Amazed at the differences... and public perception...

[JasonM]

WHAT are people thinking?? (a bit of a rant)

I grew up with a 76 chevy k20. It provided the first opportunity to rebuild a carb back in about 1988. I ended up needing help, as I had no place trying to rebuild it. In hind sight, It probably only needed a new float, but I benefited by having a kind soul as a mentor help me out, and the whole experience is a positive memory.  Fast Forward 30 years, and I have rebuilt a handful of single barrel carbs, got interested in understanding more about how carburetors work. Cliff's work  is my text book, and a pile of quadrajet's from the junk yard have been an informative and interesting lab experience. 

Last summer I got an 82 Chrysler Imperial, for little more than a song. The previous owner had removed the disastrous attempt at fuel injection, and installed a Weiand dual plane on the low compression 318... and a holley 600 vacuum secondary. Other than mild curiosity and interest in "how they did it different" I had not given it a second look until I ran out of gas, which caused the one of the  float's to stick open.... which get us to the into of this post.

I fail to see the genius behind the Holley carb, and it's fanatic supporters...? What part of having gas pour  all over the intake manifold when removing a float bowl is acceptable?
At the least, I was ready for the issue by the time I got to the rear float. 

While in principal I would like to do some tuning on the carb to see if I could get it, to run as good as it can be... the prices are a bit prohibitive of getting too deep into it... for something that I don't really have much love for. 

I sort of disagree with the theory of trash-canning anything that does not work as desired with out first making real effort to understand why, and making attempts at rectifying the issue.

In this case, I am really considering yanking the holley and the intake manifold (it is a square bore intake) to make some adjustments and get a Quadrajet on there... Guessing everything will be better with a spread bore  carb considering the stock 318, and 2.2:1 rear axle ratio..  AND I expect to be satisfied and pleased with the sight of the  Q-jet, rather than conflicted that I have left the compromise in place. MAAYBE they are great as a circle track carb, or something like that.. but I can't see it.

[Cliff Ruggles]

I rebuild carburetors for a living, and not just Quadrajets.  I've done literally thousands of other types including many found on small power equipment.

I'm not overly fond of Holley carburetors and not because they can't be made to work OK.  Like anything else knowledge is power and if you spend enough time and funds on most any carb you can get a pretty decent result out of it.

It's been about 20 years ago now that I obtained a really nice Holley 4781-2 850cfm double pumper to try out on the 455 powering my Ventura.  I wanted to do some street, track and dyno testing in preparation for writing the Quadrajet book.

So I spend considerable time on the big Holley and got it running flawlessly in all areas.  This took some work, as it had minor issues in several areas that required a bit more than just jets, power valves and accl pump adjustments.  I had to get into the metering blocks and airbleeds in the main casting.  I removed the factory pressed-in bleeds and tapped all the appropriate holes for removable brass set screws so I could drill them to customer specifications.

The big Holley ended up being a very nice running carb, idled fine, good street manners and flawless at the drag strip.

Early on I had an accl pump (one of the new green ones for modern fuel blends) fail and it not only left me walking it dumped about a gallon of fuel on top of my engine.  I was lucky it didn't burn the car to the ground as I smelled fuel but didn't stop right away to check things out as I was trying to make it back to the shop.  When I finally got pulled over I very carefully lifted the hood, and tip-toed away until all the fuel evaporated.

Never had any further issues aside from having to re-gasket the carb a couple of times.  Even the pretty blue non-shrink/non-stick gaskets eventually go out of shape and require replacement.

Over the next few years I did quite a bit of testing, street, dyno and at the track.  The big Holley only worked better than the Q-jet in ONE area.  That was heavy part throttle w/o the secondaries.  For normal driving my test loop showed 160-180 miles on apprx 14 to 14.3 gallons of fuel.  The Q-jet on the same run did 200-230 every single time. 

On the dyno the Q-jet out powered the big Holley by 3-4hp every single time, but mid-range torque was just a tad better with the Holley.  I suspected this was from having much better boosters (down-leg) than just two fuel nozzles like a Q-jet has on the secondaries.

At the track the Q-jet ran .02-.05 seconds quicker and .3-.5 MPH faster on back to back test runs, verifying that the dyno testing was accurate.......continued below......

[Cliff Ruggles]

I'll add at this point that the 1977 Pontiac Q-jet that I use has never once had a problem in any area that left me walking or even with the hood up checking things out.  It's DEAD SOLID reliable in all areas to date and been in service on 4 different engines since the late 1980's.

I have had it apart a few times, but only to test out some of my products such as the lifetime warranty accl pump seals and different size fuel inlet seat assemblies combined with varying fuel pressure (drag racing stuff).

I wanted to find out the limitations of the Q-jets design for higher power set-ups so have continued to experiment with keeping it full on hard runs with a large CID engines and very fast car at the track.  Aside from that sort of testing the Q-jet on the engine now has pretty much been flawless and perfect in long term service.

I've never once seen a Holley carb go that distance w/o issues someplace, whether it be a leaky bowl screw gaskets, blown power valve or failed N/S assembly, they just don't make the grade as well from what I've seen.

Another area where the Holley accells over a Q-jet is idle quality with big cams.  This simply happens because 99 percent of the Q-jets out there were emission calibrated, Holley carbs for the most part are not.  Since the EPA was all over the factory to meet emissions and Q-jet carbs were being used they are extremely conservative for idle fuel and fuel in the "normal" driving range.  So right out of the box most any Holley is going to give the end user more positive results with aftermarket applications or anytime changes to the engine have been made to lower vacuum at idle considerably.

The good news there is that with only a few minor changes a Q-jet will idle equally as well on any engine, that's where the knowledge part comes in and it is well addressed in my book.

If the Q-jet has any other shortcomings to the Holley design it is only having one N/S assembly vs two.  Folks to this day rant and rave about fuel bowl capacity being inadequate on the Q-jet, but that is a myth regurgitated by folks dating back 50 years or so.......continued....

[Cliff Ruggles]

What matters when it comes to bowl capacity is that fuel delivery to the carb is adequate for the power level as any carb used MUST stay completely full on hard runs or tuning is affected and if/when you are way short on delivery you find out much sooner with a carb with less bowl capacity.

That typically comes from the vehicle "nosing over" at the top of first gear on a hard run when the bowl or bowls go empty.  I've done more testing in that area than 99.9 percent of the folks who will read this and can tell you that a Q-jet will work fine in high HP applications and really fast cars that hook hard at the track IF your fuel delivery system is adequate for the power level.  It's no more complicated than that and if/when you have issues they are easy to correct.  99 percent of the time we only have to install a high flow N/S assembly and we put one in every single kit we sell (.135").  If and when you need a larger one we will add it at no additional carb per request.

Even with that said a .135" N/S assembly is easily adequate for 500hp or so with good fuel delivery.  Past apprx 500hp we often go to the .140" or even the .145" seat just to make sure we've got that covered.

Anyhow, if anyone has any questions on this topic feel free to post them.  If you are having issues in any areas with your Q-jet post the problems as well.......thanks for listening.....Cliff

[JasonM]

I guess the enthusiasm for the Holley style carb, is based upon people's experience, and as you are saying Cliff, a Q-jet was designed as a emissions street carb, so it takes some knowledge to get it to  play happy with a camshaft that is amped up over what would be acceptable to the emissions folks.

 Still from a straight rebuild perspective the Q-jet is an elegant design, compared (in my opinion) to the holley with it's 0-rings for the fuel bowl, and replaceable secondary springs, and and and. I have yet to try and tune a Q-jet for a performance engine, so I may be eating my words as soon as next summer..

[Johnb]

With Cliff