Has your hot rod been naughty or nice? Either way, we're here to help this Christmas season. If your car has been a bad boy, drop us a line and we'll try to prescribe the proper regimen to put it back on the straight and narrow. And if it's been nice, why not treat it to another gleaming stocking-stuffer? We'll help recommend the best part or combination for giving your ride some holiday cheer-all right in these pages as space permits. When e-mailing, make sure to include "Pit Stop" in the subject line and put your real full name and hometown or military unit, base, or ship in the message. If you have quality digital photos of the car or problem, and if they're at least 300 dpi at 4x4 inches or larger in size (bigger is better), send them in too.-Marlan Davis
Aluminum Radiators
I have heard a lot about aluminum radiators.Do they work well in daily driven cars? How long can I expect an aluminum radiator to last compared to a more traditional one?
Jack Howell
Fair Oaks, CA
Virtually all U.S. production cars have used aluminum radiators since the mid '80s. In my experience, they last much longer than brass radiators provided you maintain the recommended amount of ethylene-glycol-based coolant in the system. For example, my '91 Syclone's aluminum radiator lasted over 10 years, even though (I'm ashamed to admit) I didn't always drain the non-extended-life coolant every spring like you're supposed to.
Some argue that brass is a better heat conductor than aluminum. This is true in terms of metal-to-metal equal surface area, but in practice it neglects one important fact: The tensile strength of aluminum is greater than brass. This means aluminum tubes can be larger than brass for a given system pressure.Typically the tubes in a brass-core radiator are only about 11/42 inch in diameter, but they're about 1 inch or larger in an aluminum radiator. A larger-diameter tube means a greater cross-sectional area (more tube surface) to transfer heat out to the fins. Also, aluminum radiators, with wider tubes and smaller cross-sections, need less coolant velocity to achieve optimum thermal transfer. A two-row, 1-inch-tube radiator has about a 40 percent greater tube-to-fin contact area than a four-row copper-brass radiator of similar height and width. Some literature claims this translates to as much as a 25 percent increase in cooling efficiency. Of course, a thinner radiator is in itself more efficient, as any rows added to the back of the core are obviously going to be less effective than the front row.
Then there's the weight-savings benefit of aluminum radiators, which are about a third lighter than copper-brass units. That's 9 to 12 pounds off the front end. Finally, because nearly all production radiators are aluminum, the price has come way down from what it used to be, especially for universal-fit racing radiators, though in that case you'll have to fabricate your own mounting brackets.
Where Do I Get
The filler used for the lump-port mod that improves flow in stock Chevy straight-six cylinder heads (as shown in "The Joy of Six," June '05)?
Jim Casey
Brownsville, CA
Sissell's Automotive engine builder Mike Kirby says either Devcon (ITW Devcon, an Illinois Tool Works Inc. Company; Danvers, MA; 800/9DEVCON; www.devcon.com) or JB Weld (JB Weld Co.; Sulphur Springs, TX; 800/529-3530 or 903/885-7696; jbweld.net) works.
A sleeve installed to repair a scoured lifter bore in my '70 Pontiac 400 block?
Charles E. Johnson
Upper Marlboro, MD
Two hard-core Pontiac engine builders relatively close to you include Spotts Performance (Hatfield, PA; 215/362-2336; www .spottsperformance.com; approximately 155 miles from your location) and Central Virginia Machine Services (Burkeville, VA; 434/767-9915; about 175 miles away).
A power rack-and-pinion front-end conversion for a '41 Chevrolet?
Gary Peterson
St. Paul, MN
Heidt's Hot Rod Shop Inc. (Wauconda, IL; 800/841-8188 or 847/487-0150) has what you need.
A lowering kit for a '68 Cougar?
Rolando Ochoa
Brawley, CA
Cougars use the same front-suspension parts as similar-vintage Mustangs but need different rear leaf springs. Maier Racing Enterprises (Hayward, CA; 510/581-7600; www.maierracing.com) has the right parts.
