Living out in the mountains at 3,600 feet of elevation I was always interested in four wheel drive vehicles. The front wheel drive Audis went pretty well in mud and snow, but I always felt like the rear drive shafts were somehow missing. It was the year 2000 when I saw a 1961 Dodge factory 4x4 advertised in a newspaper for the low low price of $1000, and it certainly caught my eye. The project that ensued was a substantial investment of time and rather expensive as well.
Stock Motor Rebuild
Body on Restoration
Four Wheelin' Upgrades
Hot Rod Motor
It was quite a drive six hours south to where the truck was parked. The guy was a commercial fisherman who had owned it for a few years and just never really got it together well enough to use. He did not know much about the truck, but he did know that what was currently wrong with it was a burned exhaust valve. The truck was pretty rough, with lots of body damage and many missing pieces, but it was something of a classic and I saw potential in it. When the owner was willing to take $600 cash I towed it home. We had to rent a U-Haul tow dolly, many of which are amazingly wide and able to carry quite large light trucks. To tow the Dodge we had my beat up and wrecked old 1987 EFI Toyota 4x4, which did the job even if it was a bit scary and dangerous. For a 4x4 full size pickup the 1961 Dodge was actually amazingly light at under 5,000 pounds, but that is still too much to tow with a 1987 Toyota with no trailer brakes.
The hardest part about getting the cylinder heads off of the 1961 Wideblock 318 was that they were so darn heavy. Still though I had the engine torn down to a short block in nothing flat. Those old engines really are extremely straight forward to tear down, and enough space in the engine bay to stand up next to the engine is practically as good as having it out on an engine stand.
Sure enough all that appeared to be wrong with the engine was one horribly burned exhaust valve and a bunch of other valves in rather poor condition and not sealing well. I tore the heads apart and ordered a few new exhaust valves, one new intake valve and a top end gasket set. I took the rest of the valves to an automotive machine shop and had them resurfaced. The guy that ran the grinder said that they had already been resurfaced before and were getting a bit small, but I could clearly see that there was plenty of meat left on them before they sank too far into the seats so I told him to do the job anyway. The bill seemed reasonable at just $20.
Because the Wideblock 318 heads did not use hardened inserts it was a snap to cut the seats in a bit just using old valves and coarse valve grinding compound. In order to get the seat width narrow enough to be in spec I ground the old valves down to have larger and smaller angles so I could cut the sides of the seats away. Because I only had one old intake valve I first ground it to do the outside of the seats, and then I ground it down smaller to do the insides of the seats. This would all have been much easier with a regular valve seat cutting set, but it was a project done on the cheap without buying new tools. Buying new tools to work on the Dodge certainly did happen latter, but the innitial engine overhaul cost only about $150 in parts.
The cylinders had some wear, with substantial ridges several thousandths deep, but they were uniform and looked to have been sealing well. The stock cast pistons rocked back and forth in the cylinders a bit more than I expected but I decided they would do for the time being. I pulled a few main and rod caps off, and the bearings looked good and were well within spec testing with Plastigauge so it looked like the short block was serviceable. While I was at it I measured the volume of the combustion chambers with a piece of polycarbonate sheet and a plunger type precision two stroke oil measuring thingy. After taking into account the dish in the pistons, the deck height above the tops of the pistons and the head gasket thickness I got a compression ratio of 7.8:1. Rather low compared to the 9:1 and 9.5:1 that had become standard in the 1990's, but my gasoline powered Audis were for the most part at 8.2:1 so 7.8:1 was not much of a reduction in compression ratio.
In short order I had the Wideblock up and running on the stock two barrel carburetor and stock points ignition system. I was disappointed that it did not seem to run very well compared to other gasoline engines, but the big 318 cubic inch displacement V8 certainly did make enough power to get the job done.
I was able to special order an original 1960 and 1961 Dodge Trucks Factory Service Manual set through a local used book store, and this was very useful for putting the truck back to stock settings. With the carburetor and ignition system all setup according to the 1961 specifications it idled smoothly and delivered an amazing 15mpg on the highway in fourth gear at 2,000 to 2,500RPM.
