Chevy Car Questions & Answers - Performance Q & A

Kevin McClelland Oct 1, 2009 0 Comment(s)
0910chp01_z Chevy_car_questions_answers Faq 1/2

Our New Home Track
As you all know by now, the Mac family is back in Southern California. After a 15-year stint in Northern California, we have a new home track to figure out. Up north we had one of the toughest tracks in the nation to dial because of changing weather conditions, especially the wind. Infineon Raceway (it will always be Sears Point) is in the beautiful microclimates of wine country, Sonoma County. From the staging lanes you could look out over San Francisco Bay and have the hot winds blast down from Sacramento Valley to the north. Atmospheric conditions would range throughout the year from 500-feet-below-sea-level corrected altitude to the mid-3,000-foot range. The conditions are things you can easily measure with weather stations, but what you can't read with instruments are the subtle changes that create big performance differences. And just when you think you've got it all figured out, the track would leave you scratching your head!

Luckily, Southern California is blessed with a very nice race track. Auto Club Dragway at Fontana is an incredible facility adjacent to the Auto Club Speedway. The big difference between its northern counterpart is that, for lack of better words, it's basically in the desert! Yes, the Inland Empire is developed today, but 30 years ago it was just the desert on your way to Palm Springs! We've gone from moist sea-level conditions to 1,000-plus feet of elevation with humidity numbers that will dry out the waterbox in minutes. Yes, it's just another quarter mile of timed tarmac, but every track has its own personality and performance changes that cannot be measured. This is where experience comes into play. You must learn these differences by running at all hours of the day in varyingweather. Also, keeping a close eye on the wind conditions from head- to tailwind, and how much the crosswinds affect the performance of your car.

My son Daniel and I have now been racing at Fontana for about three months. My Roadster is parked for a complete rebuild and SFI chassis recertification. Once my garages are in working order, we have to add helmet bars, rollcage gussets, and a few new sidebars to the driver's compartment to comply with current rules. Daniel has been carrying the family racing torch. Last weekend he raced the Super Chevy Show, our sister publication's marquee race, and won eight rounds to take the non-electronics class. It was a great day having three generations of Macs in the Winner's Circle for photos.

One thing that gave us the edge throughout the day was watching the changing conditions at our new home track. You can only pick these things up over time. Anytime you roll into a new track you must pay attention to all the details. Remember, the locals who race there every weekend have quite an advantage. You can never have too much information when it comes to dialing your car. Good luck to all this summer.

Flame-Broiled Rods
Q: The Horsepower TV series has some very good tips and techniques for building high-performance engines. The machinist on the program shows heating the small end of the rod until it's cherry-red to slip the piston pin through it and load the piston on. I always took press-fit pistons and rods to a machine shop to have them hung or pressed them together. Is this a proper way to do it, or are viewers going to find their heated-on rods on the road? I've been building engines since the '60s and never heard of this.

Kerry Schaefer
Villa Ridge, MO

A: Heating the small end of a press-fit connecting rod is a standard practice and has been done for decades. Yes, you can heat the rod with a torch, but the preferred method is to use a rod-heating oven, either gas or electric. These usually heat two rods at a time. You take one rod out to assemble and put a fresh rod into the oven for heating. Then take the second rod from the oven and repeat the process. This two-rod method is perfect for achieving the correct temperature and timing. The good folks at Goodson Shop Supplies offer electric, natural gas, and propane rod heaters. Goodson also has the Temperature Indicating Crayon in 450-, 500-, and 600-degrees ranges. This will give you confidence that you do not overheat the rod and damage it.

If you follow safe practices, like using temp indicating tools, you can use a torch and not damage the rods. Using the heated method to assemble (hang) the pistons is the best to prevent damage to your very nice pistons. It doesn't take much to damage soft aluminum pistons, so the assembler should be very experienced and have the correct tools to support the piston.Source: goodson.com

Can't Get There From Here!
Q: My '84 Chevy 1/2-ton SWB pickup is powered by a tired 305, a TH350 transmission with the lockup converter, and 3.08:1 gears. It's my daily driver and I pull a single-axle lawnmower trailer every now and then. I love the truck, but would like to improve the 13-14 mpg and the performance too. I don't have to worry about the smog police. My goal is 18-19 mpg. I was thinking of investing in a Goodwrench universal 350, a Performer intake, a 1406 Edelbrock carb, an MSD Street Fire distributor, headers, and 2 1/2-inch dual exhaust.

Do I need to change the cam? If so, what do you recommend? Do I need to keep the ECM? The Street Fire distributor has the four-pin plug for it. Do you have any other suggestions? Thanks for your time.

