Читать книгу Project Street Rod - Larry Lyles - Страница 17

Having installed more than my share of engines and transmissions over my career as a car nut, this is an easy task to accomplish when all you have to do is drop the engine and transmission into the car and bolt the units into place. It is quite another story when there is nothing to which the units can be bolted, and in this case, even if I could bolt them down, the transmission would be bumping the X-member. That is where I am with this project. I have an engine bolted to a transmission, but what I don’t have is a frame willing to accept them.

I could hang the engine and transmission over the frame, then when I think things look right weld in some mounts and hope for the best. I might even get away with that type of installation if the car were destined for the garage and not the road. But that isn’t the case. This car is being built for the same purpose I have in mind for every other car I’ve built: to be driven. That’s a shame, because now I have to get technical, and I never like to get too technical.

WEARING MY TECHIE HAT FOR PHASE ONE

If you recall when I first started this project, one of the problem areas that stood out was the lack of clearance between the transmission and the X-member portion of the frame. The transmission was rubbing against the frame on the right side and had less than 1/2 inch of clearance on the left side. The only solution for this problem is to widen the front X-member rails to gain some space for the transmission.

To do that, I need to cut both X-member rails and bend them outward by 2 inches. Notice in photo 1 I’ve already made the first pie cut (left arrow) on the top flange of the left rail and marked the area near the X-member center brace (right arrow) for cutting the rail in half. Once the lower rail flange has been pie cut and the rail is cut in half at the brace, I can then bend the rail out-ward, and the end result will look like photo 2.

PHOTO 1: The left arrow points to the pie cut already made in the frame rail. The right arrow indicates where the rail will be cut through.

PHOTO 2: The two lower arrows indicate the pie cut locations on each rail. The upper left arrow points to the steel plate used to space the rail outward. The right upper arrow points to a bracket that had to be shortened to accommodate moving the rail, and the center arrow points to the new transmission mount.

So the question is, how did I get there from here? The first thing I did was to pick up pen and paper. This frame rail bending procedure is a very simple operation, but the cuts require specific angles so that when the rails are pushed out, the pie cuts will close and the reinforcing plates used to bridge the 2-inch gap at the X-member center braces will abut perfectly against the cut ends of the rails.

Photo 3 is a shop drawing I made to determine the precise angle for each cut. Notice on the drawing that the ends of the bent piece are drawn at 90 degrees. This helps me determine the angle of the cuts if I align the 90-degree mark on a protractor with the 90-degree drawing and measure the angle produced at that point. Notice the darkened wedge-shaped area near the left end of the bent piece as well. This is the area of overlap onto the uncut portion of the rail. When a protractor is laid over this darkened wedge and aligned with the 90-degree cut end on the drawing, the angle comes out to be 10 degrees. In this case, both the pie cuts and the through cut on the rail will be made at 90 degrees.

PHOTO 3: This may not be rocket science, but knowing where to cut and how much to cut saves a lot of headaches later on. Cutting the rail on paper first keeps me headed in the right direction.

PHOTO 4: The information from the template is now transferred to the rail for cutting.

To transfer my 10-degree cut angle to the rail, I cover the rail with masking tape (photo 4), then use the protractor and a straightedge to lay out the cut lines. Nothing to it, but it does require a little precision.

The actual cuts will be made one rail at a time, starting with the right rail. That allows me to make the cuts using a reciprocating saw with a metal cutting blade attached. I use a hydraulic ram pressed against the left rail to push the right rail out until the 10-degree pie cuts close and the 1/8-inch-thick, 4 x 6-inch steel bridging plate perfectly spans the gap between the rail and the center brace. Once that is accomplished, the pie cuts and the bridging plate can be welded, and the widening process can be repeated on the left rail.

PHASE TWO

I actually have to start this phase with the driveshaft since this is the link between all that power up front and the rear axle, where that power is put to the pavement. To rephrase a phrase I heard somewhere, if the driveshaft ain’t happy, ain’t nothing about this drive-train gonna be happy.

To make the driveshaft happy, I have to think about two factors: transverse vibration and torsional vibration. Transverse vibration is simple, so I’ll talk about that first. Transverse vibration is a bending vibration and is the result of an improperly balanced or bent driveshaft. The cure? Never install a driveshaft without first having a qualified driveshaft shop check it out to be sure it is perfectly straight and balanced.

Torsional vibration is a twisting motion that usually occurs as a result of improper U-joint angles, and that is what all this is leading up to. Looking at an extreme case, if I installed the rear axle dead level 12 inches from the floor and the engine dead level 24 inches from the floor, the angle of the driveshaft between the two components would be severe, approaching 30 degrees, and torsional vibration at higher speeds would become a problem. It is this extreme type of driveshaft angle I need to prevent.