Even though I was able to get the rest of the truck together well enough initially to drive it needed a lot of work. I made several new body mounts, and I welded quite a bit of the torn and rusted body back together splicing pieces of other car bodies in to fill the gaps. All covered over with bondo and rolled and brushed with thinned acrylic enamel automotive paint it looked pretty good. Rolling the large areas of the body panels with a house paint roller in direct sunlight on a hot August day made for a rather nice looking custom paint job. The very slightly "textured" surface from the house paint roller did a good job of hiding slight imperfections in my amateur bondo work, and it was usually able to pass for some sort of a professional job.
At that time there were still some of the old "Sweptline" Dodge two wheel drive trucks in junk yards so I was able to collect up some of the missing pieces I needed to make the truck mostly complete. As useful as the junk yards were for finding missing pieces such as the parking brake system, turn signal switch, tailgate and original gauges I also wasted quite a bit of time and money trying to use more disposable parts out of the junkyards. Brake master cylinders and hydraulic clutch master cylinders rebuilt with new rubber were a disaster, and I eventually had to buy new replacement cylinders for what seemed a quite high price of just over $100 each. The problem was that all of the cylinders in the junk yards had the same problem that the cylinders that came on my truck had, small amounts of corrosion where water had been laying in the bottom of the bore.
The truck had some nice eight inch wide aluminum rims on it, and when I measured clearances I realized that 35s would fit with no lift kit and almost no fender trimming. By shopping around I was able to find a set of four 12.5x35-15 mud tires for only $500 installed. At the tire shop the guys doing the work said it did not look like the 35s would fit. When I assured them that I had checked the clearances the tires were installed. The new tires looked great, but when I headed out on the freeway they shook around horribly. I went right back to the tire shop and they said that they would try flipping the tires 180 degrees and rebalancing. This worked and the tires rode nearly perfectly smoothly at all speeds. Because the large displacement engine was so radically oversized for the truck and not geared all that high going up to the much bigger tires did not adversely affect gas millage. The truck still got 15mpg at 63mph (2500RPM).
The only trouble I had with the cheap tires was that the ten inch tall single ply sidewalls were very vulnerable. I poked holes through them quite a few times when off-roading and got quite good at putting on giant internal patches that the local tire shop where I bought them assured me should never be used on side walls. The giant internal patches did work with good glue from Germany, but they were so heavy that the tires were then too far out of balance. By putting the patched tires on the back of the truck I was able to continue using them, but it was not a good situation. I also fixed a number of smaller sidewall punctures with push through tubless tire repair kits, and this also worked pretty well with good glue.
There were quite a lot of other issues I had to deal with on the 40 year old truck as well. It had a fairly new ring and pinion in the rear that had not been setup correctly and started to hum after just a short time. Resetting the location of the gears to get a better engagement pattern removed the hum and I had no further trouble with the ring and pinion. It also needed new brakes, but once I put new shoes in all around they lasted for a long time. The floating center pivot 12" drum brakes with dual piston wheel cylinders actually worked really very well even withought a power brake booster, requiring only quite light peddle pressure to engage.
I had to replace all of the U-joints in the drive shafts, and once I even had to replace a U-joint in the steering knuckle. I had to replace both front wheel bearings at different times, and steering knuckle cover seals also had to be replaced. If I had done all of these operations on the front end at the same time considerable labor could have been saved, but as it was I just waited untill things failed to replace them and I had to take the front end apart a few times.
The front U-Joint on the front drive shaft was a particular problem. With the stock setup the caster angle came out negative and the truck wandered horribly and was hard to drive. I installed a set of 10 degree wedges to get the caster to come out possitve, and this made a huge difference in handling and controll. Even though 8 degrees was probably too much positive caster for a truck it still worked great. The problem with the 10 degree wedges was that then the angle on the front U-joint was even worse. That front U-joint ended up having to be replaced several times but it did sort of work. It always irked me considerably that somehow the ends had been welded on that stock Dana 44 axle quite a few degrees off from where they should have been.
The four speed transmission and divorced two speed transfer case were in fine condition when I got the truck, but I ended up taking them both apart a couple of times on a whitch hunt for a mysterious vibration. The vibration turned out to be a spring loaded coupler set in the transfer case. All of the springs were broken and the coupler just bounced back and forth causing horrible drive train vibrations. When I replaced the springs the vibration went away for quite a while, but then came back. When the vibration came back I replaced the transmission with a smilar used unit I happend to get cheap, but that was not the problem and the vibration persisted. The vibration was only in third gear at 2,500RPM to 3,500RPM, so it was kind of suprising to find that the problem was not with third gear in the transmission itself. It was actually a harmonic set up between third gear and those loose springs, and finally years later I discovered a round about solution that was somewhat unexpected.
