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Quadrajet Carb Talk and Tips / Cadillac Q-jet 7040230
« Last post by Glutenfreecarbs on May 07, 2021, 10:45:55 AM »
Just wanted to show off my winter carburetor: a 1970 Cadillac unit, modified with electric choke, Chevy throttle linkage, and a special adapter for 3/8" fuel line. It's been a great daily driver, and very simple to work on!












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Lobby / Re: Low-emissions Quadrajet
« Last post by Cliff Ruggles on May 07, 2021, 04:11:35 AM »
I like it, might give Deb one for Mothers Day.  I'm sure that will earn me a night or two on the sofa!.......LOL...
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They don't use good parts in those builds so for sure it should work better with one of my kits installed.  Keep us updated....tks...
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The learning curve with the Ventura (I also help out with 4 other cars raced out of the shop) has been a long one and I've tested just about EVERYTHING that's out there.  This includes distributors, intakes, all sorts of spacers, air cleaners, exhaust systems, mufflers, and scores of carburetors.  I've also tested some camshafts, hydraulic flat tappet, solid flat tappet, and hydraulic roller, camshaft timing, and a truck load of converters, plus at least 6 different types of tires.

I also dyno'd just about every engine we built here, and have a nice learning curve from the dyno as well.  So if anyone has any questions don't hesitate to ask, but I'll warn you that I don't hold back when it comes to giving advice.  There are a LOT of parts out there that don't make the grade, TONS of "propaganda" to go with it, and folks have vested considerable money in some of it.  So wear your big boy panties if you are wanting me to give straight advice based on direct testing with parts you may be using........Cliff
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You are most welcome. 

One of my goals is to help customers obtain the best performance possible from their combination. 

I still remember my first track outing with the Ventura decades ago in Richmond VA.  At that time it was powered by a 400 engine with 6X heads and about 7.7 to 1 compression.  The cam was a Crower 60240, 210/221/112LSA.  Backed by a TH400 with a stock converter and 2.73 gears it still managed 14.0-14.20's at 98-100mph. 

I was able to "tweak" that combo to a best of 13.87 @ 101mph.  Since then I've powered the car with two different 428 engines and two different 455 engines.  Each engine was a step up in power and required changes behind it to effectively use the power.  I've had 3.23, 3.42 and 3.73 gears in the rear as well.

The first 455 was pretty "basic", just nicely cleaned up 6X heads, 9.97 to 1 compression, Crower RAIV cam, Rhoads lifters, and 1.73 ratio rocker arms.  That engine was AMAZING and very difficult to hold on the starting line.  After busting up a driveshaft, a transmission, two diff's and testing a half dozen different types of tires I managed to get it to run into the high 12's at 107-108mph.  Two more seasons tweaking the suspension, welding in sub-frame connectors and wham went right to mid-12's at 108-109mph.  It still felt a little "soft" past 5000rpms but rock solid otherwise, and running solidly in the 12.40-12.60's with a best of 12.37 @ 110mph.

Over one Winter I upgraded the fuel system, sumped the tank, 140gph pump behind the tank and 8AN lines/fittings everywhere.  The first two runs with the new fuel system was 12.10/12.11 @ 112mph!  I actually over-revved the engine as it spun past my 5500rpm's shift point and on past 6000rpm's so quick I didn't move the shifter fast enough!  I caught on quickly and the next runs were 12.02, 12.03 @ 112mph shifting at 5500rpm's. 

That was a solid .3-.4 seconds and 2-3 mph improvement over the previous set-up.  I had no idea at that time that I wasn't keeping up with the engine.  I had even tried (on the advice of many non-believers) running a Holley 850dp carb and with the old fuel system it ran no quicker than the Q-jet.  That pretty much debunked the myth about not having enough fuel bowl capacity, you are either keeping up or you aren't.

Anyhow, made some more changes and right into the 11's we went.  I continued to exploit that 455 and got hooked up with KRE to test their new aluminum heads.  That made HPP and Popular Hot Roddings Engine Masters edition and the car ran in the 11.60-11.80 range for several more years with a best every 11.52 @ 116mph. 

In 2009 I built a 428 with a 4.21" stroke crank topped with CNC ported KRE heads and it's still in the car.  It's WAY too quick for 1/4 mile tracks (runs under the roll bar rule) but typically good for 7.20-7.25 @ 95-97mph in the 1/8th mile.  On 1/4 mile track I add 200lbs in the truck, retard the timing 4 degrees and short-shift at 5000rpm's and that usually keeps the officials from visiting my pit-sight and giving me my walking papers!

....continued

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I unfortunately only put 1000 miles on it last summer, had some issue with lifter bores and am only now getting it back together (waiting on exhaust). I will keep you posted during the next month.Hoping to get it on the road by the end of the month
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Quadrajet Carb Talk and Tips / Re: Suggestions For Next Drag Strip Testing Day
« Last post by Brian B. on May 06, 2021, 04:25:19 PM »
Cliff...you've given me great tips throughout this thread.  I really appreciate your time and the depth to which you went to help.  I saw some you made some early morning posts too.  We're fortunate to have you as a resource and your firsthand experience to utilize.  Thank you!
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Interesting.  How do you like that cam for a daily truck?

I considered the 180235-10.  It looked like a fair match with 49 overlap and 57 ABDC.  I saw Howards also offers a -12 (112 lobe separation).
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I had a super rich idle at one time after some idle tuning mods, kept going leaner & leaner on the idle circuit, still rich.  Only thing I could find was one of the sec. idle bleeds was plugged.
I don't know if it was siphoning or what.
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The secondaries do close all the way and seal.

Just ordered an SR kit.      i'd like to try that as a last effort.  If that doesn't work, time for a new/different carb.
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