Let me preface my question with the statement that of all the years I've dealt with Q-jets and Holleys, I simply prefer the Edelbrocks because I've always had good luck with them, so I'm going to stick with it. I'm looking at the Performer series, but I am unsure of getting the 600 (1406) or the 750 (1411). Or should I step up to the AVS, which has a 650cfm model (18069) I read in another thread that a guy didn't have good low-end with his 750, but he was also running a single plane intake. I will be upgrading to a Performer intake at some point soon - but the carb comes first because my existing Q-jet is hemorrhaging gas. The engine is stock, and all I'm really looking for is to pick up a little performance - mileage really isn't an issue where I live. Thanks in advance for your input!
Ok - let's say I don't want to discount the Q-jet entirely, if you have any input about a rebuilt Q-jet, please include that. I live in a relatively small town, so the odds of someone rebuilding the carb who "knows what they are doing" are pretty slim. But with the right arguement, I suppose I can be open to buying a rebuild Q-jet, too.
I've tested the Edelbrock carburetors extensively, street, dyno and at the track. The AFB clones are useless, IMHO. They lack any adjustment for the opening rate of the secondary airflap. They are calibrated for SBC engines (or any other low torque engine) pushing around relatively heavy cars. The support for them is excellent, so tuning them in is NOT a problem. The problem is that you can not tune them for a smooth transition onto the secondaries. Also keep in mind that the AFB design was obsoleted in 1967 because it would NOT pass emissions. They are going to be thristy units in comparison to Q-jets and TQ's. I would also add here, that if anyone is paying attention, the AFB clones are most popular with the SBC crowd. This is marketing more than anything else, backed up by page after page in the popular HP magazines about how many zillion HP they will make on Westech's dyno sitting on little tiny engines with "modern" heads and "whiz-bang" cam profiles in them. The enthusiast checks them out, and finds out for less than the price or completely/correctly rebuilding his factory q-jet, he can buy a new carburetor and an aluminum intake. Cripe, the intakes don't even make any more, if as much power (average) as the factory SBC iron ones, but it's enough to sell about 20,000 of them a month....FWIW. Anyhow, Edelbrock is fully aware of the shortcomings of the AFB clones, so they gave it an AVS airdoor, which is adjustable. BIG improvment for them. In actual testing on my own vehicle, and another one vehicle donated by one of my customers, we flogged the Edelbrock units to death at the track on a private track rental. Tested a total of 8 carburetors on two cars. The AFB clones wouldn't work at all, period. They just "puked" all over themselves anytime we went quickly to full throttle, then ran fine once the engine recovered. No way to correct this as their is no adjustment, or accl/POE system for the secondaries. The AVS unit was much better, but required a LOT of spring tension to avoid a lean condition (puking all over itself) on the starting line. This occured moreso with my low 11 second car than the low 12 second car we also tested it on. We ended up getting clean runs with the AVS clone, and it was the slowest of the lot by .08 seconds and down 2mph over the next closest unit. My advice, completely/correctly rebuild the Q-jet, calibrate it EXACTLY for the application. The fuel inlet location is correct, choke, linkage, vacuum fittings, etc for the application. There isn't an aftermarket carburetor out there than will make more power, and none of them will equal the efficiency for "normal" driving.....Cliff PS: Some of our back to back testing was witness (and requested) by representatives from some of the HP Magazines. Since my lowly 1977 Q-jet outran every other type/make/model of aftermarket carburetor we tested it against, dyno and at the track, you will NOT see any of this information in print anyplace, wonder why?
Thank you for the backstory on the Edelbrocks, it's appreciated. The more I read here, the more it seems like my experience with Q-jets have been bad perhaps because they were never rebuilt correctly, or I just had an old crappy one that needed a proper rebuild. I've got an email into John Osborne, who seems pretty highly recommended here on the boards - any other good Q-jet rebuilders out there that can be recommended?
Ok, so Cliff R (from above) - you rebuild Q-jets as well? If so, here is my information and questions: I am running a 1968 Buick Riviera, 430, 4bbl. Stock engine, stock intake - but will soon be putting on a Performer intake just to get a little more performance. Stock drivetrain, no air conditioning and stock exhaust. Not sure what other factors you might need, but that's all I can think of at the moment. What is the cost and procedure for having my carb rebuilt, along with the expected wait time? Thanks!
Jason, rather than waiting to see if he visits this thread again, just send him a private message or contact him at http://www.cliffshighperformance.com/ . Devon
Thanks, and those things are better discussed via emails or by calling the shop anyhow. We're on the Forums to help folks, but still have to pay the bills!....Cliff
