Dumb question....Help please - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BADPURPLE70CHEVY · 10-19-2010, 01:47 PM

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

coryalexander · 10-19-2010, 02:04 PM

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.

BADPURPLE70CHEVY · 10-19-2010, 03:08 PM

Anyone else run into this problem?

Jacfourteen · 10-19-2010, 04:24 PM

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.

**bigsnookmaster** · 10-19-2010, 11:09 PM

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!

llowlife · 10-19-2010, 11:16 PM

What leads you to believe its a valvetrain issue?

pat 70/71 · 10-20-2010, 12:14 AM

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

corvetteman10 · 10-20-2010, 12:14 AM

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.

coryalexander · 10-20-2010, 11:20 AM

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

BADPURPLE70CHEVY · 10-20-2010, 11:41 AM

Quote:

Originally Posted by corvetteman10

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.

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.

BADPURPLE70CHEVY · 10-20-2010, 11:42 AM

Quote:

Originally Posted by coryalexander

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

Miss is all the time....

*stich626* · 10-20-2010, 11:45 AM

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?

coryalexander · 10-20-2010, 12:38 PM

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.

BADPURPLE70CHEVY · 10-20-2010, 06:02 PM

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

*stich626* · 10-20-2010, 06:27 PM

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..

BADPURPLE70CHEVY · 10-20-2010, 06:34 PM

Quote:

Originally Posted by stich626

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..

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

*stich626* · 10-20-2010, 07:00 PM

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

10-19-2010, 01:47 PM	#1
BADPURPLE70CHEVY 406 Powered Join Date: Aug 2009 Location: waynesville,n.c. Posts: 877	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 __________________ 70 GMC 68 c10 2002 silverado 72 4x4

10-19-2010, 02:04 PM	#2
coryalexander Registered User Join Date: Sep 2010 Location: Tyler,Tx Posts: 25	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.

10-19-2010, 03:08 PM	#3
BADPURPLE70CHEVY 406 Powered Join Date: Aug 2009 Location: waynesville,n.c. Posts: 877	Re: Dumb question....Help please Anyone else run into this problem? __________________ 70 GMC 68 c10 2002 silverado 72 4x4

10-19-2010, 04:24 PM	#4
Jacfourteen Big Red - Now its a SWB! Join Date: Jun 2009 Location: Oroville, Ca Posts: 1,624	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. __________________ 68 3/4 ton (Project)-350 Small Block, .030 over, 10:1 comp, 3998993 heads, C3BX edelbrock intake, comp cams XE268, Holley 670 SA, long tube headers, dual flow 40's, E-fan, Alum rad, currently under the knife getting shortened and bagged build thread 41 3/4 ton (wife's)-flatbed, fully restored to original 01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's 02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's

10-19-2010, 11:09 PM	#5
bigsnookmaster Senior Member Join Date: Jan 2008 Location: St.Petersburg,Fl Posts: 1,270	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! __________________ greg http://community.webshots.com/user/68406Stepside

10-19-2010, 11:16 PM	#6
llowlife Registered User Join Date: Jan 2010 Location: Elgin Mn Posts: 112	Re: Dumb question....Help please What leads you to believe its a valvetrain issue? __________________ In the beginning of a change, the patriot is a scarce man, brave hated and scorned. When his cause succeeds however, the timid join him , for then it costs nothing to be a patriot. I am a revolutionary...so my son can be a farmer...so his son can be a poet. If there must be trouble, let it be in my day, so my child may have peace... 72 short step w/ 388 /4l80e/ and 3.08 gears.

10-20-2010, 12:14 AM	#7
pat 70/71 Registered User Join Date: Nov 2009 Location: newbury park california Posts: 1,038	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

10-20-2010, 12:14 AM	#8
corvetteman10 Registered User Join Date: Jun 2009 Location: riverside,ca Posts: 32	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. __________________ '72 cheyenne10 tilt, tach, a/c, posi '70 custom10- daily grind

10-20-2010, 11:20 AM	#9
coryalexander Registered User Join Date: Sep 2010 Location: Tyler,Tx Posts: 25	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?

10-20-2010, 11:45 AM	#12
stich626 Account Suspended Join Date: Sep 2010 Location: hingham ma Posts: 1,721	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?

10-20-2010, 12:38 PM	#13
coryalexander Registered User Join Date: Sep 2010 Location: Tyler,Tx Posts: 25	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.

10-20-2010, 06:02 PM	#14
BADPURPLE70CHEVY 406 Powered Join Date: Aug 2009 Location: waynesville,n.c. Posts: 877	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!!!! __________________ 70 GMC 68 c10 2002 silverado 72 4x4

10-20-2010, 06:27 PM	#15
stich626 Account Suspended Join Date: Sep 2010 Location: hingham ma Posts: 1,721	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..

10-20-2010, 07:00 PM	#17
stich626 Account Suspended Join Date: Sep 2010 Location: hingham ma Posts: 1,721	Re: Dumb question....Help please I'd replace them all with arp studs if it does it again a girdle



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.