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April 2010 Techline

Posted in How To: Tech Qa on April 1, 2010
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TBI 350 Into Old Blazer Swap
Q. I have a 1977 Chevy Blazer and a 1995 Chevy Silverado, both with 350s. I want to swap the '95 engine with the TBI into the Blazer. Can you give me a list of things I'll need or need to do, wiring harness, motor mounts, fuel pumps, etc.?
Jon Tomlinson

A. The good news is that the engines use the same motor mounting system. Considering that the "new" engine is still some 14 years old, it would be a good idea to buy new rubber mounts.

Now the hard work comes into play. You're going to need the complete wiring harness from the Blazer, not forgetting the wiring that goes to the "Check Engine" light and the oxygen sensor, along with the ECM unit (computer). Be sure you mark every wire's "goes to" location. Don't forget the MAP sensor (manifold absolute pressure), which reads manifold pressure, or engine load. It should be mounted within 12 inches of the throttle body, above the vacuum source. Also be sure to grab the Electronic Spark Control, which feeds the distributor key data.

You're also going to need the 02 sensor, which will need to be installed into a welded-in bung on the exhaust manifold. Probably would be a good idea to replace the old one with a new one. You're also going to need what is called a vehicle speed sensor, installed in line between the transmission and the speedometer.

Gathering up the wiring harness can be a real pain, so maybe you want to spring for an aftermarket wiring harness such as the one Painless Wiring offers ( It's pretty cool in that all the wiring is pre-labeled, and some great instructions come with it. If you go with the factory wiring harness, I suggest you somehow access the wiring schematics for both trucks. It will make things a lot easier when you know where things go.

Now you have to deal with the fuel system. GM fuel injection uses an in-tank electric fuel pump. However, to make things easier, you can mount a special pump on the outside of the frame as close to the fuel tank as possible and as low as possible. You will want to add a fuel filter in front of the pump as the internal rotor clearances are quite tight, and being that it spins at about 3,500 rpm, it only takes a small particle of crud to damage it. Arizona TPI ( ) has what you need. You may be able to adapt the fuel sender and pump assembly from the Blazer into your truck's tank. Oh, and don't forget that you will need a fuel return line from the throttle body back to the fuel tank. You will have to find a way to get the returned fuel back into the tank if you can't use the Blazer's fuel pump unit. Usually, you can solder a fitting to the pick up/sender plate.

Okay, what else did I forget? Probably a lot of things, like transferring the throttle-body linkage over to the truck, as they are a bit different. I only kind of covered the basics here, so be prepared for a bit of work.

If you decide that you don't want to go to all of that work of making the TBI work, you can swap the Blazer's engine over to a carburetor. Between 1987 and 1995, Chevy went to a new-style intake manifold where the two center bolts on each side are not angled. You can take the manifold off the '77 truck engine, have these holes machined to the proper angle, and use it and the truck's carburetor-or you can buy a correct aftermarket manifold that definitely will improve the engine's performance. You also will need to swap over to the older distributor or go to an aftermarket unit.

V-8 Toyota Needs Drivetrain Beef
Q. I'm looking for any ideas or input on how to make my '87 independent suspension Toyota survive my small block V-8 with 15 pounds of boost. Will adding ladder bars help? I am running 40-inch tires with stock gears and stock housings.

A. Ladder bars, depending on the design, may control wheel hop but generally limit articulation unless properly designed. But the ladder bars are the least of your problem. A small-block V-8 with 15 pounds of boost and 40-inch tires means instant destruction to most of the drivetrain components when the throttle is hammered. You need to sit back and realize the drivetrain that was designed for 150 or so horsepower, and while it's quite stout, it will never live for long when the power is more than doubled. The IFS is particularly subject to breakage, even with a few steps above stock in tire size in its factory configuration. I suggest that you browse through websites such as All Pro Off Road ( to get a better handle on just what is needed.

Torsion Key Lifts: Pros & Cons
Q. Question for you on something that's been bothering me for awhile. In the Jan. '10 issue, there was an article on lifting torsion-bar Chevys with a replacement torsion key. I've seen these before. The article says you can lift the Chevy by cranking the torsion bars, but it ruins ride quality and accelerates front-end parts wear. The solution, as I understand it, is to replace the torsion key with one that is indexed differently to allow you to crank the torsion bars even more than the factory key. How, pray tell, is that any different than just cranking the factory key? It still achieves lift by increasing the twist on the torsion bar, you still have increased angles on the CV joints, and you still have different angles and stress on front-end parts unless you drop the front axle assembly with spacers to match the lift, right?

