one of my 66's has a squarebore and the other a spreadbore I have the choice for a new 401 I am building any comments both are Qjets rocky
spreadbore all the way Rocky: I would opt for the spreadbore and QJ all the way. I've tried several different manifold/carb combos over the years and the 66 spreadbore and a good QJ outperformed 'em all. I even prefer it over the factory dual 4 set-up. I ran a 65 GS 4-speed for years and while the dual 4 setup "looked" cool and pulled pretty good at the top end, the QJ arrangement performed better overall, it was noticeable enough that I removed the dual 4 setup and kept the QJ on it. You mentioned in your post that both carbs you were thinking about were QJ's???????? The QJ will only fit the (one year only) 66 spreadbore while the square bore was designed for a Carter AFB and was used for 65 and earlier. What year manifold is the squarebore? Are you talking about the old 4-jet Rochester?
carbs dave I checked the carbs and the squarebore is a rochy 4 jet and the spreadbore is a rochy Q-jet the squarebore manifold has 65 on it while the spreadbore has no date cast on it the spreadbore rochy Q-jet may well be a late model but that does not explain the spreadbore manifold! any ideas
Hot Rod magazine had an article where they claim they got 16mpg on the road with a Qjet on a 65 GS. I can get you the specifics if you want them.
Q-JET OR DUAL QUAD TO ADD TO THAT NOTE I HAVE A 66GS SKYLARK WITH THE AFB CARB AND CAR CRAFT ALSO HAD A 66GS 401 LIKE MINE THAT THEY WENT FROM THE AFB TO THE Q-JET AND CLAIM 17MPG AS LONG AS YOU DRIVE LIKE A HONDA BUT FOR MINE LIKE THE CAR CRAFT BECAUSE HIS AND ALSO MINE ARE OFF 66 RIVS THEY HAVE TO BE RE-JETTED FOR THE 401 AND I AM ABOUT TO BUY THE DAUL QUAD SETUP ALSO BUT IT WILL BE MORE FOR SHOW AND ALSO WILL REQUIRE RE-JETTING TO BREATHE ON MY 401 AS IT IS OFF A RIV ALSO A GOOD PLACE TO INQUIRE ON THE CARB AND ITS JETTING WOULD BE JET PERFORMANCE CARB DEPT AT 714-848-5500 GOOD LUCK AND SMOKE SOME CHEVYS MIKE 66GS SKYLARK 401 65 SKYLARK 455:Brow:
What I used to like to run was the spreadbore manifold with a 1000 cfm thermo quad carb. The other set-up that I really liked was a reworked square bore manifold that we opened up for a holley 850 throtle bore size, but we also opened the primary to secondary holes on each side so the manifold looked like it had 2 oval shaped openings side by side. We also matched a carb spacer this same way so the holley carb would bolt up. Today, I'd run a demon 850 or 1000 on that intake. I did one of these manifolds for a customer a while back and he could not believe how good it ran. Jim Burek
spread bore Do Quadrajets really work that well on nailheads? We used call them quadrabogs..when I was a kid. But I respect my fellow nailheaders here. Ide love my 65 Electra to get better mileage! Are these intakes still around? Or can I modify my reg 4 bbl to fit? :beer
Re: Re: squarebore vs spreadbore interesting application Jim, I found an adapter plate under a holley modified in the same manner on a 425 and I tend to think the range of a spreadbore from economy to total cfm flow to be ideal not that i really care about fuel economy, but at low revs they really can't suck that much fuel hence the single and double pumper configs of the holley's etc.
Re: Re: Re: squarebore vs spreadbore One thing to remember about Buick's though, and this applies to the nailhead as well as the 455, these engines have relatively small ports for the size of the engine, so port velocity is pretty high, compared to other engines. As a result , these engines tend to really respond favorably to large carburators. Jim Burek
Q jet Mileage I can vouch for the mileage. I have a 800 CFM Q Jet on my .060 over 401 with mild cam and porting and it consistently gets 17 on the road and 14 in town. The mileage with the stock jets and rods was far better.
