The good aftermarket aluminum timing covers are fitted with a small tapped hole that can b
Matt Kopocs, Akron, Ohio: I hope you can help me solve a timing problem. I have a '73 Chevelle SS with a 0.030-over 454, a 200-4R trans, a 2,400-stall-speed converter, headers, an intake, stock oval ports, and a Comp XE274H cam. I have 38 degrees total timing in by 3,000 rpm. When I rev the engine to 3,200 or higher, the timing retards by several degrees and it jumps erratically. I have tried several different distributors, coils, and timing lights with and without the 6AL box with the same result.
I currently have a new 8361 MSD distributor installed, and the problem persists. The MSD website states that this could be caused by cam walk. I do have the stock timing cover installed. I can turn the crank 21/2 degrees before the rotor starts to move. The timing chain was not very tight when I put together the motor. I have since discovered that timing chain slop can be caused by align-boring, and my engine was align-bored. Do I need to get a non-tin timing cover, as the MSD website suggests? What is your suggestion for a timing chain? The car is e.t. unresponsive to different carbs, jetting, and so on. I am convinced the erratic timing is why. Hope you can help.
Jeff Smith: Because you included enough information in your letter, Matt, you've really answered your own question. We called our pals at Jim Grubbs Motorsports, the shop that does all my engine machining. Machinist Ryan Peart performs the align-honing jobs, and it seems they align-hone just about every big-block Chevy that comes in because the main bore saddles are off.
This is Cloyes' suggestion for measuring the center-to-center distance for any engine. The
Align-honing requires cutting the main caps slightly to create an undersize condition, and a long honing bar is used to ensure that all five main caps are in line with the same inside diameter (id). The same procedure is used for align-boring, which is mainly done when adding new main caps. In this case, more material is removed from the block and the caps. Peart says that most of the big-blocks he does require the block to be machined around 0.004 inch. This means the main bore centerline has been moved by half the distance, which would be 0.002 inch that also reduces the centerline distance between the crankshaft and the camshaft by the same 0.002 inch. As you can probably guess, this will create a loose chain condition.
You might think that once the engine is running, the chain will be loaded and even if it is slightly loose, the constant load will not affect the timing. The reality is that even at a constant rpm, the crankshaft is subjected to instantaneous accelerations and decelerations as each cylinder fires and pressure pushes on the crank. This is one reason all engines require a harmonic damper. Now add a loose chain between the crank and the cam, and it's easy to see how the cam and ignition timing will be especially erratic. It's also worth emphasizing that for every degree of engine timing evidenced with a timing light (caused by a loose timing chain), the cam timing is also moving around a similar amount. This means the cam timing is also retarding- this is not a good thing.
The solution is easy, however. We'll assume the machine shop took a significant amount out of the main saddle, requiring a shorter chain. The part number for a typical Cloyes Original True Roller timing set for the big-block Chevy is 9-3110. If you already have this timing set, you can order a 0.005-inch-shorter chain, which will compensate for the machining operation. It would be best to first determine how much material the machine shop removed from the main saddle area. If the shop can't supply that information, you can measure the center-to-center distance. We've included a simple drawing from the Cloyes website on the previous page that shows how to measure this distance. Measure the diameters of the crank snout and the camshaft journal. Then measure the overall distance of those two installed components (called measure over shaft or MOS) in the engine as shown. The formula is: center distance = MOS - (crank diameter/2) + (cam diameter/2).
I measured a 496ci Chevy I'm building that had been align-honed. Using Cloye's formula, I
The point of this exercise is to determine the distance between the two shaft centerlines. Compare this measurement on your engine with the stock big-block crank-center-to-cam-center distance of 5.152 inches. As an example, let's say the crank snout diameter is 1.605 inches, the big-block Chevy camshaft journal diameter is 1.948 inches, and the MOS is 6.922 inches. Doing the math, this makes the center distance 5.146 inches, which is 0.006 inch shorter than stock and would make a stock chain a loose fit. A 0.005-inch-shorter chain will reduce the distance and tighten the chain. Cloyes makes shorter chains in 0.005- and 0.010-inch under sizes. I priced all these pieces and discovered something interesting. The Summit Racing price for a 9-3110 Original True Roller set is $43.95. If you just buy a replacement stock-length chain, the price is $59.95. The 0.005-inch-longer chain (PN 9-3110-05) is $68.69.
