LBZ: Pro Stock Diesel Pickup Build

[Michael]

Episode 21

I swear there is always something that keeps me from spending time on this build. In this case I lost a few days to clearing up a case of ID theft! I went to file my taxes and found out that someone had already filed a fraudulent return using my information. It turns out that a large percentage of people who volunteer for Catholic schools in our part of the country had this happen, apparently by someone in the company they used for the legally required background checks. Too bad they couldn't have paid the tax bill I actually had due!

After filing tons of reports, I went back to the chassis and quadruple checked positions on everything, thenI finish-welded the left side strut support bar:

Next up I welded the left upper strut mount with its gussets:

The plans from Chassisworks called for the crossmember for mounting the steering rack to be about 1.5" higher than the bottom main chassis tubes, so I couldn't just tie between those tubes like the front crossmember I previously installed.

My plan was to add a couple of angled braces from the main frame rails to the strut support tubes, both to reinforce the strut mounts, and to give me a spot to tie the steering crossmember to. Unfortunately the strut tube and the main frame rail are at a compound angle to one another, so it is VERY difficult to fit the tube to both sides. I managed to notch the first tube a little too far, and had to start over. Good thing I have some extra tubing!

After I test fit that tube I suddenly realized that even a slight change in the position of the steering crossmember would change the length & angles on this tube! I decided to fixture up the position of the steering crossmember to be sure.

As I was starting to test fit the steering crossmember I realized that since the bottom of it was just below the top of the main frame rails, it would require a double notch on each side.

Since all of those dimensions and angles would change with a slight change in position, I used a shorter piece to make a temporary steering crossmember, so I could make sure the steering rack position was perfect.

I clamped it into place on my previously added jig fixture:

At this point I was relieved that I had done all of this as a mock-up, as the dimensions for the steering mount placed one side too far outboard, where the clamp would hit a bulge in the rack that was there to hold the boot:

I remember the Chassisworks tech guy telling me that they don't make the steering racks themselves, and it has been getting harder and harder to find a place to build them. It appears their current supplier has the dimensions a little off from the original Pinto application that used these.

Now for a little boring sidebar on steering geometry:
The most critical part of all of this is eliminating what is known as "bump steer", you need to make sure the front tires do NOT change direction even the slightest bit as the suspension goes through its full articulation. In order to accomplish this the pivot point on the steering needs to be perfectly aligned with the pivot point on the lower control arms, and the height such that the steering tie rods are parallel to the lower control arms.

I decided to pull both boots so I could see for sure where the pivot points were. Sure enough, even with the steering rack centered as far as its travel, I needed to move the whole thing 0.5" to the side (in addition to moving the clamp mount as mentioned above).

At this point I really needed the control arm & strut assemblies together so I could check the aforementioned parallel requirement. I pressed the bearings out of the lower control arm ends:

The tubes needed to be drilled for rosette welds:

I just tack welded them together for now, in case I need some adjustment in length. While there is adjustment in the rod ends, I want to start out with them right in the middle of their adjustment!

As I went to assemble everything, I pressed the spherical bearings back into the A-arms without too much effort, but when I went to press the bearings into the upper strut mounts I found that the weld distortion made it so hard that I was bending the biggest C-clamp I had! This was even after freezing the bearings! I was prepared to heat up the sockets as well, but decided to come up with something different for pressing the bearings in. I ended up using some specific cut sections of tubing with a 3/4" fine thread grade 8 bolt, which had the secondary effect of forcing everything into alignment as it pressed it together. No need for heat as this pulled the bearing right into place.

I used shims between the control arm and the jig to hold the strut assemblies exactly at ride height, then measured off where the updated tie rod tubes and the original tie rod shafts needed to be cut in order to weld them together.

I learned that this was another area where the reproduction Pinto rack was different than the factory ones. This one used a MUCH larger diameter tie rod shaft than the originals, and the originals normally fit into the tubes I am supposed to weld them to.

I made the cuts, counterbored the tubes (they were counterbored for their ends, but needed to be rebored since I was cutting them so short), then used the lathe to cut down the tie rod shaft diameter to where it would fit:

Now I should be able to tack everything together and verify that the steering geometry holds up throughout the suspension travel.

 

[LtEng5]

Nice work!:thumb:

Just read thru from the start...... lots of work you have done here. Keep it going, and maybe enlist some of the shop guys to get them interested/involved once you get into the bigger parts.

It will be a mean Mo'Fo once its done.........

 

[DaJokr]

Loving the progress! Keep it coming

 

[orangeastre]

Badass build!

I have a Vega with a square tube chassis that looks like it was built by the same person who built the chassis you bought. Except my main crossmember was 4 pieces bubble-gummed together,then ground and filled.

