push rods rub??

Grumpy · Dec 2, 2016

First post here, but been reading a while so hang with me:

Hello all i am new to the v8 scene i have a new to me 1970 nova with an unknown 350 in it. It has 041 heads and for the most part seems very stock. The engine seems very low miles but has defiantly sat for a long time, as when i first got the car the valve covers were full of milkshake sludge but there is no coolant leak, just to give an idea of the condition...

I was in the process of finishing a tune when it developed a valve tick, i pulled the cover to find that the number 2 intake rocker had rotated off the valve. I found that that pushrod is slightly bent, and had marks from rubbing the head. I pulled the other covers and have now found that 3-4 other pushrods are rubbing in a similar fashion. I only ran the car tapping the side of valve for a few minutes before looking, and only at low rpm.

Who ever had been running the car before me had the timing set at something like 22-30 degrees btdc INITIAL timing, but other than that the car was running just fine, and when i put it back to 12 it was happy as a clam.

So my first question is this a chicken or the egg problem, could the super detonation timing have caused some of my pushrods to bend? or likely something else?

The second question is now that some pushrod holes in my heads have been rounded out weirdly to the sides do i stand a chance of this not happening again? I don't want to have to pull the heads and install pushrod guides on a mostly stock motor...

Thanks for reading

Edit: one of the first things i did when i got this motor was run around and check the lash on all the rockers, i was looking for a different sound and needed to eliminate valve lash tapping. All the valves seemed to have the recommended loose 0 setting, and nothing was crazy off.

due too the design of most rocker stud girdles and the locking nut designs in many cases your choices will be limited ,
but I prefer to keep the lower rocker girdle surface a minimum of about .060 from any portion of the roller rocker in its arc if I can manage that

SOME ROLLER ROCKERS CAN AND DO BIND ON ROCKER STUDS, or rocker adjustment nuts, youll need to check carefully

some roller rocker too retainer combo clearance issues cause problems easily solved with beehive springs and smaller retainer diameters

the POLY LOCKS that are used with most roller rockers AND ROLLER ROCKER SIZES, (come in a variety of lengths AND DIAMETERS AND THREAD SIZES) so you might find you need tall valve covers to allow clearance BUT in most cases swapping to shorter poly locks reduced that problem from mandating taller valve covers, be aware that the outside diameter of the locks is a darn important factor in allowing the rocker to reach full potential lift!
it should be obvious that youll need to carefully check clearances over the full rotation and lift in several areas if you chance valve train components and retainer to rocker and internal rocker clearance slot to poly lock are two of many potential places the valve train may bind if theres not the correct clearance

check all valve train geometry and clearance on any engine you assemble or modify the valve train on.

this is sure a case,
where a couple hour's of
reading links, and sub links carefully
and dealing in known facts and meassurements,
would most likely
save you a good deal more time,and CASH
that random guessing would here!
heres a bit of useful related push rod length info
Big Block Chevy, Standard Length Big Block Intake 3/8" / .080" 8.275"
295-7941-8 Big Block Chevy, Standard Length Big Block Exhaust 3/8" / .080" 9.250"
295-7969-8 Big Block Chevy, Standard Big Block +.100" Long Intake 3/8" / .080" 8.375"
295-7979-8 Big Block Chevy, Standard Big Block +.100" Long Exhaust 3/8" / .080" 9.350"
295-7951-8 Big Block Chevy, Standard Length Big Block Tall Deck Intake 3/8" / .080" 8.675"
295-7961-8 Big Block Chevy, Standard Length Big Block Tall Deck Exhaust 3/8" / .080" 9.650"
295-7800 V8 396-454 Retro Fit Pushrod Set, Intake & Exhaust, 1965-Present
3/8" / .080"
3/8" / .080" 7.725 Int.
8.675 Exh
295-7913-16 Small Block Chevy, Standard Length Small Block Chevy 3/8" / .080" 7.800"
295-7984-16 Small Block Chevy, +.100" Long 3/8" / .080" 7.900"
295-7934-16 Big Block Ford, Standard Length Ford `72-'78 429-460 3/8" / .080" 8.550"
295-7951-16 Big Block Ford, Standard Length Ford `69-'71 429-460 3/8" / .080" 8.675"
295-7582-16 Oldsmobile, Std Length 455 5/16" 9.550"

http://www.superchevy.com/how-to/engines-drivetrain/sucp-0202-rocker-arm-ratio/

http://www.hotrod.com/articles/ctrp-0703-rocker-arm-comparison/

http://www.hotrod.com/articles/roller-rocker-ratio-test/

push rods rub??

Grumpy

The Grumpy Grease Monkey mechanical engineer.