It might also be a good idea to run a cam button on the engine even though flat-tappet camshafts are designed to prevent the cam from moving fore or aft in the engine. This is accomplished by grinding the lobes with a slight taper that pushes the camshaft rearward to counteract the distributor gear thrust that pushes the cam forward. Roller cams cannot be machined with this taper, which explains why roller cams need a cam button or thrust plate to prevent cam movement. If a hydraulic or mechanical roller cam is installed in an early engine without a cam button, the distributor gear thrust will push the cam forward and retard the cam and ignition timing at higher engine speeds. A roller cam button such as the Cloyes PN 9-200 ($16.88 from Summit Racing) is a good choice, since it is equipped with a roller bearing. The buttons can be shimmed to limit cam movement to between 0.005 and 0.010 inch.
Fort Smith, AR
This is a shot of an aluminum block 5.3L motor that we're about to drop into our '67 red R
LS and Tremec Swap
Manny Red, San Diego, CA: I just bought a '68 Firebird with two years of hard-earned money. Should I go with the motor that's in it now? The person I bought it from said it is the original Pontiac 350. It seems to be a Powerglide tranny since it only says P R N D L on the tree. What I want is more power and better gas mileage. I have a 50-mile round-trip commute to work. I would like a five- or six-speed, but I don't want to hack up the car. I could settle for a four-speed overdrive trans. I'm only looking for 300 to 400 hp. Should I use my current motor, a Gen I Chevy 350, an LT1, or a newer LS motor? I know someone who has a 5.3L from a newer truck. It has aluminum heads and an iron block. I'm pretty sure it's similar to the one you guys used for a buildup once. I'm looking for the most I can get for the least money. I could see spending maybe $5,000 over the next year. Now that I've got this baby, I hope to be joining you guys at one of your cruises, a race, or whatever I can get myself into.
We saw this at a vendor booth at the Grand National Roadster Show in Los Angeles recently. The kit comes in assorted colors!
Jeff Smith: We're about to embark on a buildup series on a 5.3L GM LS-series engine, since it is by far the most prevalent of the LS engines. According to one GM source, an unofficial estimate places 5.3L production numbers at more than 14 million just since 1990. The 5.3 uses a 3.78-inch bore and a 3.62-inch stroke, creating a displacement of 326 ci. The obvious comparison is with the original '62 to '69 327 small-block Chevy, but that early motor used a larger 4.00-inch bore and a 3.25-inch stroke. The 5.3L suffers from a smaller bore, yet still offers excellent overall power and torque. You should be able to wrangle 310 to 320 hp out of a stock engine equipped with headers, which is close to 1 hp per ci. To bolt it into your Firebird, you could eliminate the EFI and swap on an Edelbrock carbureted-style dual-plane intake manifold and ignition conversion box that's all under one part number (7118, $649.95). The timing control module drives the distributorless igni-tion with interchangeable chips that establish the timing curve, so no laptop is required. Using a carburetor instead of EFI might add another 10 to 15 hp with the stock cam, and it will probably make around 350 lb-ft. With a little carb tuning, you should be able to pull down decent fuel mileage. Swapping the 5.3L motor into your Firebird isn't difficult but will require a different oil pan, headers, and motor mounts, which are available from companies such as Hedman or Hooker. Stay tuned for a complete story on those swap details. Also be aware that the truck accessory drive will work, but it's a bit clunky. If you want to convert to a better-looking system that retains the factory alternator and truck harmonic balancer, take a look at the Kwik Performance swap kit-it's inexpensive and will get the job done. We've used the Kwik Performance kits in the past, and they work very well.