Even though the national average fuel mileage for passenger cars was only 17MPG at that time I was used to getting around 30 to 35MPG with gasoline powered Audis so the 15MPG still seemed pretty poor. Because of the high fuel consumption and mediocre practicality as a daily driver I began to modify the '61 to be more of an off road buggy.
When I first started driving the truck the factory limited slip unit in the Dana 60 rear end was not working very well. It did aid traction a bit, but it just seemed to do a lot more slipping than gripping. I ordered a new clutch kit for the factory limited slip, but when it arrived it was the wrong plates. They were close, but they did not fit. The new clutch plates did however have bonded friction material, where the old stock clutch plates were just steel on steel. I really wanted to get the limited slip gripping well, so I modified the new clutches and butchered them into the unit. This butchery job sort of worked. At least it worked well enough for me to see what a functional limited slip unit could do. The poorly fitting clutch plates were loose in the housing and I could feel them clunking around coming out of turns. The poorly fitting and clunky new clutch plates seemed like they were unlikely to hold up well so I took them out and put the original steel plates back in. What I also put in was some special friction modifying additive that was supposed to get limited slip units locking up better. This additive did wonders for the performance of the stock steel plates, and the limited slip unit worked dramatically better right away. Over a period of months the old unevenly worn and scored stock steel plates wore in and the limited slip unit just worked better and better.
It was really amazing what a difference a real limited slip unit made in off road performance. The 1961 Dodge W100 could tackle rough terrain a whole lot better than anything with open differentials. Another aspect of the off road competence of the '61 Dodge was the frame flex. That frame would just twist up into a pretzel in order to keep all four tires on the ground. The frame twisted so much in fact that my repaired body mounts began to loosen up and I was worried the whole cab might fall off some day. To address this excessive frame twist I welded pieces of plate onto large areas of the stamped channel frame. It was not a fully "boxed" frame, but just stiffening the frame from the rear mount of the front leaf springs back to the cross member for the divorced transfer case worked really very well. the frame still had some substantial flex to it, but the body was no longer in danger of being ripped off of the truck when out wheelin' on uneven terrain.
With less frame flex the truck was not quite as good in challenging terrain. It still went really darn well, but I knew it could do better. I wanted a selectable locker for the Dana 44 front differential, but I did not want to put out all the cash for a ARB unit and air compressor.
What I did instead was just weld the front spider gears up. I had read that welded spider gears sometimes came apart, so I put a whole lot of rod on them and welded everything to everything so that they could not break apart. This modification worked well in that it never broke and did improve traction immensely. With the welded front end and limited slip in the rear the truck was essentially as good at steep climbing as anything out there.
The problem though was that it was extremely reluctant to turn with the hubs locked in, and this quickly lead to a power steering upgrade. I bolted a "Saginaw" box off of a Chevy onto the Dodge frame and made up a custom drag link by welding the front of the Chevy link onto the back of the Dodge link. With a few angle blocks to get the box in at just the right orientation the system worked really well. The Saginaw box turned out to be as powerful and reliable as people said it was, and I was amazed how the power steering system could lift the whole truck up when the 35's were down in a hole descending an extreme sidehill.
The power steering made it easy to spin the wheel even with the locked up front end engaged, but the truck still would not turn well without unlocking a front hub. This turned into a whole lot of getting out of the truck to lock and unlock a hub when running an off-road trail. I picked up another open differential for the Dana 44, but I never installed it. Instead I just ran the truck in two wheel drive nearly all the time, and only locked in the hubs after I got stuck.
Two wheelin on off road trails is a fun challenge with a powerful engine, but it also tears up the trails more than four wheel drive with open differentials does. The '61 Dodge short bed with the divorced transfer case gets quite a bit of weight on the rear end, and with the limited slip rear diff and aggressive 35s it really went amazingly well without using the front drive at all. Being able to get out of any sort of a predicament with the fully locked front diff also helped considerably. When you are trying to get through challenging terrain using two wheel drive, power and momentum you can get really really stuck in a hurry.
