PROBLEM with my motor after spring swap-Little help?
 

Quick summation: busted #1 valve spring, inner and outer spring, at a sitting idle and had to replace them (replaced with the same Crane duals).

The car idled without incident for an hour and a half under a fan. I've driven the car for ~60 miles without incident staying below 3K rpm's (I was paranoid). Did a part-throttle tap run at ~45 miles for about 10 miles with nothing out of the ordinary with 0 knock.

Comin' home from work this morning I heard a fluttering/tapping noise emanating from what sounds like the valve-train.

This morning was also the first morning I didn't baby the throttle since the swap; nothing WOT or crazy and still under 3K rpm's.

The flutter/tap does not sound like internal engine noise eg. as in if the valve touched the piston without dropping.

My oil pressure is perfect. The oil level is perfect. The oil looks clean. Running coolant temp is the same at 176*. No smoke whatsoever. No stutter or hesitation.

The car is running the same as it did before the spring failure except for the fluttering/tapping.

The mech dropped the retainer lock and never found it. He said he is . . . "100% sure it did not go into the head . . . I saw it drop on the ABS wire and go somewhere in the chasis . . . ". He checked the pushrods (hardened from Thunder Racing with ~45K miles on them; they were in the old blown motor) and made certain they were straight.

Possible hypothesis: could my #1 rocker (stock rockers with 78K miles) be bad or going bad? When the spring went at idle could the lift of the cam (.598/.595) have stressed the #1 rocker too much? Would this cause the above conditions?

Any and all input is helpful and appreciated.

Thank you!



Christopher

did you replace all the valvesprings or just the failed spring

I replaced all the springs. I wouldn't recommend replacing a single spring unless the others had less than a couple of hundred miles on them; let alone ~30K :)

Update: haven't heard the noise again. During the 3 days since the install it was really hot and humid down here. When the noise occured it was the first cold night on the new springs.

My mech said the inner springs were a tad shorter than the inner springs on the old cranes. I think that's just because the old springs were so worn. He said that maybe one of the inner springs was just finding it's seat.

Anyway . . . I raced a modded GN and a new CL 55AMG from a light and whooped 'em both so I guess I'm in the clear . . . for now :crossesfingers:

Anybody else have any ideas concerning this anomaly?

Do you have your crane duals shimmed? My buddy broke a dual n a matter of days before he learned he needed to shim them out .030

I was unaware of the fact they needed to be shimmed. I'll have to ask my mech about that tomorrow. Thanks!

They don't need to be shimmed! Shimming just changes the seat pressure and seat pressure is only necessary with relatively rough cam profiles. Shimming has absolutely no affect on valve spring harmonics or valve spring life and will absolutely not shift any harmonic point. That is determined by physical design characteristics of the spring such as wire diameter, # of coils (both active and inactive), free length, O.D. of the coil pack, etc. Crane had some early issues with material, but they came out with an improved version of the 144832 springs that has blue and yellow stripes. These seem to be holding up extremely well.

Many people have had to shim the springs to get higher seat pressure to prevent "pump-up" at higher rpms when valve train separation is starting. The stock LS1 rockers are advertised at a 1.7 rocker ratio but actually start the valve off the seat and return it to the seat at a ratio of 1.54:1. Extra seat pressure is necessary with these slow acting rockers because of their poor mechanical advantage. The Crane 1.7 rockers start the valve off the seat and return it at a ratio of 1.79:1. This quick lift ratio has better mechanical advantage than the stock rockers and requires lower seat pressure. That is why Crane springs set up at 112#@1.800". Their 1.8 rockers actually start the valve off the seat at 1.89. Many guys want 140# on the seat with stock type rockers (140# acting through the 1.54 stock ratio gives 216# acting on the lifters...140# x 1.54 =216#) With the Crane 1.7 rockers, you only need 120# of seat pressure for the same pressure on the lifter...120# x 1.79 = 216#. With the Crane 1.8 rockers, you only need 114# of seat pressure..114# x 1.89 =216#. Vinci High Performances website has a great deal of info on this subject. Check it out!

The idea that springs must be shimmed to make them live or that they must be heat cycled on the engine to make them live are two of the biggest misconceptions generally accepted by so called "experts" on this forum. As long as you have the new blue and yellow stripe springs, you won't have any problems!!

Sorry, I only meant they needed to be shimmed for my friends application. I believe he had some valve float that killed atleast one spring.

Thank You! Some very good info there and I appreciate the reply :cheers:

For the record: my mech said the same thing you did; albeit in different terms :)

He also showed me the instructions that came with the springs and they refer to their adjustments and also recommend no shimming :)

Thanks to everybody who replied!

I chalk another one up for Tech :chug: