[scott-462]

How well does an out of the box carb work on a mild built 455, lets say a holley for example? It has an XE284 cam. From research it sounds like a Qjet needs lots of work to run well.

[2manyT/A'S]

If your car is a keeper....driven on the street primarily...you will way ahead of the game to get a correctly set up Q-jet.......amazing performance...low maintenance...decent fuel economy... and far LESS likely to burst into flames than a holly...

[CROCIE JR]

I have been having good luck with out of the box Air/Fuel readings at WOT and cruise with the Quick Fuel Hot Rod series 750s-Super Street series 750-850 and Holley Ultra 4150 Aluminum Double Pumper as well as the 4150 Street HP (no choke). The JET stage 2 is a good choice for a Q-Jet based carb. They all seem to be a little conservative on the the jetting (rich) on the engines I have put them on. Stay away from the Avengers. I have had to do more work to get them right than the others I mentioned.

[Don 79 TA]

i'd suggest for a few $$'s more getting a custom built carb
there are some nice places you can get various models from
i've used JET and AED, and actually i don't think when i did it the cost was that much more
i've never had an issue with any of them, maybe i have been spot on lucky but each one was basically drop on and go, of course had to give full specs and all details when they were built

[Cliff R]

Completely "hit and miss" to find any "out of the box" carb to work well with that combo. Compression is "low" for the cam, cam is ground on a 110LSA, so it's going to require considerable idle fuel delivery and idle bypass air to be happy.

Most of the "aftermarket" Holley based carburetors will stand more of a fighting change to idle and drive OK as they are not emission calibrated, and quite generous for idle fuel delivery, and pig-ars rich on the primary side. We still find ourselves custom tuning most everything these days, as the combinations folks come up with for engine set-ups are far from "ideal" in terms of vacuum at idle and smooth/strong power right off idle and in the rpm range where the engine will spend most of it's time.

Distributor tuning is also extremely important, as a custom engine combo requires more initial timing, and typically less total timing at cruise, combined with a quicker mechanical advance curve. It all works together to get a good end result, so a "custom" carburetor isn't always the only thing one needs to purchase to get a good end result with these things......Cliff

[DOC]

Scott,
I have almost the same engine as your sig. Minus the RPM intake and studs. Cliff did my qjet back in 2004/2005 time frame. all I have to say is I have yet to foul a plug or have any fuel related issues. Does not burn your eyes at idle either. Not sure what kind of magic or voodoo he put into the carb but it works great! Glad I got rid of the holley that was on it.

[72LuxuryLeMansLa.]

Originally Posted by scott-462

How well does an out of the box carb work on a mild built 455, lets say a holley for example? It has an XE284 cam. From research it sounds like a Qjet needs lots of work to run well.

Call Sean and tell him your specs and you will have a Qjet in days. I would guess it wont be as good as a Cliff Qjet but I don't think Cliff sells them outright, he rebuilds them and has a year long waiting list.

http://www.smicarburetor.com/product.../productID/839

[PONTIAC DUDE]

The only out of the box carb I have ever found to work is the Thermoquad 9800 (800cfm) series for GM useage.

Wish they still made them. It flies and cruises like a dream. Will burn the tires off the car all thru 1st & 2nd. Have to short shift it to hook or stay out of the ditches. LOL.

Like to thank The Carb King. Jon for the Thermoquad he sent me awhile back for Karen's 79 455 T/A.


http://www.thecarburetorshop.com/


for this bolt on out of the box insight.

