Valve lash / false knock

92Ty#1524

New member
I've been battling false knock with my recently built motor. Its so bad that I'm getting kr just from reving the engine and while driving under light throttle. Its retarding at least half of the spark under light throttle and all of it in wot. I went out on a limb and replaced the trans (RPM) and Raptor TC just to rule that out. Naturally, I'm assuming that since the motor was assembled by an NHRA pro, nothing could be wrong with the engine. Right? I'm having doubts.

The thought cossed my mind that the problem may be in the valvetrain because it was probably the biggest change in the engine that was made (2.02/1.60, pushrods, lifters, 412 cam, Crane 1.5 roller tip rockers, new studs) and it wasnt there before. Not to mention, I cant hear anything unusual with the naked ear. I inquired about how he set the lash. He set it to zero lash plus 1/8 turn " because it will allow you to take advantage of more lifter plunger travel at higher rpms..", I was told. I've searched the site for lash settings and in spite of the various recommendations made, nobody seems to have set thiers as such.

Its my feeling that mine need to be turned in a bit more. I've read anywhere from 1/4 turn to a full turn.

Any suggestions?
 
Last edited:

tbauer03

TRBOBOX
Re: Valve lash / false knock

i did 1/2 a turn, i once had one of them loosen up on me and it makes a very audible noise you would hear it if that is the case. might try moving your knock sensor to the front of the block away from the tranny and torque converter to really eliminate it. there is a few good holes on your lower intake to mount the knock sensor up front
 

jwaller

Evil Genius/SyTy Guru
Re: Valve lash / false knock

the valve lash setting all depends on the ones you purchased and the cam installed. I know stockers like 1/2 turn and so do most lifters(except race stuff like the comps I use), but the ppl who make my custom cams only reccommend 0.010 preload.

1/8 is not enough but I am not sure thats what is causing your false knock. is your flexplate tight? how about the conv, did you use red locktite? do all your plugs look good(even patterns, no salt and pepper)
 

HotRudyRod

New member
Re: Valve lash / false knock

All those ideas sound good for my clicking noise, hope its just a lil tightening of the rocker's nut.
 
Last edited:

92Ty#1524

New member
Re: Valve lash / false knock

I hope so, too. I'll turn em all down one day this week and go from there. I'm certain the TC and flywheel bolts are sound. Rechecked when I put the trans in this weekend. Keep the suggestions coming in the mean time. Kinda feel like a jackass after all the money I've pissed away at this and my wife's blazer can still kick my butt. lol
 

mattw

Active member
Re: Valve lash / false knock

There has been a couple of threads that suggest that forged builds cause false knock.. Relocating the knock sensor to the lower intake usually seems to be the fix..

-Matt
 

92Ty#1524

New member
Re: Valve lash / false knock

Forged, as in pistons? I'll look into that.

If so, the pistons were also in my last motor. Same block and pistons...new probem.
 
Top