April 2011 Chevy High Performance Q&A

Fuelish Pleasures

Kevin McClelland Mar 8, 2011 0 Comment(s)
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Have you ever noticed that we tend to cause most of our own car problems? Well, this weekend I caught myself, and I was just about to make a problem that could have been hard to find.

1101chp_01_o Chevy_high_performance_q_and_a Editor 2/2

We all like to build nice packages for our street/race cars, and, over time, we generally end up stepping up the combinations, right? Let’s say you have a Chevelle or Camaro that runs in the high- to mid-12-second range and has run perfectly for the past several years. And more recently, you’ve got the itch to transform your street car into more of a weekend warrior than a cruiser. Let’s also say that mid 11s is your goal and you’re going to use most of the hardware on your current combination, like your single-plane performance intake and the 750 double-pumper Holley.

This carburetor worked perfect when it was running 60-foots in the 1.80 range, but all of a sudden it dropped to the mid 1.50s, causing the engine to bog off the line and roaring back to life just as quickly as it left. Have you ever run into this? These parts worked fine on the mildly warmed-over 350, and quite frankly, the new 383 setup isn’t that far off with your current carb and manifold. Well, sometimes we can overlook the simple things, like being a quarter of a second faster in the first 60-foot; what you may have not noticed is that with standard Holley center-hung float, the fuel is running away from the main jets on the secondary side on the launch.

So that’s where I almost was. This weekend we were swapping out the stocker 305 and trans, dropping in the 350-bracket engine with a transbrake Powerglide into the wagon. We usually use a modified 750 Holley on the 350 engine, but since the engine had been out for six months, I grabbed it and put it on Daniel’s 406 in his Caprice. It worked like a dream, but it left me without a carb for the wagon. Since the plan is to drop an L92 in the wagon within the next year, I decided to dial in a race 850 that I’ve used on the engine dyno for the past 20 years. I knew this carb would work well with our combination, but I almost forgot to install the secondary jet extensions and attending float to clear them. Holley sells a notched float kit with jet extensions for center-hung floats that includes two extensions and a new float relieved for the extensions (PN 116-10).

If I wouldn’t have remembered that this thing needed extensions, there’s a good chance I would have been scratching my head during the first outing. Remember, you can’t always catch everything the first time around, so try to be patient when you run into problems and think of what you’ve changed; listen to what the car is telling you.

LQ4/LQ9 I.D.

Q: I’ve heard many times that the LQ4/LQ9 truck engines are simply great, inexpensive iron LS1 blocks. Which trucks do they come in, and how can they be identified? I want to be absolutely certain I have one before I pull it. Thanks!
Jack Stackewich
Via email

A: The LQ4/LQ9 6.0L engines are outstanding low-cost building blocks for any project. The LQ4 was introduced in 1999 and was a two-year release with cast-iron cylinder heads. They also had an odd to the LS engine family rear crankshaft flange location that was only on the ’99-00 model years. These two things would steer us away from those engines. The LQ4s from ’01 and up were equipped with aluminum heads and came in with 9.5:1 compression. The power came in at 300 hp and 360 lb-ft of torque. This engine design was found in many Chevrolet and GMC trucks and vans. In the pickups they were installed in the Silverado/Sierra 2500, 3500, Crew Cab, cab and chassis, Denali, and 1500HD Crew Cab. They were also in the Suburban, Yukon XL, and the Hummer H2 SUT, as well as the Chevy Express and the GMC Savana vans.

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