[scott-462]

Thanks for the input guys and cliff i've messed with my HEI some but still needs more work. Changed the weights and put in lighter springs, but from many comments it sounds like the mr gasket light springs wear out quickly and i should change them. The car doesnt bog or stall but it does buck at idle at a stop light. It also still has a stock converter. I havnt really pushed the engine yet (~700 miles fresh), but have done a few burnouts and obviously broke in the rings. I'm concerned about this stock reman Qjet from 1998 being too lean and causing damage. I dont have an A/F meter or the money for a dyno tuning session. I havnt done a plug chop either. It looks as though the throttle shaft may be worn as it appears its leaked fuel from that area down onto the intake. Seems strange it would be wore out so soon unless the company didnt bush the shaft when it was remanufactured. I really want/need to get this thing tuned so i can stop being concerned if its running too lean or going to cause damage. Like i said though, it just gets driven normally. I've checked out cliffs site and noticed the 12 month turn around so thats not an option. I've considered getting a kit, but would need some pretty good directions on what to modify in the carb. Enlarging the tubes/ports in the idle circuit ect.. I've been doing a lot of reading, so i'm trying to educate myself but still a little nervous. I have rebuilt a Qjet before for an RV and it ran better afterwards but the engine still had a burnt valve or something and never drove so i cant attest to it being correctly rebuilt LOL.. My original question mainly comes up because i've found several holleys for sale on craigslist for about 100-125 bucks and was curious how well they would be setup for this engine in an out of the box state. I've also read it isnt recommended to use a reman Qjet for a build since often times the components to the carb get miss matched and causes them to be difficult to tune properly. One carb i found was a holley 850 DP and he was looking to trade it for a 650 DP, which i just so happen to have one laying around somewhere that needs rebuilt.

[Skip Fix]

I've had two carbs pretty darned close out of the box for my 455 cars. Demon 850 DP on one(race gas 455) and a Holley 850 DP on my current pump gas 455 in the 78. The 78 needed one step smaller jets for a better AFR. It had a better cruise fuel curve than the Demon did on that motor.

The Demon also was not too far off for the 500" IA it now sits on.

As far as Q jets a 73 SD SR out of the box has been pretty close fo a lot of my combos.

[Cliff R]

For the most part we avoid commercially "remanufactured" q-jets here, they are not only full of crappy parts, they are typically "butchered" beyond easy repair.

As far as Holley and Holley clones, you've got to get into the more expensive units or you are just throwing money out the window, IMHO. It's not really that difficult to get one that will work flawlessly at full throttle. Most still need some tweaking on the primary side with jets, airbleeds and metering block mods to clean them up enough so your aren't looking for fuel every 100 miles or so.

The Performer series Edelbrocks have no adjustment for the secondary air door, so it's hit and miss there, more misses than hits from what I've seen with them. Haven't tested one yet that didn't puke all over itself on a high HP to weight ratio set-up. They seem to fair pretty well on applications like 6000lb Chevy trucks with 36" tires, 3.08 gears, stock converters and 195hp 350 engines. Those folks absolutely LOVE them, as does a pretty big percentage of the Chevy crowd.

Edelbrock's AVS faired pretty well in the testing we did with them here, pretty much the standard AFB clone with the AVS air door on the secondaries. It took two runs at the track to nail down a smooth launch, but it still ran slower than every other carb we tested that day on two different vehicles. I still don't like them much, they are shiny, ugly, take up too much room and most require some "cobbling" with Shaker and Ram Air set-ups, not to mention they don't fit the stock intakes without an adapter.

When the smoke clears and dust settles, I'll still take the Q-jet over anything else. They will use less fuel to do the same thing, and run right with and even outrun even the best prepared Holley/Holley clones. They will be dead solid reliable in long term service, all secondary tuning is external and only takes seconds, and no place to leak below the fuel level.

I don't say that because that's the main stay of my business. Our backlog is nearly a year, and I turn down ten times more work than I take in. With no "dog in the fight", my comments are simply based on over 3 decades of building/driving and racing these cars, and tuning many thousands of them for folks doing the same thing......Cliff

[gtofreek]

Originally Posted by 72LuxuryLeMansLa.

Call Sean and tell him your specs and you will have a Qjet in days. I would guess it wont be as good as a Cliff Qjet but I don't think Cliff sells them outright,he rebuilds them and has a year long waiting list.

http://www.smicarburetor.com/product.../productID/839

That's what happens when you're good at what you do.

The guy I work with, Jeff Koerner, is one of the best there is with the Holley carb. People have waited a long time to get a carb from him. Bitched at times, too, but in the end, had huge smiles on their face when they drove them, and were happy to wait. Just sucks waiting sometimes!