Even if you don't go with that 5.3L right away, definitely dump that frumpy two-speed Powerslide. There are several paths to swapping in a manual five-speed, which would be an excellent combination with the 5.3L motor. We won't go into all the details on the swap ideas, but Keisler has a system as does Hurst Driveline Conversion (it used to be called Classic Motorsports Group). If you don't think you can handle the swap by yourself, Hurst is located just up the freeway from you in Carlsbad, California, and can do it for you. Both companies offer complete conversions with the trans, shifter, bellhousing, clutch, crossmember, and driveshaft. Both use the Tremec TKO five-speed-either the TKO-500 or TKO-600. Choose the TKO-600 because it offers a more ideal 2.87:1 First gear ratio combined with a tall 0.64:1 Overdrive. This overdrive ratio means that if your Firebird's cruise rpm at 70 mph is currently 3,000, the 0.64:1 Overdrive will knock down that rpm to 1,920. This will be worth roughly 2 mpg or more over that Powerglide. These overdrive trans conversions are somewhat pricey-more than $3,000 for an entire kit depending on which options you choose. The Tremec TKO-600 is a great transmission that is light and compact for its strength (rated at 600 lb-ft), and for an early Firebird, it requires no floorpan butchery except the hole for the shifter.
If you've ever seen the movie Ben Hur with Charlton Heston, the bad guy in the chariot race had a set of hubcaps just like these, except the blades were bigger and nastier.
A less expensive option is the T-45RS transmission offered as a rebuilt unit through Keisler. This is a five-speed originally offered in late-model Mustangs that replaced the aging T-5. The only thing I don't particularly like is the transmission's 3.35:1 First gear ratio that is very deep. With a 3.08:1 rear gear, this is OK, but then its 0.67:1 Overdrive really drops the cruise rpm to where it might lug a little small-block. I'm exercising extreme restraint in not going into all the details on these boxes since I think this new generation of overdrive manual boxes offers outstanding opportunities for car crafters. To complete your drivetrain conversion, look for a '72 to '75 Nova 8.5-inch 10-bolt rearend to swap into your Firebird. This is much stronger than the 10-bolt that's in your car now. It's almost as strong as a 12-bolt. Bolt in a good limited slip like the TrueTrac from Eaton (PN 913A481) and have fun.
Hurst Driveline Conversions
Keisler Automotive Engineering
Can you spot the '59 Plymouth in the Atomic Punk? Car Craft's roots come out of customs, so it's fun to touch on that occasionally. The Atomic Punk is Aaron Grote's adventure, complete with a 392ci Hemi and the Roth-esque bubbletop.
Fuel For Thought
Randy Daviduik, Winnipeg, Canada:
I currently own a fully restored, numbers-matching '69 SS 396 L34 Camaro and have decided to replace the original motor with a new 540 stroker short-block. My goal is to disguise the 540 and reuse as many external parts from the original 396 as possible. Since this is a nice, stock-appearing car without a 'cage, 98 percent of my driving is on the street as a Sunday cruiser or tire fryer. We do drag race it for fun once or twice a year. I have a question regarding upgrading the current stock fuel system.
Do I need to replace the stock 3/8-inch fuel line and stock tank pickup for aftermarket 1/2-inch lines and fittings and an expensive 1/2-inch pickup that drops into the stock fuel tank? What mechanical pump would suffice? Do I really need a fuel regulator? Does anyone make a stock-appearing, big-block, higher-flow, mechanical fuel pump without a regulator?
I currently run a 750-cfm Holley HP double-pumper. Can I just increase the jets and shooters and use this carb on the 540 until next year when I can afford an 850- or 950-cfm carb?
This isn't a drag car. I just want to have some fun with a 540, and this motor will give me more power than I can ever use on the track or off. I currently run Firestone wide ovals on the street (they smoke really nice) and 275/60R15 M/T drag radials at the dragstrip.
Optimizing the 540's power capability isn't a real concern. Reliability, fun, and cost are more important.
