Bonneville Comanche 4.9 build

[SIXPAK]

Silver, the trust plate is nothing more than a reinforced stock timing chain cover. Incorporated in this front side of the cover you thread the NEW reinforced front pice with a pusher bolt. That "snub" bolt I will call it holds a torrington thrust bearing and is on the same centerline of the cam bolt. You lightly machine the front of the cam bolt to accept the thrust bearing. Adjust it so it has a few thou and clearance and NO more cam walk.

[Plechtan]

I don't know about the Hesco setup, but i will ask Lee when i see him on Saturday. If you have a later block, or wanted to drill and tap the eariler block for the Jeep thrust plate, you could use the later style cam. I believe Clifford has cams available with the newer design. the older style cam gear locates on the OD of the front cam journal. the journal sticks out of the block about 1/8" . since the cam sprocket is bigger than the cam journal, it rubs on the front of the block preventing the cam from walking to the rear of the block. The pin on the front of the cam keeps it from moving foward. with the newer design the thrust plate is sandwiched between the cam and the pulley, similar to many V8 setups. I have never seen anybody use a thrust plate with an older cam.

[I6FAN]

What exactly is causing the harmonic at 5400 to 5600 rpm, or wherever it is? I think the biggest problem with the camshaft is that the innermost two cylinders, that fire 360 crank degrees apart has the respective cam lobes, for those two cylinders, 180 camshaft degrees apart. The intake lobe for cyl 3 is 180 camshaft degrees from intake of cyl 4, and the same with the exhausts. I'm imagining the center section of the camshaft reverberating back and forth with no journal between them, where the pump/dist. gear is to to support and dampen the movements. There is a cool video on youtube of a 4.7l stroker doing a dyno pull, and if you watch the water pump belt it does some pretty interesting things. I would like to see the timing chain at these engine speeds. If it does anything like this it wouldn't be hard to imagine the cam sprocket snap off at the end of the camshaft. A gilmer belt set-up would probably be a better set-up, and a gear drive would best that. Something I learned recently is that a chain n sprocket doesn't have a constant rpm; it changes faster to slower to faster with regard to the "pitch" of the set. A fluid damper on the end of the camshaft seems like that could have some benefit. The video is titled "Jeep 4.7 Stroker Turbo Dyno Pulls" (not sure how to post a link). Watch it!!!

[Plechtan]

Read this thread : http://www.jeepstrokers.com/forum/viewt ... ?f=5&t=391 There was another post with a link to a description of harmonics in general with inline 6 engines, i can find it, maybe sombody else can and post a link here.

[I6FAN]

Quite a bit of theories going on in that thread; 13 pages!

Plectan Wrote:
Now to get the 4" bore. I checked several blocks, and found that the 2000 and up blocks have thicker cylinder walls. the walls end up about .100 or so in the front and back of the bore, but will generally still have .250 of material on the thrust side.

I've heard the Renix era blocks have thick cyl walls. Have you investigated those as well? I'm also curious about the actual weight of the bare blocks from each era i.e. Renix, Cryco, NVH, & 2000+. I have presumptions about the evolution of this block (my opinion, might be bs???, but I know how big companies like this work$$$):

Renix- Was inherited from AMC with original design (4.2l)
91-95- Chrysler entered in and made a few "up-grades" probably started taking weight out, and someone got a cost savings bonus.
NVH- The factory that supplied Chrysler with their V-6's were desperately trying to get their "smooth" v-6 installed in Jeeps, launched a phony law suite-white
paper campaign on what was wrong with the I6.....Block was redesigned using FEA giving it a main superstructure while loosing weight in other areas
The lighter weight aided quicker warm-ups to combat higher emissions from a rich running, cold engine.
2000+- Enter the 0331 head (this baby was reeeeal light!) for an even quicker warm-up. And probably thicker cycls to aide the even lighter block giving it more
superstructure (yea EPA will get'em).
2006- Victory at last, we now have a common engine for our full line....only it's the v-6 we had been trying to get in there the last ten yrs.