To go along with higher speeds in two wheel drive I also did some suspension upgrading. Quite early on I had put a set of Rancho RS5000 shocks on all around, and these did work quite well. They improved the ride quite a bit and all in all they seemed to work extremely well. At the front end though the new shocks just had a huge amount of rebound damping, it seemed like way too much for the quite soft stock front springs. I still liked the new shocks a lot though, so instead of throwing them away I upgraded the front springs as well. I swapped in a set of front leaf springs out of a one ton Dodge four wheel drive. These springs turned out to not be quite the right thing. Not only did they not exactly fit, but they were also just way too stiff of a spring rate. The ride of the truck got a lot harsher, and most of the time at low speeds it seemed like the front suspension was not moving at all. I did however notice that at higher speeds over rough terrain the new springs were just right. The stiffer spring rate was actually a perfect match for the large amount of rebound damping provided by the RS5000 shocks, and the truck got a whole lot faster in aggressive off road driving.
The other thing that the rather light '61 W100 with 35s and a locked front differential was good for was going through the snow. Just on the mud tires it would go through quite a bit of snow, better than anything else around really. Once the snow got a few feet deep though it simply would not plow anymore. To go through the even deeper snow we sometimes got at 3,600 feet of elevation I bought a big aggressive set of tire chains. It did not seem to matter whether I put the chains on the front or the back, the truck went equally well. With the chains it would not only go THROUGH snow, but it would actually get up on top and go over the snow. There was essentially no depth of snow that it would not traverse. If the fresh powder was really deep and light and fluffy the truck would not get up on top of it, and would instead plow a mountain of it out front. Eventually this mountain would get so big that it would stop the truck. The truck did not however get stuck. All I had to do was back up and get a little run on it to bounce over the mountain of snow and I would be off and plowing again for a while. This was a slow and laborious way to traverse deep fresh powder, but there was never a place where I absolutely had to turn around unless the hill just was too steep to climb in the snow.
Plowing through the snow was what really began to turn up severe limitations of the stock motor. The main problem was the big two to one jumps between first and second and second and third gears in the transmission. These big jumps meant that the engine had to run over a wide range of engine speeds, and this it just did not want to do with the stock setup. As with all gasoline engines there was not much power bellow 3,000RPM, and with the small stock two barrel carburetor the engine would hardly rev past 5,000RPM. It is easy to see that an engine speed range of 3,000RPM to 5,000RPM is insufficient for two to one jumps between gears.
The first upgrade I made was replacing the stock cast "log type" exhaust manifolds with welded tubular steel headers. There was one company down South that was making shorty "truck" headers for the Wideblock, and the price was only a bit more than for production welded headers for more popular engines. For the slight price premium the Wideblock headers fit very nicely and were made out of very thick material for long life. To go with the new headers I also went for new pipes and mufflers. I measured the lengths and bend angles for the pipes and found a muffler shop that was willing to part with some rusty old heavy gauge two and a half inch tubing they had for just $50 including the few bends I needed.
This new exhaust system made only the slightest bit of difference in performance on the stock engine, but it was good for enough extra revs that I managed to bend an intake valve at about 6,000RPM. The valve springs that were in the heads seemed even weaker than stock, I could just push them down easily with my palm. The aftermarket springs I ordered were rated at only a slight bit more seat pressure than the stock springs, but they seemed a whole lot stiffer.
I put those springs and a new intake valve in right away and was back up and running with no danger of further bent valves. At this point I began collecting parts for a more substantial engine upgrade. I found another 0.030" over short block with stock type cast pistons in a junk yard that looked better than the one I had been running and I ordered some more "speed equipment" as well.
The main additional upgrade was a camshaft, but I also found a used aluminum Weiand four barrel intake manifold. The camshaft was from a custom grinder who somehow had blanks for the Wideblock. The price was again not all that high at about $150, and the cam profiles were very interesting. The cam I got was strange in that the lift was the same as stock, and the duration at 0.05" was only about 230 degrees. The big difference was the shape of the lobes. It was just a whole lot more aggressive of a camshaft with much faster opening and closing ramps and a whole lot more duration at near maximum lift. When I installed the new camshaft I also put on a new timing set (gears and chain) and a 1.5 degree offset key. The cam timing on the Wideblock had always been comming out a degree or so retarded, and I wanted to make sure that the new longer duration cam was installed erring on the side of advanced as oposed to being at all retarded.