Jeff Smith: I think you can feed up to 600 hp with a 3/8-inch steel fuel line as long as that original line is not kinked, has minimal sharp bends, is not restricted by stock brass fittings that are not nearly 3/8-inch on the inside, and is not corroded. If you feel confident that reusing a 40-year-old fuel line originally intended to feed a 300hp engine is sufficient to justify risking your expensive 540ci big-block, then sure, reuse the line. But let's dig a little deeper into this exercise. You mention that to maintain the 396 illusion (which is very cool, by the way), you'd like to use a stock-appearing mechanical fuel pump. Carter makes a PN M4889 pump that is rated at 120 gallons per hour, which sounds like more than enough (this calcs out to 780 pounds of fuel per hour), but this is the free-flow rating and not very useful, since a carbureted system normally operates at between 4 and 6 psi. The thing to remember is that as pressure increases, flow decreases. However, even if we cut the free-flow capacity in half to compensate for 5 psi, it should be sufficient for your needs. If I had to guess, I'd go with 550 hp on your 540.
What's more important is that any kind of pump is more efficient at pushing than pulling. This is especially critical when working with engine-driven pumps because the pump must pull the fuel over a 10- to 12-foot circuitous route before it pressurizes the fuel up to the carburetor. Given this, the best way to make a stock-appearing mechanical pump more efficient is to minimize the restrictions on the inlet side. That does not mean you need to go with a 1/2-inch line, but it would probably be a good idea to go with a new 3/8-inch fuel line. Classic Tube offers brand-new mild steel or stainless tubing fuel lines that are accurately bent to reproduce the original factory layout. This ensures that the inside of the line is clean, rust-free, and can feed the most amount of fuel. You mentioned expensive fuel inlets. I'm not sure if that is in reference to the RobbMc 1/2-inch fuel pickup, which I think is pretty cool. It is a fabricated pickup complete with a new sending unit and float fitted with 1/2-inch tubes on the inlet and return lines. It may be slightly overkill for your system, but it's a good buy at $149. A lower cost option is to purchase a new stock replacement pickup assembly from Year One, and modify it by removing the stock 3/8-inch line and replacing it with a 1/2-inch line that can then be adapted to the 3/8-inch line that runs the length of the car. That way, the pickup is as efficient as possible.
As an added precaution, it would be wise to temporarily connect a fuel pressure gauge to the cowl where you can see it and run the car down the dragstrip (or a test place that's safe) and watch the fuel pressure under load at peak rpm. You need a minimum of 4 psi of fuel pressure. The Carter pump we mentioned is rated at 7 to 8 psi and does not require a regulator. As for the carb recommendations, since peak power is not a concern, then your Holley 750 HP is a good choice. You may not even need to rejet, but inspect your plugs closely after a quick test run. If the plugs look glazed or bone white, add four jet sizes on the secondary side and run the car again. If the mph improves, more tuning is necessary, but you're moving in the right direction.
Year One; Braselton
This is the CalTracs bar located on John Calvert's 428 Cobra Jet Mustang drag car. The bar
Adam Stanton, Menomonie, WI: I have a '73 Mustang fastback with a 400hp 351C, a T5 trans, a 9-inch rearend with a 3.89:1 rear gear, and 18-inch Torq-Thrust wheels with 275/45R17s out back. I have owned the car since I was 16, and I'm now 27. I'm always modifying it. It has horrible wheelhop. Launching hard or soft . . . it just broke the spider gears in my Traction-Lok posi, and I need help.
I have new KYB shocks and bushings, new motor and trans mounts, a new driveshaft with 1330 U-joints, a rebuilt rearend, and five leaf springs. I had traction bars, but the car still hopped, so I upgraded to those under-ride or Shelby bars and subframe connectors. This didn't help-I still have wheelhop. My driveline angles are trans -1 degree, driveshaft -1 degree, rearend -4 degrees (negative means pointed toward the ground). I have researched this and have found nothing more than what I have already done. I know you guys can help me. I want it fixed so I can lay into the throttle.
