what potential damage from overtightening roller rockers?

[ari666]

so i have had an ongoing erratic vacuum issue on my latest build, manifold vac has been bounching rapidly over about 6 inchesHG. i redid my inlet manifold 3 times, tried three different carbys, checked rechecked and re-recheck all hoses ports etc etc etc.

a little history; one fine day about 3 months ago a valve spring snapped on me while i was sitting quietly in traffic. wasnt revving, just idling and the vac starts going mental bouncing from 0-15INHG. so fixed that. and vac just goes back to being erratic.

now, two days ago i re adjusted my roller rockers, but this time, rather than the "find zero lash the tighten 1/2 a turn" that crane recomended i just did zero lash and about 1/100th of a turn. start the car, vroom, erratic idle still *sigh* no worries, i need to look elsewhere. anyway as i drive the vac gets more and more stable. to the point where this morning it was rock solid on 9 inches...

would over tight rockers snap a spring?
would they burn out valves?
would it burn valves, but then clean the burn off once they start seating properley?
would it cause pinging?
crack the head?

or anything else horrible you can think of. it has crane anti-pump lifters if that makes a difference. and it is rather fast too it still got its 147.5 with erratic vacuum and tight rollers. the dyno guy didnt mention it.

thanks fellas

 

[VN_chris]

I over tightened the rocker arm bolts when i rebuilt my V6 and 3 of them just snapped after driving about 30km, got the bolts out and did the job properly the second time and i havent noticed any of the nastys you have mentioned as possibilities.

 

[strgas]

sounds like a valve problem from when you snapped a valve spring may have a bent valve and not reseating correctly . was it a intake or exhaust valve spring that broken ??? do you have a popping sound back thru the carby at all . overtighting the rocker and removing all lash can hold open the valve ,affect the lifter operation burn the valve face cause backfiring ......

 

[vyjess]

sounds like u could of bent a valve! mite pay to do leak down test on that cylinder!

 

[ari666]

intake valve, number 6. popping as in back firing through the carby? no not really. compression test results after we changed the spring was 160 psi. which is average to the others.

whats involved in a leak down test?

 

[vyjess]

have a look on ebay under leak down tester they r on there for under $100 and it kinder tells u how they work! but u can do a back yard 1 by making up a air fitting that screws into your spark plug hole and with your piston at tdc with both valves shut on compression stroke pump a bit of compressed air into that cylinder,if u have a problem u will here air leaking out of the cylinder into the sump if rings arnt sealing, into the inlet manifold if inlet valve is leaking and into your exhaust if the exhaust valve is leaking! start with a low air preasure and increase until u find a leak but be careful to much air preasure can spin ya motor over!