M151 Rock Buggy Build

feel the need to change or modify your mutt? This is the place to discuss it.

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Re: M151 Rock Buggy Build

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Re: M151 Rock Buggy Build

Postby muttman » March 15th, 2011, 8:16 am

Horst wrote:I am eagerly waiting how the little 151 engine will do in that beast...


The engine ran great, with the propane it has instant throttle response, and will lug down to just a couple hundred rpm before stalling. Of course more power would be nice, but I would probably say that even if it had a V8 :D . It had enough power to launch me up some near vertical ledges, and smoke all 4 tires.

One question: I noticed that the oil pressure would start out around 40 psi, but as the engine warmed up it would drop to about 10-15 psi, which seems low to me. I'm running shell SAE 30, and the readings came from a new VDO mechanical oil pressure gauge with the capillary tube installed at the base of the oil filter towards the rear. Should I be concerned?
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Re: M151 Rock Buggy Build

Postby Horst » March 15th, 2011, 10:29 am

Oh, very good then. I for sure like the power/torque band of the engine.

Concerning oil pressure I believe you have a slightly worn engine assuming you talk about the pressure at idle. (if that pressure is at load, it is really worn).
Horst

1972 USMC M151A2 w/ROPS and M416
1962 M201 and trailer
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Re: M151 Rock Buggy Build

Postby rickf » March 15th, 2011, 11:31 am

Remember, if you are going vertical there is a point where the oil will run away from the pick-up and you will be running dry. Will not take long at all to wipe out bearings.

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Re: M151 Rock Buggy Build

Postby muttman » March 16th, 2011, 12:00 am

Horst wrote:Oh, very good then. I for sure like the power/torque band of the engine.

Concerning oil pressure I believe you have a slightly worn engine assuming you talk about the pressure at idle. (if that pressure is at load, it is really worn).


The pressure does not change at all with engine load or rpm; it just slowly drops over about 15-20 minutes.
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Re: M151 Rock Buggy Build

Postby muttman » March 16th, 2011, 12:04 am

rickf wrote:Remember, if you are going vertical there is a point where the oil will run away from the pick-up and you will be running dry. Will not take long at all to wipe out bearings.

Rick



I understand what you are saying, but the pick-up is in a good location and I never saw a pressure drop during steep climbs/drops. Also, after I stop and let it cool down, when restarted, the pressure is back up to 40 psi.
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Re: M151 Rock Buggy Build

Postby rickf » March 16th, 2011, 6:32 am

Sounds like a worn engine, If it were a small block Chevy I would say the drainback holes are plugged but there would have to be a massive amount of sludge to do that here and I have never seen a sludged mutt engine. Try going to a 40 or even a 50 weight oil and see if that changes the reading. If so you have worn bearings. Does not always have to be rods and mains, cam bearings will drop pressure also but if they are worn the others will be also.

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Re: M151 Rock Buggy Build

Postby MaxTran » March 18th, 2011, 8:20 am

Jeep No.1 :D
www.saigonjeep.com

www.jeepvietnam.com
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Re: M151 Rock Buggy Build

Postby muttman » March 28th, 2011, 9:14 pm

I didn't like the way the tires performed on the shakedown run, so like everything else, I decided to modify them.

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I heated up a wood chisel with a propane torch to cut every other lug off. I used a grinder with a wire wheel to clean them up; it was messy.

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Re: M151 Rock Buggy Build

Postby armybuck041 » March 29th, 2011, 6:37 am

Crazy... Looks great.

This used to be my old Hobby (Rock Crawling), but I still can appreciate some nice fab work when I see it. Its funny how it all starts out small and by the end of it there are only a few parts left from the original vehicle.