The wideblock uses the same size lifters as the Chrysler early Hemi, and special lightweight aftermarket lifters were available at that time for a seemingly low price of just $40 a set. To top it all off I went with a Quadrajet off of a Chevy, but the "poor man's fuel injection" turned out to be difficult to setup and generally undesirable. The primaries worked great, and the vertical slide float did a good job of keeping the engine running cleanly going up and down hills and on extreme sidehills. The problem was that the secondaries did not seem to work well.
At first I tried taking the vacuum flaps off of the Quadrajet because it seemed to be running too rich on the secondaries. This did not work though, with the needles removed the mixture control was not good and it had horrendous lean spots.
Eventually I got a few different sets of needles and managed to set it up with a minimum of spring pressure on the vacuum flaps so that the secondaries did sort of work. This got the engine really running like a gasoline engine for the first time. It was a big mountain to climb with the stock 7.8:1 compression ratio, but I did eventually get the power at 7,000RPM.
It took not only a rather rich mixture, the headers, cam, intake, four barrel carb and premium gasoline but also 40 degrees BTDC on the spark timing to get going. The engine did however light off on late compression ignition and pull hard from 5,000 to 7,000RPM.
Because the camshaft was only slightly longer in duration than the stock camshaft the hot rod engine did not give up much from 3,000 to 5,000RPM either, but the big two to one jumps between gears continued to seem like a large problem. With the much more substantial hot rod power output up at 5,000 to 7,000RPM I was all of a sudden very disappointed to have to start at 3,000RPM in third gear where there was a whole lot less power available. The truck was easier to drive with the new hot rod motor, and it was more useful in every way as well. Fuel mileage did drop off to 13 to 14mpg on the highway, but part of this was that the truck simply went faster much of the time.
The real reason for the reduction in fuel mileage though was that the vacuum advance mechanism could not be made to work on the Quadrajet. The vacuum ports just where not in the same places as on the old stock two barrel. I had to give up on the vacuum advance when using the Quadrajet, and this turned out to be somewhat of a problem. Not using the vacuum advance the engine was actually smoother and quieter under light loads, but it did use a whole lot more fuel at low speeds on dirt roads and off road trails. I could just watch that fuel gauge drop idling along at 15mph on a small dirt road.
I can't imagine now why I bought the Teflon bushed 6-71 blower when I saw it at a swap meet. I guess it was the wads of hundreds my dad and I had burning wholes in our pockets. The guy selling the blower said it worked real well other than a leaky oil seal on the gear case, and he was willing to take $900 without the Small Block Chevy intake manifold he was selling with it.
The blower came with a 10% pulley set, a belt and an idler, so I already had a good start on the installation. The seller said he had run the blower 10% overdriven on a Chevy 350 but something had gone wrong. He was a bit vague as to just what he thought had gone wrong, but he did hint that excessive boost had something to do with it.
Looking at books, magazine articles and sizing charts for aftermarket blowers it seemed that a 6-71 7% under driven on a Chevy 350 was supposed to yield about 5 to 7psi of boost for use on the street. Since my 0.030" over wideblock was a bit less displacement at 324 cubic inches it seemed that going 10% under driven would be about correct. Seven pounds of boost on the 7.8:1 stock compression ratio would work out to an effective compression ratio around 11.5:1, which at the time was considered the most that could possibly be run on pump gas. Even before I got the blower mounted I was already thinking that I might want to go more like 15% under driven.
For a blower manifold I cut up a second Weiand four barrel intake for the wideblock. I just cut a big hole in the top of the manifold and fabricated a blower mount out of half inch aluminum plate with a quarter inch steel mounting plate bolted on top. When I tried to weld the aluminum pieces together with an oxy acetylene torch and special gas welding aluminum rod it only sort of worked. I got some substantial inch long tack welds done, but it also warped the intake manifold something awful. Feeling foolish for having ruined a perfectly good intake manifold I took the partially completed project to a welding shop where the guy buzzed beads to seal all the pieces together for just $20. With all that gas welding mess all over the manifold he did not even bother to give the standard line that welding might warp the pieces.
It took quite a bit of RTV silicone sealer to do it but I did manage to bolt the intake manifold onto the engine after elongating some of the mounting wholes to get the bolts to go in. Fabricating custom brackets to mount the alternator and power steering pump out farther and a custom adapter plate to put the Chevy blower drive on the Dodge went much more smoothly. With the new custom mounts smoothed out and spray painted to match the body the installation looked pretty nifty.
