E-mail: HOTROD@primedia.com * Mail: HOT ROD PIT STOP, 6420 Wilshire Blvd., Los Angeles, CA 90048 * Fax: 323/782-2223 * Message Board: HOTROD.com
Does your engine sound like a laughing hyena when it should be purring like a kitten? Is that last needed piece tearing you "a part"? Are the "Y's" keeping you from getting "Zzz's"? Relax, you've come to the right place: Pit Stop, where we get to solve real people's real problems. Send in your questions and I'll answer as many of them as possible in these pages. When e-mailing, don't forget to include "Pit Stop" in the subject line, as well as your real full name and hometown or military unit, base, or ship in the message. I'd also like to see quality digital photos of the cars or problems that you're working on, and if they're at least 300 dpi at 4x4 inches or larger in size, we may throw them in as well.-Marlan Davis
Pushrod Length
I am building a small-block Chevy with 9.5:1 compression. I am putting in a custom-ground camshaft (270 degrees advertised duration, 0.465-inch lift, 108-degree lobe separation). I have a good set of lifters but am unsure about the proper pushrod; will standard-length work? I have not chosen rockers yet. I was thinking of roller-tipped rockers. I am not racing my car (an '81 GMC Caballero); it's just a cruiser. Can you please suggest pushrods and rockers?Dwayne GundrumDelta, BC, Canada
Stock-length pushrods should be in the ballpark with your relatively mild cam, but the hard truth is that on a custom-built engine, there's no telling for sure. A decked block, milled heads, various thicknesses of head gaskets, sunken seats and different valve jobs, nonstock-length valve-stem heights, different aftermarket rocker designs, aftermarket cylinder head stud-boss height and location variations, and reduced camshaft base circles can throw things off. Depending on how all this stacks up, it may call for longer or shorter pushrods. The only way to know for sure is to trial-assemble the engine and check the valvetrain geometry.
What is valvetrain geometry? In a perfect world, the rocker arm would push against the exact center of the valve stem. But in the real world, the rocker travels in an arc as it moves up and down-this arc of motion is what we call valvetrain geometry. Achieving correct valvetrain geometry means keeping the rocker tip contact point as close to the valve stem's center as possible. This minimizes valveguide wear, reduces friction in the engine from valve side-loading, and prevents possible valve breakage due to bending the valve stem.
How do you check valvetrain geometry? Trial-assemble the engine and lash the valves, then turn the engine over by hand. Carefully watch the rocker arm-to-valve-stem interface from the side as the valves open and close. The contact point should be slightly offset toward the rocker-arm fulcrum (pivot) with the valve closed; the contact point at mid-lift should pass across the valve centerline and move slightly toward the outside edge (away from the fulcrum); and beyond mid-lift, the contact point should swing back through the centerline and return to the original position (slightly inboard of centerline) as the valve hits full lift. If the contact point moves toward one edge as valve lift increases, the pushrod is too short or too long. On a custom-built, ground-up engine, pushrods are generally the last things to be ordered. Adjustable checking pushrods or dummy rocker arms are available from aftermarket sources for deriving the correct pushrod length.
As for rocker arm choice, the greatest durability and reduced friction benefits are achieved by using a rocker with a needle-bearing roller fulcrum. The roller tip, while it can't hurt, does little or nothing to decrease valvetrain friction.
Locked Motor
I have a '91 Chevy S-10 with the 4.3 V-6. The motor was getting rough and had 170,000 miles, so I decided to rebuild it. I took it out and tore it down. I cleaned all the parts with Chem-Dip, honed the cylinders, and cleaned out all the junk and deposits. Due to lack of time, I put it back together about six months later, heavily greasing the pistons, rods, and bearings. I got all the pistons in handtight, but the motor would not turn. (I didn't have the heads on and used a pull-bar on the harmonic-balancer bolt.) I don't have much experience in a complete rebuild, but this doesn't seem normal to me at all.Levi FloydDallas, GA
It could be any of the following:* Wrong-size main or rod bearings or incorrect bearing clearance (check with gauging plastic)
* Mismatched connecting-rod body and cap, or cap installed backward on the body. An even-fire Chevy 4.3 V-6 does not have paired rod journals like the V-8, so the entire rod assembly can be installed in either direction, provided the piston valve notches (if any) are correctly oriented.
* Main-bearing caps installed on the wrong journal or installed backward
* Incorrectly installed piston rings popped out of ring grooves and gouged into the cylinder walls
* Debris On The CrankNext time, be sure to number-punch the main caps and both connecting-rod halves so they can be reinstalled in the same position and orientation from which they were removed.
G-Body Manual Trans
I own an '86 Monte Carlo SS. I want to swap the 200-4R automatic overdrive trans for a manual trans. Does anyone offer a manual trans for late-model G-bodies or do I have to go to a salvage yard to get one? What other parts and mods are needed?Shawn GlasseeNew Britain, CT
Any stock or aftermarket manual trans designed to bolt to a Chevy V-8 can be made to work, but the exact modifications and additional parts required depend on the specific trans. Remember that there was a factory manual trans option for '78-'81 GM A/G-bodies (rear-drive intermediates, the same basic chassis as your Monte), so in theory this swap could be accomplished using stock parts. In reality, A-body manual-trans cars of this vintage are extremely rare and it is unlikely you will find one in the wrecking yard.
