Stroker issues have me wondering what's up
Posted: February 27th, 2017, 5:26 am
New member, first post but long time reader of the board. I have a stroker that I had built for my 84 Scrambler. I had Cleggs build the stroker but I did the head install and put it in the jeep. The motor only has 600 miles on it but has left me wondering why the power is not what I expected. I also have to go easy on the throttle or the engine clatters. Here are the particulars of the build as I remember without having the paperwork in front of me.
92 engine block and 7120 head bored 30 over, decked.
Keith Black forged pistons (new ones that are supposed to give 8.8 compression ratio.
4.2 crank, 4.0 rods
High flow air intake, 4.7 v8 throttle body, 99+ intake manifold
High flow exhaust and header
93 XJ OBD1 computer and wiring
24 lb/hr injectors, adjustable fuel pressure regulator set at 48 psi
Don't have the cam specs, I'll add them later but it was the one Cleggs uses most of the time
4.56 gears, 33" BFG MTs
Custom cage, 4 link and other off road goodies that make it a bit heavy
I have three other stock 4.0s in the jeep herd at my house and my son's 87 comanche with a tired engine outperforms my jeep so I know something isn't right. With the other Jeeps at my disposal I have been comparing compression, timing and vacuum. I have a wide band AFR meter that will be used to test it once the gauge shows up that goes with the controller.
The compression I am reading is only 100 PSI which seems too low (my daughters 96 4.0 with 80 K miles reads 110 at our altitude (4600 ft)
The vacuum on all of the jeeps is the same
The motor is still quite tight
Starts great and idles very well
Timing is a bit different: My jeep reads 12 degrees advanced at idle but jumps up off the cast scale on the front of the engine when I give it gas. My kids jeeps both seem to start out further advanced at idle but don't jump as much when the throttle is bumped up. My jeep has always been a bit touchy with pinging even on the old motor that I replaced (99 TJ 4.0). I always had to use premium to keep it from pinging. This problem seems to have been made worse with the stroker. Does anyone have any ideas for me to try ?? I am getting quite frustrated with this motor.
92 engine block and 7120 head bored 30 over, decked.
Keith Black forged pistons (new ones that are supposed to give 8.8 compression ratio.
4.2 crank, 4.0 rods
High flow air intake, 4.7 v8 throttle body, 99+ intake manifold
High flow exhaust and header
93 XJ OBD1 computer and wiring
24 lb/hr injectors, adjustable fuel pressure regulator set at 48 psi
Don't have the cam specs, I'll add them later but it was the one Cleggs uses most of the time
4.56 gears, 33" BFG MTs
Custom cage, 4 link and other off road goodies that make it a bit heavy
I have three other stock 4.0s in the jeep herd at my house and my son's 87 comanche with a tired engine outperforms my jeep so I know something isn't right. With the other Jeeps at my disposal I have been comparing compression, timing and vacuum. I have a wide band AFR meter that will be used to test it once the gauge shows up that goes with the controller.
The compression I am reading is only 100 PSI which seems too low (my daughters 96 4.0 with 80 K miles reads 110 at our altitude (4600 ft)
The vacuum on all of the jeeps is the same
The motor is still quite tight
Starts great and idles very well
Timing is a bit different: My jeep reads 12 degrees advanced at idle but jumps up off the cast scale on the front of the engine when I give it gas. My kids jeeps both seem to start out further advanced at idle but don't jump as much when the throttle is bumped up. My jeep has always been a bit touchy with pinging even on the old motor that I replaced (99 TJ 4.0). I always had to use premium to keep it from pinging. This problem seems to have been made worse with the stroker. Does anyone have any ideas for me to try ?? I am getting quite frustrated with this motor.