Comp Cam K68-239-4 help!

[billy_bob]

Hey, i just bought the Comp Cam K68-239-4 Xtreme Energy 4x4 Cam and Lifter Kits for my 1990 stroker. Has any one used this set up before? My specs are...

1990 4.0 block, Kb 945 21cc forged .060 pistons, 4.0 rods, late model 258 crank, and a 94 high output cylinder head.

Cam Style Hydraulic flat tappet
Basic Operating RPM Range 1,400-5,700
Intake Duration at 050 inch Lift 218
Exhaust Duration at 050 inch Lift 226
Duration at 050 inch Lift 218 int./226 exh.
Advertised Intake Duration 262
Advertised Exhaust Duration 270
Advertised Duration 262 int./270 exh.
Lobe Separation (degrees) 111
Outside Diameter of Outer Spring (in) 1.475 in.

my main concern is how big the springs are, they look massive next to the stock springs. I know im going to half to get the head worked on so the springs will fit, but i was wondering if they will fit next to each other and under the valve cover ok.

[dwg86]

Springs, retainers and locks from the comp kit will not work on the Jeep 4.0 valves. Those springs are made for the 258 valve which has a larger stem diameter than the Jeep 4.0 head. The only drop in spring, that I know of, that will work with the Jeep 8mm valve stem is the Mopar Performance spring P5249464 and retainer P4452032. Some have used chevy LS valves and springs. But there is added machining cost to use them. I used SBC 1.94/1.50 valves because my valves and guides where worn, and I needed to replace the stock guides and valves. So it was cheaper for me to use small block chevy parts. The SBC valves are the same length as the Jeep valves, and the intake is only .030 bigger in diameter(keeping valve shrouding down). The machine shop opend up the guides for the 11/32 valves and slightly opened up the intake throats. This is still more cost than buying and installing the Mopar Performance parts.

[gradon]

That cam looks like a higher end(high hp) cam. What is the amount of lift(not amount of duration, but height in .4x-5x")? Are you going to use all 5700rpm? If not, advance it some and change the power range to 1000-5300rpms(this will also reduce overlap, and raise dynamic compression, thus more low end torque). And as rec'd, go with the mopar springs, retainers, and locks.

[billy_bob]

oops i forgot to put the lift.

Exhaust Valve Lift with Factory Rocker Arm Ratio 0.512 in.
Valve Lift with Factory Rocker Arm Ratio 0.493 int./0.512 exh. lift

im going to go with some 1.6 roller rockers also

im definately looking to go to 5700 with this thing if the cam makes the power that high, only thing its going to be used for is pure street.
but good chance im going to send the kit back and get something else. any sugestions? its going to be a hard driven daily driver, i like that lift size and with the 5 speed manuel im wanting the higher RPM power range.

[Plechtan]

There are several threads on this board that talk about Crank harmonics, the general opinion is that they are worst in the 5400-5600 range. People do run at this rpm and higher, but experience timing chain streach or breakage. Six Pac runs his drag Jeep up to 7,000 rpm, but can see his et's drop as the timing chain streches.