The stock manual-trans options were either various models of three-speeds or a Saginaw four-speed. With the factory bellhousing, mechanical clutch linkage, clutch-pedal assembly, clutch-linkage frame bracket, and a manual trans or TH200/TH350 trans-support crossmember (GM PN 473721 for V-8 cars, discontinued), they bolt right in. Dimensionally similar (but stronger) OEM-style manuals include Muncies and Super T-10 four-speeds. Aftermarket-trans options include Richmond five- and six-speeds and the TTC (formerly Tremec) TR-3550 or TKO five-speed. With these non-stock transmissions and depending on the specific model, shift-linkage changes, floorpan alterations, crossmember mods, trans yoke replacement, and driveshaft length changes may be needed. Instead of modifying a stock crossmember, you may want to check out G-Force Performance, which offers a line of double-hump crossmembers for the late A/G-body chassis.
Any of the above trannies bolt up to a Chevrolet stick-shift bellhousing's normal depth and bolt-pattern. However, due to the stock '78-'81 A-body mechanical clutch linkage's revised geometry, universal musclecar vintage Chevy or aftermarket-equivalent bellhousings won't work when using the stock clutch linkage and fork. This fork (GM PN 14007356, discontinued) has a downward drop and is designed to mate with a lowered bellhousing ball-stud installed in a special, now salvage-yard-only, '78 A-body bellhousing. For a 168-tooth flywheel, use casting No. 464997 or 469697. If using a 153-tooth flywheel, get casting No. 462606. Clutch linkage, forks, and pedals are available from several sources, including Original Parts Group. Speed Direct offers stronger linkage utilizing rod-ends (PN CMP 7130).
There is also the T5 five-speed and T56 six-speed, available in both production and aftermarket versions. In the T5, you want the '88-'92-style GM V-8 World Class version, but it must be used with a corresponding T5 bellhousing due to its rotated mounting bellhousing bolt-pattern. T56s installed as original equipment in '93-'03 F-bodies require a unique bellhousing and hydraulic-clutch actuation; they also lack mechanical-speedometer cable provisions (however, Abbott's Cable X box interfaces the VSS signal output to a speedometer cable). The '98-and-later version used behind Gen III engines is different from the one used behind '93-'97 LT1s. McLeod Industries sells a modular bellhousing system that lets you use either of these OEM T56s with conventional mechanical-clutch linkage. It also offers universal hydraulic linkage solutions. Another alternative is TTC's aftermarket-only T56, which mates with V-8 T5 bellhousings and has conventional speedo cable provisions.
Disc Brake Caliper Location
Does the location of the caliper matter on a disc brake? It would seem the nine-o'clock location might add to lift during braking, and the three-o'clock location might cause better squat and more tire contact patch. Yet in the real world the car companies mount these randomly.Paul A. KalenianPrinceton, MA
What you say is basically true in theory, but in the real world any effect of caliper mounting location on the vehicle's antidive or antisquat characteristics is trumped by other factors. Chassis builders can achieve the desired amount of antisquat on acceleration and deceleration by altering suspension-control-linkage angles versus the vehicle's center of gravity. The changes to be gained through this suspension tuning are huge compared to any derived from altering caliper mounting locations; therefore, caliper-to-chassis clearance, positioning the bleed screws in approximately the 12-o'clock position to avoid trapped air, and achieving optimum brake-system cooling for the application are the primary factors governing caliper mounting location. Additionally, some chassis builders may elect to position the calipers closer to the vehicle's center to enhance weight distribution by mounting the front calipers in the trailing position and the rear calipers in the leading position. This might be significant on a lightweight open-wheel race car, but whether it really makes a significant difference on a heavy sedan is questionable.
Lt1/4l60e Spark And Shift Woes
I have a '94 Firebird Formula with a rebuilt, tricked-out LT1 motor. Two problems remain:
The Opti-Spark ignition has a life of about 60,000 miles. I have run through two and the misfiring at 5,800 rpm tells me I am now ready for a third; they start to break down at 6,000 rpm and get progressively worse. Apparently no one makes a replacement for the factory junk. Do you have any suggestions?
