Stepping stone to big block engine - JeepForum.com
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post #1 of 33 Old 08-01-2020, 04:13 AM Thread Starter
79CJ7t18a
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Stepping stone to big block engine

Good Morning,

I have decided to start a project, will take some time as it is my daily driver for now. I have a 1979 CJ7 with a 304, t18a 4 speed, Dana 20 with Dana 30 front and amc 20 rear. Currently has 4 inch lift and 35s. 304 was rebuilt by a po and was bored .030 over and has a larger cam, though I have no info on what cam. Also has a 4 bbl Holley on it and DUI distributor. Manual steering and manual brakes.

I want to first build up the front axle, then swap out the rear to a dynatrac Dana 60 with all options. Stage 3 th350 rated for 600hp, a np205 and Tom Woods drive shafts. The brakes would be converted to power brakes with the rear drums going to discs in the rear since it will be a Dana 60. Steering column will be swapped out for a factory tilt/auto on column. The 304 will get replaced with a 350 with 350hp which will allow for the cooling system to be overbuilt to eventually handle a big block. The ultimate goal is to lower it to factory height, run 30x 14x15 rear and 30x11.50 or 12.50 x15 front. Mickey Thompson sportsman. The 350 is going to be used as a stepping stone to break in the leap in hp from the boat anchor 304. Then about 2 years or so after this I will swap out to a 454 pushing 500 hp. I do not plan on this going off road, will be a street only Jeep sleeper. Eventually Ill pick up an old willys for off road fun.

My questions are as follows: what hp and torque can a np205 withstand? Also can the cooling for the transmission be mounted in the rear of the Jeep, as in inside the cargo area as I will not have a back seat? I Would like to do cut outs in the tailgate and mounting a radiator and fan setup there for the transmission. I would like to have everything done driveline wise and cooling wise before going to the 350, thus making it a fairly easy swap once engine mounts are fabricated. I want to do this because I never had the chance when I was younger. I also live where they have the corvette homecomings and eventually would like to build my CJ to the point that I can embarrass some of these corvette owners in front of their buddies, all in good fun mind you. I plan on keeping the outside of the body looking kind of rough with the tires being the only give away besides the sound.

Anyone done a swap from manual to automatic? The only thing I am unsure about is cooling.

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post #2 of 33 Old 08-01-2020, 05:09 AM
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Not sure a big block will fit in a narrow frame CJ. Great for a J truck or a YJ Wrangler but the frame rails are further apart.

The SBC has been fitted to loads of CJ7, all is knowable from this Forum!!! You may find a high end LS9 etc fits better and is quite capable of blowing a stock Corvette. Which is fine until 60mph and a bend, when the Corvette will get away from you. But for traffic light bragging, sounds great!!!!

The NP205 came in lots of configurations, you can probably make it work if you choose carefully and match it to the right transmission and driveshafts etc. Can be modded for more strength, that iron case makes it quite the beast. If you put power to all 4 tyres with LSD, you may have the edge when the lights turn green and that power hits the black stuff!

Were you thinking tH400 transmission? It can take 450 ftlb of torque in stock form, more when modified. 4l80E needs electronics to drive it but is an even better transmission, but the 6L80 is maybe too much trouble in this application. Again, all is knowable from this Forum!!! Failing that Novak Transmissions is a great source.

I have seen radiators in the back of Jeeps, but only hardcore rigs. It is relatively simple to pipe the water along the frame rails to a radiator and fan package in the back seat, some 2" galv pipe and fittings will do it. Not great for the rear seat passengers!!! They all ran without tailgates but you could mount the radiators at 45 degrees and blow the hot air over the top of the tailgate.

The Dana 60 is a big boat anchor, comes into its own with big tyres and super low ratios due to the size of the ring. Have you checked out other axles to see if they can take the power with less weight, like a built Dana 44? Less unsprung weight = better performance. With that amount of power the front axle will not last long in 4WD, you may want to buy a stronger front axle as well, a built Dana 44 again would be suitable.

And if you are going to take off at full power with 600hp+ in a leaf sprung Jeep, you may want to upgrade the suspension both ends to avoid axle wrap.

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post #3 of 33 Old 08-01-2020, 06:56 AM
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One problem you are going to have if you want to embarrass Corvettes off the line is that you will need (numerically) lower gear ratios in the axles that wont do the Jeep justice when you want to crawl. You will also want to keep the weight down so that means getting rid of the winch, beefed up tire swing, full size spare tire, doors, hard top.