 

[Michael]

Nice work!:thumb:

Just read thru from the start...... lots of work you have done here. Keep it going, and maybe enlist some of the shop guys to get them interested/involved once you get into the bigger parts.

It will be a mean Mo'Fo once its done.........

Yup, I am hoping to get a little help when it comes time to do the built engine.

Badass build!

I have a Vega with a square tube chassis that looks like it was built by the same person who built the chassis you bought. Except my main crossmember was 4 pieces bubble-gummed together,then ground and filled.

Yikes, it DOES sound like mine! Why the heck would someone spend so much time hiding a splice instead of doing it right???

 

[Michael]

Episode 22:

To start out, I wanted to give a shout-out to Hughes Performance. Early in this build I had decided to use their XP-5 Lockup Pro Mod Powerglide transmission, which was the most expensive of the options I was considering, but was rapidly achieving a track record of being the most durable option out there. When I bought it, they told me to keep in touch with them since this was a new design for them, and they may have updates to the design periodically. My cynical side was thinking "sure, come up with more ways to charge me more money". As I was getting closer to having this truck completed I decided to contact them to see what updates were available (and whether I could afford them). To my surprise there was no charge, and they took care of everything. One significant change they made was to switch to a larger steel bellhousing, which allows the use of larger torque converters. This has been necessary to hold the increased torque of compound-turbo engines (their earliest test units had used parallel charger arrangements).

Back to the chassis and the steering. I drilled the tie rod extension/adapter rods for rosette welds, then tack welded the tie rods together, assembled them back to the steering rack, clamped the rack into my jig location, then assembled the rest of the steering:

With the suggested position from the instructions, the tie rods appeared to be parallel to the control arms:

For measuring toe-in, I bolted some aluminum tubing to the caliper brackets (which stay parallel to the rotors). The tubing was much longer than the diameter of the wheels (where toe-in is normally measured), which would magnify any toe-in problems. I can scale the toe-in changes back to the dimensions of the wheels for comparison with known standards, but I wanted a very precise measurement as I adjusted things to minimize the toe-in changes.

Checking the suspension at various heights, I found that toe-in changed an unacceptable 0.26" through the full travel.

Consulting a couple of chassis building books, they recommended dropping the rack position with such a result. I dropped it 0.445", then reassembled and remeasured. Visually the tie rods looked almost too low, but I verified that they did not come close to contacting the control arms at any position or suspension articulation.

The result was a total toe-in change of 0.036" (well below the 0.060" that the books recommend as a target).

At that point I went to fit up the angled braces with the revised position of the rack crossmember. Remember when I mentioned trimming one too short before? With the repositioning of things it ended up almost the perfect length, just needing some minor trimming.

Remember that I had cut a longer one and began fitting it? It turns out there was enough material to change the angle at the top to its mirror image, and use it for the other side!

I guess I was too excited from all of this reusing of parts, when I clamped the 1st brace into place and tack welded it, I tacked it on the outside, such that the weld draw of the tack weld started pulling it away from the mating tube on the other end.

This required using my good old friend the ratchet strap to hold it in place to weld the other side! After that I remembered to tack on the side where the weld draw will help hold the bar in place...

I welded around on the inside of the tubes at the top, but avoided the outside until I removed the spherical bushings to keep from damaging them with heat.

With no such bushings close to the bottom of the braces I was free to weld them all the way around, but still only welded about an inch at a time to prevent excessive weld draw.

As I was doing that I suddenly realized that I had forgotten to drill vent holes to allow the gases to expand into the adjoining tubes! Fortunately I would have the crossmember covering the lower end of these braces, so I was able to sneak a hole in down near the end, and drill all the way through to the tube underneath so the gases can still flow when I weld in the crossmember.

With the holes in place I was able to fully weld around the tubes (after removing the struts and the spherical bearings to protect them from heat damage).

While those welds were cooling as I did the aforementioned skip welding around the tubes, I decided to try removing the threaded rods I had used to brace the 4-link brackets while I welded them into place. This turned into a classic case of painting myself into a corner! I had sorted the nuts to find ones with the exact width (with two stacked together) for the inside dimensions of the 4-link brackets, then carefully threaded them together when the brackets were still separate pieces. This worked great for holding everything steady while fitting and welding, but now that they were one piece it provided a bit of a challenge!

The first one I had done a while ago, and it took waaay too long. Literally it was like working a stout locknut (that took probably 80 ft-lbs of torque) for about 3' of threads, where you had to turn one pair of nuts one flat, then the other pair one flat, over and over a few thousand times. This time I decided to cut the rod in half, figuring I could then just thread it out the short way (maybe 3" of threads). I had to use a piece of sheet metal to let the ends at the cut pass each other while I did the 1st side.

