I was able to finish up the hyd roller install in the 408 motor, fire it up and take it up/down the road a couple of times on Saturday. I can tell you it is noisy and I am most likely getting valve float by 5600 - 5800. I readjusted the valves (reset them in 3/4 turn from "0" lash-will have to see how this does) and did a compression check while I was at it, while the motor was still plenty warm.
Cylinder pressure is only 165+/- a couple of lbs. - very consistant cylinder/cylinder. I am kind of surprised at the low cylinder pressure. I was expecting to see something in the 190 - 200 range. For comparison, before we freshened up the motor (which also included .012 cut off the deck and .008 off the heads) we had on average cylinder pressure of 172- with a couple of abnormally low cylinders thrown in there, hence the rebuild. This was with an old design Crane 280 cam [280/290 adver, 222/234 @.050 on 114 LSA/112ICL and a worn/loose timing chain]. I never checked it with the Crane 286 Powermax hyd flat tappet. But with the Comp NX279HR I expected it to be higher. 279/294, 230/242 on 113LSA installed at 108ICL. I know cylinder pressure is not a tell all, but I really thought it would be higher.
The plan is to pull the 408 motor and set it aside for install in a lighter car down the road {Camaro or Nova}. The cam swap was intended to do a little in car test/tune, back to back comparison.
The motor should be in the 9.5-9.6 CR range based on the measurements I have. And for what it's worth, the motor was spinning fast for the test. I ran each cylinder on a charged battery with the charger on full boost for each test.
Any thoughts?
Cylinder pressure is only 165+/- a couple of lbs. - very consistant cylinder/cylinder. I am kind of surprised at the low cylinder pressure. I was expecting to see something in the 190 - 200 range. For comparison, before we freshened up the motor (which also included .012 cut off the deck and .008 off the heads) we had on average cylinder pressure of 172- with a couple of abnormally low cylinders thrown in there, hence the rebuild. This was with an old design Crane 280 cam [280/290 adver, 222/234 @.050 on 114 LSA/112ICL and a worn/loose timing chain]. I never checked it with the Crane 286 Powermax hyd flat tappet. But with the Comp NX279HR I expected it to be higher. 279/294, 230/242 on 113LSA installed at 108ICL. I know cylinder pressure is not a tell all, but I really thought it would be higher.
The plan is to pull the 408 motor and set it aside for install in a lighter car down the road {Camaro or Nova}. The cam swap was intended to do a little in car test/tune, back to back comparison.
The motor should be in the 9.5-9.6 CR range based on the measurements I have. And for what it's worth, the motor was spinning fast for the test. I ran each cylinder on a charged battery with the charger on full boost for each test.
Any thoughts?
