difference between 71 and the 72. and an idea.

hey guys, i hope everyone is doing well.
i still havent started putting the turbo motor in my 68.
i am thinking i might drop back to the odd fire heads for the smaller intake runners, add epoxy to the intake of the grand national motor to line up with the small port heads and keep the torque. when i need to pass, the turbo will help that, but when i am crawling, i have the small runner for velocity.

i am also thinking of going with the odd fire flywheel to help crawling.

there is another delimah i am debating tho and the reason for the post.
i want to do technical crawling. i have the holbrooks for the v6 and am getting some good 33's and going with the 4.27" as in my bio.
that should give me a good foundation. but i want to go lower in the gear range. below tera gears. i have looked into double xfer cases and stuff like that, but again, its a 68. i like the passenger side drop and its just too short for adding all that.

then the idea struck me. i "think" the 71 is really close to the 72 except with the extension of the frame when AMc bought it. the motor towers were set for the strait 6. if i were to put my d44 in the rear of the 72, my d30 in the front (it all should bolt right in, correct?) and put the holbrooks on it instead, then run the d18 instead of the d20 and keep it all passenger drop, i should be able to run the klune underdrive in front of my d18, then sm420 all attached to the build v6. instead of going backwards with everything, i can just extend the drivetrain into the new dog house. it might make my tranny gear shifter sit forward some, i would have to weld in the towers from the 68 for placement, but it "should" do well in this configuration, right?
the 72+ would give me longer wheel base, still look factory (body) and give me tons of gearing options. fuel injected v6 with odd fire torque and flywheel, plus thumb throttle will make angles easier so i can concentrate on spotter and my 2 feet.

what i need to know if how much difference between the tubs, frame and grill are between the 2 years. i know the hood and fenders are longer, and from what i have seen, the soft tops and whatnot between the years interchange, so i am lead to believe, they only lengthened the frame, hood and fenders. if thats the case, when i finally get time, i can pick up a 72+ frame and axles, setup the spring changes and bolt up the drive train for placement. then drop the block in and weld mounts.

this lighter v6 should help, plus gears and wheel base.

being disabled, i hurt my damn back and knees everytime i get out on the 77 ford (extended cab F350 on 38"s) or my jeep, so i only want to build this once. thats why i keep researching whats going on.
some folks say that 74:1 is low enough (sm420, d18, 4.27), but i had this jeep, plus an 84 gmc with a 350, sm465 and descent gears and it wasnt anywhere NEAR slow enough for what i am looking for.

does this sound like a solid buggy? am i missing anything? ideas?
thanx in advance
rowdy

 

I just don't get it unless this is also going to be a road jeep.
Why not simply reduce the final drive ratio ?
You can go as low as 120 to 1 crawl ratio with SM 420, Terra low 3.15 and 5.38 FDR

 

yeah, its going to be a street jeep. that i can take off road through like the moab, los cruses or globe. i dont want a dedicated off road beast, just a descent appearing jeep with gears ad suspension i can take into some wicked places and suprise people.
its to be s "stock appearing" jeep with great capabilities.

 

Just my opinion here, so don't anyone get mad but....

I think the turbo is only good for the road unless you need to sling lots of sand and mud.
Adding a turbo will only detract from simplicity and reliability when way outback.
If you want more power then keep it simple by installing a larger discplacement engine.
Remember engine selection is the main decision to make after model selection.
For more ideas, read one of my incompleted articles here: http://z4.invisionfree.com/CJ3B_Bulletin_Board/index.php?showtopic=2591

4.27 final drive ratio {FDR} with O.D. yeilds a very high compound final drive ratio of 3.20
I suggest no higher than 4.89 FDR with .75 O.D. which yeilds a very usable 3.66 compound FDR.
4.89 FDR helps to lower the "crawl ratio" to very capable levels.
Add a 3.15 Tera Low kit and the "crawl ratio" becomes excellent (dependant on transmission that's selected).
Besides 3.15 transfer reduction is very much in syncronization with typical transmission "take off ratios".
With 3.15 reduction you don't have "duplicate" gearing when you shift from high to low transfer range.
3.15 transfer reduction is virtually perfect.