This actually worked pretty well, but of course it still ended up a mess as I was trying to do the remaining half, one of the nuts stripped. I had maybe 3/4" to go, but it will just get cut out with the angle grinder now. In retrospect, I probably wasted $50 of time saving $10 worth of threaded rod!

While doing this "outside the box" thinking I realized that I could always move the rack mounts slightly lower and use shims to bring it to the optimal height. However the position was already against the top of the jig crossmembers I had placed for positioning the rack crossmember. Who says I can't modify those crossmembers? I trimmed out the top surface and ground the edges down to a specific height, to allow a little more adjustability in the rack crossmember position.

As I do the final rack crossmember mounting I will see if I can find a spot that yields less than the 0.036" of bump steer.

 

[Burn Down]

Looking good Michael. Excited for you to get it done:thumb:

 

[SmokeShow]

Do you plan to make a pass in the truck this season?

Sure is fun watching you build it! :thumb:

 

[slowlb7]

Nice fab work i tried to make my own control arms before not all that easy to get them right

 

[Michael]

I do hope to get this running by the end of the season, but it will be tight! I'm hoping to borrow a truck just to make a qualifying pass in Pro Stock so I can qualify for the NHRDA World Finals.

Episode 23:
Before I get too wrapped up in this update, I have to throw out a pic of something I have been looking forward to a long time, my daughter and I managed to both win at the same event (and I also got a perfect light during qualifying, earning me the #1 spot and a T-shirt).

Yes, I know the plaques and shirt are being held upside down, it was my daughter's idea to make the photo more interesting.

The general theme of this update is that there have been more cerebral than physical accomplishments lately. As I approached some of the remaining details of this chassis I decided to spring for the 2-book set from Jerry Bickel Race Cars covering chassis construction. I considered buying them before, but IIRC they were close to $400 for the two books. They eventually lowered the price AND had a sale, so I picked them up for $120.

A large portion of the books covers the weird little details that I had to learn for myself and documented in this build, such as drilling pressure relief holes. They do give a lot of tips on areas I still have to do, like brake pedal and master cylinder mounting, and interior tinwork.

Speaking of brakes, I picked up a couple of master cylinders (plus a spare to keep in the trailer).

Most of the aftermarket braking companies use master cylinders based on the Chysler design they used on their mini vans and some pickups. I just bought Raybestos versions of the Chrysler parts.

I resurrected the 3D solid CAD model of the race truck so I could figure out where to place a number of components.

I started by adding some gussets to triangulate the firewall. This is a critical area, as this is where the torsional load from the drivetrain is transmitted into the chassis. However, I still needed to leave plenty of room for the up-pipes to pass through and up to the high pressure turbo.

Next up I needed to figure out the angle and height of the engine/transmission combination. The overall goal is to aim the output of the transmission directly at the yoke of the rearend. I also wanted enough ground clearance to use a standard Duramax lower oil pan. This required a 2.9° downward angle in the chassis.

Next up I needed to model the outside surfaces of the transmission, so I could figure out how to build the tunnel and the transmission crossmember. I just simplified the shapes into stepped cylinders and a partial donut shape for the bellhousing.

I was worried about how I was going to squeeze the fuel cell and dual batteries in the back, but eventually worked out a plan.

I originally planned to have the transmission mount come up from the existing floor crossmembers, so I added them to the model:

I ended up deciding on a simple additional crossmember to go between a pair of double frame rail uprights. Since there is not a significant load on the tail of the transmission (the torsional load is carried by the midplate), this can be a lightweight crossmember.

One of the next key items was figuring out how the brake pedals were going to mount. I finally decided on a stationary shaft which would be clamped to the chassis, with each pedal having roller needle bearings where it rides on the shaft. I can use simple spacers to move the pedals side to side until I am happy with their position.

My plan is to hook the left pedal up like a normal brake system, and the right pedal will be dedicated to the 2nd set of rear brake calipers. When I am building boost before bumping into the beams I can straddle both pedals with my left foot, getting as much braking force as possible.

Probably the single item in the build that I put the most detail into for the CAD model was the master cylinder. With its complex shapes and the tight fit with the floor crossmembers I figured I needed all the detail I could get.

Once those were positioned I designed a crossmember to support them. I tried two versions, one was made from 1" x 1.75" rectangular tubing with cutouts, but the final version is using 0.125" plate stock. I ran the calculations for which one would be stronger, and this one won out (although they were close). I figured this one would be easier to build as well.

