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Jasper engine question

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Has to be less then 50k on this engine. Been over looked by several garages and can't find the problem. ANd had many overhauled tune ups, changed everything, and has good compression.


Why do Jasper engines suck? Their is NO power. I can barely go 65 mph steadily on the interstate with 30" tires and 3.5" lift. Driving over a curb, almost stalls every time. aka no low rpm torque.


The engine will run forever and is reliable atleast.


Soon as I get out of the Army, I'm swapping over my 95k mile 1990 Eliminator engine, That has 10x more power then this Jasper engine. 


End of rant/question lol

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I haven't heard good things about Jasper, but I didn't know they were that bad... Does it have a piece of round bar stock for a camshaft or something? No engine in good condition should be that weak.


Is the exhaust plugged? When my cat went bad I had a hard time going 50 uphill with my foot to the floor and it would occasionally try to stall. I would look at either that or badly off ignition timing if it has good compression. If the motor has good compression (should be mid 100s PSI) there's something else going on.

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If the axles are original to the vehicle, the 4.0L 5-speeds ALL came with 3.07 gears. And that's a good part of the reason why you're not feeling a lot of power. IMHO that gear ratio should never have been used. It keeps the engine WAAAAAY under the torque peak at highway speeds. 5th gear is useful only for maintaing speed at highway speeds. Under 55 MPH 5th gear is useless, and for passing you still need fourth gear on the highway (unless you're out west where they have 70 MPH speed limits.


Let's put it in perspective. The torque peak of the '88 4.0L engine was at 2,400 RPM. With 30" tires, at 65 MPH in 5th gear the engine is turning at 1760 RPM. If you downshift to 4th gear at 65 MPH, then you get near the torque peak -- 2345 RPM.


I don't think your engine is as bad as you think it is. It's just handicapped by the axle gearing.

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That sounds right about the speeds and shifting. My 90 Eliminator can accelerate in 5th at 40mph. Idk what ratio thst is either, tabs too rusty.


I been 110 mph in that eliminator the day I bought it. Downhill interstate lol. The GPS said 110.


I do want to swap d44's locked front and back with 4.10 ratio with 33" someday. Hope I can atleast get the rear axle soon.

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I had 3.07s with 32" tires for a short time.  Boy that sucked.  


Has anyone actually checked cam timing or dynamic compression (as opposed to static)?  Those are engine-related problems that aren't always checked into.  


Have somebody hook up a back pressure gauge into the O2 sensor hole and check the cat that way.


Don't be so quick to say your engine is junk.  There is way more to a vehicle's performance than the engine itself.  As mentioned you've got gearing, ignition timing, and exhaust systems in play, but you there's also things you might not think about (intermittent dragging brake(s) for instance) that can contribute to poor acceleration/lack of power concerns.  

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