Remember the early vintage stock standard CJ's don't handle well at speeds over 65 MPH.
The relatively poor high speed handling can be partly overcome with corrected suspension and steering.
In my opinion longer intermediate CJ wheelbase is a plus for on-road use but it detracts from the turning arc and central ground clearance when off-road.

 

My first thought would be that it's much easier to go with a lower R & P.

I've got the V6/d18/sm420 and 4:11's for a final around 70 to 1. Low enough for a versatile trail rig but not technical rocks. Switching to 4:88's would be too low for me but maybe just right for you. I don't see the point of going lower than 100 to 1.

It's difficult but if you want more capability you could build towards 35 inch tires without too much lift. Also a difficult build but I think it would get you farther into the extreme wheeling locations. Probably would require something stronger than a dana 30 front.

Just my opinions.

 

good points. again, the turbo is for passing and accelerating (not a maniac, but i have almost been killed when my jeep fell on its face. carb was bad, points distrbutor was rounded and the points not operating correctly and a few other things. i have since fixed them).
another reason for the turbo motor is that its fuel injected, and i have everything to wire it in and make it run except the fuel pump.

dropping the ring gear would mean over all lower gear and i still want it close to "factory" ratio. for the 33" tire, thats around 4.27 from the charts i have seen.
i deffinately see your point about compunding gears and duplicating them. the 3.15 is an attractive option with the 4.27 and 7.05 tranny. that would be 94:1. right now, i have 3.73, 2.46 and the 7.05 (not running of course). thats almost a 25% lower ratio offset by 33's.

i knew about the longer wheel base issues, but i didnt know if the 5.5" (or close) would change much in navigating. i do like the short wheel base, but they tend to roll when climbing water falls or up steep inclines (from what i have been told and seen. i havent rolled mine yet).

i dont want to double up on gears, and the tera setup is much cheeper. plus, i can get the OD at the same time and save on the main gear.

the comment made about more cubes. i have a buick 350 i could just rebuild and bolt right in. i could take the pistons out of the odd fire and buy 2 more and throw em in the 350. ad a leaf to the front suspension, but now i am back to carb and pulling more gas than the fi 3.8. with the turbo, itll generate a tad more heat due to restriction, but i have a good radiator (better than factory) and itll only give power when i need it (spooling above 2200 or so). and with the thumb throttle, i wont be bouncing off the skinny pedal (spool on demand only).

i could buy the OD and tera low and throw it all in my d20 heavier case for durability for the same price or cheeper as the klune V. i think i will stay wth the shorter jeep.
anyone know where i can get a rear drive shaft? i thought i lost the front and bought another from a great guy on here, but when i took it outside to measure, its was the same as what i had. so, i guess i lost the rear shaft..lol.
also need 4.27 gears. d44/carrier and d30.

i will prolly start this after i get my 77 mud truck going again. the river is calling...cat fish!

 

The turbo does nothing at low rpms, therefore in my mind it is not much of an offroad improvement.
It's certainly not a crawling improvement.
So you must ask yourself... Does the engine really need extra power at spool velocity ?
Engine torque output at idle velocity is the primary crawling consideration as I will show.
And I believe that an engine can potentially produce too much (unused) torque.
That is why we strive for the complete synchronous system.

But yes, running fuel injectors certainly merits consideration.
Besides the steep incline advantages the use of fuel injection can potentially decrease fuel consumption.

AKCJ is basically correct about the crawl ratio.
With super low crawl ratios one eventually encounters THE POINT OF NO RETURN.
Not to be confused with the music of KANSAS. http://www.youtube.com/watch?v=o-R8gHj_7v8

The CRAWL RATIO POINT OF NO RETURN is actually dependant upon two factors.
Human reaction time, and engine torque output at idle velocity.

