Newb Question- WHAT DO I NEED??

[Blown7]

It's all relative. IF you gave me a choice between 1100 hp at 7000 rpm or 450 ft lbs of torque at 800 rpm.. bet ya can't guess which one I want..in my jeep.. in a gremmy or something i'll take the other.

Why not both??
Jeff

[Holeshot]

Oh.....crawling ONLY again......I guess I just have FAST of the brain!!! Comes from the love of speed, I guess. I just LOVE to blow away the off-brands. Never did learn how to go slow, damn it.

I guess I don't understand why it is that you guys need so much torque for going less than 1 MPH.

My first vehicle was a tired '66 Scout, 4-cylinder, with a big plow. I could plow so much snow that it would spill over the top of the blade. Never got stuck & never had a problem pushing snow as far & high as needed, even in the BLIZZARD of '78!!! In Michigan, we had drifts of over six feet & snow pushed to 10+ feet high, in some cases. That thing wouldn't even spin the tires in snow!!!

No need for big numbers. Probably was around 80 HP & 100 ft/lbs of torque, eh?

Amazing what gearing does for torque multiplication, is it not?

[Holeshot]

Is this thread strictly about rock crawlers?

It would seem to me that the above dyno example would be super for everything BUT crawlers.

What is the hot tranny setup for crawlers. Seems to be stick, since people are talking about driving at 800 RPM.

The dyno software does not chart below 2000 RPM, but I would have to say that if you have nearly 400 ft/lbs of tq at 2000 RPM, it would not be that much less at 1000 RPM. If you were using automatic trans, you would just be getting stall when the torque comes on like gangbusters. The 1100 CFM carb could be traded down for an 850 with very little HP reduction.

My dad was a lifelong certified master mechanic, working for Hudson, Nash, Rambler, AMC, then starting his own shop. I started there at 11 or 12, was THE first freshman at my high school (600 students) to EVER be promoted to AutoII, went to college for Auto Mechanics (#1 in my class), became certified as a Master Mechanic in Auto Repair + Auto Tune and Performance, then switched to motorcycles in time for the multi-valved DOHCs, becoming a certified Honda & Suzuki mechanic for 5~10 years & Service Manager for around the next 15~20 years, with a job as Hovercraft R&D + flight instructor training squeezed in between, & a Computer Programming degree in my spare time. I was taught that putting a load on an engine with standard trans at idle & just above, would hammer (destroy) the bearings, which makes a bunch of sense, since you would only be having 10 psi or less of oil pressure (at the pump!!!)

Seems like the hot setup for crawling would be an auto trans modified to not roll backwards when the throttle was lifted.

[82Waggy]

Holeshot,

Have you actually run the engine shown in your sim? I'd be curious to see what it does in reality.

The problem with most if not all of those sims is that they do not predict detonation, induction flow problems, or scavenging circumstances very well.

With such big valve overlap, huge carb, open plenum intake, and excessive dynamic compression trying to run on pump gas, I'd be surprised if it idled reliably below 900-1000rpm and would predict that the actual torque curve would be much more narrow and much lower output than indicated at the bottom end. In fact, I would predict that power would be almost unusable below 3000rpm and that it would need a 3500 or higher stall converter if an auto tranny was used.

Having said all that, it may be just fine at the strip if launching at high RPM - assuming it would not ping itself to death with that dynamic compression ratio of 9:1 or more. DCR of less than 8:1 is generally considered the limit for gasoline.

[Holeshot]

Please investigate Dyno2000, it is well agreed upon that it is within 10% of real dyno results.

As far as CR goes, the AM design is very much detonation safe and can be run up to 11.5 on pump gas, when built correctly!!! Search "Norm Brandes AMC"

As far as the "huge carb" theory, I have run 1320 CFM (2x660 CFM) on top af my UltraRam on the street quite a bit and it was WAY more responsive than the Torker/850DP combination on my 390!!! Left the line like a stocker. The AM engines are way power friendly and an 850DP can be considered minimal on 360 & up engines with bolt-ons. Even AMC sold Holley 950 three-bbls (no y carbs offered) to go on the Edelbrock R4Bs they sold!!!

