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E-mail your tech questions to us at carcraft@primedia.com (include the words "What's Your Problem?" in the subject line) or fax them to 323/782-2223. All correspondence must be signed with the sender's real name (not a nickname or a screen name) and include the sender's hometown and state or province. While mail cannot be answered personally, Car Craft will publish as many letters and replies as space permits. Photos are welcome, but no materials will be returned.
Rear Gear ReduxI have an '88 Mustang LX with the 5.0L engine and T5 five-speed manual trans. I've owned the car for about a year, and I've been experiencing a drivetrain vibration that's getting really annoying. I've been told by a few friends that the problem is probably the rearend gears. A previous owner replaced the stock 2.73s with aftermarket 3.73s, and I can hear them whine whenever I drive over 40 mph. The vibration kicks in at slightly higher speeds.
My actual question is, can I use used gears? I can get a set of Ford Motorsport 3.55s that a friend had in his Mustang for only a month or so before swapping up to 4.10s. He says when he had his gears installed, the tech-a Ford dealership mechanic-told him that the Ford gears could usually be installed by simply bolting them in, while keeping the shims in the same place. Allegedly, the car made no gear noise afterwards. Do you think I could bolt the gears into my Mustang with success? Or do I have to have them set up professionally? Tim GeffertHanover, PA
It sounds like you have more than one issue to deal with, Tim. Although the whine you hear may well be coming from the rear gears, it is unlikely that they are also the source of the vibration. Let's address the gear issue first.
Your Mustang's rearend gears were probably not installed properly, and that's the likely cause of the whine you're hearing, whether they were aftermarket or not. The Ford 8.8-inch rear-axle assembly, as found in all '86-and-later 5.0L Mustangs, requires that the installer set pinion depth and backlash between the gears, usually with a crush collar or shims on the pinion, and more shims between the carrier and the housing. This procedure requires precision measurements for successful results, though bolting the gears in without checking anything is physically possible. We've also heard tales from experienced Ford wrenches about bolting in new gearsets without having to move any of the shims around, but this was back when the cars were new, and even then, luck probably played a big role. Most axle shops will set up gears for around $150-$200 for a common axle like the 8.8, and that's money well spent, since operating the vehicle with new gears for any length of time establishes a wear pattern, which then negates later attempts to quell any gear noise with further adjustments. For this reason, your used 3.55s may not eliminate the rearend noise. There is the possibility that those gears were set up properly during the first installation, and that your current installer could also attain the proper gear positioning, but he would have to take the time to establish the same wear pattern to ensure there was no noise and that the gears continued to wear properly-most won't take the time with used gears, and fewer will guarantee the work. Ford Racing's gearsets are relatively cheap, so it's probably worth stepping up to a fresh set.
As for the driveline vibration, we mentioned that the rear gears were unlikely culprits. However, there's a good chance your vibration is coming from the driveshaft, either because it is out of balance, or because one or more of the universal joints is faulty. Pull the shaft and check the U-joints for play and to make sure their retaining clips are intact and secure. If the U-joints are in good shape, have the shaft checked by a driveline shop on a spin-balancing rig. The shop should be able to balance the shaft with minimal effort so long as it isn't somehow damaged or bent. Note that Ford Racing offers a complete aluminum driveshaft for Fox Mustangs that comes complete with universal joints and yokes at an extremely reasonable cost that may be a better choice than investing in your stock shaft, should it prove faulty.
If the driveshaft checks out OK, check the runout of the rear axle shafts at the wheel mounting flanges. This can be accomplished with a simple dial indicator using a clamp-on or magnetic mounting base. You should find virtually no runout on either shaft. Any significant runout detected on the face of the wheel mounting flange is probably a good indication that you should replace the shaft. Have the axle shop verify your findings before ordering new shafts. While you're at it, make sure the axle bearings, transmission mount, and rear-control-arm bushings are in good shape.
Z Real Thing?I have had my '69 Z/28 for over 30 years. Lots of fun and lots of combos. Now that I am considering selling it, the first thing people ask is "Is it the DZ 302?" The guy I got the car from (the second owner and a personal friend) worked at a speed shop and had the 302 engine "balanced and blueprinted," which naturally included having the block align-honed and decked. Therein lies the problem.