I own a 66 Electra with a 401 and a 725 vac sec Holley which sits on the stock manifold with an adapter plate - I bought it this way. I am waiting for a '66 425 spreadbore manifold to arrive from the States any time now (I live in South Australia) onto which I will be installing a brand new old stock Q-Jet which (according to the numbers) was linkaged up for a 76 Pontiac. I'm guessing that it's an 800 cfm model as I seem to read that most later model (74 up?) Q-Jets where that size. At the moment I'm not that impressed with the Holley (as I have mentioned in other threads here before) it get's a best of 12MPG on the highway driving at 70ish MPH and seems to have no top end at all and even the midrange seems 'soft'. The bottom end performnace is all Buick though and I can smoke the tyres from the lights at any time. Not that I do that too often as my favourite style of take off is the type that chirps the tyres a couple of times before I get to the other side of the lights. Anyway,...I'm hoping that the Q-Jet will restore the 'lost' midrange performance and may even pay dividends in economy and top end as well. If y'all are interested I'll post the results here. Bill
Check this thread for pictures of the 2 side by side. http://www.v8buick.com/showthread.php?s=&threadid=3759 Bill
I have just finished installing the 425 intake and q-jet on my 401 and can definitely say that it out performs the Holley in many areas but not all. When I nailed it at the lights the Holley was slightly more responsive and would spin tyre from the start. It would also do excellent 'chirping' take offs. The Q-Jet however, just seems to take off. The wheelspin is less which at first made me think that it had less power but then I looked around and man was I covering some real estate:shock: ! It seems that the Q-Jet just plain gets down to buisiness. I wouldn't call it a hesitation but would somehow describe it as a more gradual feed of more power across the board. I've added slightly richer secondary metering rods and a 'K' hanger and it seems to respond well to those changes so I might try going a little richer. I removed the choke assembly entirely so it takes a little bit of throttle 'carressing' during the first 2 minutes to keep her running on cool mornings but as soon as it's warm. I would have to say that I much prefer the Q-Jet over the Holley for dragging my Electra around. I haven't dynoed the new setup yet but I'll be very surprised if I don't achieve a measurable increase in power. My last dyno with the Holley netted 200 rear wheel horsepower which the technician estimated was worth around 300 horsepower at the flywheel. He also mentioned that the factory horsepower readings where probably achieved without any accessories like generator, air-con, fan, etc. I'm booked in next saturday for a Dyno and will post the results. Bill
Thanks for asking. I have posted some videos for your enjoyment. They're pretty low-qual and only 15 seconds long but they capture some sound and are worth listening to if you want to hear a nailhead at full song. http://www.v8buick.com/showthread.php?s=&threadid=4478 Unfortunately, I only achieved 175 horsepower (130kw) at the rear wheels. My last dyno achieved 200 at the rear wheels. The engine feels much, much stronger through the entire rev range. The only explanation I can think of is that they where different dyno's. I asked about this and the guy operating the dyno said that some dyno's vary but usually not to that extent. I want to get a proper (with a readout) dyno one of these days and will post some more results when I do. For now, I feel happy with the improvement in power I gained by going to a 66 425 spreadbore with a Quadrajet from my original square bore 401 maifold with a Holley 725 (4118). I'm not convinced that I have lost 25 HP. It really feels like I have gained so - like I said - I don't know what's going on. Bill
Actually my speedo stopped working a couple of weeks ago (where do these usually fail - cable?) but I can already tell that it uses quite a lot less fuel (quite a lot). I've been sitting around the 3/4 mark for the last 4 or 5 days and that's with about 10-15 miles a day travel back and forth to work (it's my everyday car). With the Holley I would've had to fill up by now for sure if I started the week with 3/4 tank so I'm fairly pleased with it on that score. I'm going to try to get a session on the original dyno because I swear it feels much stronger than before. Did you see the short video I posted of the dyno run? Bill
