Big Block valvetrain issue advice needed

-
mycuda

mycuda

FABO Gold Member
FABO Gold Member
Joined
Feb 15, 2011
Messages
5,217
Reaction score
3,490
Location
Chicago/ Metro
Built this engine early 90's. Might be 1000 miles on it.

383 .60 over, 11:1 SC, open chamber heads, geardrive, Crane [email protected] X 540 solid lift cam.
108*. 1.5 cast rocker adjustable setup, ball/cup crane push rods. 3500 stall 4.10 gears

Last fall did a test run in industrial park, 100 shot nitrous 5500RPM.
Did many times prior, no engine miss, or valve float, actually ran good.

Fairly loud exhaust so couldnt hear then.
Went to start yesterday and noticed excessive valvetrain clacking passengerside bank.
So adjusted valves .019 as recommended. They were not far off at all, onlyadjusted
a couple. But #8 intake had more lash. After adjusting put valve cover on started and no
quieter at all.
Took off rocker assembly to investigate. Oil to all parts,Push rods all straight, rockers,springs seem fine
except #8 intake rocker wear (see photos) and #8 exhaust valve wear??

Before I proceed wanted some input on possible problem? Bent valve? Valve guide?
Also engine runs good no misses as is???

Thanks, Dave
 

Attachments

  • 20160324_142322_resized.jpg
    34.8 KB · Views: 438
  • 20160324_142458_resized.jpg
    41.8 KB · Views: 423
I would pull the spring and make sure nothing is broken there. Did you measure lift at the lifter? Any chance the lobe is going away? Leak down test will tell you if valve is bent.
 
pushrods look pretty good, might be photo along with oil distorting Pic.
 
slide the 2 cylinder #8 rockers off and inspect. how big was the lash? a worn lobe is smaller=less load on the valve and spring. something is worn wrong, better go safe than sorry. look for broken springs
 
Marco-

when i first adjusted it, it was out ,but not enough to hear the noise I heard.

and by looking at threads on adjuster,under rocker, this is the only one where i dont see 2 threads under rocker adjuster at pushrod , from beginning????

Again, dont seem to here any change in accereration or misperformance as it is??

Other than sounding like .030 gap on lash????

Thanks,Dave
 
Check your flexplate! Bolts could be loose or you may have a crack and it often sounds like valve train noise.
 
Just throwing some other simple stuff out there. How's the end of that shaft look under the rockers? Is it still round when torqued down? Flatness across all rocker posts good? Consistency of rocker tip wear across the bank?
 
Daves69 said:
Just throwing some other simple stuff out there. How's the end of that shaft look under the rockers? Is it still round when torqued down? Flatness across all rocker posts good? Consistency of rocker tip wear across the bank?
Click to expand...

All rockers, no play on shaft and spin around freely with no bind.

Gonna find old valvecover somewhere cut it so i can start up and pinpoint exactly
where noise is coming from.

Thanks
 
EZ enough to pull that valve spring and rotate the valve, see if the stem is bent or valve binds on the seat. The rattling may be the valve sticking in the guide, and the increased wear on the rocker could be part of that issue.
 
If you feel the rockers while running does it change? Mechanical fuel pump? Someone else here had a fuel pump arm that was "knocking". Also any exhaust leaks? It's definitely rhythmic sounding in the video. By chance when you had rockers off did you straight edge across the valve stems to see if they're all the same height?
 
Hi, Electric fuel pump. Did straight edge on valve tips looked good.
What gets me is its not misfiring, and clacking doesnt seem to get louder at higher rpms.

Thanks.....
 
Watch the fourth valve stem from the rear, either it, or the rocker is moving laterally, and appears intermittant as well.

Put a screwdriver between the valve springs and move retainers sideways, and back and forth.

There's definately something screwy there and a coupla valves ahead of it too.

check for bent pushrods.. roll them on something flat (floor)
 
Thanks for response.
pushrods 100% straight.
will move springs/ retainers 180 degrees
on cylinder 6/8.

Thanks.
 
I found #6 ex. rocker is not being pushed back on shaft to spacer by spring cause it is hitting part of head stock?

Can I grind part of rocker or shim entire shaft up and readjust lash on entire bank?

Or is that not something that could be the culprit of noise?


thanks D
 
Listening to your video it sounds like an exhaust leak to me. Possibly a crack at the headpipe and flange...maybe under the wrap? Noise sounds to be in concert with the cylinder firing rather than valve train action. Got a stethoscope with a small metal tube attached?
 
Old Man Mopar said:
Listening to your video it sounds like an exhaust leak to me. Possibly a crack at the headpipe and flange...maybe under the wrap? Noise sounds to be in concert with the cylinder firing rather than valve train action. Got a stethoscope with a small metal tube attached?
Click to expand...

Hi, OMM

Video audio doesnt do justice to clacking sound.
Sound is definitely coming from The cam up to valvetrain somewhere.
Honestly sounds like echoing from under intake?

I just want to do all I can up top before I have to do start disassembly.
I will grind suspicious rockers possibly scraping head stock first,
then shim up rockershaft assembly and re lash valves.
Maybe Ill get lucky.

Thanks D.
 
You must log in or register to reply here.
-

Back
Top