Long-tube headers for a '72 Pontiac Grand Prix with a 400 and auto tranny?
Richie Chavez
Albuquerque, NM
Hedman Hedders (Whittier, CA; 562/921-0404; www.hedman.com) specifically catalogs a '72 Grand Prix application (PN 28140, painted; PN 28146, HTC-coated), but it's a three-tube design (151/48-inch primary end tubes, a 2-inch center-tube, and a 3-inch collector). However, headers for the same vintage GTO or LeMans also fit. Hedman lists a 131/44x3-inch, 4-into-1, long-tube GTO set under PNs 35260 (painted) and 35266 (HTC-coated)
Exhaust headers for a '66 T-bird with a 428ci engine?
Ray Masino
Sierra Vista, AZ
The only headers available are shorties from Ford Powertrain Applications (Puyallup, WA; 253/848-9503; www.fordpowertrain.com).
Sonoma AWD
I have a '96 Sonoma V-6. I want a V-6 AWD turbo road-racer pickup. Any info on what front-wheel-drive, suspension, engine, block, and turbo I should use would be very helpful. I plan to use a ladder-bar rear with coilover suspension and Edelbrock fuel injection with the turbos.
SPC. Michael Boyle
Ft. Hood, TX
Why reinvent the wheel? GMC already built a turbo 4.3L V-6 all-wheel-drive (AWD): the '91 Syclone (based on the four-wheel-drive Sonoma pickup chassis) and '92-'93 Typhoon (based on the four-wheel-drive small Jimmy SUV chassis). GM slightly redesigned the '94 chassis, but basically you can still take the entire driveline and transfer it over into your '96 Sonoma-provided it's a four-wheel drive (the T-chassis). Minor crossmember and driveshaft mods could be required (especially if your wheelbase is different), but basically it's all doable. The two-wheel-drive (S-chassis) frame and front suspension is totally different and can't be used as a basis for this conversion.
OK, factory turbo AWDs don't exactly grow on trees, so what other relatives come close? Like just about all GM AWD vehicles, the Syclone and Typhoon used the Borg-Warner Model 4472, chain-driven, viscous-clutch-type transfer case. In lieu of actually finding a rare Syclone/ Typhoon, you can grab the entire AWD system out of any AWD-equipped '90-'95 Astro van or '91-'94 Olds Bravada (Hollander salvage interchange No. 270). Later Borg-Warner 4472 transfer cases from similar AWD-equipped GM vehicles up to the present could also be made to work, but detail changes in those later years may generate additional driveline modification and interface requirements.
Likewise, any 4.3L GM V-6 can serve as the basis for your turbo engine. The original turbo 4.3L engines were none too strong anyway, so most people who seriously leaned on them eventually ended up (by choice or necessity) with a custom-built heavy-duty 4.3 stuffed with GM Performance Parts Bow Tie blocks and heads, along with aftermarket forged internals and custom cams.
The Syclone/Typhoon used an application-specific Mitsubishi TD06-17G turbo. If you can't find the original complete turbo system with its dedicated mounting and ducting provisions, it is better to use a universal-mount aftermarket solution tailored to your intended usage and performance requirements. Assuming a large intercooler (in place of the undersized liquid intercooler used stock) and premium unleaded pump gas, Innovative tentatively leans toward recommending its SH58 turbo, but you should contact the company or your favorite turbo manufacturer for more detailed recommendations and guidelines.
Edelbrock's new end-user-configurable Pro Tuner fuel injection system should be out late this year or very early in 2006, and with the proper two-bar or higher MAP sensor is suitable for use with turbos or superchargers. Your AWD drivetrain has no need for ladder bars, whether used for a handling (road-race) or drag application.
Backpressure: Good Or Evil?
