MY 1968 had a very poor overhual done on it over the summer where the cam, lifters, fuel pump and oil pump were re-done. The local hotrod shop who did the work could never get the lifters quiet. I've since have had it looked at by someone else and they couldn't either? The motor has less then a 1000 miles on it. (Engine, Pontiac 350).
Any suggestions to quiet this sewing machine down?
There is no valvetrain adjustment on a standard Pontiac engine.
Nuts on the rockers are tightened to the specified figure, and that's that.
If you have roller tip rockers, adjustable drivetrain, replacement rockers or pushrods, incorrect lifters, incorrect installed valve height then you will experience valvetrain noise.
Pull off a rocker cover and post a couple of pics.
It's not a Chevy, and adjusting it like one won't work.
Vikki 1969 Goldenrod Yellow / black 400 convertible numbers matching
And if you have stock-like upper end components, in which 20 lb/ft is the 'adjustment' and you have ran the engine while chebbyzied, you have destroyed the lifters. The only correction in such a case is to tear it down and install new lifters.
What length pushrods you using? Rockers? Locknuts or stock?
Could be the wrong rocker geometry, improper studs for the rockers or the nuts bottoming out prior to proper valvetrain adj. Which leads back to geometry.
Which heads?
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
I had the 5C heads on a 400 motor with Comp Cams Rockers and BBC studs. That was the motor from my black 67.
I was having issues with bending pushrods at high RPM soon after I bought it and was breaking up after 4k. After 3 bent pushrods, I pulled the covers and tried to re-adjust after buying and installing the new pushrods.
Problem was the pushrod length was stock and was not allowing me to adjust the valvetrain. I had to go to 9.375" BBC exhaust pushrods across the board to quiet the valvetrain. This was based on stock stamped rockers and bottleneck studs/stock nuts not being used with a stock pushrod length. When they changed out to Comp Cams rockers and studs, the adjustable height/length increased.
Some heads will have different deck heights depending on whats been done. You have to properly measure that length with a "pushrod length gauge" and can not necessarily rely on "stock" applications as far as pushrods.
When I installed a set of 46's, I had to decrease the pushrod lenght back to stock with the same rocker setup.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
Sorry to hijack this is an extension of this conversation-so you're saying for rocker adjustment you don't bring each to bottom and zero lash? You just set each rocker to 20 ft/lbs? (on stock valvetrain)
Yes on a stock valve train...stock castings, lifters, pushrods, rockers, stock installed height of springs and cam...just run the nut down till it bottoms out on the stud and torque it to 20#.
You have to be careful with a cam change though because as the lift gets higher you can run the risk of pulling pressed in studs out. And as always, you should check for coil bind and seal interference before starting up.
You can only 0 lash with poly locks. Factory nuts will back off allowing the push rods to come out. Most everyone i know turns the poly's a 1/4 to 1/2 turn more after 0 lashing.
Birdll, we need pic's to see what type of rockers-n-nuts where used.
