Building a Mopar 360 Stroker Motor
Assorted Problems and Quirks
|Prelude to Madness|
|At the beginning of the 2005-2006 school year, I
enrolled in an engine building class at
Saddleback College in Mission
Viejo. At the beginning, I thought that it would be a guided
course through the ins and outs of building a traditional V8 engine,
with parts being supplied by the college.
Boy was I wrong.
As it turned out, each student was required to produce their own parts and build their own motor. After getting over the slight shock, I realized this would be an excellent opportunity. I had been interested in motors for quite a while, especially those produced by Chrysler. After reading several articles on how many gearheads were taking regular small blocks and producing high power monsters out of them simply by lengthening the crankshaft stroke, I decided to build my own 360 stroker motor. After purchasing a book on rebuilding small block Mopar engines, and a book dedicated to building stroker small blocks, I set to finding a used 360 block in the nearby junkyards.
|A couple weeks in to the class, I located a used 360 long block at All Cars Auto Parts, located here in Santa Ana. The motor itself came out of a junked Dodge transport truck, and was pretty beat up. Luckily, most of the damage was merely cosmetic, and only a few parts had to be discarded. The water pump and timing cover had completely corroded through, and had to be beat off with a cold chisel and sledgehammer. The exhaust manifolds were in good shape, but the studs holding them to the block had completely rusted tight to the heads. Some beating was necessary to remove them.|
|After the motor had been completely stripped down to the bare block, it was hot tanked and cleaned before being put on an engine stand. After preliminary cleaning with soap and a stiff brush, I took the block to Burlington Engineering in Orange for a chemical dip. This procedure almost completely dissolved all the rust and corrosion inside the water jackets, as well as stripped off all the paint. The block is now down to bare metal. The casting flash, common on Mopar engine blocks, was ground off, and after another wash with soap and water, the bores were miked for roundness and taper, and the block is ready to be bored and honed.|
|The Parts Arrive|
|After a brief downtime due to lack of funding, parts
for the short block are ordered from
Summit Racing and
arrive a week or two later. They include:
|Pulling Itself Together|
|During the downtime while waiting for parts, the
block was bored to 4.028 inches. After receiving the parts and
miking the pistons, each cylinder bore was fine honed to four
thousandths larger than its respective piston to allow for thermal
expansion of the forgings. Accuracy was within five
ten-thousandths of an inch. Installation of the bronze distributor
gear was also done at this time, using a bushing driver and reamer made
by Miller Special Tools.
Because the pistons had a slight step, they were milled down to flatness in order to fit closed chamber heads without interference. After milling, the rotating and reciprocating assemblies were weighed and ground down to equal weights, and the crankshaft was balanced. Approximately forty grams had to be removed on either end of the crankshaft. After balancing, the short block was assembled and bagged up.
|The Motor Finds Its Heads|
|After yet another lull in assembly due to lack of
funding, parts for the top end were ordered through Summit.
Other miscellaneous parts were also ordered off of eBay.
|Getting Gussied Up|
|A couple weeks later, more parts arrive from Summit
The intake manifold gaskets were dressed with Permatex gasket fastener and located on the heads and block. The intake manifold was then dropped into place and secured with ARP bolts. After torquing down the intake manifold, the carburetor was bolted to the manifold with regular 5/16th bolts, the front cover, water pump, and fuel pump are installed, and the valve covers are put on temporarily. After a failed attempt at installing the harmonic balancer, the engine was bagged up and is now awaiting being transported off campus to my garage.
|The Motor Comes Home|
|After finishing the last final of the semester, the
motor is loaded into my dad's pick-up truck. I had already built a
wooden transport cradle, so it was only a matter of getting the motor
strapped down and secured for driving thirty miles up Interstate 5 to my
home. The engine stand was partially disassembled and loaded in
the truck as well.
Once at home, the stand is reassembled, the motor is lifted out of the truck with a rented hoist and loaded back onto the stand, and the entire package is wheeled into the garage to be stored and worked on over the summer as funds and time permit.
|Putting on Makeup|
|After a few weeks of sitting around, I resumed
working on the motor. I attempted to cut the intake manifold
gaskets, but inadvertently ripped one of them apart at the intake ports,
so the manifold had to come off. This wasn't a total loss, since
it gave me an excuse to get a nine piece Craftsman wrench set and a
wheel cylinder hone to use on the damper.
After returning with the tools and getting the manifold off, I painted the front cover and oil pan with Bill Hirsch's engine paint. After the paint had dried, I installed a new front seal, put the front cover and water pump on, and put on the oil pan with its gaskets in order to get them set to the block with silicone while I painted the rest of the block. After spending a couple hours masking off all the bolt heads, open spaces, heads, lifter valley, crankshaft flange, and water pump I bagged it up and called it a night.