The same article comments about putting Loctite on shock bolts. I'm about to replace my pickup's shocks, and Loctite is the furthest thing from my mind. I'm planning on lots of anti-seize. I've never had a nut loosen from the shock bolt, but I've spent hours with a hacksaw cutting out a bolt that's permanently rusted inside the sleeve in the shock eye.
Bruce Erickson
Frenchtown, MT

A. Generally you don't have a lot of adjustment on the torsion bar key or cam, so with an offset key you can get more lift than just with the adjustment screw. Yep, you're right, it ruins ride quality and accelerates wear on front-end parts. Think about it as pushing the wheel downward. Now you have limited (to no) downward wheel travel, depending on the amount of lift. With no downtravel, ride quality and traction suffer in that direction, and as the torsion bar has to twist more to allow upward travel, the spring rate increases, which doesn't do ride quality any good. It also puts more load or twist on the torsion bars, which shortens their life. With the suspension at full droop, then most of the time the axle CV joints are running at maximum angles, which really shortens their life, too.

What you're saying about shock bolts and Loctite is also true. I can't ever remember having a shock bolt work loose, but I guess it could happen. I generally either use some type of locking nut on all my fasteners and tend to shy away from lock washers. When I was racing, we used Loctite on every nut and bolt as a safety precaution. The advantage of using a low-strength Loctite on such a bolt would be that you would block out any moisture from getting on the threads where the nut made contact and the resulting rust. My vote is for the nasty silver stuff and a locking nut.

Wheelhop Rx: D.I.Y. Traction Bars?
Q. You had a letter in the Dec. '09 "Techline" dealing with wheelhop, or some variation of it. Wheelhop has killed many trannys, U-joints, spiders, and ring gears. To cure that, you need what old-time drag racers called traction bars.

To replace the housing is going to incur considerable time and expense. So don't replace the housing, straighten it. How? There's an old-time roundy-round trick for this as a lot of roundy-round cars banged tires (rear) and bent the housings. Use a straight edge to determine where it is bent, then cut the housing on the opposite side and bend it straight-use a straight edge or dial indicator or whatever. I actually made a jig out of a piece of 5-inch channel and used some large C-clamps to pull the housing straight. I had some bent so badly that over a half inch of material had to be removed to get the housing straight. When it's straight, weld it up. I finally got smart (a little, not much), and welded a 5-inch piece of 1/4-inch flat stock on edge from one backing plate to the other.

A. Thanks for your input. I always like to hear different solutions to problems. However, conventional "traction bars" may work just fine for a car that only turns to the left, or for a drag race car with limited suspension travel, but on an off-road vehicle they are a "no-no." Why? Because they really limit suspension travel, and when articulation exceeds the movement of the traction bar, something has to break or bend, which it quite often does.

Yes, there are some specially designed ones that work off of a unique shackle design, but one is better off designing the suspension system correctly in the first place to prevent axle hop from happening.

As to straightening an axlehousing using the method you describe, well, it may work, but it's not something that I would recommend. Generally speaking, the axletube of a vehicle used off-road usually bends right at the location where it enters the housing, or right at the spring mounts. Both of these locations would be difficult to locate and/or straighten with just a straight edge. Cutting the opposite side would allow you to more easily move the axle tube, but I just can't see that one could do it without some kind of giant C-clamp and lots of brute force. Then you have the problem of controlling the bend in the opposite direction from the heat of welding when you weld the cut back up.

I have scratch-built many axlehousings over the years and found it is quite difficult to keep them perfectly straight when the final welding is done. The only way that I've been successful in keeping them true is by using an "alignment bar," which mounts on bushings, that center it on the outer ends of the axle tubes as well as the carrier bearing location within the housing. I have used various methods to straighten bent housings over the years, ranging from applying heat and quenching, to a come-a-long and some special fixtures, to a very large 100-ton press and special fixtures. Any way you do it, it's a lot of work, and in reality has to be done with an alignment bar to ensure that the axletube is straight when you're finished.

Horsepower Tips For 5.9L Dodge
Q. I have a 2001 Dodge 3/4-ton extended-cab pickup with a 5.9L V-8. It's a nice truck, but it's a little short on power. It has stock exhaust and a K&N air filter system. I also have a JET performance chip installed that has helped somewhat, but this system is still underpowered when I haul and tow things. Do you have any ideas as to what would help me out here? As with most people during this recession, I have fairly limited funds.

