(Words and Photos by Scott Liggett) If you have been following along on my build of 1967 GMC pickup we call Project Hay Hauler, you will have seen I took a 383 I had collecting dust in the corner of the garage and rebuilt it. Then I had it dyno tested where it made right at 450 HP and 450 Torque! People who have been regularly reading this column might be asking “What happened to the BluePrint Engines 355?” Nothing. It is still running great. But, I wanted more horsepower. It’s a sickness. I would tell you I was seeking help, but it would be a lie. Of course like any sickness, there are other symptoms that pop up. Same for horsepower. Add more, there are more symptoms to address. Getting it to the ground is one of them.
The BluePrint 355 made a generous 420 HP/420 TQ. But, particular part number was rated at 375 HP/405 TQ with 10:1 compression, a rather small flat tappet cam, and BluePrint’s 195cc aluminum heads. The power comes from BluePrint’s heads and are super killer for just $900/pair. I drove the 355 20.000 miles with zero issues and sold it to a friend. John and I helped him put a bigger Comp Cam in it, 1.6 roller rockers, and a whole new look. We will be putting it in his 71 C10 at a later date.
This is what the 383 looked like as Installed, minus the headers. They are for my 65 Impala.
I yanked out the 355, put it on a stand and installed the new 383 in one weekend. I will skim over that part of the build, because you have probably seen a small block being replaced by a small block a million times on TV. I will tell you that it went in without much fanfare and fired up instantly and I was out driving pretty quickly. To keep things on the cheap, I reused a stock 11 inch clutch we had on the shelf and the same GM ‘621’ bellhousing that was in the truck with the previous engine.
I got news that Rocky Mountain Race Week was still a go. With nearly every other event being on hold this year thanks to Covid, I wasn’t going to miss it. I drove the snot out of it over the following 6 weeks to break in the engine. I like the added power of the new 383. Traction and wheel hop was my new problem. And, I liked it. While real fun on the street, these problems are not good for drag racing. I had work to do in order to get ready for Race Week.
The two big things I needed to fix was the stock clutch and the pinion angle that was result of lowering the truck. The pictures show how the pinion angle was pointing down at about 10 degrees. Not good for traction and possibly the cause of my wheel hop issue under hard acceleration. The stock clutch was fine for running around town, but the engine’s 450 HP was pushing through its ability to grip.
The first thing to do was get the truck back in the garage and rip the 12 bolt out it. In order to get the pinion angle correct, I would need to cut the spring perches and shock mounts off the differential and rotate their location forward to bring the front of the differential up. Ideally, the pinion would still point down, but only a couple of degrees, not the 10 or 11 I had measured. With the driveline and differential angle out of whack, it can cause axle wrap and wheel hop. I was hoping this would fix my problem. Since cutting off and rewelding the perches back on the differential would require getting angles exact and good weld penetration, I took the differential over to a local machine shop. The guys at Marlatt’s here in town did a great job and only cost $160.
With the differential back in and the pinion angle much improved, I thought I would make a safety change. Because I wanted to run drag tires of some sort for RMRW, I wanted longer studs with more lug nut engagement. The aluminum wheels I am running have pretty thick lug nut flanges that limit thread engagement using the stock length wheel studs. On these truck 12 bolts, changing out the wheel studs is pretty easy. You just stick the axle in a bench vise, and bash out the old studs with a BFH, then install the new ones using less caveman tactics. In order to save some money, I used a death wheel to cut off the caps on my lug nuts to allow the longer studs to pass through. It worked great.
Here’s the shot of the rear differential all back together in with sway bar, brake cables and brakes bled.
Now, it was time to do something with the stock clutch, so I spent an evening ripping all the stuff out you see here. The four speed will be reused. It’s an A833OD that was used in GM trucks during the 80’s. Fourth gear is overdrive, and it has ratios almost identical to the 700R4 automatic, 3.06, 1.82, 1.0, and .70-something. I did this before I had purchased a new clutch, much less had one picked out. I was looking at several clutches and was leaning towards an organic single disc set up from McLeod.
It was at this point where I was chatting with Chad Reynolds about his plans for Rocky Mountain Race Week. Though our conversations have Chad doing most of the chatting. It was May and he didn’t hadn’t settled on what car he was bringing yet. I think he was just saying that to ease my stress. I wanted a good holding clutch, but didn’t want to deal with ones that had stupid stiff pedal, or was not very drivable in day to day running around. Chad suggested we contact the folks over at McLeod and see what they recommended because he said they have clutches to handle any power level and any driving style.
After a few conversations with McLeod’s techs about my plans for the GMC, and how I drive it, they suggested their RXT Street Twin clutch. My first reaction after reading about it on their website was that it was way overkill for a pickup making 450 HP. I thought these twin disc set ups were for full race deals making four digit horsepower. After talking with Chad about it a bit, I followed their advice and went with it. I also got a 30 lb steel flywheel to go with the new clutch. A couple weeks later the flywheel and clutch package arrived on my door step. I’d be using a Lakewood Bell Housing that I already had for the installation as well.
McLeod’s website description of their RXT line of Street Twin clutches is below:
“Intended for the high horsepower street/strip fan, the McLeod RXT Street twin clutch kit is able to handle 1000hp, this clutch can handle almost any horse-power you can throw at it and still remain street-able. Ceramic lined clutch discs will provide smooth engagement with a soft pedal effort to make this clutch kit ideal for the street performance enthusiast. This clutch is perfect for the person that wants the best of both worlds. You want to drive to the track then rip off a bunch of track passes then drive back home, the RXT is what you’ll need! This series of clutch comes in 3 different configurations to best suit your needs. Adapter ring version. Another McLeod Racing exclusive. We build a twin disc clutch using a Patented Approved adapter ring to bolt to your supplied flywheel. Complete Unit with Dedicated Flywheel. No need to search for the clutch as one number and the flywheel as another number. McLeod Racing has you covered with one part number and a complete dedicated unit ready to plug and play. You have the choice of running a Billet Steel flywheel for your street applications or a Billet Aluminum flywheel for your track cars.”