Best of luck...


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post #4 of 33 Old 08-01-2020, 07:25 AM
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If all you want is to get to 500HP, then why not go with something that will be less of a headache fitting in the engine compartment. A SBC 383 with some breathing heads and a roller cam would get you there. If you want the power a little lower in the RPM do a 408 stroker, 4.0 crank stroke. Heads are the key and SBC heads are a dime a dozen.
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post #5 of 33 Old 08-01-2020, 08:25 AM
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Quote:
The ultimate goal is to lower it to factory height, run 30x 14x15 rear and 30x11.50 or 12.50 x15 front. Mickey Thompson sportsman.

I think the key is this sentence. A "drag race" style set up can do wonders for reducing shock loads and unsprung weight, Both which are major contributors to drivetrain carnage. This means you don't have to build an insane drivetrain.



Ford 9" front and rear. Brutally strong, smaller, and the much simpler option of gear ratio changes. You can also get a locker (steer clear of the factory LS).



D300. These can be modified with stronger output shafts and a girdle can be fab'd to reduce rotation.


Turbo400


SBC rodded and modded for carb applications. Newer engines such as the LS1's can provide added HP out of the box without any real mods.


I would skip all the added cooling in the rear. You can upgrade the existing system and add larger transmission coolers to the front. Not as visually cool, but a lot less to plumb, and eventually leak/fail.


While insanely expensive, a highly modded 401 would bring the added sting of embarrassment to the Chevy crowd. We had a member, fuzzy401 that ran a drag modified CJ with a built 401. Not sure if he can be contacted, but he would be a wealth of information on what you are trying to accomplish, both engine and drivetrain wise.

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post #6 of 33 Old 08-01-2020, 08:41 AM
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If you are going use different sized tires front and rear you won't be able to use 4WD so save some weight and use a straight axle--postal Jeep maybe. You could just get a postal Jeep and put a FG body on it. If I wanted 'Vette performance from a CJ Id just get a 'Vette. Probably be cheaper too!

Did I mention that my wife sold a 'Vette to buy our Jeep?

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post #7 of 33 Old 08-01-2020, 08:57 AM
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hello

have you thought at all about the amc 401. a medium built one makes about 450hp with over 500 torque. more then enough power to pretzel a light cj frame. it already fits, the block is a high nickel iron as were all amc blocks. the crank,rods,are already forged out of the factory. had extra webbing in the block at the crank journals. there is quite a bit of information on theamcforum.com .

if going to BBC then wouldnt it be easier to get a new frame that is extended in the front to handle the length and wider to handle the width of the motor? build all the drive train on it. once all that is ready take your body and swap on.

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post #8 of 33 Old 08-01-2020, 09:25 AM
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Quote:
Originally Posted by jeepdaddy2000 View Post
I think the key is this sentence. A "drag race" style set up can do wonders for reducing shock loads and unsprung weight, Both which are major contributors to drivetrain carnage.

While insanely expensive, a highly modded 401 would bring the added sting of embarrassment to the Chevy crowd. We had a member, fuzzy401 that ran a drag modified CJ with a built 401. Not sure if he can be contacted, but he would be a wealth of information on what you are trying to accomplish, both engine and drivetrain wise.
A set of cal trac bars will work well for a leaf spring setup.

Im all in for the added sting of embarrassment...lol

An AMC 401 will cost more to build, but Im not sure I would call it insane. And the cool factor would be worth it in my opinion. A well built 401 street engine making 500 lb/ft of torque will rival a stock 454 or a built 383 SBC.

https://www.hotrod.com/articles/amc-401-build/

BBC and SBC = cheap

AMC 401 = more $ but the cool factor of a Blue engine is priceless

If I was going to build a CJ-7 to be quick off the line for the purpose of winning a drag race, I would go 2WD. I would shed as much weight as possible. I would start with an engine that makes good torque, an automatic transmission with a 3000-3400 flash tight torque converter and a rear differential to handle the power level, there are many to choose from.

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post #9 of 33 Old 08-01-2020, 09:54 AM
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Quote:
Originally Posted by Dryseals View Post
If all you want is to get to 500HP, then why not go with something that will be less of a headache fitting in the engine compartment. A SBC 383 with some breathing heads and a roller cam would get you there. If you want the power a little lower in the RPM do a 408 stroker, 4.0 crank stroke. Heads are the key and SBC heads are a dime a dozen.
While I tend to agree with you, 500hp out of a 383 is going to end up being pretty snotty. You can blow right through that number with a 468 and it'll be much tamer but your expenses just went way up. The price of your heads just doubled, your intake manifold just went from $300 to $450, on and on.

