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March 2012 Chevy High Performance Q&A

What’s going on out there?

Kevin McClelland Jan 20, 2012
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People always come up to me at the races, swap meets, or car shows, and tell me how much they enjoy the escapades of the Mac family with our cars, and the projects we’re working on. Unfortunately, because our local track, Fontana’s Auto Club Dragway, has had a very limited schedule this past year, we’ve mainly stuck around the house. So what do you do when you’re bored and broke? The price of fuel has limited us to racing close to home, and when we do spend the money to take two cars, let’s say to Vegas and stay overnight, our pocketbook takes a real hit. You have to win in at least one class just to break even!

So you’d think Daniel and I would have finished all our projects. We have made quite a bit of headway on his RX-7, and we’re down to final assembly on his 404-inch LS2. We’ve also finished all of the suspension updates, the rearend rebuild, and posi blueprint. We deleted the ’94-vintage ABS braking and replumbed all the steel brake lines in the front system. We may be done with it someday … if project cars stop following Daniel home.

chp 02 O  Chevy High Performance Q A Drawing 2/2

I also have Charlie Allen’s F-bomb 302 stocker engine ready to slap together. He just picked up the rotating assembly from the balancer, and I’m sure he’ll be pushing soon to get it into his race car. The current engine is a 150,000-mile dead-stock engine and the heads have never been off. All he did was stuff a stocker cam grind in the engine and replace the trans, converter, and gears. The car has run as quick as 0.25 second under the O/SA index. We’re really hoping to pick up about a half second with this new engine. It has the best of everything and dead-legal cylinder heads. Hopefully, the tech inspectors will agree with my interpretation of the rules.

I would really like to hear what you guys and gals are up to. The other day I was thinking about how cool it’s been writing for the magazine all these years. The first issue I contributed to was way back in 1992. If I do my math right, I’ve been trying to answer your questions for 20 years. Coming up with new ideas and fresh info to share can sometimes be a challenge. I always appreciate people stopping me and letting me know how much they have learned and the time our advice has saved them with their projects. Keep sending in your questions and letters for us to help.

LT1/S-10 swap

Q. I’m sure you are asked this all the time and are probably tired of rehashing all the details, but here it goes. I have a ’94 Caprice classic wagon with the LT1 with factory cast-iron heads. It’s ready to give up the ghost, but the drivetrain is too good to throw away. I have an ’01 S-10 with the four-cylinder and five-speed manual tranny. I’ve seen pictures online of S-10s with this engine swap, where it all tucks away under the hood, but I’m having trouble getting a parts list for the swap. The automatic in the wagon is trouble-free, but I’m partial to manual. I’ll use the automatic if I have to, but was hoping a five- or six-speed manual would fit. I’m not sure about the rearend either. If you can grit your teeth hard enough to help me out I’d appreciate it.

Randy Weaver
Via email

A. Yes, this is a very popular swap, and there is tons of information out there. One of our good friends has been swapping these engines since the S-10 came out. His company name might not sound like a go-to for help with a Chevy swap. Mike Knell is the owner of Jaguars That Run. He started his love for engine swaps with dropping small-blocks into Jags in the mid ’80s. The small-block engine swaps were much cheaper than repairing the blown Jaguar engine, and gave you a very reliable driver. He writes very comprehensive conversion manuals about specific swaps with illustrations of the modifications and part number lists from regular suppliers, like Chevy dealers and national auto parts chains. He’ll be the first to tell you that his manuals are not for building race cars or off-road trucks, and will supply you with a detailed manual to do an OE-quality swap, making it a very reliable truck for everyday use. Now, we’re not saying you couldn’t step up the performance with bolt-ons or larger displacement. Knell delivers the how-to guide for your S-10 swap. The manual will also outline how to install the engine with a T5 five-speed or T56 six-speed. As for the rearend upgrade, many of the later S-10s came equipped with an 8.5-inch ring gear corporate rearend. These rearends will hold up to whatever you throw at them with aftermarket upgrades, all of which Knell covers in great detail. You can purchase the manuals directly from JTR, or they are available from Summit under PN JTR-S10 or Jegs under PN 116549.