To do that, I start by lowering the engine and transmission toward the cross member until I reach a point where I think the engine should mount. Where is that? I want at least 1 inch of clearance between the oil pan and the cross member so when I reach that point. I’ll stop. Now I take a measurement from the output shaft on the transmission to the floor. That reading is 15 inches.

TIP

Transmissions are heavy, made of aluminum, and tend to sag at the output shaft. To prevent the transmission from sagging, I support the output shaft housing by tensioning a ratcheting cable puller between the housing and the hoist chain.

With that done, I carefully shift the engine until the motor mounts bolted to the block are centered over the cross member. That’s because the plan calls for welding the new motor mount brackets to the cross member. With the engine in position over the cross member and still suspended by the hoist, I need to give the engine 3 degrees backward, or negative, tilt using the magnetic protractor.

But here’s the catch. Most carburetor intake manifolds have 3 degrees positive tilt built into them to compensate for the negative 3 degrees the engine should exhibit. That ensures that the carburetor sits level in the car. It also means that if the engine is setting level, the magnetic protractor, when placed on top of the carburetor mounting plate, will read 3 degrees positive tilt. To achieve the 3 degrees negative tilt I need for the engine, the magnetic protractor must read 0 degree (photo 5). I’ll explain the need for this degree setting in a moment.

I also level the engine from side to side to make determining the length of the motor mount brackets a little easier (if the engine is level, both mounting brackets will automatically be the same length).

DETERMINING THE DRIVESHAFT ANGLE

It’s time to screw the Techie hat down tight. Every time my brain shifts into overdrive, I can smell a clutch burning.

TIP

Bulky units like the engine and transmission tend to swing and move at will when you’re trying to install them. I use tie-down straps to hold the engine steady while I work.

Recall in chapter 2 that I gave the rear axle assembly 3 degrees positive tilt during installation. If I extend a straight line forward from the center of the pinion shaft while exhibiting the same 3 degrees positive tilt as the rear axle, that line will slowly rise to intersect the transmission about 2 1/2 inches below the center of the output shaft. If a straight line is drawn from the center of the transmission output shaft when exhibiting 3 degrees negative tilt back to the rear axle, that line will intersect the rear axle housing 2 1/2 inches above the center of the pinion shaft. Now consider that both of these imaginary lines are parallel to each other and separated by 2 1/2 inches. I have reached perfection.

Confusing, isn’t it? Refer to photo 6.

Assume the left end of this bar is the engine and transmission and the right end is the rear axle assembly. Now assume the top surface of the bar is indicative of a line drawn straight through the crankshaft and transmission tail shaft, all the way back to the rear axle, and the bottom of the bar is indicative of a line drawn straight through the rear axle pinion shaft forward to the transmission tail shaft. It is easy to see these two lines are parallel to each other. That is what I’m looking for, the line drawn through the tail shaft to intersect the rear axle housing just above the pinion shaft, and the line drawn through the pinion shaft to intersect the transmission just below the tail shaft.

PHOTO 5: With the engine still on the haist, it is first leveled side to side using the 12-inch level, and then it’s given a 3-degree backward tilt using the magnetic protractor.

PHOTO 6: A visual example of how I set up the drivetrain to ensure that the driveshaft angle is less than 5 degrees.

And now the clutch really begins to burn.

I know the measurement from the center of the tail shaft to the floor on this ’46 Ford is 15 inches and the measurement from the center of the pinion shaft to the floor is 12 1/2 inches. That’s a difference of 2 1/2 inches. Falling back on what little I learned in Calculus Approximation 303, I elevate the left jack stand in photo 6 until I get a measurement of 15 inches from the top of the bar to the floor, and I elevate the right jack stand until I get a measurement of 12 1/2 inches from the top of the bar to the floor. This represents the centerline between the transmission and the rear axle pinion shaft.

What the heck am I doing? Long, long ago in a world filled with bent driveshafts and broken U-joints, someone discovered that a driveshaft operating at an angle of less than 3 degrees from true horizontal could be safely spun at rpms exceeding 5000, whereas driveshaft operating angles exceeding 6 degrees could be detrimental to a driveshaft spinning at less than 4000 rpm. My makeshift template in photo 6 gives me the operating angle of my driveshaft.

The verdict is? The magnetic protractor in photo 7 tells the tale. My driveshaft should have a normal ride angle of 2 degrees. That means this drive line should operate very smoothly and last almost forever.

PHOTO 7: Using my makeshift driveshaft template, I can determine the driveshaft angle using a magnetic protractor. In this case, the driveshaft angle is 2 degrees.