I own a '68 GS 350 Buick with a built engine. I am very happy with its performance (a best of 11.88 at 112 mph). I currently have a 2.5-inch dual-exhaust system and am considering a 3-inch system with an X-pipe from Poston. Friends tell me I need some backpressure and the 3-inch exhaust will kill my performance. However, I've noticed that cars always go faster with open headers, and there is no backpressure there. So what's the deal? As performance director and tech advisor of the Buick Performance Group, I thank you for your answer.
"Lil' Davy" Gramlou
Fargo, ND
While it's true that an overly restrictive exhaust system combined with excessive cam overlap can kill performance by diluting the incoming air/fuel mixture (think of it as passive EGR), the real concern is not backpressure, but velocity versus engine speed. Larger, oversize pipes decrease low-rpm exhaust-gas velocity. This can reduce scavenging effects, making the headers less effective at low speeds. Larger pipes can improve top-end performance, but depending on the total combination, it may not make up for what you lost downstairs.
Running modern high-flow mufflers and a full exhaust system in addition to headers does not necessarily decrease performance compared to running fully open headers with no pipes and mufflers. In some cases, the added restriction of a full exhaust may actually improve overall performance by upping velocity in the lower speed ranges. In other cases, muffler design can improve scavenging by using chambers that effectively create a low-pressure area within the muffler that aids scavenging (Flowmaster is one example).
Another possibility is adding collector extensions to an existing open-header design. Playing cut-and-try with extensions can pick up significant torque below the torque peak with only a slight loss in top-end horsepower.
Generally around 450 hp is the threshold where moving up to 3-inch exhaust pipes usually yields a benefit. Between 400 and 450 hp it's more combination dependent. Judging from your e.t. and mph, that Buick's probably making around 420 hp right now. If running steep rearend gears and a high-stall converter in a 3,800-pound car, you're probably buzzing that small-block fairly high. Assuming the engine's operational rpm range is at or above the engine torque peak through the entirety of the run, it should see a gain with a 3-inch exhaust.
4l60 / Th700-R4 Parts Interchange
I have a 4L60 GM trans, but all I can find are parts for a TH700-R4. Does this mean most of the parts are interchangeable? If not, where can I go to find some high-capacity parts?
Brandon Turner
Phoenix, AZ
The extent of interchange depends on whether you have a 4L60 or a 4L60-E. The 4L60 is basically the same trans as a TH700-R4 and nearly all parts interchange. Used stock from 1982-1993, TH700-R4/4L60 transmissions can be identified by TV-cable mounting provisions in the case, a governor, and a small four- or five-terminal wiring connector (all terminals may not be wired, depending on the application). Although these transmissions have a lockup torque converter and a vehicle-speed sensor (VSS), shifts are still handled by mechanical or hydraulic controls, and in retrofit applications they can be wired to work without a computer.
First introduced in 1993, the 4L60-E is completely computer controlled, with electronic solenoids added to the valvebody. It can be identified by no TV-cable or governor mounting provisions, a large (usually 13-pin) connector (not all terminals are used in all applications), and (starting in 1996) a two-piece main-case with a separate bellhousing and an extension housing with six mounting bolts (in place of the previous four).
Most 4L60-E internal hard and rotating parts interchange with those used on earlier TH700-R4/4L60 transmissions. In fact, the later the trans model year, the stronger or better the parts-so many hard 4L60-E parts (particularly from its late up-rated 4L65-E sister) can be used to strengthen earlier TH700-R4/4L60 transmissions. However, the 4L60-E's valvebody and related electronic controls are unique and won't interchange. TCI is one source for beef-up parts or complete TH700-R4, 4L60, 4L60-E, or 4L65-E transmissions.
Pushrod length vs. Valve lift
I have this fellow who claims that you can increase valve lift by installing longer pushrods. Is he right?