Eddie Woodard
via email

A: I wish I had a quick answer to your mileage quest. I've seen many of the engine swap you've described, and the best mileage they get comes in right where you're at now! This isn't the answer you're looking for, but I thought we'd save you a little time. I had a very nice little two-wheel-drive '80 Blazer that originally came with a 305 and the lockup TH350. I installed the Goodwrench 350, a very mild Crane cam, a 3701 Edelbrock Performer (to keep the smog police happy), Doug Thorley Tri-Y headers, and complete 2 1/2-inch dual exhaust. The truck ran great and towed great, but the best mileage was in the 12-13 range. We've also gotten many letters over the years with the same results.

You could freshen up your 305 with a few performance goodies or install a later fuel-injected 350. You can't beat the fuel mileage that the L-98 tune-port engines or the LT1 small-blocks delivered. In your pickup we'd expect to see fuel economy in the range you're looking for. If you really want to bring your truck into the 21st century, go with a 5.3L LS family of engines. While you're at it, drop in a four-speed overdrive trans. Go with the TH700R-4, 4L60, or 4L60E gearbox. This will help dramatically in your quest for mileage by slowing down the engine speed at cruise. There are a multitude of engines and trans lying around in junkyards across the country. Also, Street & Performance can help you with all your wiring and calibration needs for any of the above engine/trans packages. S&P also has all the mounting hardware to swap in the LS-style engine into your '84. Yes, this may be biting off a little bit more than you planned, but you will get the results you're looking for. Good luck.
Source: hotrodlane.cc

Sprinting
Q: First, I've been a subscriber for about a year now, and, well, frankly, what a great mag. Last year I had a '77 GMC Sprint given to me-yes, given to me. It has 79,129 original miles and for the most part is in primo condition. It's bone stock, right down to two-barrel 305 under the hood. Where is a good place to find resto parts? I've scanned the 'Net. If it were a '72 or older I'd be set, but no one seems to stock items for '73-77. That's a real drag. I'm really looking for a new crossmember so I can make it a dual-exhaust when I swap in the engine I'm putting together. Any help you can give me sure would be great. Thanks.

Tim Huggins
South Paris, ME

A: Where do I get in line to have a car given to me, especially one that has 80,000 miles on the clock? Yes, the mid-'70s A-body GM cars were not very popular. They basically fell off the map in 1973, when the emissions regulations choked any performance they had right out of them. As for restoration parts availability, they are just about a popular as the cars were! I think we can help with the trans crossmember.

Check out G-Force trans crossmembers by Performance Transmissions and Parts. The dual-exhaust crossmember is fabricated from square-tubing steel with provisions for dual exhaust. This crossmember (PN 37XM-2) will fit all '73-77 A-bodies except for convertibles with boxed frames: four-speed manual, TH350, TH400, TH700R-4, and 4L60 transmissions.

Take care of that freebie ride.
Source: transmissioncenter.net


Chasing Your Tail, Part 2

Q: Regarding the "Chasing Your Tail" article in May '09, I just wanted to pass my experience on to Herb. I had the exact same problem he is describing with my GMC pickup. It ran fine under low loads, but once a load (trailer) was introduced the thing would start falling flat on its face. I went through all the painful troubleshooting (part swapping and tracing all of the grounds), and my problem ended up being a bad (weak) ignition coil. I would have sworn it was fuel-related by the way it was acting, but ultimately it was the coil. I figured it is cheap enough that he may want to try one.

Bill French
via email

A: Thanks for the tip. Yes, spark and fuel can be very difficult to pinpoint. Unless you can run a vehicle on an oscilloscope, it's hard to know if the coil is keeping up with the demand of the engine's cylinder pressure. Even then, unless you can run the engine under load and watch the secondary spark energy, you may not see the problem. The best is to have a scope when a vehicle is on a chassis dyno to apply load. It gets really tough running next to a truck with a scope on your back. Thanks again!

