S52 sticking lifter?

[m3f_MaynardZed]

So finally got a replacement S52 put in may race car after blowing mine in May. The head on this replacement engine had to be rebuilt because it ended up having 6 bent valves (dishonest seller). Seemed to run fine up and down the street near the shop after the rebuild.



Dyno'd it for classing purposes and it comes in a little low on torque compared to my old engine. 233hp/208tq vs 237hp/230tq on my old engine. Also it sounds like it's missing sometimes intermettently. Repeated compression check like 3 times, all 6 come in around 134psi give to take a few lbs. Plugs look good and the same in all 6 holes too. Did the coil swap drill also. Best we can figure is a lifter/follower is sticking / collapsing? Maybe not opening all the way? Ran a tad rich like 11/1 A/F while on dyno.



Our current consensus it to go ahead and run it, thinking maybe its a sticking lifter / follower?, hoping it needs a little break in? Maybe add a little ATF to the oil?



Any thoughts?

[m3f_Double E]

Vanos issue?

[m3f_mpwrcpe]

Tom, 134 PSI seems a bit low no? Was the motor warm? I would think you should see at least 150 on that motor.

[m3f_MaynardZed]

Vanos issue?

Makes some sense, could explain loss of torque yet peak hp close to normal?

Tom, 134 PSI seems a bit low no? Was the motor warm? I would think you should see at least 150 on that motor.

Agreed. Motor not fully warm but not totally cold either. Didn't check temp gauge unfortunately. Dyno shop only a few miles from race shop. Probably about 30-40 minutes after last dyno run. Checked compression while on trailer still.



Update: Yesterday here at home I let car idle to fully warm. Purrs like kitten at idle. Rev too 2000, 3000, 4000 and hold for 20 seconds each time, after 3000 it sputters and stalls after letting off throttle. Repeated the process and its fine each time.