The second problem is the 4L60E tranny, which was rebuilt using a street/strip aftermarket kit and a 2,800-stall converter. With no trips to the local strip, that rebuild lasted 16,000 miles before the sprag-clutch broke and I lost Third and Fourth gear. The tranny builder says the computer is telling the trans to shift too early under part-throttle, which is tearing up the trans. GM Motorsports makes a shift-control mod for the 4L60E (developed for off-road racing) for $1,000 that lets you set 4L60E shift-points (including part-throttle shifts) with a laptop PC once you dial in the rearend ratio and tire size. Before I spend the big bucks, I need some rodder's experience with the strength of the basic 4L60E unit. I have been told that rather than spend money on the existing unit, I should get a tricked-out 700-R4 unit with a three-speed electronic overdrive. That would be approximately $2,300 and involve welding a crossmember in place to support the overdrive. What do you suggest?Dana N. NasutiCherry Hill, NJ
Seventy percent of the time, Opti-Spark problems are caused by the cap and rotor, which may exhibit carbon tracking, cracking, or water intrusion. GM used to make you buy an entire new distributor assembly (big bucks), but a service cap and rotor repair kit was finally made available (as reported by dealer TSB No. 87-65-27). MSD has also introduced a new cap and rotor kit made from better-quality materials than the stock part. For application data, see the accompanying table.
Ultimately, in extreme high-performance or racing applications, the stock ignition module and underpowered single coil may not be up to the job. There is a solution in the form of Delteq's Opti-Direct system, a four-coil distributorless ignition that eliminates the stock Opti-Spark module, coil, cap, and rotor. It works with the factory computer, does not require removal of the original Opti-Spark unit, and plugs into the existing wire harness. Installation time is said to be less than two hours.
You seem to be confused about the transmission. The 700-R4 is basically the same trans mechanically as the 4L60E. Both are four-speed overdrive transmissions, and Camaro/Firebird small-block V-8 versions are dimensionally interchangeable in your chassis. The major difference is that many functions in the earlier 700 are still handled hydraulically, whereas the critical functions on the 4L60E are primarily controlled by electronic interface with the engine management system. There is no strength advantage in downgrading to a 700-R4. Besides, the earlier unit won't interface with the late computer and wire harness.
What you may have been thinking about is installing an earlier, musclecar-era TH400 three-speed, backed by an add-on Gear Vendors planetary overdrive. This is definitely a bulletproof combo, but floorpan mods may be required, you'll have to figure out how to mount up the torque arm, and it won't interface with the computer, either. Critical outputs like the VSS won't be available (VSS is needed for the engine-side of the computer and also to run the speedometer).
Therefore I'd stick with the 4L60E. It is not necessary to buy the expensive GM off-road controller. Carputing's LT1 Edit software allows remapping the vehicle's computer with a standard laptop PC. That of course would encompass 4L60E trans parameters, including shift points and line pressures. A one-car software license is about $250, not including any required hookup cables. Correcting the shift points and raising line pressure should take care of any trans problems, rebuilt as it has been with heavy-duty parts. If further strengthening is required, consider installing a fully enclosed diode sprag in place of the normal sprag, and sleeving the 3-4 drum. Contact ACT Performance for more info on these upgrades.
Where Do I Get . . .
...a cheap limited-slip differential for a '66 Bronco 28-spline 9-inch Ford rearend installed in my 350hp small-block Chevy-powered '70 Gremlin?Jimi CoffeySyracuse UniversitySyracuse, NY
Under-$500 conversion-style limited slips fit in a standard differential case and can be installed by the average hot rodder without any special tools. They include the Detroit E-Z Locker (PN 813A027 for your application) from Tractech Inc. (Warren, MI; 800/328-3850 or 810/759-3850; www.tractech.com) and the Powertrax (PN 92-0690-2800) from Richmond Gear (Liberty, SC; 800/583-GEAR [nearest distributor] or 864/843-9275 [tech]; www.powertrax.com).
...performance parts for the 4.0L Olds Aurora V-8, a member of the Cadillac Northstar family?Patrick LewisConowingo, MD
Contact Cadillac Hot Rod Fabricators (Fallbrook, CA; 760/451-8796; www.chrfab.com) or MechTech Motorsports (Escondido, CA; 760/432-0555; www.mechtech-ms.com).
...headers, a four-barrel intake manifold, and a performance cam for a '63 LeSabre four-door with a 0.030-over 401 nailhead?Jacob HildebrandtEllsworth, WI
TA Performance Products Inc. (Scottsdale, AZ; 480/922-6807; www.taperformance. com) sells a wide variety of nailhead parts, including shorty headers, cams, and multicarb intakes from Offenhauser Sales Corp. (Los Angeles, CA; 323/225-1307). At present there are no aftermarket single-four-barrel intakes, but TA is said to be working on one, so watch for it.
...a five-speed overdrive manual transmission and adapter for an FE Ford 390 in a '69 Ford F-250?Kent M. WilliamsHesperia, CA
The TTC Transmission Technologies Corp. (Farmington Hills, MI; 248/471-3200) TKO five-speed can take anything a 390 can dish out. Bolt it up using the modular bellhousing adaption system from McLeod Industries (Placentia, CA; 714/630-5129 [sales] or 714/630-3668 [tech]; www.mcleodind.com).
...exhaust-tip flame-throwers for a pal of mine?Greg GehrisEl Segundo, CA
BSeek LLC (Nebraska; 402/486-0545; www.axdo.net), www.flamingexhaust.com, and www.flamedexhaust.com are just a few of the dozens of outfits offering these parts. "Your pal" . . . sure, right, whatever.