All of this CAD work makes me want to get my hands dirty on the real chassis! I added two more diagonals to support the upper strut mounts, and to tie into the front engine mount plate (this was another reason to get that CAD work done so I could figure out where that plate would end up).

Once those tubes were fully welded I pressed the spherical bearings back in and reassembled the steering, so I could fine tune the steering rack position and minimize the bump steer.

At this point I realized that part of the jig was hanging up the struts and preventing them from fully extending. My previous "success" at finding the optimum rack position turned out to need some fine tuning. Once I removed the jig section that was interfering, I had more front end travel to contend with!

With this additional travel I had more potential toe-in movement (bump steer) than I thought. I ended up fine tuning the rack position and getting it even better than the "short stroked" result I had before! Total toe-in change through the full travel range is now 0.02" per side, and through the main travel range it is zero!

I was hoping to have the steering finished in the chassis and the rearend at least temporarily mounted, to have as a display at this weekend's NHRDA Pacific Coast Diesel Nationals Presented by ISSPRO (yeah, that is a mouthful to say OR type). However, I decided to keep focus on the build rather than trying to get it off the jig and out to the track. Don't let that stop you from coming out to Woodburn Dragstrip on June 28th to see a great show of diesel racing and sled pulling! There will also be a lunch served compliments of ISSPRO. Hope to see you there!

 

[SmokeShow]

If you've said it, and I'm sure you have, what transmission are you going to go with?

As always, great update & congrats to you & your daughter's wins!

 

[Michael]

If you've said it, and I'm sure you have, what transmission are you going to go with?

As always, great update & congrats to you & your daughter's wins!

Sorry, I didn't see that there was a response here. I'm using the Hughes Performance XP5 Lockup Pro Mod Powerglide. I'll cover some details on that in the next entry.

 

[Michael]

Episode 24:
Sorry for the lack of updates, too many things going on between work and other racing, but finally getting more time on the race truck.

First off, a belated "Thank You" to all who attended the Pacific Coast Diesel Nationals Presented by ISSPRO! While we had scorching heat in prior years, this time we had torrential downpours, but somehow squeezed in the racing and sled pulling between rainstorms. We still had a huge crowd of spectators who braved the rain to cheer on the competitors.

A few details on the other items:
My Vega, which has always hooked really well (once I had the suspension all dialed in) suddenly started spinning the tires badly, and it turned out to be the original Koni shocks finally getting worn out. I picked up a set of QA1 double adjustable shocks and got it working well again. Just as I was fine-tuning the new shocks, it suddenly started spinning again. I was able to fine tune it and pick some ET back up, only to discover the slicks were down to the cords! I guess the suspension is REALLY working well to be able to hook up with cords showing!

My next fiasco was at a race with a really bad crosswind at the top end of the track, it ripped the scoop off on one pass, and blew the driver's window out on another! Weird crap to be happening at 147+ mph! A couple other cars had their side windows blown out too, including one with original glass that made a huge mess on the track.

I ended up trading some parts for a complete Vega hood with scoop, and made a new side window.

Back to the race truck, I started working on the steering mount crossmember, which was positioned at a weird compound angle (and offset from center) of the diagonal strut support bars.

I used a spacer and longer bolts to allow me to do the offset notching on the tube:

Of course, after carefully notching one side, then carefully measuring the other side (keep in mind, the length of this tube varies dramatically with its height since it is dropping between angled bars), I was horrified to discover this gap:

And of course it was the last piece of tubing I had in that size! I really hate ordering only one piece of tubing, with the associated shipping charges!

As I waited for my replacement tube to arrive, I notched and fitted the rear vertical bars that tied in some of the rear suspension, and would be the anchor point for the double frame rails:

Fortunately I remembered a lesson from earlier in the build, when working with weird compound angles like this: I used my properly-notched but too short piece of tubing to make a card stock template. If I would have planned better I would have used a short scrap of tubing to rough in the notch, but hindsight is 20/20!

After marking and notching the new tube I was able to get a nice snug fit:

I had precisely positioned the height of that tube with shims, after adjusting it (and leveling the steering rack mounts) when adjusting for bump steer (detailed in the last entry). I went ahead and fully welded this tube in place:

Next up was positioning the rack mounts. Rather than just making them perfectly level, I had a sudden epiphany that I could precisely adjust the height of the rack at this point, perhaps getting even less bump steer in the process. I bolted back on my bump steer checking apparatus, and used some threaded rod to make very fine adjustments:

I also marked the extremes of the rack steering travel so I could line everything up with the rack perfectly centered in the chassis:

With those adjustments done I was able to get the total bump steer below 0.01" per side through the entire suspension travel!

