Future engine swap for my 98 TJ?

dan lee

dan lee

TJ Addiction
Supporting Member
Joined
Feb 26, 2017
Messages
259
Location
Berthoud, CO, United States
So, my inline 6 (4.0) has roughly 115,000 miles on it, which some believe it is just getting broke in. I've noticed over the last few years after adding a lot of weight to this rig, it's starting to work harder.
Adding a hard top, 33" tire's and tire carrier with receiver hitch, front bumper & winch, tube fenders & rock guards as well as a large smitty built storage box, and of course tons of tools, recovery gear, spare parts
Anyway, I was wondering if and when this motor shells out, should I be looking at a motor conversion? It would be nice to have a little more power to lug over the passes here in Colorado, or look at building up the 4.0 more?
 
Lower gears would really help. It seemed like I got added power when I rear geared. I have 33s and a 5 speed and geared down to 4.56. What a difference! Might be different gears with your auto.
 
dan lee said:
So, my inline 6 (4.0) has roughly 115,000 miles on it, which some believe it is just getting broke in. I've noticed over the last few years after adding a lot of weight to this rig, it's starting to work harder.
Adding a hard top, 33" tire's and tire carrier with receiver hitch, front bumper & winch, tube fenders & rock guards as well as a large smitty built storage box, and of course tons of tools, recovery gear, spare parts
Anyway, I was wondering if and when this motor shells out, should I be looking at a motor conversion? It would be nice to have a little more power to lug over the passes here in Colorado, or look at building up the 4.0 more?
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With all the research I’ve personally done, a SC is the best cost effective solution for more power in a TJ. Its a linear boost so really helps through the RPM range (TJ’s stay low anyways). I wouldn’t consider one till you are perfectly geared.
 
lowranger said:
SC?
Click to expand...

Super Charger
dan lee said:
So, my inline 6 (4.0) has roughly 115,000 miles on it, which some believe it is just getting broke in. I've noticed over the last few years after adding a lot of weight to this rig, it's starting to work harder.
Adding a hard top, 33" tire's and tire carrier with receiver hitch, front bumper & winch, tube fenders & rock guards as well as a large smitty built storage box, and of course tons of tools, recovery gear, spare parts
Anyway, I was wondering if and when this motor shells out, should I be looking at a motor conversion? It would be nice to have a little more power to lug over the passes here in Colorado, or look at building up the 4.0 more?
Click to expand...

X2 on regear
 
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Just do what I did, buy the Scat stroker kit and turn it into a 4.7:
https://www.summitracing.com/parts/sca-1-96015bi

I figure this should be good for maybe an extra 40-50 hp.

I won't be installing it for a while, but I ordered one in the meantime.

Doesn't require boring your block either, but you will be forced to run premium fuel. I read nothing but good things about it.
 
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While manual transmissions seem to be much more finicky with resect to gear ratio, the vehicles (even the ones with automatics) that I have had with 3.73 gears performed progressively more poorly as the diameter of the tires got bigger than about 28"

I agree go for gears especially if you can do the work yourself (not necessarily an easy mod; care and attention to detail is very necessary in addition to tools).
...think the last re-gear that I did for myself (3.73 to 4.11s with used gears) was around $200, not including the ARB or Torsen & seals etc.

Knowledge and skills are expensive; those without will pay for them more than once...

Enjoy!
 
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So, you are in a weird spot as far as gearing. With the 3 spd you should be around 2700 at 70, which is the usual rec for gearing. A 4.10 will put you close to 3k at 70. 4.56 at 70 is 3300. 3300 is a bit much for any distance cruising. The 4.10 would be the way to go unless you can live with not running 70+ down the hwy.

Sounds like you have that thing loaded down. Unload it, unless you are heading up wheelin. Make sure it is running in top condition. Proper tire pressure is important.
 
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dan lee said:
Rob, so your thinking if I re gear at 4:10 I will have issues running above 70 mph on the highway?
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You will be right at 3k at 70 with the 4.10. I personally wouldn't make long distance runs at 80 mph with that combo. 75 is 3200+, 80 is 3400+
 
Chris said:
Just do what I did, buy the Scat stroker kit and turn it into a 4.7:
https://www.summitracing.com/parts/sca-1-96015bi

I figure this should be good for maybe an extra 40-50 hp.

I won't be installing it for a while, but I ordered one in the meantime.

Doesn't require boring your block either, but you will be forced to run premium fuel. I read nothing but good things about it.
Click to expand...
Definitely let us know when you get around to it. I'd be very curious to get your opinion, that may be something I look into in the future
 
Northwood said:
Definitely let us know when you get around to it. I'd be very curious to get your opinion, that may be something I look into in the future
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Will do! Everything I read is positive, and the extra power is quite signifiant. As long as you don't put a different cam in it, most people are saying they're actually very reliable long term!
 
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Chris said:
Will do! Everything I read is positive, and the extra power is quite signifiant. As long as you don't put a different cam in it, most people are saying they're actually very reliable long term!
Click to expand...
What's the torque curve look like, before and after, on that kit? It would seem that it might move peak torque down some, which is good for a TJ off road. The premium fuel requirement would bug me some, but is livable, I guess.
 
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