Now that I realize how valuable my car is with all the original parts, I find myself looking at an engine block with no visible numbers. I had never even noticed that the numbers were not there until I was looking at the stored block in my garage recently and realized that they would have been machined off during the decking process. I know this is the original engine because I have had it apart many times and have verified all of the parts, but how can I prove that this is indeed the engine that originally came in my car? What do other people do when having an engine decked? Can the numbers be raised? I'm getting kinda tired of being asked, "Is it a real Z/28?"Wendell E. SmithSpokane, WA
As you've found, the '69 Z/28 is not only one of the most desirable cars of the first musclecar era, it's also one of the more difficult to authenticate. This is largely due to the relative lack of factory distinctions that designate a Z from other more common Camaro models. Of course, the 302 small-block was unique to first-generation Z/28s, but unfortunately, since it was based on a fairly common production block (the 327, and later, 350), there are no factory casting marks to separate an original 302 block from much more common engines. For the '69 model run, which actually included nearly 16 months of production, there were three block casting numbers used for '69 302s, including the "010," which many Chevy guys will recognize as a super-common 350 casting.
You do have one hope, however. Although you didn't mention when your car was produced, or at which assembly plant, some '69 engines had the VIN stamped in another location in addition to the front of the passenger-side deck. Look on the driver-side of the block at the rear, near the oil filter adapter, and find the flat surface that faces outward, parallel to the bellhousing mating-surface at the point where the dowel pins are located. There you may find the original VIN stamped into the block, but not the other codes that would have been stamped in the deck.
If you don't find the VIN there, you're pretty much out of luck. If you're determined to find proof, you might consult with a Corvette restoration specialist in an attempt to find someone that can "raise" the numbers that had been machined off, using acid or infrared scanning or some such means of utilizing forensic science for auto restoration.
Seal In The FreshnessI have an '87 Buick Turbo T engine that I rebuilt over the winter. I had it bored 0.030-inch over and had it O-ringed. I'm having a problem with antifreeze going somewhere, and it's not going on the ground. I used SCE copper head gaskets and sealed the water jackets with Permatex Hylomar high-perf gasket dressing and flange sealant. I was wondering if you could tell me how I can seal the head gasket better when I tear it down again.Charles Good Muncie, Indiana
The combination of SCE copper head gaskets and Hylomar sealant with O-ringed blocks is a common approach to sealing the cylinders of high-boost Buick turbo V-6s, but this method can be somewhat unforgiving. The copper head gaskets don't have the ability to conform to imperfections in the sealing surfaces like conventional composite gaskets do, which necessitates the use of gasket dressing. Unfortunately, that still doesn't guarantee successful sealing.
Before you tear into the engine, try retorquing the heads again. You should be using the torque sequence prescribed in the Buick factory manual and the torque specs for the bolts you're using-for example, aftermarket performance fasteners, such as ARP, often have higher torque specifications than factory fasteners. Also verify that the specs you're using are intended for bolts with lubed threads and shoulders-dry bolts will give higher torque readings with less stretch due to the increased friction. There's a chance that you'll get lucky; re-torquing the heads may do the trick if they simply weren't tightened enough previously, or if they were never retorqued.
Another potential source of your problem that should be checked prior to teardown is the factory oil cooler. Assuming that your Buick still has this unit, pressure-test the cooling system to see if this is the source of your coolant loss. The original oil coolers on Turbo Regals were notorious for developing internal leaks as they aged. If this were the case, you'd probably be experiencing the dreaded crankcase milk shake effect-a creamy, gooey mess that results from the mixture of oil and coolant, which would be evident when looking into the oil filler, or possibly even on the dipstick. If you can't get a clear view inside the crankcase, pull a valve cover and have a look.
If and when you do have to pull the heads to reseal, check the heads and the block decks for trueness, preferably with a machinist's straightedge. Once that's been verified, clean the sealing surfaces thoroughly with a good solvent, making sure to wipe all the solvent residue from the surfaces once they're completely free of any sealant, oil, antifreeze, and so on. Then, begin the process of installing the new copper head gaskets using the Hylomar, following the instructions to the letter. Once the heads are in place, torque the bolts, again following the factory sequence and stepping and using the final torque spec that corresponds with the bolts being used. Once the heads are installed and torqued, don't start the engine. Instead, let it sit, at least overnight, and then go back and retorque the bolts the following day. This time, go around the heads and loosen and retorque each head bolt one at a time using the normal sequence. After the engine has been run for a few days and has reached normal operating temp a few times, repeat the retorquing procedure one more time. Hopefully this will ensure a positive seal.
Killer Cougar?My '91 Mercury Cougar has a factory-installed 5.0L and AOD, and it's done a fine job for 160,000 miles. I love this car, but now I want it to roar with today's performance cars. Lots of people tell me to get a 'Stang or a Camaro, but I like my ride, even if it's heavy. I've read many articles on engine swaps and many more on crate engines and strokers. In your opinion, would a swap to a stroked 351W with EFI be better (in terms of cost and labor) than boring, stroking, and adding Trick Flow or Edelbrock heads to the existing 302? Are the factory '91 heads performance units or just standard 5.0 heads? Does anyone offer headers for the 302 or 351 in this application? How about a cowl-induction hood? I also think I need to change the rear gears to something in the 3.50 to 3.70 range, and possibly add a 2,500 to 2,800-stall converter. I value your input and suggestions. K. ForwardFranklin, TN
First off, you should probably forget about the 351W in that Cougar. When that body style was first introduced, the V-8 was not even offered, so when Ford had to go back and fit it because consumers wanted the extra power, a new, lower-profile EFI intake manifold had to be designed to fit under the car's extra-low hood line. Since the 351W is a tall-deck version of the standard small-block Ford, the extra height will be a problem, as will the added width.
If you're bent on extra cubes, build a stroked 5.0 using a 347 kit, available from a number of sources. This will allow you to effectively gain a significantly larger displacement while maintaining the stock external dimensions. If you are going to build an engine, you might want to source a 5.0L H.O. block from a Mustang or Lincoln LSC. These blocks have the taller lifter bores and retainer provisions that will allow you to run a factory hydraulic-roller cam.
Even a basic rebuild of a 5.0 H.O. will provide a sound foundation for more power. Using aftermarket heads as you suggested will make a major improvement, as your stock heads are lame standard-output units. Combine the upgraded heads with a better intake-try the Cobra manifold for the '94-'95 SN95 Mustangs, which is also designed for low-profile applications. We were unable to find headers for your application, though it's possible that Mustang shorty headers will work. Check with some of the Fox Mustang header makers for possible insights.
The rear-gear swap is a good idea, though we'd probably go with either 3.73s or 4.10s and leave the torque converter alone for now, or at least until you have the trans rebuilt.
Balance JobI understand that most Chevy 383 stroker kits incorporate external balancing by using a Chevy 400-style damper and flexplate. Even kits that are sold as balanced rotating assemblies frequently use the 400 damper and flexplate. Some kits, however claim to be "neutrally balanced." I have been lead to believe the GM Performance Parts HT383 crate truck motor is internally balanced like a standard 350. If this is true, can you clarify the differences and advise which is better, assuming a new crank is required? Robert l. KeelingLouisville, KY
When balancing an engine, the mass of the components hung on the rod journals of the crankshaft must be brought into balance by offsetting weight on the counterweights of the crankshaft. The balance factor takes into account the motion of the components, factoring 100 percent of the reciprocating weight and typically 50 percent of the rotating mass. Unfortunately, the standard GM 400 crankshaft traditionally used in these engines does not have enough counterweight mass to bring the assembly in balance. While the crank's counterweights themselves lack the required mass, GM's clever powertrain engineers simply hung the required weight at each end of the crank with eccentrically balanced dampers and flywheels/flexplates, creating "externally" balanced engines.
The GMPP HT383, similar to the traditional 350/400 production-based strokers, is externally balanced, but the balance factor is different from either a 350 or a 400. GM lists a specific damper, PN 12498008, for the new HT383 application, while at the output end a PN 14088765 flexplate, common to '86-and-later one-piece rear-main-seal small-blocks, is specified. Follow the directions from GM and proper balance will be taken care of.