DETERMINING THE DRIVESHAFT LENGTH

But the driveshaft angle doesn’t help much without an actual driveshaft to couple the transmission to the rear axle. This is a task I turn over to a qualified professional, as this driveshaft will have to be custom made. After all, I’m connecting a GM transmission to a Ford rear axle. It’s like putting ‘58 Cadillac taillights in an ‘83 Honda Civic. It can be done, but only if you know what you are doing.

I know of two ways to determine the length of a new driveshaft. Both should be done with the full weight of the vehicle on the floor. That’s not possible in this case, but I do have the entire chassis set up to simulate the correct riding height of the car. That should be close enough.

The first method calls for measuring from the end of the transmission output shaft to the center of the U-joint on the pinion shaft. That measurement is 53 1/2 inches. I also measure the distance the tail shaft housing extends beyond the output shaft, 1/2 inch. I’ll give both of these measurements to the driveshaft shop along with the necessary transmission and rear axle information (makes and models), and they will be able to build me a custom-made driveshaft to connect my GM transmission to my Ford rear axle.

The other method calls for installing the old transmission U-joint yoke in the transmission to a point where the shiny wear pattern on the yoke just disappears into the oil seal. This is the normal ride position of the yoke. Then a measurement is taken from the center of one of the U-joint caps on the transmission yoke to the center of one of the U-joint caps on the rear axle. That’s the length of the new driveshaft.

BACK AT THE ENGINE BRACKETS

When this car first came into the shop, the engine was already mounted to the frame. The mounting brackets were generic bolt-on aftermarket items, but they were solidly constructed, and I knew they could be easily cut and trimmed to adapt them to welded-into-place units.

For added strength, I wanted the brackets installed at a slight angle, about 20 degrees, as shown in photo 8. Had I cut the brackets so that they would sit level after installation, the weight of the engine would have placed undue stress on the welds, and eventual failure of the welds could have resulted. However, installing the brackets at an upward angle allows the weight of the engine to press outward on the brackets, thereby eliminating all stress on the welds. These brackets will be there until they push a hole through the cross member, which is very unlikely to occur.

Then there is the subject of motor mount bolts. These mounts are stock GM mounts, and they use three 5/16 x 1-inch bolts to attach each mount to the engine and one 3/8 x 4-inch bolt to connect the mount to the mounting bracket. All of these bolts must be grade 8 or stronger, particularly the 4-inch bolt, as it will be subject to sheer stresses. The garden variety home improvement center bolt won’t do here.

SOME UNFINISHED FRAME TASKS

That leaves three things unfinished on this frame before the body can be installed. The first is constructing a new transmission mounting bracket. This proved to be a very easy task, as all that was needed was to shorten a 1994 Mustang transmission mounting bracket I had stashed at the shop and bolt it to the bottom side of the X-member. It is visible in photo 2.

The second task consists of building up the front suspension, as shown in photo 9. At a future date, I’ll be routing the steering shaft, so that means the rack and pinion setup must already be mounted. I’ll also want to mount the front fenders and fender skirts later, so I need to be sure no clearance problems exist around the control arms and steering linkages. It is far better to find clearance problems now, before the paint goes on, than later when I have to start hacking and welding on my fresh paint job.

The third issue concerns the emergency brake cables. I have them routed to a point just behind the transmission but no way to connect the cables to a brake handle. Notice in photo 10 that I mounted a rotating 1-inch steel tube underneath the rear arms of the X-member. Also notice the 1-inch-tall, 4-inch-long steel plate welded to the tube between the arms of the X-member. This plate serves as the mounting point for the brake cables. To keep the brake cables in place, they are slipped into notches at each end of this plate and secured with an additional bolt-on top plate (photo 11). The top plate is removable should one or both of the brake cables ever need replacing.

In photo 12, you can see the elongated pull handle welded to the end of the tube. This will serve as the mounting point for a cable leading up to the brake handle inside the car. When the brake handle is pulled, the tube will rotate and apply tension to the brake cables attached to the center plate on the tube, thereby activating the rear brakes. Very effective.

PHOTO 8: A little cutting and trimming, and the bolt-on engine mounting brackets were converted to weld-on units.

PHOTO 9: At a later date, I’ll be hanging front sheet metal around this suspension. It is better to find clearance problems now, before the paint goes on.

PHOTO 10: When the lever is rotated, or pulled forward, tension is placed on the cables, activating the rear brakes. Simple, but very effective.

PHOTO 11: The brake cables slip into notches cut in the bracket and are held secure by adding a plate on top of the bracket. The bolt allows easy removal of the plate should the cables ever need replacing.

PHOTO 12: Lengthening this pull handle will allow me to add an even longer adjustment bolt to ensure that the emergency brakes will activate with very little effort.

Now throw into the mix the ability of the shock to resist side-to-side roll—that is, how much the vehicle leans as it moves into a deep curve—and suddenly the lowly shock has become something of a very important item to be considered when setting up a new suspension.