I figure it will do me no good to travel at speeds of less than 50 feet per minute.
A simple test proves that statement.
Try walking the slowest possible speed that you believe is sensable for offroad.
How far did you travel in that 1 minute of lapsed time ?
Repeat the test 3 times for accuracy.
I determined that 50 feet per minute is a very slow pace that allows ample reaction time.
That is what I call the CONTROL POINT OF NO RETURN.

With 31" tires the speed of 50 ft per minute is achieved with engine at idle (600 rpm) and a crawl ratio of 100 to 1.
So in my mind 100 to 1 crawl ratio is the CONTROL POINT OF NO RETURN.
Adjust the 100 to 1 crawl ratio for other tire diameters.

The FULL GRADABILITY CRAWL RATIO allows a specific engine to theoretically climb a 100% grade (45* angle ) at idle RPM.
There is yet another point of no return defined as the FULL GRADABILITY POINT OF NO RETURN.
The FULL GRADABILITY POINT OF NO RETURN is relative to selected engine torque at idle velocity.
In other words a Hurricane engine could potentially benefit from speeds below 50 ft per minute because of it's low power output.
I see no advantage to installing any engine smaller or larger than is required to climb 100% grade at idle RPM at or near 100 to 1 crawl ratio.

By the way 3.73 is the factory FDR for Dauntless 225 CJ's and 4.89 FDR was a factory option.
Installing 4.89 with .75 O.D. essentailly priovides both the standard and optional FDR's for Dauntless powered CJ's.

 

Interesting post :

Phalanxx : Your wish to use odd fire heads on a later even fire turbo motor will not work without extensive modifications..........first the odd fire oiling system to the overhead is through a port in the block and into the head to the rockers, the even fire feeds the overhead from the front. Second the water ports in the heads do not match up between the even fire block and odd fire heads and although they could be welded up , I ask why? The later tall port heads off a 78-79 3.8 Buick casting #8445 are far superior than the old odd fire head for flow and port speed.

You also make mention about using the heavy flywheel but also desire the need for passing speed...........Turbo technology has come along way since the Grand National motors of the late 1970's , but in its stock form the spool time coupled with a heavy flywheel will kill your acceleration.

Your turbo motor would far better respond with a 30 lb flywheel and with the use of a low gear in first like a 6:32 or 7:1 and a suitable crawl ratio. I doubt you'll ever miss the "motion induced related torque" that a heavy flywheel brings along as in reality the heavy wheel just adds "inertia" as it spins and is then loaded.........a great tool to gap or bridge the odd firing sequence of the early odd-fire motors but in some cases a penalty to accelerate the extra weight.

Turbo's as Ken mentioned don't really do well in a crawling environment at low RPM's without having the ability to spool the motor and make some power.............an Automatic transmission would be a better choice in that case.

The ratios that Ken has pointed out I think are spot on..........Be it 6:32 in low through a 2.46 or 3.15 Transfer case and a 25% Overdrive with 4.88's in the back makes a nice package with 33 inch tires.
I think a 75:1 or maybe up to 85 -90:1 CR is more than capable. At around a foot per second @ 700 Rpm's will do a good job almost anywhere............and I used anywhere because it really is hard to have a great road vehicle and also a capable technical crawler...........somewhere in between is where we all would like to be.
Good luck with your project!

 

i have a 78 small port even fire engine that i found a couple years ago. so, in a sense, i have the odd fire heads on the even fire block but from the factory. i thought the intake would bolt up and all i had to do was epoxy the intake to match the heads. and that would give me SFI, small ports and a turbo. smaller ports for the rocks and if i need, spool it up for mud, sand or passing.
its a thought. im not afraid of porting or epoxy. i love learning.

i made this other post, hit enter and it vanished....

anyway, i am trying to keep the rpm at 2100 at 65 with an od and 33". that leaves right around 4.27 gears. once geared down, in granny and maybe tera low, it would be 94:1 and thats about the max u guys said. i have 74:1 now, but when i get the 33"s on, the gears will be too high for street. need to tone em down or they will lug big time!.

i have to keep the revs below 2200ish so i dont spool. =)

so you guys are suggesting stay with the tall port heads even though the small ports have better torque? i kinda thought building small ports with the heavy flywheel would interest alot of odd fire guys here. i was thinking along the lines of a diesel engine. small runners and a turbo to wind it up.

the turbo is like a pto winch. you dont use it everyday, but when u need, its invaluable.
lets see if this one will post...