If you’re looking to swap any small-block, including Gen III engines, into Jags, Datsun Z cars, Mazda RX-7s, Volvo 200 and 700s, and Astro vans, Jaguars That Run can help with installation manuals and component parts, and even offers engine mounts, headers, cooling system components, and oil pans for many of these swaps.


Elky Upgrade

Q. My ’86 El Camino has a factory 4.3L V-6 TBI, TH200-R4, and 3.08 rear gear. I’d like to install a 400 small-block, retain the TBI, and change the rear gears to a 3.42:1. Can I use the factory computer without making any changes to it? I know I’ll have to change the heads and intake to work with the TBI. I plan to use stock Vortec heads. Also, could you recommend a mild camshaft that would work with this stock 400 combo? Thanks! 

Eric Patton
Hiram, GA

A. You have a great plan that is somewhat difficult to execute. GM didn’t make it easy to play with the throttle-body fuel-injected engines. These systems are called Speed Density fuel injection. What this means is that the engine is developed, assembled, and dyno-calibrated to generate the fuel and spark map. This calibration is specific for every engine configuration developed. Anytime you change the airflow demand (volumetric efficiency) of a given calibrated engine it requires another complete calibration. Something as subtle as a small performance camshaft and intake manifold will drive the fixed calibration right out of range. Switching from a 4.3L engine to a 6.6L (400 cid) is a 54 percent increase in displacement. You should be able to swap out the calibration chip with the proper cylinder count, displacement, and injector size, and the engine would run. Now, for the engine to be calibrated and run properly, you would need to spend a tremendous amount of time on a chassis dyno to get the fuel and spark tables where you need them. Edelbrock offers calibration for its TBI engine packages that are built around its engine components. It is a complete cylinder head, camshaft, and manifold package, but it is only offered for a 350 displacement. The stock 350 produces about 190 hp at 5,000 rpm, and with the complete heads, manifold, and cam package with calibration, it steps up to the 250hp range. You may be lucky and find a calibration for a large-displacement small-block.

Using the Vortec cylinder heads is going to be a challenge. There isn’t a TBI manifold on the market that offers the Vortec cylinder head bolt pattern. Again, we would suggest using the Edelbrock Performer cylinder heads that will work with the Edelbrock Power Package. Call for more information. These packages are getting some dust on them. The TBI engines have been out of production since 1992 in passenger cars, and since 1995 in trucks. The aftermarket really didn’t step up to the TBI systems in the first place. Many aftermarket companies have moved on from this technology. If you’re going to do something we would do it soon. Good luck.


Factory Plumbing

Q. My friend has a completely stock ’65 SS 396 365-horse with a factory Holly 600 vacuum-secondary carburetor. The problem is that he purchased it from an individual and they had to replace the fuel pump, and when they did, they replaced the factory fuel feed lines to the carburetor. Where can he get the factory fuel fittings and line? He has asked around and they said that they don’t carry this fitting, and he would have to make his own. I read your tech section all the time and would like your help on this problem. Thanks for your input.

Roger Bear
Kansas City, MO

A. During our early hot rodding years you couldn’t tell us the factory stuff was good enough for performance use. We would immediately rip off the factory fuel feed lines from the pump to the carburetor and replace it with Holley dual-feed kits from the speed shops. Well, over the years we found that the factory wasn’t that stupid, and that it usually built in a safety factor to allow higher performance. The fuel feed lines for Holley carburetors is a perfect example. Anytime we’re building a street or moderate performing race car, we’ll fabricate the fuel feed system out of steel lines and brass flare nut fittings. They may not be as blingy as steel-braided hose and AN fittings, but they will last forever and perform leak-free forever.

With a lot of these very specialized lines and fittings missing from our muscle cars, YearOne has come to the rescue with reproduction fuel pump-to-carburetor line kits, featuring the correct bends, contours, and lengths. The main piece is a very specific brass three-way fuel block that splits from 3/8-inch feed to two 5/16-inch lines to the carburetor. They offer the kits in both steel (PN RS415), and stainless steel (PN RS415S) for your buddy’s Chevelle. These kits have saved many a restorer from the hacking we did in the early years. Sorry!


