500HP YJ Build Questions Thread

71chevytruckguy

71chevytruckguy

Well-Known Member
Joined
Nov 8, 2008
Location
Kernersville, nc
Going to the use thread for any questions I have for my build. Build thread here, http://www.nc4x4.com/forum/index.php?threads/500hp-yj-build.132136/

Still in the early planning stages of the build and trying to make sure I have my ducks in a row before I dive in. Main question is right now is what transmission to run, have it narrowed now to a TH350 or a TH400. I know regardless I'm goin to run a NP205 t-case. Due to the large cam in the motor, will need a stall somewhere in the 3000-3500rpm range. I know the 400 trans will hold up no prob but are hard to find. Also a 350 can to built to handle the power but my main concern with 350 is the 27 spline output shafts veruses the 32 spline on the 400. Any thoughts?
 
Find a TH400 mated to a 205 and call it a day. I wouldn't trust anything else.

The 4l80e I plan on running is only rated for 450 hp and I'm sure a Th400 is about the same.
 
Before I get any haters asking, most transmissions can be built to handle more horsepower but out of the ones you mentioned a th400 will do the trick.
 
XJsavage said:
Find a TH400 mated to a 205 and call it a day. I wouldn't trust anything else.

The 4l80e I plan on running is only rated for 450 hp and I'm sure a Th400 is about the same.
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As i understand it, 4l80e is a electronic controlled th400 with overdrive.
 
I know you said you need the high stall for your cam. Im just curious if that stall will be too high for what we do though? Maybe someone with more experience and knowledge can weigh in on this one. It seems that you would want to lower stall for less slip, unless you are planning on 3000rpm launches regularly.
 
Either transmission would work just fine. A lot of guys that drag race run a TH350 because they don't rob quite as much power as a TH400. Either trans can easily run an NP205 and will be plenty stout. If you ever do break anything with the 350/205 setup, it'd probably be cheaper to fix because the 27 spline 205 doesn't demand as high of a cost as the 32 spline. Then again, it also depends what 32 spline 205 you run. Most likely it would be a "figure 8" pattern, the "round pattern" 205 generally costs even more since they were only made from 85-91 in 1-ton trucks.

Post up some cam specs and we can help you out with the stall situation. It shouldn't be too noticable though as far as wheeling it is concerned, but then again, you'll have a crap load of power in a YJ, so you can probably throttle your way over or through just about whatever you'd need to :D

EDIT: I looked up the cam specs. Nice cam, but you may find you'll want something with a lower torque curve, IE: tighter LSA, perhaps a little less duration. You're right though, that'll need about a 3000 stall and it'd be much happier with 9.5:1 or higher compression.
 
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The turbo 400 is the only way to go. go big or go home lol . Witch ever one you do use be sure to brace
tcase. or you will brake the transmission housing in two. i broke two turbo 350 wirh out it lol.
 
tim robinson said:
The turbo 400 is the only way to go. go big or go home lol . Witch ever one you do use be sure to brace
tcase. or you will brake the transmission housing in two. i broke two turbo 350 wirh out it lol.
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^ truth, I remember JT went thru a few unsupported TH350s in the jeep/blazer stumpjumper
 
Good info guys, after some hearing with yall have to say, think I'm going to go with a 350 trans. Being built internally to hold the the power wont be prob and hearing what Croatan Kid had to say as well as some googling, haven't been able to find one single case of a 350 breaking an out put shaft.

Good thoughts about bracing the case on the trans, remeber a thread from 67-72chevytrucks.com about a guy with a K5 having the same problems.

Agreed with the cam not being ideal for what I'm doing with it but it should work with the right stall. I briefly had the truck on the street after racing season, and suprisingly it was a very streetable, but then again, I can deal with a lot more issues than most. I could punch the gas a 1500rpm in first gear and it would pull hard, but once I got 3000rpm it was a whole nother animal. Hence the reasoning for a stall somewhere in the 3000rpm range. With a 4.10 gear, 275-76-15 street tires, it would burn threw 1st, 2nd, 3rd, and bark 4th. Also plan to run a giant trans cooler hanging from the cage with its own fan, I know the loose convertor will generate a lot of heat while trying to crawl, and the crappy crawl ratio wont help either, should be around 25:1.

My next question is what to do about motor mounts and headers. Trans Dapt makes a weld in kit similiar the Advance Adpaters and Novak at a much fairer price. Any first hand experience? For headers, would really like to find a set of long tubes and avoid block huggers or shorties. Hedman makes a set of SBC swap fenderwell headers for a CJ7, Seems like they might work on a YJ. For exhaust with fenderwells, was thinking run the pipes close the frame and floor boards, wrap with heat wrap, then boat side for protection. Still not sure where to put the mufflers, I HATE glass packs, and fitting a flow master in there would be tight. Figured for the sake of others more than myself, mufflers would be a good thing on this rig.
 
Chad is running the same engine setup is his cj. Not sure what headers he is running but i know he is running dual 3" pipes with single chambers underneath.

Maybe Paul might know what headers he is running. I think they are long tubes.

I think the fenderwell headers are nice, maybe with collector mufflers or single chambers could be tucked under a boatside.

Sent via telegraph
 
Crawler Nut said:
You are going to be making alot of heat with that 3000 stall. Make sure you run a fan cooler with it, or it will die an early death.
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That's the plan.
paradisePWoffrd said:
Chad is running the same engine setup is his cj. Not sure what headers he is running but i know he is running dual 3" pipes with single chambers underneath.

Maybe Paul might know what headers he is running. I think they are long tubes.

I think the fenderwell headers are nice, maybe with collector mufflers or single chambers could be tucked under a boatside.

Sent via telegraph
Click to expand...


Ill have to look into that, thanks.
 
Still think you need to put this Clark 5 speed I got in your yj. Hard to break. 6.99 1st gear.
 
I like the 350 because it doesn't have as much clearance issues as the 400. As far as the spline count. I have seen a output shaft twisted, but not sure what did it.
 
I ran 600hp through a 350 in my old race buggy. It held up until the case broke. I'm a fan of the 350 over the 400 but the cases are weaker. I still have a 350 and 2400 stall in my 4 seater with a 475hp LS6 and it is great. I haven't had an ounce of trouble out of it.

That being said my new buggy is getting a 400. Hill killing with 710hp is just a bit much for a 350 IMO.
 
can you lockup a 350 torque converter? I can in my 700R and LOVE it. my $.03 (inflation and all...)
 
For what it's worth I'm running a Powerglide and 4 speed Atlas behind a 525hp LS2 in the YJ Jim built for me. The combo works bad ass.
 
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