Mine was a 97 Jeep TJ. Most of the mods were the run of the mill JeepsUnlimited (at first) and then POR Forum fare:
Circa 2002 (The beginning):
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Circa 2005:
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Circs 2008 (The last week before I sold it):
Image

What I find interesting is that you retained the Powerpack. Reason I mention it is not the Engine, but the Tranny/Transfer Case. They are Puny to say the least. I remember spending tons of cash first upgrading my NP231 to a Fixed Yoke, then a 32 Spline Fixed Yoke, then 2WD Low, then tossing it completely and getting Dana 300, Flip Kit, Twin Stick, 32 Spline Kit........ Seemed like the never ending quest for a bigger and better Case. My good friend is now running a STAK.

Either way, keep on MUTTin... It appears the DOM Tube is slowly replacing sheetmetal :)
Scott Bentley
M151A2 CDN, SN 43813, CFR 74-09195
Gone but never forgotten: Sgt Shane Stachnik, Killed in Action on 3 Sept 2006, Panjwaii, Afghanistan
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Re: M151 Rock Buggy Build

Postby muttman » March 29th, 2011, 8:12 am

armybuck041 wrote:Crazy... Looks great.

This used to be my old Hobby (Rock Crawling), but I still can appreciate some nice fab work when I see it. Its funny how it all starts out small and by the end of it there are only a few parts left from the original vehicle.

Mine was a 97 Jeep TJ. Most of the mods were the run of the mill JeepsUnlimited (at first) and then POR Forum fare:

What I find interesting is that you retained the Powerpack. Reason I mention it is not the Engine, but the Tranny/Transfer Case. They are Puny to say the least. I remember spending tons of cash first upgrading my NP231 to a Fixed Yoke, then a 32 Spline Fixed Yoke, then 2WD Low, then tossing it completely and getting Dana 300, Flip Kit, Twin Stick, 32 Spline Kit........ Seemed like the never ending quest for a bigger and better Case. My good friend is now running a STAK.

Either way, keep on MUTTin... It appears the DOM Tube is slowly replacing sheetmetal :)




Thanks, I've been trying to finish this project for too long.

I also had a '97 TJ back in high school, but I grew up in S. E. Texas where there is only mud, so it wasn't seriously modified like yours. Just 6" lift and 33" x 15.5" Swamper SX's; it was a clean, pretty boy jeep (back before I knew better :D ).

The main reason I kept the powerpack is I already had it, and I honestly figured it would be the weak link. However, after beating it mercilessly at Crusher Ridge a couple weeks ago and breaking a Dana 44 stub shaft, I'm beginning to think the little powerpack might somehow hold up. But, if it breaks, I have a line on some good condition powerpacks for dirt cheap, ha ha.

The lack of low range is the next problem I need to address. It has the power to smoke all 4 tires on rock with 5.43 gears in the axles, but there is zero finesse - pretty much just pour on the coal and hope for the best. There is no room for a traditional t-case without giving up a bunch of ground clearance, so I'm planning on building a 609 front axle. It will be a rear ford 9" with Dana 60 knuckles and shafts, which will allow me to go down to 7.33 gears, and the differential will be centered to match the front output on the transmission.

I can't afford DOM, it's all 1.25" SCH40 poop pipe bent with a Harbor Freight kinker. :mrgreen:
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Re: M151 Rock Buggy Build

Postby rickf » March 29th, 2011, 8:43 am

Will that pipe have the structural strength for a serious rollover? I would be afraid of not having the impact resistance of DOM. I was wondering about the lack of low range. 7.33 gears are going to have a pinion the size of a pencil!!!! What you need are portal axles, NOT CHEAP!

Rick
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Re: M151 Rock Buggy Build

Postby armybuck041 » March 29th, 2011, 9:15 am

rickf wrote:Will that pipe have the structural strength for a serious rollover? I would be afraid of not having the impact resistance of DOM. I was wondering about the lack of low range. 7.33 gears are going to have a pinion the size of a pencil!!!! What you need are portal axles, NOT CHEAP!

