December 2010 Chevy High Performance Q & A

Kevin McClelland Nov 15, 2010 0 Comment(s)
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California Dreaming
Back in 1965, the Mamas & the Papas first released the song "California Dreamin'." According to Wikipedia, the lyrics "are about a man in a cold winter landscape longing for the warmth of California." This may have been back in 1965, but today my family and I experienced California dreaming firsthand. We made the mistake of going to the Southern California tradition, the George Cross and Sons Pomona Swap Meet, the place to pedal parts and vehicles for over 35 years, and on any given swap meet date, you will have more than 3,000 vendors selling performance parts and accessories.

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Where the California dreaming comes into play, Daniel and I were checking out our storage shed and there is a 400 small-block and TH700-R4 sitting there, taking up space. We thought (that was our first mistake) we could pick up a quick project and condense parts into a driver we could bracket-race and street-cruise. Our goal was to pick up any pre-smog Chevy so we stay out of the Smog Police jurisdiction. We struck off this morning to wander around the cars for sale and were quickly stunned by the asking prices for these vehicles of questionable quality. Now, we all look on the Internet and check out Craigslist and eBay for deals; however, these prices took my breath away. I didn't know a '65 El Camino-in just about any condition-is going for $10,000 plus! There was one there that was rough in several areas, and when you made your way around to the passenger-side rear quarter-panel, it had been crushed by something falling on it ... and they were asking $7,600 for this beauty. Any first-gen Camaro commanded over $10,000, and this included ones that had just been drug out of the barn; cars I wouldn't drive to any local convenience store.

The winner of the day was a '67 Chevelle Convertible whose owner claimed was a number-matching, factory A/C-equipped red on red for $42,500. It was a nice car, but did the guy pay $70,000 at one of the popular auctions and was trying to recover some of his money? The going price for any car of quality-with decent paint, tires, wheels, and clean interior-was between $20,000 and $30,000. So the next time that you think that the cheaper cars are out here on the Left Coast, think again. Look around your own neighborhood; you may find a gem in the rough right under your nose.

Too Many Rules
Q: What can I expect in horsepower from the LS1 I'm building under these constraints? The engine is a standard LS1 5.7L engine with an Edelbrock dual-plane intake, a Quadrajet carb, Hooker headers, and an MSD Street Fire ignition. As you can see, I don't want to add a cam or stroke the engine. Suggestions?
Neal Weaver
Via email

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A: Upgrading-or downgrading (as many people think)-an LS1 with a carburetor, headers, and standard ignition is a very popular swap for early Chevy engine bays. Freeing up the breathing with full-length headers, a Performer dual-plane manifold, and an adjustable timing curve should yield you 1 hp per cubic inch of displacement. Back in the day, this was hallowed ground you would be crossing with a Gen I small-block. However, with the outstanding cylinder head flow of the factory late-model design, relatively high compression, and low-friction rotating assembly, a pony per inch is very doable. Yes, the factory EFI/emissions designed camshaft will be a major limiting factor in horsepower development.

In the future, if you wish to step up your engine's power, the camshaft would be our first stop. You could easily pick up 30-40 hp with a very mild performance camshaft. We'll leave you with that thought. When you get the car running and get used to the power, it will start eating at you for more. Have fun.

Inches Are Us
Q: What advantage does a 377ci (destroked 400) have over a 383ci with a 4-inch bore? I have a circa-'78 400 block and crank, machine shop checked, and all is good (still stock bore at 4.125 inch) with the castings centered. Rods, slugs, and heads were deep-sixed. What combo would be most reliable yet give best performance on a typical budget, let's say around $1,500. I'm open to any parts suggestions. Thanks, hope to hear from you.
Mike Helbig
Airville, PA

A: Back in the day, the 4.125-inch bore ruled for big airflow. The larger bore would unshroud the intake valve and you could stuff more air into the engine. Shortening the stroke to the standard 3.48-inch 350 stroke gave you the 377ci. These things would sing and rev really nice. Then along came the shortage of good 400 blocks and everyone started building 383s (4-inch bore with 3.75-inch stroke). These ended up being the mainstay of small-block engine builds for the past 10 to 15 years. Today, with the affordable aftermarket blocks from Dart and World Products, a 400-plus-inch small-blocks are becoming the norm.

Several years ago, David Reher from Reher/Morrison Racing Engines commented that with the cylinder head technology available today, he would always go for the inches either with bore or with stroke. The selection of cylinder heads around today will give you the ability to feed almost any bore size over 4-inches.

We would build some variant of your 400 combination. Obviously, for budgetary reasons the simple answer is bore the engine 0.030-inch over and put your 406 together. The components necessary to screw together a 400 are plentiful and very affordable. Spend your money on the best cylinder heads you can afford. This will give you the best horsepower for the dollars.

You didn't mention what you were building your engine for. For all-around good performance, pick up a set of 190cc-inlet-port-size aluminum heads. This will give you a good balance of torque and horsepower from your 406.