The next day I wheeled the motor outside to be painted. A light coat is misted on, allowed to set for a couple minutes, then the final coat is applied. A few touch-ups were necessary after it had dried, mostly in places where I couldn't see if the paint had reached. After drying for about fifteen minutes, I took off all the masking, installed the fuel pump, and then bagged up the motor to await new manifold gaskets.
|School has started up once again, and the motor is
back in the shop getting the finishing touches put on. I made
another attempt at installing the harmonic balancer, but since it came
from the factory at six thousandths undersized, there was no way I was
getting it on. CAT instructed me to heat it up in boiling water,
but that was unsuccessful. After attempting to hone it out with a
wheel cylinder hone and failing to install it, I decided to junk the
damper and just purchase a new one from Summit.
I also received a set of Weiand cast aluminum valve covers from a very nice lady in New York. Since they were used, I had to bead blast and hot tank them before mocking them up on the motor for installation. I have not yet decided if I want to paint them, or just clear-coat them and leave them au naturale, but I'm leaning more towards the clear-coat.
Since it's also a new school year, I have to do all the assignments over again. This means cylinder boring, honing, decking, and other assorted tasks on an entirely new motor. I have been looking for a 440 block, since I want to learn about big blocks, but all I have currently managed to find is one long block for five hundred dollars in Huntington Beach. However, my professor asked me if I was interested in doing a Chevy 383 stroker for a member of the college computer staff, and since I'm fairly broke, I accepted. That might have its own write-up, but I am not sure what my customer wants yet.
|Living in Harmonics|
|With the arrival of a Summit-brand harmonic balancer,
the proper tool to install it, and a few other parts I still needed, I
was ready to finally get this motor fully assembled. I
double-checked the internal diameter of the damper to make sure it had
the proper interference fit with the crankshaft snout, and seeing that
it did, I applied a small amount of anti-seize on the internal diameter
and some motor oil on the outside of the hub so it wouldn't tear the
front oil seal when it was pressed on. I then set up the tool,
slid it through the damper, and threaded it into the internal hole in
the crankshaft. Using a standard 15/16 wrench I pressed
the damper onto the hub, made sure it was seated properly, and then
installed the crankshaft retaining bolt, torquing it to 100 lb/ft as per
After dealing with the damper, I then installed a one-inch spacer under the carburetor. A spacer is a simple and inexpensive way of adding torque and horsepower, and also helps keep the fuel temperature down. While I don't think I'm going to have any problems with boiling fuel, I do like having a little bit of extra oomph and a slightly snappier throttle response, so for twenty-five bucks, it's hard to go wrong.
All that's left to do now is to purchase exhaust headers and spark plugs and attach the flywheel, and the motor will be ready for its first start-up.
|The exhaust headers are the next and almost last
thing to install on the motor. These are plain-Jane Summit brand
painted headers that will fit a multitude of Mopar vehicles, and
supposedly massage a decent amount of horsepower out of a good build-up.
From my inspection, they do appear to be of good construction, though
there are a couple problems regarding bolt clearance on the inside of
the outer two pipes. The pipes are bent a bit too close to where
the head of the bolt needs to be in order to thread it into the head,
and as such, those bolts don't get installed. I'm planning on
going to exhaust studs instead of bolts, though I might also have to do
a bit of grinding on the pipes in order to make the fastener fit.
After I bolted the headers to the motor and hooked up the reducers, I added valve cover gaskets and fastened the valve covers down. The ARP bolts that came in my kit last year again gave me problems, and were far too short to pass through both the cover flange and the rubber gasket, and I had to scrounge up ten quarter-inch bolts of about an inch in length in order to actually fasten the covers to the heads. Luckily I could use the ARP washers on the bolts, so my covers are still fairly protected from getting gouged or scuffed by a rotating bolt head.
When the valve covers were on, I attempted to install the spark plugs, but for some reason they will not fit in my Edelbrock heads. I'm able to thread them in about two-thirds of the way, and then the hex part of the plug comes into contact with the head, effectively preventing me from getting a spark plug socket in there or allowing the plug to do any further rotation. Extremely odd, since the Edelbrock heads are supposed to be the same exterior dimensions as a stock 360 head, and indeed, the plugs fit in my Doba's 360 motor. So apparently I need a smaller plug.
With the headers and valve covers on, all that's left is to get a new set of spark plugs, some header studs, a few pipe plugs to plug up some holes in the intake manifold, an oil filter, and an oil pressure sending unit. After that, it's only a matter of putting the motor on the run stand, installing the flywheel, bell housing, and starter motor, wiring up the distributor to the coil and ignition computer, getting the base timing set, filling it up with five quarts of Rotella 15w-40 diesel oil, priming the oil system, and finally firing it up.