 

"4.27 final drive ratio {FDR} with O.D. yeilds a very high compound final drive ratio of 3.20"

"i have a buick 350 i could just rebuild and bolt right in"

A factory setup for a 1969 Jeep Wagoner = 350 V8, auto and 3.21 gears. You are on the right track



"The turbo does nothing at low rpms, therefore in my mind it is not much of an offroad improvement."

A turbo can be setup to produce high output at very low RPM's. That is really just a generalization that does not necessarily apply since this turbo could be setup for purpose. I think the problem is, turbo is generally used to get better MPG and it cannot do both MPG and low RPM power. I have a feeling the OP wants both, it will not happen.

Personally I think a supercharger or high output engine would be easier but it is a matter of choice.

I am seeing a lot said about both the turbo and crawl ratio - here is a thought on that. The Unimog is widely considered one of the ultimate off road vehicles. From the factory the Unimog can be ordered with both Turbo and a 4000:1 crawl ratio using the “Cascade” auxiliary gearboxes. It is worth mentioning that the recommended crawl ratio is indeed 100:1 as mentioned in the thread

 

Phalanxx,

There is an obvious difference between an odd fire head as mentioned earlier versus a later even fire head.........not only in port design but combustion chamber volume and shape notwithstanding the later head was designed around smog requirements and lower compression. Using a smaller 78 head as you now have suggested is fine except without any flow numbers or testing it would be anyone's guess how the motor would respond to it.
Here is what I do know..........a good flowing head even at low RPM's will develop more power at that given RPM since in theory it is bringing more fuel to the combustion chamber each cycle. And since torque is an equation of Horsepower at a given RPM more power & torque would then be available.........Not to confuse all this with the need for proper timing both valve and Ignition and compression to burn the fuel.
And with a turbo of that vintage at full spool RPM 's only developing about 12 lbs. of boost and at Idle maybe only 0-1 lbs again the Turbo may be of no consequence.
Sounds like you have a fun project ahead of you.......I would suggest that you keep it simple in the motor department and that you approach your Crawl ratio needs based on how you think the vehicle will be "Most" used.

 

whoa! i do NOT want boost at low rpm.
i will have to reread the OP and find out what i might have stated to get you guys side tracted.

on the port velocity. a certain port size will be best for a certain amount of airflow. either low cubes and higher RPM or high cubes and lower RMP. its about air velocity.
i want the port sized for low RPM crawling NON-BOOST. i want it to creep and crawl on its own CONTROLLED power (without turbo causing it to roll over on spool).
thats why i want the lower volume ports. the engine came out with 8:1 compression which is what the 84 FI GN motor had. main difference is the size of the intake runner (they are 1/2" taller on the later even fire). same compression ratio, just smaller runners. i thought i scored big time with this engine.
now, if i match the intake's intake runners to the heads intake runner and keep it small, it should keep the low end velocity up (which equates to low end torque).

if..i hit the mud, i can rev over 2200 and spool the turbo up. but ONLY when its safe and i wont break stuff.
i think my GN turbo only yeilds 8 lbs of boost since its a non-intercooled one. any more than that, and itll detonate.

again, turbo OFF until i hit the highway and need to pass or in the mud/sand. NOT during crawl.
8:1 in the 3.8 is plenty of power for crawling @ 100:1 (gears being torque multipliers). and the FI part will allow better angles than the holley 470 truck avenger i have (which will be for sale shortly..) =)

tarry, i think you might have it backwards. hp is a derivative of torque. torque @ rpm/5250 etc. etc.
i am building a low RPM torque motor (hence the smaller intake runners).
if i need it to breathe (power @ higher RPM), i will force air via turbo.