Next up I tacked then finish welded the rack mounts in place:

Next project was to fabricate some tabs that would serve the dual purpose of gusseting the top strut mounts, and providing the top mount for the front suspension travel limiters.

I mocked the pieces up in cardboard first, using long threaded rod to make sure they were perfectly aligned with the point on the lower control arm where the limiter cable would eventually attach.

I used the cardboard to mark and cut out the metal pieces:

Next up was the initial fitting and tacking of the metal piece, where I discovered that the cardboard flexed just a bit more, requiring some additional cutting on the metal:

Next up will be wrapping up these mounts, then moving on to the double frame rails.

 

[SmokeShow]

Nice update!

 

[Schwinn68]

Glad to see you back at it. Really looking forward to seeing this progress

 

[JoshH]

I'm amazed at the precision you're using to build this chassis. It's making the idea of building a chassis myself seem a little intimidating. I'm starting to understand why the professional race chassis builders charge so much money.

 

[Michael]

I'm amazed at the precision you're using to build this chassis. It's making the idea of building a chassis myself seem a little intimidating. I'm starting to understand why the professional race chassis builders charge so much money.

IMHO this is why there are chassis from "expensive" shops that work well, and from other shops that don't work as well! I'm hoping all this time and effort makes mine handle more like the ones from the expensive places! The good news is there is no rocket science to it, but it is a lot of work to do it right.

 

[lutzjk913]

When you hoping to have it all done?

 

[Michael]

When you hoping to have it all done?

Shooting for early in the 2015 race season (June or so), but earlier if things go well.

 

[Michael]

Episode 25:

After maneuvering the gusset/mount into a few positions, I figured I would tack it, weld it, then cut off the excess;

On this side I welded it in several short beads (making sure to not overheat the bearing in the nearby strut top mount).

On the other side I was in such a "groove" with a nice bead going, I forgot to take my time to keep from heating up the bearing! I immediately wrapped a wet rag around the bearing to keep it cool.

After that it was a simple matter to trim the excess, and test fit the eye bolt:

My next big delay in the project was the SEMA trade show, our biggest event of the year. We discovered that all of our table-top gauge displays from prior years had been destroyed in shipping, so it was a mad scramble to make more in our 3D printer and get things set up.

We had a great show, highlighting our new datalogger as well as our new line of waterproof gauges (displayed to the right in a fishbowl complete with live fish).

I got to hang out with my old friend Steve Darnell, star of Vegas Rat Rods on the Discovery Channel. We had a fun time playing with the welding simulator at the Lincoln Electric booth.

I also got to spend some time hanging out with my buddy Aaron Hagar, as well as his new business partner Brad Fanshaw (TV host, former BMX racer & executive, and Boyd Coddington protege').

Our booth was so busy all week I swear everyone on the planet must have stopped by. Even Elvis, who seemed more interested in our sales associate Jen than in any gauges...

After all of that I finally got back to the race truck and its double frame rails. Double frame rails are seen on higher powered Pro Mod type cars, but with the torque of a diesel they have become necessary even for something running in the 8's or 7's, as several of the original NHRA Pro Stock Truck chassis (which are not double frame rail) have seen issues with the torque of a diesel.

Fortunately the first steps included 10 different tubes cut and notched identically. I could finally feel like I was making progress in more of an asssembly line approach, making 10 identical parts. Sure, I still had to swap hole saws (different sized notches at each end), but I'm sure that is the most cuts I have made with my notcher without adjusting the angle!

Even the metal prep (removing mill scale from inside and outside the tubing at the ends) was seemingly easier since I was doing so many at once.

I prepped all of the matching spots on the chassis for each of these vertical supports for the double frame rails:

While I was at it I went ahead and drilled the pressur relief holes for both these tubes and the upcoming diagonal tubes. I have a bad habit of forgetting those holes!

I even got carried away with my prep and hole drilling on the top rails of the double rails, as I forgot about the length loss due to notching, so I will probably be re-drilling those holes (and welding these ones shut).

I started with the two end vertical supports, wanting to make sure they were perfectly vertical, then using them as a guide to position the remaining tubes:

The next tubes sometimes needed some "adjustment" in their position after tack welding them in place. This was accomplished by placing a larger diameter tube over it, and applying some good old fashioned brute force:

Hopefully when I am done with all of the vertical supports they will align perfectly with the top tube of the double rails. Then I will get the fun task of carving a weird shaped notch in the end of each of those rails, where it intersects the strut tube right at a bend! Hopefully I have a scrap piece long enough to use for that, so I can use my trick of carving it to fit then making a cardboard template!