I'm pretty much figuring that my gas mileage will not get much better if at all, around 11 to 12 mpg, so if I could get some more horsepower out of this engine, I would settle for that. It's a very nice truck with several new items installed including a new automatic transmission, so I'm hesitant to get rid of a paid-off rig right now.
Fred Maurer
Bend, OR

A. I used to own a '97 Dodge with the five-speed and 5.9L motor, so I am well aware of the overall lack of power and the poor fuel mileage. I went with some short-tube headers from a major manufacturer, a new low-restriction muffler and an aftermarket air cleaner. There was some gain from the air filter, but not a bit of gain in either performance or fuel mileage from the headers. I kind of expected that because of past experiences with short-tube headers, but had to give it a try and at the time they were the only ones available. Perhaps if you could find some long-tube headers you could gain a bit, but the payback will be a long time with only a mile or two increase in fuel mileage.

On a good day of interstate driving, I would see a high of 14 mpg if I was careful and kept the speed low. With a camper in the bed and pulling a trailer to, say, Moab, and fighting a headwind, sometimes I got as low as 5 mpg. The reason I am telling you all this is that there is not a lot to be gained with modifications. You have to live with your truck and accept the fact that it is paid for, and it just might be cheaper to pay for gas up front and not have truck payments. Oh, and I don't care what the TV ads say: In the real world, the new 3/4-ton 4x4 trucks do not get 20 mpg, but a lot closer to what you're presently getting.

Newly Rebuilt 350 Losing Power
Q. I bought a small block 350 Chevy from an ad on a local bulletin board to put in my 1970 Blazer. The motor had been rebuilt with some quality parts about five years ago, but had never been run (the seller showed me all the receipts). It had forged pistons, "pink" rods, and a Chevrolet factory performance cam package that included valvesprings. I removed the distributor and spun the oil pump with a driver and electric drill as well as following all the tips from one of your "Willie's Workbenches" some years back that I had saved on new motor start-ups.

Everything went fine, but after a week or so, the motor has developed a miss at idle, and the power seems to have been reduced even though I have never done any full-throttle runs yet. I've gone through the ignition components, and even replaced the distributor, rechecked the timing, swapped the carb for a buddy's, and checked for vacuum leaks. I even did a compression check, and the cylinders were all between 150 and 165 psi. The engine runs clean and doesn't smoke out the tailpipe or the breather.
Marty Smith
Los Angeles, CA

A. Well, the compression pressures should be a bit closer together, but that could be attributed to the rings not totally seating yet. My guess is that you have a valvetrain problem. You didn't say what type of oil you used, or if you had added a break-in lube.

What I suggest is that you pull off a valve cover, start the engine and watch the operation of the valves and rockers. My guess is that you're going to find one or more that are not coming up as high as the rest. If so, this indicates that either a cam lobe has gone flat or you have a bent pushrod, or even one that's not properly seated in the rocker. Look closely at the valvesprings and make certain that a coil isn't broken. However, being that the motor is five years old and had never been run, I'm going to guess that at least one cam lobe has gone flat from improper lubrication. Sorry to tell you this, as it's a heck of a lot of work to change out the camshaft.

Here is where the problem lies. Some years back, the oil companies and the vehicle manufacturers got together and figured that they could meet emissions regulations and prolong catalytic converter life by taking several high-pressure additives out of the oil. Not a problem because all the new engines had roller camshafts, which did a much better job of distributing the load over the camshaft than did the old flat-tappet design. Every aftermarket cam manufacturer, as well as specialty oil producers, now offer a special break-in oil or additive designed for the "old" flat-tappet cam that will prevent this wear.

Ford AOD Tranny Tips
Q. I have an '86 Ford Bronco with a 302 EFI V-8 and an AOD tranny behind it. I burnt out the Overdrive and need to replace it. What is the difference between my transmission and an AOD from an '89 model? I can't find anything out online, so hope you can help.
James Talliere
Virginia Beach, VA

A. The '89 AOD will work in your '86. There are things that a trans shop can do to improve it in the form of upgrades. You can swap newer geartrain components for better gearing.

Overdrive is this transmission's weakness. There are companies that make high-performance bands and high-performance servos for it, which are a good idea.

Just like a 700R4, the AOD throttle cable adjustment is vital to this transmission's life. It is not just a kickdown cable! Do not drive around with it disconnected or broken.

Where To Write
Address all correspondence to: Techline Four Wheeler, 831 S. Douglas St., El Segundo, CA 90245. You can also reach us by e-mail at; be sure to type the words "Tech Line" in the subject line. All submissions become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department also can be reached through the Web site at Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

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