Personally, I'm with you; I'd do the half-snotty 383 because all the conversion stuff is already out there. 10.5:1 compression, Profiler 195cc heads, hyd/roller 228/232 at .050 on a 107 LSA, Performer RPM Air Gap or Super Victor single plane depending on transmission, gears, converter, etc, annular-boostered 750 carb... oh yeah, fun stuff!


Shawn

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post #10 of 33 Old 08-01-2020, 10:11 AM
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Originally Posted by bob4703 View Post
If you are going use different sized tires front and rear you won't be able to use 4WD so save some weight and use a straight axle
Actually you could. By varying the ratio combinations, you could come up with a serviceable combo that would be effective and still retain the ability to run sand or other offroad adventures.


I do, however agree that dumping the added weight and and complexity of the four wheel drive system would make the rig faster. I get the feeling, however, that the OP wants to beat the competition in an actual 4X4.

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post #11 of 33 Old 08-01-2020, 10:24 AM
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Originally Posted by Axhammer View Post
Im all in for the added sting of embarrassment...lol

An AMC 401 will cost more to build, but Im not sure I would call it insane. And the cool factor would be worth it in my opinion. A well built 401 street engine making 500 lb/ft of torque will rival a stock 454 or a built 383 SBC.

https://www.hotrod.com/articles/amc-401-build/

BBC and SBC = cheap

AMC 401 = more $ but the cool factor of a Blue engine is priceless
the question is will it really be more expensive to build when compare apples to apples. if you want to build both engines equal. you will have to buy a forged crank and rods for the BBC. the 401 was already a forged bottom end.

now if you really want to go for the cool factor what about a 500hp turbo inline 6. like the one they built for indy in the early 70's. but will cost more to build probably alot more.

https://www.sr-ix.com/AMC/Navarro-turbo-motor/

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post #12 of 33 Old 08-01-2020, 10:35 AM
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Originally Posted by bob4703 View Post
If you are going use different sized tires front and rear you won't be able to use 4WD so save some weight and use a straight axle--postal Jeep maybe. You could just get a postal Jeep and put a FG body on it. If I wanted 'Vette performance from a CJ Id just get a 'Vette. Probably be cheaper too!

Did I mention that my wife sold a 'Vette to buy our Jeep?
He said he want to run 30 front and back, the only difference he listed was the width.

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post #13 of 33 Old 08-01-2020, 10:51 AM
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Originally Posted by oldschool74cj5 View Post
the question is will it really be more expensive to build when compare apples to apples. if you want to build both engines equal. you will have to buy a forged crank and rods for the BBC. the 401 was already a forged bottom end.

now if you really want to go for the cool factor what about a 500hp turbo inline 6. like the one they built for indy in the early 70's. but will cost more to build probably alot more.

https://www.sr-ix.com/AMC/Navarro-turbo-motor/

oldschool
If I had it, I'd drop six grand on a turbo kit just to hear it spool up and dump the blow-off valves on an upshift

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post #14 of 33 Old 08-01-2020, 12:02 PM
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Here's a crappy clip of a twin-turbo C5 from many years ago from a rolling start to 100 mph and then a hard downshift dive to make the turn; which I missed, lol. I had to be really mindful of my upshifts because the damn thing was drifting sideways the whole time and I had to keep it pointed the right way. My buddy shooting the video was two 4Locos deep, as I'm sure you can probably tell.

This is the same car that I drifted into freeway traffic at 115mph, hit 4th gear and ran it up to redline. Just stupid, make-you-shake fast no matter how many times I drove it. Just silly.

I guess my point is that with a well-thought-out-turbo, you'll quickly out-power the limits of a Cj. Don't get me wrong, the sound of spooling turbos is music to your ears but they're so damn powerful. If you go that way, keep the engine size fairly small (don't build a twin-turbo 401 because you either can't use it or you'll kill yourself trying in a Cj) and drop a few bucks making it bullet-proof.

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post #15 of 33 Old 08-01-2020, 12:02 PM
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Just go get the drivetrain from a Jeep Cherokee trackhawk.


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