Truckin'!
Q: I have an '86 S-10 pickup with a 388 that I think is about 10.5:1 compression with a Comp Cams 268 Xtreme Energy cam, a set of Brodix Street heads, 170cc intake runners with 69cc chambers, and a cast 400 crank with 5.560-inch rods and flat-top forged TRW pistons. The engine is topped off with a Performer intake and a 750 Speed Demon mechanical secondary carb, and is backed by a TH350 trans with a stock converter. The truck has a Dana 60 full spool and 4.10:1 gears and 35-spline axles. This may be a little overkill, but no worries with the Cal Trac bars. I shift the truck at 5,300 and have a 5,800 high-side chip in the MSD. What is max rpm with this crank and rod? I have a 2,300 to 2,700-stall converter; would this help or hurt the truck? It has run as fast as 8.05 in the eighth-mile, and 10.31 at 100 in the 1,000-ft on a true 275/60 street tire with 4.10:1 gears. Also, would a set of 15/8 long-tube headers help, and roller rockers? I'm currently running stamped steel rockers and I also thought about switching to an Edelbrock Air-Gap Performer RPM. The truck is now a toy, as it was my daily driver for 31/2 years. Any info would be great.
Brian Parker
Barling, AR

A: Nifty little truck you have there. The only problem is they aren't as light as you might expect. Obviously, there are many models and options of S-10 trucks, but the lightest curb weight of a V-6-equipped S-10 is around 3,400 pounds. Slap in an aluminum-headed small-block and a Dana 60 rearend and you're probably in the 3,500-plus-pound range. Back in the day, we would stuff small-blocks in the very lightweight Chevy LUV trucks. Those were a handful when you dropped in a 400 small-block, TH350, and a 12-bolt rear. You're going in the right direction with your parts selection. Let's take a look.

First, we'd limit your max rpm to 6,000. You didn't mention if you replaced the rod bolts on your build. With the piston speeds the 3.75-inch stroke produces and the weight of those TRW forged slugs, spinning the engine past 6,000 is looking for trouble. With the cam and heads you're running, going past 6,000 would be a waste of time anyway. You need to move your truck on torque.

Swapping to the RPM on your 388 will give you a good boost in horsepower and torque. You'll see around 15 hp over the standard PN 2101 Performer. The torque will follow suit with a smaller gain. The peak horsepower should go up around 300-400 rpm. As for the stock stamped steel rockers, they work pretty well for what they are. They're very lightweight, which helps valvetrain stability. Roller rockers really wouldn't give you more power sticking with the stock 1.5:1 ratio. Unfortunately, we haven't had much luck running higher ratio rockers on the Xtreme Energy profiles. The Xtreme lobes are so quick that when you increase the rocker ratio you can run into high-speed valvetrain stability problems. Going to a true roller rocker will put less stress on the valveguides and usually have better off-seat ratio based on the design of the rocker.

You asked if full-length headers would be a benefit. A benefit over what? Are you running stock exhaust manifolds or shorty headers? If you're running stock-type manifolds, yes, you'll see a big gain in performance. On this engine, you could see gains of 30 lb-ft of torque and well over 20 hp. If you currently have shorty headers, you'll see some of that torque boost but very little horsepower increase.

Finally, we'd swap out your stock converter for the slight stall converter you have. This converter will allow the engine to reach its torque peak quicker and will allow the engine to flash, meaning that the engine gets a run at the stall point of the converter. This will hit the tires harder and move the truck quicker. Your eighth-mile time of 8.05 converts to a respectable 12.65 quarter-mile. With the converter change and intake manifold swap you could see a 0.2 reduction in quarter-mile time.

This is a perfect truck for making little changes and gains over the years. With the rearend and suspension setup, you can throw a good deal of power to it with no concern of breakage. Very soon, you'll need some sticky street radials or little slicks. Have fun ... we see 11s in your future.

Truckin' 2!
Q: You may have covered this subject before, but here it goes. I have a '77 Chevy 1/2-ton and a '73 Chevy 1/2-ton. I want to replace the cab on the '77 with the cab from the '73. Now, the California Highway Patrol officer I spoke with could not give me a good answer-well, I think it was in the gray. What year will the truck be if this is done? I was hoping to have a ride without smog controls. What's the deal? Can it be done? Thanks for the help.
Jose Chavez
Via email

A: Well, after asking several questions of people in the know, things are still very gray. In my opinion, the body is the main section of the vehicle, and the VIN tag is riveted to the cab/body of the truck. The frame, engine, and trans are all component parts that are attached to the main section (cab) of the vehicle. We believe the vehicle would be registered as the body/cab. As you stated above, you have both of these cabs. We assume you have a clear title and pink for the '73 cab? This would be the only holdup we see about the swap.

Next, if you really want to get down to it, if you replace the cab on your '77 with the '73 cab and leave the complete running gear from the '77, it'd be considered an engine swap into the '73 vehicle. The engine has the VIN stamped in the deck from the '77? If this is the case, a smog tech could require you to have all the emission control systems in place and functioning for the '77 powertrain. This is a stretch, but that is the law.

As we said in the beginning, the answers we got were probably just as gray as the answers you got from the CHP officer. You should have enough information to make a decision which way you are going to go. Good luck with your project.