It's almost a shame to see it come to an end.
|Sparks and Wires|
|After realizing that the only way I was going to get
a spark in the cylinder would be 5/8s sized spark plugs, I purchased a
set of Autolite 3924s at my local Kragen. I took these, along with
a piece of scrap wood from a household re-flooring project and the
ignition coil bracket, to class to trial fit them in the heads.
Upon seeing that I would indeed be able to fit both the plug and a
socket into the plug recess, I slathered some anti-seize on the plug
threads, and snugged them down. After all eight were in the motor,
I labeled the wires, then routed them while making sure to criss-cross
adjacent plug, and plugged them onto the distributor in the correct
After installing the spark plugs, I started building the mount for the ignition computer, ballast resistor, and ignition coil. I bought a couple metal braces from Home Depot, drilled two 13/32 inch holes at one end of each, and bent them in the specific spots to get the right angle for mounting the board. Once the braces were properly shaped, I mounted the board to them with wood screws, mounted the computer with a grounding wire, and bolted the mount to the heads. I measured the coil wire, and mounted the coil so there would be just enough slack to allow engine movement without interrupting the ignition voltage. I then mounted the ballast resistor, did all the preliminary wiring, and tidied it up with zip-ties and masking tape. I then installed the temperature and oil pressure sending units, and called it a day.
All that's left now is to bring in five quarts of Rotella diesel oil, mount it on the run stand, and fire the bitch up.
|A Minor Setback|
|After getting a set of motor mounts, I attempted to
mount the motor on the run stand. However, when I attempted to fit
the mounts to the engine block, they would not line up with the mount
holes, and the mounts themselves hit the headers. After trying
every possible orientation, I realized that the mounts wouldn't work
anyway, because they were intended for use with a cross member in a
passenger car, not a simple stand mount, and I would need mounts
intended for use in a pick-up truck. Unfortunately, I had thrown
away my old mounts because I though they were junk, and Freeway Auto
Supply would not be able to get the proper mounts in until the next
morning. However, there was another person in the class doing a
Dodge small block, and he had a set of truck mounts he didn't need.
After bumming them off him, I bolted them to the block, and set about
mounting the motor to the stand.
After the motor was bolted to the stand at the mounts, I attempted to install the flywheel. At first, there was a problem with the holes not lining up. Mopar motors use a special bolt-pattern on their flywheels and flexplates, where one hole is offset from the others. Each hole must line up, otherwise the flywheel can not be installed. Mine was only lining up with four holes, not all six. Since it was near the end of the class period, I had to leave it for the next week.
At home, I thought about this problem some more. I didn't understand why it wasn't lining up, since the flywheel was made for Mopar motors. Then, while on the can, an idea hit me: why not use my old crankshaft to mock up the flywheel and see what's what? I hadn't had a great perspective with the motor at school, because I had to hold the flywheel with one hand and crane my head around in order to see, so having an unobstructed view of the flange and flywheel would be very advantageous. After finishing up, I got the flywheel from the car, and went out to the garage.
Turns out I was putting it on backwards.
The next week I tried again, this time with the flywheel properly oriented. Using a set of ARP bolts I had purchased, I tried to thread it into the hole. No-go. The bolt was too short, and would not even reach through the flywheel to the flange. I was enraged, because the problems I've had with ARP have now come to a head. I'm swearing off ARP forever, except for main, rod, and head bolts, where it's fairly easy to get it right. Otherwise though, I'm going with Mr. Gasket or some other brand.
After doing some other jobs that needed doing, I went home and ordered a set of Mr. Gasket bolts.
After receiving the bolts, I tried again. This time, the bolts were too large in diameter. Turns out that Summit's online catalog system had listed a set of Pontiac bolts as also working for my Mopar. Obviously, this was incorrect. I finally went down to Freeway Auto Supply and purchased a set of Help! brand bolts for six bucks. Of course, these worked perfectly. It's always the cheap stuff that works, while the expensive stuff fails to live up to its name.
After buttoning up the bellhousing and installing the starter motor, I poured in five quarts of Rotella diesel oil and started to prime the system. Almost immediately oil started hemorrhaging out around the oil filter adapter plate. After cleaning it up and asking my professor what the deal was, I learned there is a gasket that goes between the block and the plate, which I had not known about. Neither book I bought or the shop manual mentioned this gasket, and I thought the circular rubber gasket in my set was just a left-over. So another week goes by without a start-up.
The next week I install the gasket and prime the system, checking for leaks. This is the extent of my work for that week, since I knew we would have a guest speaker in class and I had not planned on starting it up. The motor sits dormant.
|It is the week after Thanksgiving, and there is no
work left to be done on the motor. All that's left is to prime it,
time it, fuel it, and start it. I immediately roll the motor
outside next to the water hose and begin wiring up the ignition system
and hooking up hoses.