Eat My Words
Q: In the May issue you responded to a question about the LT/LS engines, stating that you would never consider the Gen III engines small-blocks. What is your reasoning on this? I have two old-school small-block Chevys (a '66 Chevelle with a 383, aluminum heads, a hydraulic roller, and a carb; and a '65 Corvair setup for Open Road Racing with a mid-mounted all-aluminum 400, a solid roller, and a carb). I also have a '04 Tahoe that came with the Gen III 5.3 engine, which I just replaced with an LQ9 6.0 using a LS6 cam. So I do have a little experience with both Gen I and III engines. The bore spacing is the same for both, at 4.400 inches, and the outside dimensions are pretty close. I know the Gen IIIs are better in every way than the Gen Is and have more room for a stroker crank. In fact, I guess GM is coming out with a 454 Gen III crate engine. However, in my mind, the Gen IIIs are still small-blocks. And World Products is introducing a new block that will use all the "old" small-block internals but will accept the Gen III heads and intakes. So if they aren't small-blocks, then what are they? I've had this conversation with a few other gearheads. What makes a small-block? Is it outside dimensions, cubic-inch possibility, or weight? I thought it was primarily the outside dimensions regardless of how many cubes it may have.

Charlie Friend
Alamogordo, NM

A: Maybe I was a little strong when I said Gen IIIs will never be small-blocks in my mind. I guess it comes from when I started working on these engines for GM back in the mid-'90s, before they were released in the Corvettes in 1997. They were completely foreign to us back then. With its four head bolts per cylinder, Y-block crankshaft placement, and crankshaft snout-mounted oil pump, we thought it was more of a Ford engine than a GM. A small-block Ford engine's head gasket fits almost perfectly on the deck of an LS engine. Yes, over the years they've grown on us, but with all the history of the original Gen I small-block from 1955 to 1995, it was a 40-year-old engine and it makes it hard to call the LS engine a small-block.

For instance, I'm not trying to draw parallels with the small-block Ford, but here I go. The small-block Ford was released back in 1962-1963. When Ford came out with the Modular engine in the trucks and the Mustang, the engine wasn't called a small-block; it was called the Modular engine. Was its weight, size, displacement similar to earlier small-blocks? Yes.

It doesn't really matter. The Gen III-and now Gen IV-engines are great powerplants. We're about to use Gen IV engines in two projects at our house. One will be used in a racing application, and another in a very hot street conversion project. When we're done will I call them small-blocks? I doubt it. That's my two cents' worth.

Panning For Gold
Q: I spent the winter putting together an awesome, built '96 350 to install in my '69 Malibu. Tonight I tried to drop it in and discovered that the oil pan is too deep and rests on the crossmember. The stock pan off the original 350 won't fit the later-model block because of the dipstick location. Who makes the correct pan for this application? And more importantly, what is the part number and where can I get one? Thanks.Jerry ZimmermanElma, WA

A: There's nothing worse than having your fresh engine build on the engine hoist and it won't fit into its new home. All the anticipation of the first drive and the sense of satisfaction knowing that you built your own engine... We have the answer.

Milodon offers a complete line of oiling system components for all makes and models, including direct-fit pans for all Chevy small- and big-block applications. The proper pan for your late-model ('86-and-up) one-piece rear main seal, righthand dipstick is PN 30902. This is a low-profile, 8 1/4-inch-deep pan featuring a 7-quart, triangular-shaped sump. This fully baffled pan will give you extra oil capacity and keep the oil pump pick submerged in fresh oil all the time. The proper oil pump pick-up is PN 18314. To round out the installation, we recommend going with the louvered windage tray, PN 32102, and the windage tray installation kit, PN 81150. This kit consists of the extended-length main studs to mount the tray properly. This package of components will give your oiling system a bulletproof setup. Also, Summit and Jegs both stock Milodon products and can have them out to you the next day.
Sources: jegs.com, milodon.com, summitracing.com

Too Many Choices
Q: I have a '74 Chevy Nova with a 406 SBC in it, and I'm having trouble deciding if I should change my intake. The current setup is 11.5:1, AFR 210 Eliminator heads, a Comp XR294HR cam with 1.6 Pro Magnum rockers, Total Seal rings, a Speed Demon 850 (changing to Mighty Demon 750), and all forged internals-everything with ARP studs. Currently I have a Victor Jr., but when I read the CHP article with the 16 different manifold test on the 383 ("Manifold Learning," Sept. '08), the Jr. didn't impress me. The car is a street/strip car that weighs 3,550 pounds with me in it and has 3.70:1 with 26-inch tires, a 3,000-stall converter, and a TH350 transmission. The best e.t. is 11.54 at 117, with a badly slipping Third gear (on pump gas). The trans is being rebuilt as I write this. My cam is relatively small for my displacement, and I want to keep the rpm in the 6,200-6,300 range because it's a factory four-bolt block. I was thinking about switching to the RPM Air Gap because of my cam, but this year I'm planning on throwing a 150hp shot of juice at it (plate kit), and I don't know at that point which manifold will work best. With my setup, will an Air Gap be too small? Thanks for the help.