Not really knowing what I was doing with supercharging an engine I read everything I could find on the subject. The general recommendation was that a boost dependant timing mechanism was a really good idea. Not wanting to spend a bunch more money on custom electronics though I decided to give the blower a try just with what I had. What I did do was back off on the static timing setting by about 15 degrees of crankshaft rotation so that the starting and idling timing was right at top dead center. This left just the 25 degrees of crankshaft rotation of mechanical advance in the distributor for a total advance of 25 degrees. Of course I left the vacuum advance disconnected as well as that absolutly could never be made to work with the carburetors before a roots blower.
With two 750 cfm Holley "Street Avenger" four barrel carburetors atop the blower the setup did work quite well. The engine of course fired up easily even with no cranking advance, all I had to do was crack the throttle a bit while cranking and it burst to life. Idling and driving around at low speed the thing most obvious was the whine of the blower drive. The engine itself was much quieter with the timing backed off so far. Eerily quite in fact. And the vibration at 2,500 to 3,500RPM in third gear was totally gone.
At 1500 to 2,000RPM where the old Wideblock had previously been loud, harsh and pretty weak the blown engine was smoother and of course more powerful. When the throttle was cracked open just a bit at low engine speed there was considerably more power with no additional noise other than some "blowing" sounds.
Somehow I knew that getting a lot more power out of a gasoline engine at low engine speed was not possible, so I went very easy on the throttle at low engine speed. I revved the engine to over 3,000RPM before giving it any substantial amount of boost, and it really jumped to life when I did crack the throttle.
Opening the throttle just a bit at 3,000RPM there was again a lot of "blowing" sounds and only moderate amounts of additional power. Then at 5psi it lit off on late compression ignition and made a whole lot of power. Way more power than anyone would have expected from just 5psi of boost. And the power just kept building hard at higher engine speeds. By 6,000RPM at 7psi of boost it was pulling at probably something like 600hp. Silly useless amounts of power and the secondaries were only just the slightest bit cracked open.
I drove the truck around for a little while gingerly feathering the throttle and never allowing more than about 7psi of boost but it was obvious I needed different pulleys. At a speed shop that sold aftermarket 6-71 and 8-71 blowers I was just laughed out the door when I said I needed new pulleys for less boost. The salesman said that they did not even offer the 10% set I had, they only sold 5% and 7% pulley sets although he did also mention that 3% pulley sets might be available by special order.
I backed off on the static timing setting even a few more degrees to make darn sure it was after top dead center and let a bit more boost in at the higher engine speeds. With the later timing it was taking more like 6psi to start to make big power, and up at the higher engine speeds I gave it 9psi where it made even more power than before. I drove the truck for only a very short period of time like this (about 400 miles), and I sort of knew it was already done for. I knew that there was no way I was going to be able to continue to limit the boost using the throttle plates, and it seemed like a stupid situation anyway. Sucking hard on the throttle plates wasting drive power to deliver less boost than the blower would be able to deliver at an even lower drive power with the throttle plates wide open just seemed wrong. As wrong as it might have been it did however run quite well at 5 to 7psi of boost.
I should have tried harder to find a drive set with more reduction, but instead I just jumped down on it. I took a few runs at just a hair over 10psi and although the engine started to sound bad it did make even a bit more power. One of these runs was on the highway in third gear and the truck was going faster than I wanted to be on 35s on a two lane road so quickly it was unbelievable.
Probably the best thing I did with the blown engine was conquer the "big hill", a loose steep climb that I had never seen anything other than a dirt bike make it up before. It was something of a tough climb on the Husqvarna WMX 610, and trucks and jeeps just stopped at the bottom of the steepest section. I had tried many times to make the big hill with the normally aspirated 318, and although it was making enough power with the cam and four barrel it just did not have the right gear. In the lower gear it would not go fast enough, and in the higher gear it would bog and slow at the steepest section.
With the blower I selected the higher gear (second gear high range) and the truck blasted all the way up the hill faster and more easily than even the WMX 610 ever had.
The end of the blown Wideblock was the first time I opened the throttle plates all the way. I am pretty sure it was a shade over 12psi and it sounded horrible with all sorts of harsh new noises. The engine did not blow up and nothing broke, but when I took the oil pan off all of the rod bearings were totally kaput. Just chewed to smithereens. In that short time the bearings had simply failed and although many of the inserts had spun they were all still intact and had not come out of the rods. The rod journals on the crankshaft where also chewed up and incredibly rough.