After all the connections have been made, I prime the oiling system by bringing pressure up to around forty pounds of pressure for about three minutes, ensuring every nook and cranny in the oil system has been lubricated. Then I reinstall the distributor driveshaft, align it, and install the distributor, making sure to align it properly as well. Once all buttoned up, I turn on the water and watch for it to come out the return hose.
Instead, it comes out from the back of my intake manifold. Apparently, one of the bolts holding the manifold to the heads had bottomed out without actually bringing the manifold into good contact with the head, while another was a bit too loose. After shimming the one bolt and tightening the other, I tried the water again. Still leaking, but not so much. Then my buddy suggested removing the thermostat.
After removing the thermostat, the water flows way it should: in through the pump and out through the water neck. With everything working properly I then fill the fuel tank with some 91 octane gasoline, and attempt to start it.
At first it would not start. The starter would turn the motor over, but it wouldn't fire. The cause was simply a lack of spark, due to not flipping the run switch to "On." After correcting that problem, I tried again.
It still would not start, but we were getting ignition. However, it was through the exhaust. I was 180 degrees out, even though I had followed the book precisely. A simple correction, as I just had to loosen the distributor, rotate the rotor, and reinstall it. The cap was snapped back on, and I tried again.
After a couple burps and belches, the motor roared to life. I quickly brought it to around two thousand RPM, and my professor played around with the idle settings and throttle screw in order to keep it there. After getting it all set, I let it run for ten minutes to seat the rings and break in the camshaft, then shut her down.
She sounded strong, really strong. At idle there's just enough throat to sound menacing, while it's subdued enough to not raise suspicions from any would-be racers. With open headers she sounds like a monster; I figure with a good set of mufflers she'll sound like a trained attack tiger.
Now to just find a car to put it in.
|Assorted Problems and Quirks|
|Oddly enough, the vast majority of the problems I
encountered with building this motor stemmed from ARP's bolts.
Their accessory bolt kit did not label which bolts went where very well,
and the front cover and water pump bolts were either the wrong size and
thread pitch, or simply too short. I later purchased a Mopar
Performance bolt kit for the front cover and water pump, and while many
of the bolts worked much better than ARP's, there were still two bolts
that simply were not long enough. I was forced to go to Home Depot
and Ace Hardware to find the right length bolts, and have yet to be
There were other problems with ARP's bolts as well. A couple intake manifold bolts were too long, though this might be the fault of the heads. The heli-coil inserts at a few locations in the heads might not be properly installed, or at the wrong depth. The head studs were also missing two extra long studs for the Edelbrock heads, though this is more of a fault of Summit Racing's online catalog system, as it did not show the proper stud kit for Edelbrock heads. In place of sending the kit back, I simply used a bolt Edelbrock provided with each head, and used the proper stud in the location indicated.
The largest problem with the ARP bolts, aside from the front cover, is that the exhaust header bolts are too short to bolt a stock exhaust manifold onto the heads. This, and the poor labeling of their bolts, has caused me to rethink going with ARP for future motors.
The other major problem I encountered with this motor was with the harmonic balancer. I ordered the balancer off eBay, and while it is a quality balancer, the inner diameter of the hub is six thousandths undersized. When I called C.A.T., they told me to heat up the hub and press it on. Given the massive undersize of the hub, this is not an acceptable method of installing the damper, as it would be impossible to remove the damper after installation, if it could even be installed in the first place without destroying the damper in the process. However, their website states that using any method other than heating the hub will result in voiding the warranty. To me this is unacceptable, and C.A.T. will not be getting my business in the future.
Another annoying problem was the water neck. The one made by Mopar Performance was not wide enough, and would not fit on my Weiand intake manifold. I do not know if this is the fault of Mopar Performance for making a shoddy water neck, or Weiand for having a non-standard thermostat hole, but I am more inclined to believe it is the fault of Mopar Performance, as a Summit brand water neck fit perfectly.
The other problems I encountered with building the motor were very minor, and are probably avoidable by anyone who is more organized than I was with this motor. All the parts were ordered in bursts, according to how much money I could afford to spend, and in the process it became fairly disorganized. Because of this, I have learned that I need to wait until I know I can afford to purchase the vast majority of parts at once, and not just piecemeal it together over the course of many months.
I also learned that I should bead blast anything small enough to fit in the bead blaster, engine internals and new items excepted.
|I am currently deciding between putting the motor in a 1968 four door Dodge Dart, a 1972 four door Dodge Dart, or a four door Plymouth Belvedere. The transmission will most likely be a manual shift, since putting all that power in front of an automatic would probably just be a waste. In the meantime it will reside on the stand until I purchase an engine cradle, which will then serve as the core for a run stand.|
|Ackowledgements and Resources|
|Full Price List|
*Total does not include shipping costs or applicable taxes.*