Production-based custom strokers typically use eccentrically weighted production 400 dampers and flexplates to achieve balance, often employing way too much eccentric weight. Better too much than not enough, though, since the assembly can be brought into balance more easily by removing weight than by adding it. Expensive custom balancing can be one of the hidden costs of a pieced-together stroker. Some aftermarket stroker cranks have a "split balance," combining an externally balanced 400-style flywheel with a neutrally balanced harmonic damper to achieve overall balance.
While at least partial external balance is the norm for 383s, internal balance may be achieved by the use of dense Mallory metal inserted into the crank's counterweights, rather than using the eccentrically weighted, external-balance dampers, flywheels, or flexplates. What's the difference? Externally balanced engines make up the deficiency in counterweight at each end of the crank, which serves the purpose of bringing the total rotating assembly in balance. However, this arrangement is not without compromise. With the eccentric weight hung at the extremities of the crank rather than at the counterweight directly in line with the piston and rod weight they are charged with offsetting, a bending movement is imparted to the crank. With a low-rpm slug like a production 400 small-block, the magnitude of this force is negligible, making an externally balanced assembly an effective approach to bringing the engine into balance. In very-high-rpm applications, however, an internally balanced engine will hold an advantage in minimizing these bending motions, which become more significant as rpm escalates. As a consolation, high-rpm race engines are more likely to hang much lighter components at the crank journal, making internal balance much more viable. On the other hand, in a typical street/strip rpm range, we'd hang our hat with the Detroit engineers and simply externally balance it and not get too hung up about it.
Pudding SkinnerI own a '95 Chevy 4x4 fullsize pickup with a 5.0L V-8, four-speed overdrive automatic trans, and TBI induction system. This combo hasn't got the power to pull the skin off rice pudding! I intend to swap out the engine with a late-model 350ci Vortec-head engine or put in my 400ci early model engine. I would like to keep the EFI, so as not to blow the budget. What problems lie ahead?Bob RedmondMarshfield, MO
You could use the 400, but that would require a new flywheel, as early engines with two-piece rear main seals have a different crankshaft mounting flange. Also, the 400 is externally balanced, requiring a specifically weighted flywheel. For these reasons, let's look at using a late-model 350. This swap would be relatively straightforward, and the power gains should be significant, if spec'd right.
Using Vortec heads is an excellent idea, as they're cheap, efficient, and offer substantial performance gains over conventional factory heads. The only obstacle here is that your existing intake manifold will not bolt up to the Vortec heads. Vortecs use a unique intake bolt pattern not found on other Chevy cylinder heads. The intake bolts go straight down through the manifold, meeting the cylinder-head mounting surface at an angle, somewhat like the arrangement used on Ford small-block V-8s. Some machinists have devised ways of re-drilling Vortec heads to accept conventional Chevy intakes, but this will result in a port mismatch that will diminish the power potential of the head swap.
Fortunately, GM Performance has recently introduced an aluminum intake manifold for TBI systems that mates with Vortec heads. The manifold (PN 12496821) is a street-performance-oriented dual-plane type that was designed with light-truck use in mind. Your existing throttle body and associated components will bolt up, but some recalibrating should be done, since these pieces were intended for a 305. Since Chevy offered the TBI system on 350ci engines from the factory, fitting the throttle body with the larger 61 lb/hr injectors used in 350 applications (305s use 55 lb/hr units) and the corresponding PROM chip would likely get you dialed pretty close. However, to maximize the potential of this combination, you might consider consulting Turbo City in Orange, California, which specializes in performance tuning GM TBI systems. Turbo City can burn a custom chip for your combination, and can also offer some guidance in selecting a camshaft for the new engine. As a general guideline, the cam selected should not have excessive overlap, and if using stock Vortec heads, lift should be kept under 0.480-inch. If a higher-lift cam were to be used, the valve guides in the heads will have to be machined for extra retainer clearance-a simple procedure for a qualified machine shop.
