Dumb question....Help please
 

My 406 is roller. I have developed a miss after putting a few miles on it. I am assuming the miss could be the valves needing adjustment already. Can valves out of adjustment cause a miss? thnx

Re: Dumb question....Help please
 

yes it could but they would have had to of backed off quite a bit , if they have backed off that much i would look into some new poly locks or maybe a set of stud girdles.


also you want to check your cam to make sure you have not scrubbed a lobe.

Re: Dumb question....Help please
 

Anyone else run into this problem?

Re: Dumb question....Help please
 

On my flat tappet cam I had a rocker lock nut that backed way off it caused a miss, but more noticeably it caused a horrible knocking. It sounded like a piston was about to shoot through the head! So if its not knocking I don't think that a loose rocker is the problem.

Re: Dumb question....Help please
 

I would re-check the lash. If you have aluminum heads the lash will grow by about .006 after the engine gets hot. Or a rocker might have came out of adjustment.You might want to check the lifters to see that all the rollers are still good. I have a 406 roller w/alum heads and Jesel shaft rockers and have had no valve lash changes with 1500 miles so far. Good luck!

Re: Dumb question....Help please
 

What leads you to believe its a valvetrain issue?

Re: Dumb question....Help please
 

could he have flattened the cam? happened to me only one time. lack of lubrication at start up? improper lash? not trying to be nasty just thinking as I'm typing. maybe run a compression test to see where your at. check to see if all plugs are firing? please let us know what you found. cheers, Pat

Re: Dumb question....Help please
 

I don't think you mentioned whether it was solid or hydraulic roller. If it is solid then it is very possible that you have a lash issue. If it is hydraulic, as long as they were properly adjusted to start with, they should be ok. But, checking it wouldn't hurt. There are so many different things that could cause a miss. do you check all the basics? New plugs? I was installing a new set of plugs at work recently and one of them didn't have an electrode right out of the box! New plug wires? Are the contacting the exhaust or rubbing on something? Carb properly tuned? does it always miss on the same cylinder? Just some thoughts. Let us know what you find.:chevy:

Re: Dumb question....Help please
 

just another question is this miss at idle , while cruising , when hammered on it when does it miss or is it all the time?

Re: Dumb question....Help please
 

Solid....I changed the plugs even though they were new. Have fire to all cylinders. Idle is up a little along with the miss. I know my brother drag races a 406 and his valve lash has done the same thing and also he said his idle goes up some along with that miss until you reset the lash.

Re: Dumb question....Help please
 

Miss is all the time....

Re: Dumb question....Help please
 

solid, then you have poly locks. the lash should not change, if it is something is a miss..
and it be the roller lifter.. if lash is changed and you have poly locks and are tight, I'd pull the intake and check the lifters, they make a mess when they fail..

have you check the plug wires?

Re: Dumb question....Help please
 

are you using the stock wiring harness? if you are , and you are running a coil ? if so run a wire from the battery to the coil and see if it changes , we ran into this on a friends car , it had a miss to it cause it wasnt getting enough juice to the coil , ran a new wire to the coil froma different fuse and it cured the problem.

also you may want to check grounds and stuff like that on your ignition, a bad ground will do the same thing.

Re: Dumb question....Help please
 

Found the miss...Broke rocker stud.....thank goodness thats all it was. Gonna fix her friday. THANKS FELLAS FOR THE HELP!!!!

Re: Dumb question....Help please
 

but why it break. might want to check the pushrod too.
is the slot in rocker hitting the stud at full lift..
is the springs going into coil bind
is the guide hitting the spring cup..

Re: Dumb question....Help please
 

Checked all that.Not always a problem. Broke some on other cars that had no other problems.

Re: Dumb question....Help please
 

I'd replace them all with arp studs
if it does it again a girdle