Sometimes experience trumps theory.

Besides that, this thread was on an engine design for "wheeling", not "crawling". I know of a lot of trails around Michigan where the 572 guys with 2x4s blow the windshields out of the Jeeps with meek 360s. There's plenty of wide open places where they can get several cars wide & pile mud, rocks & gravel upon the loser's hoods!!!

[Goose]

Nahh fast is fine.. but the part you dont get is..what you just explained about the old scout.. or a flat fender.. If I dont need to spend 5 grand on a n engine..why would I?? 'I am not just a crawler.. but I dont do the mud drags either.. and all of my Jeeps are 200,000 mile plus daily drivers..If a guy is following you with a four banger powered yj and going where you go.. which is better? the answer? neither.. different strokes for different folks. A friend I wheel with has an engine and philosphy much as you do.. the problem? he has a very fast street jeep...STREET Jeep?? yep.. off road it's a P.O.S. over carbbed over cammed every single time we go out..it;s him we are waiting for, cause everytime we have to go up something steep or out on a shelf it loads up and stalls.. at 9500' above sea level..then its loaded up and flooded and a pain to start.. his high stall converter over heats the tranny cause it never locks up and watching him try to finesse something technical? It's sad.. he has great wheelspeed but dick for traction. I can idle over stuff he cant get through at full throttle..

But really the problem here is this.. a guy posts "I am a newbie I want to build my jeep a little but I still gotta drive it to work and raise a family" and you start telling the guy how to build 600 hp and dump 5 grand in a motor thats gonna get 4 mpg and not start when the weather goes bad.. thats not what the guy asked for.. or wants and thats how come you me an waggy spend so much time talking about this.. Dude I am sure you could out build me anyday of the week.. but that isnt the point..

[Creepycj5]

I use my jeep just like bam bam and also building a 360.

What you want is to be able to have the clutch fully out and have enough power to climp over logs, rocks half the size of the tires, etc, and not have the engine dropping rpms and loosing power. You also want to be able to do all that at idle speed or alittle above so you arent bouncing all over and also breaking or bending parts.

Low gears will do this with any engine, but it is nice to have an engine built for that rpm range. From reading this post, I also think the high hp engine would be terrible. The gas consumption, reliability, and over all unused power.

Im looking at dropping in a cam alittle bigger than stock, xe256h or an engle cam, 5054. Also thinking about using the stock cam.

If you want to save your money, and the stock cam is still within spec, I would just use that cam. I have a friend using a stock cam in a 360 for wheeling and it does great and has more than enough power on the trail, and quite a bit on the street for a jeep as well. Its works well enough I am also considering keeping the stock cam.

[82Waggy]

Sorry Holeshot, but Desktop Dyno is not going to accurately model three dimensional fluid dynamics for 79.95. It MAY be within 10% in cases where valve overlap and such are somewhat "normal", but there is no way it can accurately predict scavenging, exhaust backpressure, or how much cross feed of exhaust and induction dilution you are getting between cylinders every 90 degrees with an open plenum manifold. At best it will allow you to see trends between different conditions but it is up to you to decide if what you have input is realistic.

For that matter, running on a real dyno may yield very misleading results when you place your large overlap cammed engine into a street vehicle with a muffler and wonder where all that recorded power went now that you have some exhaust backpressure to fowl up everything.

AMC's detonation resistant? Plenty of stock CR AMC's pinging around to disprove that idea. What is it about an AMC that would make it detonation resistant compared to other makes? AMC's have some of the worst quench and piston head styles there are in stock form. As goose said, put that high CR engine under a load when climbing a hill and see what happens.

If there is one place to improve on an AMC, it is quench.

[Holeshot]

The pinging AMCs are caused by WAY over .045" PTHC. And, yes, AMC pistons suck!!! That's why I ALWAYS say to get forged flattops!!! You SHOULD have known that by now!!!

[82Waggy]

Yes Holeshot.

Custom JE pistons in my zero deck 390. KB 354's in my 401. .043 to .045 quench and dynamic compression ratios below 8:1 in both.