If you are wondering why I am going this far on a truck that spends 90% of the time on the street, I would say to go to Youtube and search “Clutch Explosion” for your answer. This truck weighs 4000 lbs race weight and I will be using a line lock for burnouts with slicks or drag radials. I like my feet where they are attached. PLus, McLeod literally invented and perfected the twin disc street clutches that are all the rage now. They know what they are doing.
McLeod’s people put their hands on every part of your order. They are double checking you are getting what you ordered, and I really like this added attention to detail. They marked every part to make it super easy to put things together. Being impressed just opening the boxes is a great way to start an install like this.
The first order of business was to install the weight I needed for my externally balanced 383. The flywheel comes with several weights for the different externally balanced engines GM had over the years. The 383/400 small block, and the two different 454’s. The weights for these engines are also located on the flywheel in different places. I followed the included instructions and installed the correct weight in the correct place.
Here is how I received their RXT Street Twin Clutch kit. It was already assembled and tested. Again McLeod had double checked the order, marked every part, and checked the balance before shipping it.
Before getting started on the clutch install, I did actually read the instructions. I have to say easy to read and understandable instructions are so helpful. Nothing is more annoying than instructions that hard to understand or contradictory. Having to stop working on the car to call parts company really annoys customers. McLeod spent the time to get it right and make the install a no brainer.
(Chad Note: Damn that thing is sexy!!!)
I dug out my Lakewood scattershield to replace the stock aluminum bellhousing for added peace of mind. It’s block plate goes on the engine before installing the flywheel. The 30 lb McLeod billet steel flywheel was so much easier to install while lying under the truck than the 50 lb cast iron stock one. McLeod’s twin disc set up has two clutch discs and this adapter ring in between. They include this clutch disc centering tool which is real helpful getting to this point. The adapter ring bolts to the flywheel where a normal pressure plate normally does. You can see how McLeod dummy proof marks the clutch discs and which way faces up for us customers.
The pressure plate is the last to go on. Thankfully, the adapter plate has studs for the pressure plate. McLeod puts this mark across the pressure plate and adapter ring to show you how its clocked correctly. Again, taking the second guessing out of the installation.
After installing the Lakewood scattershield, I installed the throw out bearing to get an idea of where the clutch linkage would be adjusted. With the throwout bearing up against pressure plate, the clutch linkage was way at the end of its adjustment. Which was weird on a new clutch. For some reason the scattershield was taller than my GM bellhousing. I never noticed this when this engine block and scattershield were in my 65 Impala. So, I got the taller throwout bearing from the local Napa. This gave me the adjustment I wanted. Final adjustment of the linkage has to be done once the transmission was installed. Pro Tip: There needs to be some freeplay between the throwout bearing and the pressure plate when the clutch pedal is at the rest position in order to avoid premature wear.
I cleaned the A833OD transmission and installed new gaskets and seals because it was leaking all over the place. Mopar guys may see a familiarity to this trans. It is very similar to the 833’s used in Mopars.
Here is the trans all back together. The scattershield and block plate needs to be bolted together in order to do its job correctly.
There are about dozen 1/2″ and 3/8″ bolts to do this.
I finally wired up the Summit line lock that I installed when I did the suspension brakes. I suck at heel toeing for burnouts, so the line lock will make it easy to be a hoonigan. I installed a lighted rocker switch on the dash where the original choke cable was at. I went with a rocker switch so I could use the line lock holding the truck on hills as well. It’s close enough to grab the shifter without any awkward movements.
The last detail was buying a pair of very slightly used MT ET Street Radial Pros from our good friend, Bryan Lum. I bought a pair of American Racing 10 inch wide wheels to match the wheels I was already running on the truck. They aren’t exact match, but it works for a race tire and wheel combo.
These are monstrous 315/60/15’s. I wasn’t sure if they would even fit without rubbing, but it was no problem. These tires give the truck a insanely aggressive look.
The truck was back on its wheels exactly five days before the beginning of Rocky Mountain Race Week. McLeod’s instructions said that I needed 1200 clutch cycles to break in their RXT set up. That is a lot clutch pushing and shifting in five days. So, I drove the snot out of the truck, shifting up and down, and a bunch of times that weren’t even necessary. I managed to drive it about 200 miles in that five days. Then, I drove the truck from Kearney to Denver, about 400 miles. 150 of that was on two lane roads to get to the opening day of Race Week in Denver.
The first thing I noticed when driving it with the new clutch was how light the pedal was. It was lighter than my previous $100 stocker clutch. That seems sort of surprising, but remember that McLeod is the company that first developed twin disc clutches for the street. With every clutch company seeming to have one nowadays, it is sometimes hard to decide which one to go with, but the results here speak for themselves. Drivability was very good, but you do have to realize that a clutch capable of handling 1000 hp isn’t going to be able to be slipped like a stock clutch. It does take some getting used to but still allows you to easily putter around from a stop in parking lots, drive in stop and go traffic, and navigate daily driving with ease. But, when you want grip, you get plenty of grip. With this clutch, speed shifting was giving nice tire chirps in every single gear. I now have about 2700 miles on this clutch set up and I really like it. It takes every bit of my aggressive driving, in a truck I daily drive and use as a truck. It tows my boat, hauls stuff from Home Depot, AND does big burnouts.
Tune in to Bangshift where I tell you about my experience driving Project Hay Hauler on Race Week this year.