Just to see what would happen I put a new set of rod bearing inserts on the chewed up crankshaft and drove the truck around slowly for a few minutes. The new inserts just got torn up though and when I took it apart again they also had spun.
I should have also tried locking down the distributor and running a fixed 5 or 10 degrees BTDC spark timing setting, but for some reason this just did not occur to me. At that time I really did not even know how a gasoline engine worked. I did however know enough to realize that the main problem was that I could not get a pulley set with more reduction.
I've still got the '61 Dodge, and I have sometimes thought about trying the blower again with some sort of custom pulleys to limit the boost to 5 or 7psi. The reason I have not done this though is the simple fact that it was too much power even at 5psi. There was just absolutely nothing to do with all of that power in a short bed four wheel drive. Climbing the big hill had been fun, but on the street it was just a ridiculous useless huge amount of power.
Of course the other option for too much boost is to lower the compression ratio. Traditionally most blown engines were 6:1, and that allowed considerably more boost on pump gas. The 10% under drive would have worked fine with a 6:1 compression ratio, even 13psi of boost would be an effective compression ratio of only about 11:1. At that much boost the effective compression ratio even ends up a bit less than expected on a poorly flowing parallel valve two valve per cylinder engine. Giving just a small 5psi boost flows a whole lot more air since the intake goes from a slight vacuum to a slight boost and the valves are plenty big. Going all the way up to 13psi of boost though means that there is going to be a substantial pressure differential at the intake valves, the cylinders are not going to fill with quite the full 13psi at high engine speed.
Probably the most interesting thing I learned from the blower project was how strong all of the stock Chrysler parts were. Even when the engine failed from excessive boost the stock type cast pistons did not break, the stock rods did not break, and the crankshaft did not break. Everything held in there just fine, but of course the lubricating film on the rod bearings just could not handle compression ignition occurring before top dead center. There are actually two interesting pieces of information here. First it is obvious from this that automotive engines have in fact been designed to be blower engines. All of the parts are plenty strong. The rods and crank in the 318 Wideblock are the same as was used in the later LA series engines, and even though they look very skimpy and small compared to the parts in an Early Hemi they are obviously monumentally strong. The other thing to note is how much difference there is between late compression ignition at 15 degrees ATDC and full compression ignition at 20 degrees BTDC. It is a world of difference, the difference between a smooth, efficient 600hp from the stock 318 Wideblock and blown rod bearings.
Another big reason I never did anything more with the '61 Dodge was the fuel consumption. After I had put 50,000 miles on the truck using it as my daily driver I realized that the thing had eaten $7000 worth of gasoline. That seemed like a lot, and with fuel prices on the rise there just seemed to be no use for all that power.
I have often thought about different engines I could put in the '61 Dodge, and the most likely candidate seems to be an Audi five cylinder with a blower. The 6-71 blower could be used with a 3:1 drive set, or a smaller Buick blower would be even more convenient because it would not require as much reduction on the drive set. The reason that roots blowers are desirable is that they are much easier to install and tune than a turbocharger on a mechanically controlled engine. Blowers have a nice smooth linear boost curve that makes it easy to get gasoline engines to run well over a wide range of engine speeds. Turbos on the other hand tend to have a peaky boost curve that is difficult to apply to a gasoline engine that needs to run over a wide range of engine speeds. Even with a waste gate to limit boost you end up with slightly falling boost levels at higher engine speeds, and this is just horribly difficult to deal with on a gasoline engine. The low 8.0:1 and 8.2:1 compression ratios of the old Audi five cylinder engines seem a perfect match for forced induction, and even though they have small 1.8 inch diameter rod bearing journals they were delivered from the factory with ratings as high as 280hp with a turbo. Just right for a big fast 4x4 with upgraded suspension.
Roots blowers do suck down some power and are generally considered less efficient than turbochargers, but my experience has been somewhat different. With the dual Holley four barrels and only a 10% under drive I was still able to get 12mpg out of the 318 in the '61 Dodge. Most of that difference was probably just the fact that the timing was backed off so far that it would not burn all the fuel under light loads. A boost dependant timing device certainly is required to get a blown engine to work well over a wide range of conditions.
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