thats the idea behind the new diesels AND this motor. except i run on gas..=)

i want it simple in the dog house. these engines ran great for years. and the addition of the turbo is factory. just bolt on, run the wires and the return oil line to the pan. again, the turbo will sit idle until i hit the skinny pedal. thats another reason i thought about using the thumb throttle from a 10 speed so im not bouncing off the gas and rolling it over on its back.

heavy flywheel, thumb throttle, fuel injection, small intake runners. to me all spell low end torque (coupled with rotating mass)/controlled crawling.
just point it in a direction and let it work.
i would LOVE to put the 3800 supercharged l67 in here. i found an adapter, but thats $600 or so, plus motor, plus rebuild, new mounts, new ecu and wiring...i have all this. but again, im not trying to spool while crawling. the engine will be good enough for that. its passing, and mud where i will need the help. so, give it a gear and mash it and hope the rev limiter holds... =)

 

@warloch, i have been to your home page several times. i love the flattie.

how does that 225 run with the TBI setup? i know the ez-efi is a DAMN good system. the powerjection is another good one.
you dont get any rich spots due to the uneven firing sequence? i thought the bang/bang/pause would cause the vacuum to drop a tad.
i want to check out the msd atomic setup too. it has the venturi boosters like a 4bbl for better atomization and plugs right into my 6a on my 460/mud truck.

 

Phalanxx

There is no backwards when you talk Horsepower versus torque............the formula is simple as they both in theory equal the same at 5250 RPM's as they cross that RPM point..........Torque moves the vehicle and Horsepower sustains the movement but of course I'm sure you "Already know that"..........and your statement about air velocity contradicts the other statements you make since a small port may only work well when you have more than atmospheric air pressure pushing behind it as would be the case of a turbo or supercharger creating boost and increased port speed.........A small port statically will not have a higher velocity just because it is smaller. It is still about velocity , size, port configuration & speed to fill the chamber during that short intake sequence at sea level 14.7 lbs per sq. inch.
One last thing....... Peak torque is when you need the most fuel , in fact all motors detonate for a split second at Peak Torque as the fuel requirements are balance to the load as it is applied so if that is true how would you increase torque with less fuel and RPM's? It simply does not happen! Again Good Luck with your Project!

 

i agree with you on the port velocity. its about filling the cylinder in my opinion. a 1.0l engine breathing through a hole will not max the velocity until really high rpm, where as a 5.0l engine will max it out at a really low rpm (depending on the size of course). all i am saying is, with the smaller ports, they will top out at a lesser rpm than the tall ports. peak torque will occur at a lower rpm which is good for crawling. once you tach it up, you are short on air. thats why i am choosing to put in the turbo. itll force the air in. even though its going through smaller ports, itll still get enough through to get the jeep rolling quickly when needed.

torque vs hp, yer speaking my language.

only thing i dont understand tho is where you say 7 psi at sea level. ive always thought it was 14.7 psi at sea level. i will have to research it. is that in the cylinder itself or just in general?

 

Sorry typo............fat fingers 14.7 psi at sea level

 

when we get a little extra cash and i wanna inject the truck, i might hit u up on that. hopefully, i can get these going here shortly and join u guys on some trails. i am going to have to dig out my d20 case and start the grinding to get it ready for the tera and OD gears.
have you seen the one that was 4.88 in the transfer case? couldnt hook up an OD gear, but if you wanted crawling...lol

 

Phalanxx,
if you want to keep it stock and have good high way speeds with a sleeper for crawling check into Rockeater gears for your dana 18. they come in a very easy install of 3.06:1 and 3.6:1. they come in a case altering gear set of 4.1:1 and 4.86 to one. All for your dana 18(late case, large hole)/20 case. no changes to anything but the transfer case.

I have just completed a 3.6:1 on my 70 cj5, 225, D18-3,.6:1,4.88,33 BFG AT. It was toooo easy. If my mechanic was not so prone to errors I would have tested it by now. Test is saturday. I will post build notes and pictures after the test is done.

see this thread on Rockeater Gears.
http://www.earlycj5.net/forums/show...of-O-brien-4-Wheels-West-is-still-in-business