Bogged Down

Q. I’ve been reading your articles for many years and truly love the wealth of knowledge it provides your readers. I’ve recently been having a small but irritating problem with my ’94 GMC 1500 pickup, which I love and have had for over 12 years. It has a TBI 5.0L engine with 166,000 miles. It’s extremely reliable, but under full acceleration it bogs and then accelerates. I’ve measured fuel psi and timing, and can’t seam to resolve the problem. Thanks for any help you can provide.

Steve Guerrette
Via email

A. The sheer volume of cars and trucks produced with throttle-body injection systems is staggering. I can’t even begin to guess how many cars and trucks are running around with TBIs. They have been used on big-blocks, small-blocks, V-6s, and even four-cylinders. They used this technology from 1980 in GM’s first front-wheel-drive passenger car, the Citation with the Iron Duke four-cylinder, to 1995. So you can imagine the numbers.

TBI systems are a speed density system, the most common system today is a Mass Air Flow system. As the speed density system works off of a fixed volumetric efficiency fuel table, the mass airflow system works off of an airflow sensor in the intake air stream. This system fuels the engine based on the air ingested into the engine. It can correct the air/fuel ratio based on this increased/decreased air intake and accept part changes and continue to fuel the engine correctly.

Back to your bog on acceleration: Does the engine bog when you tip into the throttle, or after tip-in and it falls flat and recovers? You say you checked the fuel pressure; did you check it while the engine was bogging, or just static in the shop stall? If the engine bogs on throttle tip-in, look to the throttle position sensor. This is an electrical rheostat connected to the throttle shaft of the TBI unit. It tells the computer where the throttle blade is and how quickly you’re opening the throttle. There is a table in the fuel injection calibration that is called “accelerator enrichment”. This is a time-based table that injects more fuel the quicker you open the throttle—in other words, an accelerator pump. The throttle position sensor over time wears out in the idle and off-idle positions, giving the computer bad data.

Next, look at the O2 sensor. This is a sensor in the exhaust stream that monitors the burned fuel in the exhaust stream. It’s truly the lack of oxygen in the exhaust. This sensor trims the air/fuel table based on how well the engine is running and keeping the air/fuel ratio near the 14.7:1 target. When these sensors age they can trim the fuel tables to the lean side, which can also lead to a bog.

Finally, let’s go back to your fuel pressure test. The fuel filters on GM EFI (all systems), are woefully inadequate, and should be replaced frequently. The undersized fuel filter on GM trucks and cars is the main reason that so many fuel pumps fail in the field. The filters become restricted and the pumps have to work extra hard to keep up with demand. Your fuel pressure test will come up good at idle in a stall with 12 psi. As soon as you tip into the throttle and increase the demand for fuel, the pump can’t keep up pushing through a plugged filter. If you haven’t changed your fuel filter it should be the first thing you do. If it doesn’t help with your bog issue it will certainly increase the life of your fuel pump. Good luck with your bog diagnostics. Hopefully we’ve put you on the right track.

Malibu Brake Problems

Q. I replaced a 41-year-old set of drum brakes on the front of my ’70 Malibu with a disc brake kit from PST, along with new ball joints, tie rods, centerlink, springs (front and rear), control arm bushings, and cylinders and shoes on the rear drums. We removed the distribution block off the frame and put brass-flared fittings in its place. The kit came with a proportioning valve, master, and power booster.

The booster clevis is in the lower hole in the brake pedal, the sleeve is in the master cylinder with the short pushrod in the booster, and the rear shoes are adjusted up. The control arms went together with the new ball joints, rotors, and calipers. Upon bleeding the system, we could not get a pedal to come up and thought air was still in the system but could not get any air.

PST sent us a new master, thinking that was the problem. It did not help. The 350 engine has a slight cam; I don’t know the duration. The vacuum is running 15 at idle with the engine at normal temperature and 20 at 2,000. The booster feels like it is working; the pedal goes almost to the floor and then gets firm about an inch off the floor with good stopping power. It is not spongy but firm at that point.

I took it to our Chevy dealer to have the frontend alignment done. They checked it for air and said it didn’t have any in it. They told me the cam was not letting the engine produce enough vacuum to operate the power brakes and suggested I put a vacuum canister on to help boost the power brakes. At this point, I had not replaced the proportioning valve; I changed the booster with no change in the pedal. Do the front calipers travel enough to require that much pedal? They should not!