Cubic Inch And Power Range
Q: My question is about operating range and cubic inches. I've read that for every 50ci displacement increase, an engine's operating range will drop 500 rpm. If I have a 350 with a Comp Cams 256, can I go to a 400 and run a Comp Cams 268 basically in the same operating range? Thanks for all the great info you give all of us.
Paul Oterski
Antioch, IL

A: This is a pretty good swap if you're not going to change the cylinder heads, intake manifold, or exhaust header sizes. If the components are sized correctly for the increased displacement, the power peaks should fall very close to the same. Of course, you would see the attending power increase. Going from 350 to 400 cid is a 14 percent increase in cubic inches. If you have stock cylinder heads on your engine, we'd say that a 400- to 500-rpm delta in power peak could occur. If your cylinder heads are not a limiting factor, for instance, if you have aftermarket aluminum cylinder heads that are more sized for your 400, you wouldn't see as large of shift in rpm range.

Back to your camshaft change to compensate for the displacement change, the smaller camshaft in the 350 produces great slow-speed torque. The 400 with the larger camshaft raises the torque peak rpm and hurts the slow-speed torque by increasing the duration and overlap area. The 400 will give you a boost in torque in all ranges because of the displacement increase. This would mask most of the torque loss from the larger camshaft.

In the end, it's a pretty good deal what you've come up with for shifting the powerband. We agree with most of the logic for engines equipped with smaller camshafts. When you have cams over the 230-plus range at 0.050-inch tappet lift, your rpm shift is out the window by then.

It's A Truck Kinda Month
Q: I have been getting your magazine for some time now and have used some of the things you've had stories about on my pickup: an '04 1500 Silverado four-wheel-drive with 67,000 miles. It's a 5.3L with a TH-4L60E tranny. I have put 0-ohm plug wires on, an aftermarket mass airflow sensor, a 1-inch spacer plate, a cold-air kit, and a K&N air filter, and I've removed the Onstar fuse. Wow, talk about waking up a truck. It really will run hard if you want to, and it's not hard to hit 5,000 rpm or more. In addition, the mileage went up to 22-23 mpg, which I like too. One problem I have is that the check engine light will come on with 87 gas, so I burn 91. It will still come on in trailer mode. I have read the code and it says the left or right bank is too lean. The light will clear itself, though.

My other problem is that when the engine is cold at start-up, it sounds like the rods are knocking. After a while it goes away. It's like it's starved for oil. In the winter I start it to warm it up. It still will knock a little now when it's 60 degrees outside. I talked to people with the same motor in trucks, some were different years and they didn't have any add-ons, and they say they have the same noise. One guy blamed the torque converter. I changed the tranny filter and 5 quarts of Dexron 3. It runs better, but the cold start knock is still there. It seems that as soon as I start it and put it in Neutral for a little bit the noise goes away faster.

So what do you think of this? Should I change the torque converter? If so, can I find one that would help my mileage? I like my truck, and it has a lot of miles left in it. I want to keep it, but like many gearheads, I don't want to live with that noise. Something isn't right. I hope you can shed some light on this so I don't throw a bunch or extra money at it. Again, like most gearheads, we have all thrown extra money at things at one time or another. Any insight would be great! Thanks.
Pat Garrison
Via email

A: Glad to hear we can help with insightful stories that you can apply to your truck. Any performance increase is welcomed when you're pulling around a 4x4 fullsize truck with a 5.3L engine. Nice that you picked up a few mpg in the process.

The lean check engine light is because the mass airflow calibration is out of range for the factory program in your computer. The calibrators at the factory take a tremendous amount of time ensuring that the mass airflow sensor will operate in a certain range. If the sensor varies out of this range by over 10 percent it can set a light. Also, if the new mass airflow sensor is reading less airflow at your light throttle and slow engine speeds than the factory sensor did it will lean out the mixture. When this happens, the O2 sensors see that it's lean and begin to trim the fuel richer to accommodate the lean condition. If the O2s run out of trim (they only have so much room), the engine will run lean and set the check engine light. Why your light is going on and off is that in some instances the engine runs in a range that the sensor calibration is close to correct and the fuel trims come back in line.

Looking at your list of mods we'd say the lean condition is from the cold-air intake and the aftermarket mass airflow sensor combination. The mass airflow sensor may stay within factory calibration range with the stock intake system. Contact the manufacturer of your aftermarket mass airflow sensor for recommendations. Changing the mass air calibration isn't something you're going to do with a handheld flash programmer.

Your early-morning wake-up knock isn't uncommon in the LS-based engines. It's not in your torque converter or the transmission. Please save your money. The cold-start engine noise is from the short-skirt piston design in the LS engines. This is a well-documented noise that the factory has known about for years. Over the years of the engine's history, GM has made subtle changes to the piston skirt design, coatings, and clearances to quiet down the knock. To get the performance levels out of the engine, you push the design everywhere you can. The short-skirt piston creates very little friction, which robs horsepower. Try turning up your radio a little during cold start to get past it.

We know the noise can be annoying, but do you remember what a big-block sounded like with forged pistons in the morning? You'd swear that the engine was done until it warmed up.

Technical questions for Kevin McClelland can be sent to him at chevyhi@sorc.com.

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