John Jarvis
Guelph, ON, Canada
Maybe. You achieve the most lift when the rocker-arm tip develops the minimum sweep across the valve-stem tip throughout the camshaft lobe's opening/closing event. In other words, setting the valvetrain up with correct geometry yields the most lift. But because about 80 percent of nonprofessionally assembled engines have a pushrod that's too short to achieve optimum geometry (primarily because most hot cams have reduced base circles that permit their fatter lobes to slide through the fixed-id cam bearings), your friend is going with the odds in advocating longer pushrods. Just be aware that longer pushrods are not an end in themselves, but only to correct an existing geometry problem. For typical nonprofessional engines, Comp Cams designer Billy Godbold says about a 0.100-inch-longer-than-stock pushrod is usually an improvement.
Mopar 360 Cam Upgrade Slows Car
I bracket-race a '73 Plymouth Duster 360.The engine has 0.030-over Keith Black pistons (PN KB107), a zero deck, a 10.5:1 compression ratio, Edelbrock heads, an Edelbrock Torker II intake, a 750-cfm Holley double-pumper (jetting: 76/82), Crane 1.6:1 roller rockers, an MSD distributor and -6AL box, and a Milodon 7-quart pan and windage tray. I'm using a GER 727 trans and a 4,000-stall converter. Out back there's a Ford 9-inch with 5.14:1 gears and CalTracs. I have adjustable drag shocks on all four corners and six-cylinder torsion bars up front.
I was originally running a Comp Cams solid flat tappet (PN 20-248-4), which is 248 degrees duration at 0.050, 0.525-inch lift, 106-degree intake centerline, and 110-degree lobe separation. After a recent rebuild due to a spun rod bearing, I changed to a PN 20-635-5 cam, also a solid flat tappet (252/262 degrees duration at 0.050, 0.542/0.555-inch lift, 106-degree intake centerline, 106-degree lobe separation).
Ever since the cam change, the car doesn't run as good as it did before. The 60-foot time is off by 0.03-0.05 second, the e.t. is off by 0.15-0.20 second, and the trap-speed is off by 3-5 mph. Before the rebuild, the car ran 7.20-7.30 in the eighth-mile at 92-94 mph. The best I have gotten now is 7.40 at 92. Is this cam just too big?
Greg Oldham
Smithfield, NC
Compared to the previous Comp Magnum-series cam, your new Comp Drag Race cam's intake lobe has more duration at 0.050- and 0.200-inch-lift, slightly less advertised and 0.020-lift duration, and more overall lift. In other words, the new race cam has a modern lobe profile that's much more aggressive. True, the overall powerband may be narrower-probably 4,500-6,500 rpm-but the power peaks should be higher; with the correct converter and rear gears, it oughta walk off and leave the old grind in the dust. And with its approximate 4,500-rpm torque peak, the new cam appears pretty well matched to your 4,000-stall converter-assuming it really does stall at 4,000. So what's the prob?
First, unlike Comp's more street-oriented Magnum series that are ground 4 degrees advanced (106-degree intake centerline on a 110-degree LDA), Comp's hard-core drag race series are ground straight up (106-degree intake centerline on a 106-degree LDA). Your 60-foot time indicates the car is not leaving well due to a torque deficit. You need to close the intake earlier by advancing the cam. Put the cam in at a 102-degree intake centerline (4 degrees advanced from as-ground). Verify the cam position using a degree-wheel and dial-indicator. If you did not degree the cam in during its initial install, I'm willing to bet it's presently retarded beyond even its theoretical blueprint 106-degree intake centerline spec.
Next, the new cam has 10 degrees more exhaust duration than the intake side. It was originally designed for classic musclecar-era Mopar production heads where exhaust-side flow is about 68 percent of the intake. The new Edelbrock heads' exhaust/intake flow ratio is a superior 73 percent, which only requires about 6 degrees additional exhaust duration. You can change the effective cam duration slightly to reflect the exhaust-side improvements by slightly tightening the intake valve lash and loosening the exhaust lash. For example, instead of the 0.020-inch intake/ 0.022-inch-exhaust hot lash values usually specified for this cam, try running 0.018-inch intake/0.024-inch exhaust.