Seriously, I'm just curious about the actual weight of the bare blocks from each era because I think the heaviest is probably the most rigid while the lightest-smartest goes down in history with the earlier 0331 head. I also keep hearing a rant about "higher nickel" iron. It's probably Grey Cast Iron, but does anyone know the specific grade, and if that changed during the years?

[Plechtan]

It might be better to put a post like this in the "stroker performance and tech" area rather than in a project build thread. It is off topic here. I really cannot say that more weight translates into more strength, what i do know is that the later blocks were designed to go be able to go to a 4" bore. the bore spacing on the Jeep engine is 4.38" so the maximum cylinder wall between cylinders would be .190 with a 4" bore, but that would not leave any room for water to circulate between the cylinders, So if we assume a minimum cylinder wall of .125 that would leave a space for water circulation of only .130", probably enough. The cylinder spacing on the Jeep I6 is the same as the ford 289 family. The 305 does have a 4" bore, so this cylinder spacing has be proven to work with a 4" bore. The thrust side of the cylinder (passenger side) is the most critical, and a thickness of 1/4" or more is desirable. I have not seen any blocks prior to 2000 that have enough material on the thrust side to give you a 1/4' thickness after being bored to 4"

[Plechtan]

To get back on topic, I now had the rotating assembly defined, and the issue of the oil pump and cam drive straightened out. so the next issuewoulb be the cam and valve train. The desktop Dyno showed that a solid roller cam would be the best choice. But guess what, nobody made a solid roller cam for a Jeep. I took a couple of cams and made a print for a cam blank. The lobe width is different between a 4.0, 258 and aftermarket cams. I went with a widest lobe between the 3. Now i had to find a machine shop to make the round lobe blanks. After the blanks are made, they have to be copper plated. Then the need the lobes roughed in. I used Camcraft Cams. I worked with Charles. He does not have a cnc grinder, so the choice of lobe profiles and lifts were limited. Lift was a big problem. The rear cam bearing is 2" ID so the overall diameter of the cam cannot exceed 2". That is one dimention. the other size you need is the base circle of the cam. The lift will determine the maximum base circle. For example if you want .7 lift and you have 1.6 rockers, ( .7 / 1.6 = .4375) then the difference between the od of the cam and the base circle would be the lift. So if the radius of the cam is 1" and the lobe height is .4375 the the maximum base circle would have a radius of (1- .4375 = .5625) or a diameter of 1.125" So the maximum core diameter would be 1.125 you want this number to be as big as possible so the cam will be more resistant to flex. One way to cheat is to install 3 of the #1 cam bearings. the #4 cam bearing is 2" the #3 is 2.010" the #2 is 2.020 and the #1 is 2.030 So if you put in the larger bearings in the front 3 bores your cam could be .030 larger. So 2.030" This would let you go .030 larger on the cam core diameter.

Anyway after the cam profile is roughed on to the cam blank, it is sent out for heat treating. the only surfaces that will be hardened will be were the copper coating has been ground off. the cam may warp during heat treat. after the cam is returned to the cam grinder, it may need to be straightned and the final profile ground on to it. Since i have had my cam made I have found that Bullet cams does have a CNC grinder and will work with round lobe blanks. Some of the other people i contacted like Crowler would only work with a hardened blank that only needed the final profile ground on it.

So now i had a Cam, I will continue wuth the rest of the valve train later.

[I6FAN]

My apologies for getting off-topic on your thread. I haven't seen very much real data like you provided for the cyl thickness, and thought you may have other info of the internal casting as well. Anyway, enjoy and have a safe, good trip to HESCO!

