Increasing Compression

Stock FSJ Tech Area
Fast Eddie
Posts: 43
Joined: Thu Nov 30, 2017 8:18 pm
Location: South Lyon, MI

Re: Increasing Compression

Postby Fast Eddie » Tue Mar 13, 2018 6:51 pm

Thanks for great info Stuka, very helpful and I think I have a path to go now!! Much appreciated!!
1979 J20, 360 w/NV4500/D300 Twin Stick/3.73 axles :fsj:
1978 Cherokee Chief W/T Levi interior, 360 Q/T. SCRAPPED
1970 Gladiator J4800 Camper Special, Buick 350, 4spd. SOLD

440sixpack
Posts: 292
Joined: Sun Jul 31, 2016 6:31 am

Re: Increasing Compression

Postby 440sixpack » Tue Mar 13, 2018 8:03 pm

I have a performer intake and a tuned Holley on my new rebuilt 8.9 to 1 360. I didn't dyno it but it's not 300 horse I know that. let's just say I'm not going to talk chit to any KIA drivers at the light.

I guess headers are all I'm lacking to get a tire burner. but from the sounds of it I better put a chute in place of my tail gate before I dare drive it after that mod.

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Stuka
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Re: Increasing Compression

Postby Stuka » Tue Mar 13, 2018 10:52 pm

440sixpack wrote:I have a performer intake and a tuned Holley on my new rebuilt 8.9 to 1 360. I didn't dyno it but it's not 300 horse I know that. let's just say I'm not going to talk chit to any KIA drivers at the light.

I guess headers are all I'm lacking to get a tire burner. but from the sounds of it I better put a chute in place of my tail gate before I dare drive it after that mod.


"Seat of the Pants" feel also depends on a lot on gearing and tire size. If you have 33" tires for instance with stock gears, it is not going to be fast. What cam are you running?

And none of us are saying you will have some super fast vehicle. But 300hp in a 4300lb vehicle is adequate, especially compared to stock.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Stock, but not for long!
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

candymancan
Posts: 1701
Joined: Tue Mar 22, 2016 11:32 pm

Re: Increasing Compression

Postby candymancan » Wed Mar 14, 2018 1:47 pm

If youve ever driven a 5.9 ZJ youll know that 300hp is plenty fast.. The 5.9 zj has only 245hp but 345ft lbs lf torque.. weighs 4300 lbs and it was once the fastest suv in the world at one point.

The power difference between my wagoneer with its 144/280 and the ZJ at 250/350 is night and day huge. Both weigh the same. And while the ZJ is 20 years old its still faster then a lot of vehicles on the road today. You can pass the average vehicle pretty easily with onmy half throttle in a 5.9 ZJ to where as the 4.0 you gatta floor it litterally and it creeps to pass people on the freeway.. The wagoneer is like that you gatta floor it to pass anyone it just creeps inch by inch.. I believe 0-60 the wagoneer is even slower then a 4.0 and they have the nickname 4.slow lol

Hp though isnt everything.. gearing. torque convertor stall and so forth all plays a roll.. Our camaro for example is 650hp at the crankl or about 520ish at the wheels.. But with skinnies in the front drag radials in the rear a high stall torque convertor and better gearing the camaro has beat other sports car with far more hp numbers for equivalanet weight. Beat a dodge hellcat the other day by 2 car lengths and that thing has over 700hp.


Gearing is huge... Its like wagoneers with the 2.73 vs 3.31 gears.. 2.73 gears will be slower then 3.31 they basically increase torque.. a crude example is 2.73s at 280ft lbs of torque vs 3.31s the 3.31 would be like 340ft lbs for the 2.72s.

2.72 and 3.31 is 21% more leverage.. So if you took identical wagoneers side by side and raced. the 3.31s would win hands down.. The other difference though is 2.73 would get better gas mileage on the interstate
2013 SS camaro, cammed, and modded too much to say 500 RWHP/650 crank 30k
1998 Jeep Grand Cherokee 5.9L Limited 191k
1998 Jeep Grand Cherokee 4.0 I6 laredo 256k
1990 Jeep Grand Wagoneer 126k


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