4bangerjp.com
General Forums => The Mess Hall => Topic started by: DJackson1357 on July 10, 2011, 06:42:34 AM
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I recently picked up a 99 Wrangler with a blown 2.5 and am currently in the process of swapping the engine out. I picked up a complete 95 engine for the shortblock and am curious about the cam. I found the following specs online.
2.5L I4 '87-'95:
Duration advertised: 270*/270*
Duration @ 0.050" lift I/E: 197*/197*
Valve lift I/E: 0.424"/0.424"
Valve overlap: 46*
LSA: 112*, ICA: 111.5*, ECA: 112.5*
IVO: 13*ATDC (0.050" lift)
IVC: 30*ABDC
EVO: 31*BBDC
EVC: 14*BTDC
2.5L I4 '96-'01:
Duration advertised: 256*/260*
Duration @ 0.050" lift I/E: 188*/192*
Valve lift I/E: 0.408"/0.414"
Valve overlap: 43*
LSA: 107.5*, ICA: 100*, ECA: 115*
IVO: 6*ATDC (0.050" lift)
IVC: 14*ABDC
EVO: 30*BBDC
EVC: 18*BTDC
According to this the earlier cam has more duration and lift compared to the newer cam. Does anyone know if the additional duration offsets the loss in dynamic compression? Has anyone tried both? I'm leaning towards just swapping the cam out of the 99 in to keep everything stock, but figured I'd check before.
Also, has anyone here back cut their valves? I was assuming go with the standard 30 degree cut. Planning on doing that while the head is off as well as cleaning up the bowl area a bit and wasn't sure if anyone had some insight.
Thanks,
David
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I don't know how much diff it will make but more lift and duration is a good thing not bad
only thing I can see them doing it for in newer engine is for emissions standards but at power sacrifice
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interesting. I though the 87-90 tbi had different cams since they had egr and the 91-95 had no egr so had to have more valve overlap to make up for the no egr.
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I don't know how much diff it will make but more lift and duration is a good thing not bad
only thing I can see them doing it for in newer engine is for emissions standards but at power sacrifice
Within reason additional lift and duration is good and considering the small difference between the two I doubt it matters. The odd thing is I always thought the later engines were rated higher. The newer cam does give a higher dynamic compression ratio and the split pattern could make up for a weak exhaust port.
Since I'm doing head work I'll just stick with the older cam (less work too!). I'll keep the newer one just in case.
The overlap could have been there for EGR purposes. I haven't been able to find the specs for the pre 87 cam.
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Generally speaking they're interchangeable. It's also one of the reasons the TJ is rated at 120HP and not 123HP. IIRC, the TJ has a bit more torque. I think the '84-86's TBI's (usually ignored in specs since they are XJ engines. The CJ's are also ignored.) are more then likely the same as the '87-90 as the engines didn't change between that period. I don't think there is much of a difference if any between '91-95 and the '84-'90.
People have been using the Mopar Purple cams for the 87-95's in their TJ's for years with no problems.
1991-1995 do not have EGR's.
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2.5L I4 '96-'01:
Duration advertised: 256*/260*
Duration (at) 0.050" lift I/E: 188*/192*
Valve lift I/E: 0.408"/0.414"
Valve overlap: 43*
LSA: 107.5*, ICA: 100*, ECA: 115*
IVO: 6*ATDC (0.050" lift)
IVC: 14*ABDC
EVO: 30*BBDC
EVC: 18*BTDC
Jeep Wrangler TJ 2000 from FSM
Intake/Exhaust
Duration 253.3/259
Valve Lift 408/415
Overlap 41.6
so even lower than what you found.