[Plechtan]

I still think you should post in the other area, I have had good luck posting things like this. What are you trying to do or find out? All the blocks are good, Barney Navarro got 650 hp out of an rambler motor in his indy car http://wps.com/AMC/Navarro-turbo-motor/index.html and recently JP magazine got 690 hp out of one. the blocks can take it. i would suggest a 200 and up block if you want a 4" bore, but the navarro motor was only about 180 cid

[Plechtan]

Dynoed the car today, Lee was great. Engine numbers, it looks like 443.8HP and around 410 ft/lbs of torque. The rear wheel numbers were 330.7 hp and about 310 ft/lbs. Curves look good. Peak hp was @ 5,900 rpm Peak torque was about 4,750, but the curve was basically flat from 4,000 to 5,500. I will post the dyno runs tomorrow.

[Plechtan]

Well we left Friday ( April 23rd) from Chicago and drove all day to Birmingham AL. the home town of Hesco ( Hurley Engine Service Company) Most of you probably know about Hesco, but if you don't just take a look at their web site http://www.hesco.us Lee Hurley has been involved with jeeps forever and has built many of the factory trucks and many of the engines that have won major off road races. He also supplies parts to Mopar Performance, the most famous is probably his EFI kit for the 258 Wranglers. If you want to get the most out of a Jeep inline 6, Lee is the guy to talk to.

2 years ago, i never heard of Hesco. But in September of 2008 i sent an email to several companies i found on the internet asking them about building an engine for a Land speed record truck. I got a few replies, but Lee's was the most interesting. He said " I already built a 4.0L for a land speed record jeep truck". I couldn't believe it, somebody had already done it. Our plan was to build a J truck with a 4.0L because the record was only 125 mph in that class. It was held by a 50's era Ford with a small v8. But Lee's email had peaked our interest, so we did research and found out that in 1985 Jeep set several land speed records with a Comanche and their "new" 4.0L engine. It was really a stunt to show off the power of their new motor.

We did quite a bit of research, we even were able to go to the Chrysler Archives and inspect the 1985 truck and take pictures. The truck had the drivers name on the door, and we were able to hunt him down. I corresponded with him finding out things about the project and problems they had with the truck. Because of the history we decided to go with a comanche instead of a J truck. At the time we thought the class was open. We later found out that a record of 145mph had been set in August of 2008 by an S10 pickup.

But back to Lee, I had requested that Hesco build me a motor, and the inital quoted price was about $12,000. This was out of my price range, but i did decide to use one of Lee's aluminum heads. At first they refused to modify their head, but after talking to Lee i was able to get them to install larger valves and make some other modifications. Lee has supported the project from the beginning and has always helped out with advice.

2010-04-24-09.35.56.jpg

We arrived at Hesco 8:00 am on Saturday, Lee was waiting. We got the car unloaded and into the Dyno bay. We did our first run, and it came in at about 290 HP at the wheels, and about 290 ft/lbs of torque. The graph below shows final engine numbers. The dyno measures coast down and calculates drive train losses to turn wheel numbers into engine numbers. The final wheel numbers were 331hp and 310 ft/lbs of torque. Around 10:am we were doing a pull, and we lost a cylinder. OMG I couldn't believe it. to come all this way and lose a cylinder. we unpluged the injector with the engine running, and no change. We did not have allot of blow by, so the cylinder was probably ok. Bad injector? Bad coil? We put a timing light on the coil, and it fired. so we had spark. We plugged a "noid" into the injector connector, and the light showed that the injector was getting a command to fire. We had compression, fuel, spark, what else did we need? Maybe the injector was bad, but looking at the o2 sensor we could see that it was rich. So we probably had fuel. One thing left to try. a new spark plug. That was it! we were back in business. We did about 20 pulls and managed to heat 10,000 gallons of water to over 140 deg. F. We did have some problem with a leaky valve cover gasket, ut everything else went great. We knocked of at about 5:30 pm then went out to dinner to celebrate. Sunday morning we started the 750 mile ride home with smiles on our faces. The next test will be at Maxton NC on May 22, 2010. We will run a standing mile at the ECTA trials.

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