[72LuxuryLeMansLa.]

Originally Posted by gtofreek

That's what happens when you're good at what you do.

The guy I work with, Jeff Koerner, is one of the best there is with the Holley carb. People have waited a long time to get a carb from him. Bitched at times, too, but in the end, had huge smiles on their face when they drove them, and were happy to wait. Just sucks waiting sometimes!

No doubt. I only recommend SMI because of the wait for Cliff. It costs double but I figure get on the list with Cliff and buy one from SMI to use until you get the one back you sent to Cliff. Either keep the SMI for back up or ebay it to recover some of the cash. No reason to allow your car to sit idle for a year.

[Lee]

For the cost of some of the custom carbs, I would suggest buying a wide-band and a box stock HP type carb, and tuning it yourself.

I had an OLD 4779 750 DP on my old Firebird. It had jet and PV changes, but nothing else. A friend built a near-duplicate of my motor, but had a custom built carb made for his motor, and insisted we try that carb on my motor - went to the track made a couple passes with my carb, installed the custom carb and slowed down! The guy that bought the 'bird from me has tested a few different carbs on it, and still hasn't found one that worked any better. I'd even get to close to 14mpg cruising on the highway with the DP.

[David Brown]

Out of the box carbs are like one size fits all tee shirts. On average, they fit. But some people look like they are wearing their big brother's shirt, and others looked like they ate way to much for Thanksgiving dinner.

I'd rebuild, or have one rebuilt if it's beyond your expertise, a Q-jet. For street driving and in a lot of performance application, you will be much happier long term.

[scott-462]

As for Qjets i have three of them. One is a BOP thats on the car now. Its the remanufactured unit from 1998 and i think the throttle shaft might be leaking. The other two are chevy Qjets and one i rebuilt and has maybe an hour of run time on it. I dont think any of them are 850's though. One came off a mid 80's 454 RV (rebuilt) and the other was in a chevy truck owners tool box but unknown what it actually came from. When i rebuilt the one from the RV i was extremely surprised when i had to cut away some of the base plate area to replace two screws in it. Some kind of adjusting screws that were capped off from the factory?? I cant recall exactly what they are now but cutting the base plate around them to get them out WAS in the directions!!.. It doesnt effect it sealing though. I did not rebush that carb and i'm not totally sure of the condition of the seal around the shaft.

[David Brown]

Installing bushings is not that big a deal. Not sure if Cliff sells the bushings and the reaming tool, but he probably does. Makes a huge difference if they are worn.

[72LuxuryLeMansLa.]

Originally Posted by David Brown

Installing bushings is not that big a deal. Not sure if Cliff sells the bushings and the reaming tool, but he probably does. Makes a huge difference if they are worn.

Here it is: http://www.cliffshighperformance.com/bushings.html

[gtofreek]

Originally Posted by scott-462

As for Qjets i have three of them. One is a BOP thats on the car now. Its the remanufactured unit from 1998 and i think the throttle shaft might be leaking. The other two are chevy Qjets and one i rebuilt and has maybe an hour of run time on it. I dont think any of them are 850's though. One came off a mid 80's 454 RV (rebuilt) and the other was in a chevy truck owners tool box but unknown what it actually came from. When i rebuilt the one from the RV i was extremely surprised when i had to cut away some of the base plate area to replace two screws in it. Some kind of adjusting screws that were capped off from the factory?? I cant recall exactly what they are now but cutting the base plate around them to get them out WAS in the directions!!.. It doesnt effect it sealing though. I did not rebush that carb and i'm not totally sure of the condition of the seal around the shaft.

I believe you are talking about the caps covering the air/fuel mixture screws.

[scott-462]

Most likely, and i've been on cliffs site before. What about modifications to the carb itself, other than just changing gaskets/jets. Modifying the idle circuit? Are there detailed directions on this or possibly youtube videos? Right now i have 8" of vacuum and the power brakes arnt working very well.