pretty. Yet, I don't know what other parameters are at work.

BIG UGLY will be in Eric hands as soon as I procure a suitable box. I'm sure it will be less ugly once Vintage Musclecar Parts takes it to the next level.

MR MOBLEY, this is not even a remote crack on your Qjet abilities. Sir, as compared to what the other Qjet did, yours was drivable.I truly do believe the MJ467 at this output level literally sucks the air out of the Qjet DRY. As far as our trade, that nice old 750dp, would NEVER hang with this thing. It was fine on the 427 thru 6300-6500. THANK YOU for having the right core to build me one on. We'll let Eric see if he can bring it up a notch or two.... at which point i;ll stop calling it " big ugly". He'll "unhooptify" my choke removal as well.

Nice carb Tom, Thank you sir.
 

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Didn't some Qjets have a problem with leakage internally? I remember a buddy using epoxy to seal one up.

Chas

Sent from my SM-G950U using Tapatalk
 

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Discussion Starter #78
Ya, its in all the books. I did see one dripping wet. When they machined them they had to use access ports which were then plugged. They are commonly cleaned up/ epoxied when rebuilt.
 

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I went to Cliff Ruggles website and filled out his form to request a custom rebuild kit for the model 1910 I just bought. He personally responded 3 times by email asking questions about my engine. Great guy : Cliffs High Performance Quadrajets – Quadrajet Carburetor Rebuild Kits, Parts, Quadrajet Rebuilding, Quadrajet Parts, Bushing Kits, Carb Tuning
Now I have two good qjets to play with; a model 1904 that Tom Mobley built for me. I expect that one will be the one I run most of the time. The 1910 will be the drag strip qjet (y)
Anyway, it will be fun swapping them out and tuning with them.
 
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