I have never in the 40 years I’ve been working on Chevelles or any other car run in to this kind of problem. It has literally got me stopped in my tracks. Please help!

John Moore
Trenton, SC

A. Something as simple as hydraulic brakes can sometimes be a real headache. It sounds like you’ve done everything right. There are a couple of hints in your letter that may give us a direction. You’re spot-on that the front calipers shouldn’t require that much pedal travel unless they are the quick-take-up G-body metric calipers that were used on ’81-and-up G-body GM cars, for reducing rolling resistance to increase fuel economy. These later calipers used a special step-bore master cylinder, which had piston sizes of 24mm/36mm. The larger piston would fill the calipers quickly and the small 24mm piston would give you the low pedal effort. The PST website says its kit is supplied with 72mm calipers. Most of the factory-style disc brake kits on the market today use the later G-body-style calipers because they are cheaper and easier to get. The later-model G-body calipers require more fluid to bring the pads in contact with the rotor. The factory G-body calipers are much smaller than the 72mm supplied by PST, and the early factory Chevelle single-piston calipers are 215/16 inch (74.6 mm). Check what size master cylinder you have. You should be running a 11/8-inch master, or the later G-body–style caliper.

The fact that you have a firm pedal an inch off the floor, and good braking at that point, tells us you have plenty of vacuum for the booster—15 inches of idle vacuum is plenty for power brakes. You said the “sleeve is in the master cylinder with the short pushrod in the booster.” You should be able to feel a slight bit of pedal movement before the booster pushrod begins to move the master. You don’t want more than about 1/16-inch clearance between the booster pushrod and the master cylinder piston. We think you’ll find your problem in the master cylinder sizing. Good luck, and be careful until you find your pedal.

Pipe Dream

Q. My 406 small-block has 10.25:1 compression, 15/8-inch headers, AFR aluminum 200cc heads, a 650 double-pumper carb, an Edelbrock Air-Gap intake (dual-plane), and a cam with 250/256 duration at 0.050-inch tappet lift, 0.519/0.523-inch max lift, ground on a 110 lobe separation. The car is mostly street driven. It weighs 3,600 pounds and has run high 7s in the eighth-mile. I’m running a Turbo 350 trans with 3,500 stall (only get about 2,900 out of it), 4.33:1 rear gear, and a 31-inch-tall tire. The engine will turn 6,800 rpm at most. I run Flowmasters with 3-inch pipe to rearend with turndowns. Since the last 4 feet of pipe past the mufflers is 3-inch pipe, would it hurt top end performance in the eighth to go to 21/2-inch pipe the last 4 feet? What about low-end torque and midrange with my heavy car? I’m sure the car would be a little quieter too!

Ben Glouse
Via email

A. It appears that you have a couple of pieces of your combination pulling different directions. Most 400 small-blocks like 15/8-inch primary pipe headers from our experience. The 250/256 duration at 0.050-inch tappet lift is going to build some top end performance matched with your 200cc inlet runners. The 650-cfm carburetor on a dual-plane intake is going to limit the engine’s rpm range. Going with a larger carburetor, like a 750-cfm, should help the upper-rpm power without much of a torque penalty. You didn’t mention if the camshaft is a hydraulic or mechanical lifter. With your current combination, you could easily be all done by 6,800 rpm.

Let’s get back to your exhaust. You mentioned 4 feet of muffler tubing after your Flowmaster mufflers. This must mean you’ve installed the mufflers right at the collector of the headers. If this is the case, you’re killing the tuning and scavenging of the mufflers. You want Flowmaster mufflers placed as far back (mid-ship) in front of the rear axle. You also want to utilize a balance pipe between the collectors, as close to the header as possible. Best case, you’d want to run a 3-inch balance pipe and at least a 21/2-inch. These changes will help the slow-speed torque of your engine, and make an appreciable gain in horsepower. You definitely don’t want to go with 21/2-inch tube on your 406. Your engine has the potential of making 500 hp with the components listed. To support that power you will need 3-inch tubing. Rework your exhaust and enjoy the benefits. CHP


We love letters, especially technical questions. Submit your tech questions to Kevin McClelland at Regular shout-outs and good tidings are also always welcome.



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