Rick


I know DOM vs Sch Pipe was a big debate on POR back when I was beginning to digress from that sport. There was some interesting engineering info out there on both. I'm not sure how that all evolved, but IIRC, Sch Pipe wasn't really all that bad if designed, used, and welded correctly.

Thats why I find keeping the "no-low" T-Case interesting. Low Gearing was the rage and some of the Cases (Atlas/STAK etc) were all pimping lower and lower gears (4:1, then 5:1, then 10:1.......), then add an NV4500 with a Granny 1st.

Trying to "Keep up with the Jones" is what finally convinced me to leave the hobby. It got to the point where serious mods only got one or two good runs before something else needed to be updated for the next coolest idea. My buddy and I joked that each good wheeling trip worked out to costing an average of $3000 in mods. Fixing breakage probably would have been cheaper in retrospect. Nearly bankrupted me. Funny going over to the MV side where the whole goal is to recreate the original.

Thats why I like this build. Its very non-conformist. A case of using what you have on hand to the best of your abilities. Replacing the lack of Low Gears for more Skinny Pedal :D
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Re: M151 Rock Buggy Build

Postby muttman » April 14th, 2011, 3:36 pm

The last trip offroad was awesome. I showed up a bunch of V8 buggies and jeeps with 42-44" tires; they could go everywhere I could.... but it took them 10 times longer :mrgreen: . The cut tires worked great, I could tell a huge difference, have to do the fronts now. I also got it registered and insured, and I have been driving it quite a bit on the road - gotta love AL.

I flogged the Mutt relentlessly all day; I literally couldn't have been harder on it. I was catching air, crashing down on rocks, and bouncing off trees.... wide open assaults on the difficult trails, which was basically all of them. I can't believe the powerpack stood up to the abuse I dished out; I had to repeatedly rev it until the valves were floating, dump the clutch, and hammer it to squeeze enough juice out of her to bash my way up the steep sections. She just asked for more.

Here's my buddy with whats left of his Bronco. I remember when he bought it bone stock.

Image


Here's a couple of the rigs we wheeled with; they both suffered breakage. The green/silver one destroyed a front Dana 60 Lockright locker and a rear driveshaft, and the red/black one had ignition problems and broke a front Dana 60 axle shaft.

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The guy with the Rockwell buggy in the background drives it like he hates it. It is hysterically funny to watch him beat on it.

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One of the harder sections. Photos don't do it justice.

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Of course, when you beat your rig like I do, there will be breakage; on the last trail of the day I grenaded the front left Milemarker hub.

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This is all that's left of my front bumpstop.

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Upon closer inspection, I found I had destroyed a rear driveshaft u-joint.

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The set screw on the front transmission yoke kept backing out, so I modified the slip spline on the driveshaft to accept this spring. Hopefully this will keep the yoke from slipping out of the transmission and draining all the oil.

Image



Here's some of the rock rash. The driveshaft protection is doing it's job.

Image

Image
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Re: M151 Rock Buggy Build

Postby rickf » April 15th, 2011, 8:50 am

I have found that although I have close to 400 HP in my CJ-7 that when doing rocks or steep climbs it is easier and less likely to break things if I just take it easy. Now mud..............AIR IT OUT!

Rick
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04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: M151 Rock Buggy Build

Postby muttman » April 15th, 2011, 10:02 pm

rickf wrote:I have found that although I have close to 400 HP in my CJ-7 that when doing rocks or steep climbs it is easier and less likely to break things if I just take it easy. Now mud..............AIR IT OUT!

Rick


The park we were riding at, Crusher Ridge, has extremely difficult terrain, especially when wet. If we wanted to take it easy and not risk breakage, we couldn't get off the access trails. Everyone who rides Crusher Ridge breaks; the black/red jeep and the silver/green jeep built with top shelf parts were breaking, it's just part of it. Even the guy with the Rockwell buggy has broken 2.5 ton axle shafts there with a tired 350.
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