Jason Gielish
Albany OR

A: What a nice package you've assembled, mid-11s out of your combination that is street driven in a fun car! When you present 16 manifolds tested on one engine, it can be somewhat misleading, and how the data relate to every engine combination can vary somewhat.

Now that we've gotten past the disclaimer, let's talk about your manifold selection. A standard 2975 Victor Jr. manifold usually works best with 2 inches of open spacer under the carb. The plenum volume is inadequate in most cases (back to the disclaimer), and Edelbrock was trying to stay within a hood clearance/packaging constraint. What Edelbrock came up with was a great all-around manifold. Will the dual-plane design make more torque below peak and in the meat of the torque curve? In most cases, yes. Will that give you more trouble getting off the line without spinning the tires? Maybe. Again, it all comes down to working out your own combination of parts.

On top of all that you want to add a plate nitrous system. This adds another layer of possibilities. Usually we prefer to add nitrous to single-plane manifolds over dual-plane ones. You get much better mixture distribution to all cylinders with the single-plane design. Can you run a plate system on a dual-plane? Sure, it is done all the time. However, when pushing the tuning we'll go with a single-plane every time. The last thing you want to do is have a distribution issue with nitrous on one cylinder and push the tuning until you find which cylinder is lean on fuel, not nitrous. Unfortunately, you could be adding spark advance and watching the performance increase and one cylinder is going into detonation. The other seven cylinders may be happy as can be with the spark and the car runs quicker and faster. This is when it will be too late.

There is new technology out on the nitrous plate designs with the perimeter- and diffuser-type plates. This atomizes the fuel and nitrous much better, but with the dual-plane designs having sharp turns and elevation changes, the chance of mixture separation is much greater than with a single-plane manifold. If it was our engine below the plate, we'd stick with the Victor Jr.

Sure Stop
Q: I could sure use your help. I have safety concerns about the rear brakes on my '98 Chevy Silverado pickup. The rear brakes' stopping power is very, very slight, if any! The brake shoes after 100,000 miles still appear OEM new, regardless of continual adjustment, cleaning, and roughing the surfaces of the rear drums/shoes. Symptoms include the front rotors hot-spotting, three sets of front brake pads, and a long brake pedal stroke, and the occasional actuating of the antilock system at really slow stops. The ABS or its sensors are not at fault, I am sure.

Are there bulletins from GM on how to correct a problem that supposedly doesn't exist? I read that repair requires the removal (or modification) of a part in the brake combination valve or master cylinder. That information came from an individual who had the work successfully done at the local GM dealership. Searching GM's website, calling, asking local dealers, and much discussion did not produce any listed remedy. GM either does not want to acknowledge that rear brakes are my problem or couldn't care less!

I currently know of three trucks ('97-99) with the exact same brake problem! In my research I have found this to be a common complaint for these years. My last resort is to scrap my present system and adapt the brakes from a '75 Chevy pickup. Please help me, and thanks for the answers. I really enjoy your monthly column.

Lo Miler
Denver, CO

A: We have to think GM does care that you have brakes. Unfortunately you didn't give us much information to go on. Is your truck a 1/2-, 3/4-, or 1- ton Silverado? Yes, there are a few service bulletins (SBs) around the scope of your problems. We'll refer to a few of them and make some guesses based on what type of vehicle you have.

First, you stated that you have intermittent ABS engagement at slow speed. SB 02-02-25-006B explains a corrosion problem that occurs between the hub and the ABS sensor mounting. What this causes is an increased air gap between the sensor and the reluctor wheel on the hub. This generates a lower-than-spec voltage signal that goes back to the ABS computer and applies the ABS erratically. The fix is to remove the ABS sensor, plug the hole in the hub to prevent debris from falling into the hub, lightly sand the mounting surface of the hub, apply Rust Penetrating Lubricant PN 89022217, and allow it to dry. Then apply a thin layer of wheel bearing grease to the hub surface and the sensor O-ring to prevent further rust buildup under the sensor.

As for the prop/combination valve, the only bulletin for that is on '92-99 Suburbans with an 8,600-pound GVW. Another thing you may want to look at if you have a 3/4- or 1-ton truck is that some models have a brake bias valve connected through linkage from the frame to the rear axlehousing. This adjusted the rear braking pressure based on the load in the box of the truck. If this valve is malfunctioning or maladjusted, it could be causing reduced brake pressure to the rear brakes.

We hope this helps with your problem. Also, just because there isn't a bulletin on your problem doesn't mean you don't have a problem with the combination valve on your truck. It may be limiting the brake pressure also. Check it out and be safe.

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

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