We drove to Willow Springs last weekend to watch the action at a Speed Ventures track day. While we fully endorse driving your street car on the track, we can understand why one would be fearful of getting rock chips all over his new Z06. But we can't endorse covering your car in shrink-wrap. This guy needs one of those clear bras.
This close-up shows how the CalTracs bar link is connected to the front spring eye mountin
Jeff Smith: At first, the information sounded a bit contradictory, so I called my friend Doug Norrdin at Global West Suspension Components, who brought up a few excellent points. The first thing that didn't make sense was your attempt to use bolt-on traction bars, yet the car still axle-tramped. As you are painfully aware, this is a violent condition that (with leaf spring cars) is caused when the front half of the spring section wraps up, making it bend into an S shape. When the spring is sufficiently distorted, it binds, and because of this induced infinite spring rate, it bounces the tire off the pavement. The process repeats itself very rapidly and if continued can cause massive damage to the trans, driveshaft, and rearend-as you have unhappily discovered. A simple way to control spring wrapup is to use a bolt-on traction bar. A typical traction bar employs a polyurethane snubber that prevents the spring (in theory) from bending. One thing that may have happened in your case is an excessive air gap between the snubber and the spring with the car at ride height. Very few bolt-on traction bars are designed to make contact in the ideal location, which is directly under the front spring eye. Most bars are made too short, placing the snubber somewhere behind the front spring eye. If this is combined with a large air gap, the spring can still wrap up before the snubber makes contact. In extreme cases, it can still allow wheelhop. Norrdin also mentioned that the KYB shocks are not a good choice for this application. These shocks do not have the sufficient extension (more often called rebound) valving that is necessary to control wheelhop. It's possible that it was this combination of soft rebound control and excessive air gap that caused the problem.
Next, the reason you rarely see those Shelby under-ride bars on most cars these days is because back in the mid-'60s when they were developed, the hot ticket for road racing was to slide the car through the corner, hanging the back out in the turn in what is now called drifting. This was accepted practice back in the day because the tires were rock hard. The Shelby bars contributed to that technique because the front pickup point for the bar did not travel in the same arc as the front spring eye. This caused the rear suspension to bind, putting the car into a slide. This bind will also cause wheelhop.
Also aggravating the above situations are the short-sidewall 275/40R17 tires. As the sidewall becomes shorter, it increases in stiffness, the exact opposite of a typical drag tire that employs a very pliable sidewall to absorb shock loads. All this contributes, Adam, to a perfect storm of solutions that didn't work. We have a better idea. John Calvert is a Ford drag racer who developed a new-design traction bar many years ago that he calls the CalTracs. While at first glance it looks like a Shelby bar, it is far different because the front pickup point and the front spring eye swing through the same arc, so there's no bind. A stock leaf spring rear suspension pushes power through the front section of the spring during acceleration, which is why the spring bends. A stiffer front spring section will help resist this tendency to wrap up, which is why just adding a section of leaf spring to the front half of the spring will reduce wheelhop-you could try this first if you like. Adding the CalTracs bar below the spring changes the way power is transferred to the ground. The torque is now pushed through the CalTracs bar, which does not bend. Another plus is that this allows the suspension tuner to lower the rear spring rate and tune the rear suspension to allow the car to negotiate corners without excessive oversteer. This is the negative to adding an additional leaf to the front half of the existing spring because it also increases the rear spring rate, which will tend to cause the car to oversteer during cornering. The CalTracs bar is probably the best solution, along with a tunable shock absorber, such as a Koni, that allows separate rebound adjustment.
Global West Suspension Components
San Bernardino, CA
You've got problems? We've got solutions!
Car Craft Mag
831 S. Douglas St.
El Segundo, CA 90245
We spotted this Hennessey Camaro at a Sunday morning car show. This is the HPE700 with a Corvette ZR1 supercharged LS9 engine. Tweaked by Hennessey, these things make 725 hp, 741 lb-ft, and will accelerate to 60 in a scant 3.5 seconds. Keep your foot in it, and the quarter-mile will pass you by in 11.3 seconds.