Pushrod rubbing head.

Injected1

Injected1

Member
Ok so I have searched on this all morning and can't figure out what to do.

My engine build consists of Vortec heads, beehive springs, 415 cam, comp 7.200 hardened pushrods #7490, 1318-12 1.6 comp pro magnum roller rockers. The build has approx. 60 miles and during that time the valvetrain noise got progressively louder. The rockers seemed a bit loose as I only set initial lash and was going to set lash with the engine running when I noticed the rub marks on the pushrods.

Options:
1. Elongate holes to clear----no way, not pulling heads.
2. change 1.6's to 1.5's----thinking about this one
3. longer pushrods---would this work?

Any help would be greatly appreciated.
 
sytyguy

sytyguy

Moderated User
Re: Pushrod rubbing head.

What pushrod is that? I assumed Comp but can find no listing for a 7490 pushrod (in -12 or -16 configurations). My recommended pushrod is the Manley 25733/25734 ones. One piece 5/16" rod that has proven to be incredibly durable.

Double check the PN, length, and diameter of your pushrods. Length should be 7.200-7.250 and width should be 0.3125" (5/16").
 
S

Syclone #1721

I LOVE 4UM SUPERSTARS
Re: Pushrod rubbing head.

Its the 1.6 rockers doin this...they move pushrod closer to the rocker stud.....solutions are enlarge pushrod holes....or just use 1.5s.....go with the 1.5s...the gain if any isnt worth the hassle.
 
sytyguy

sytyguy

Moderated User
Re: Pushrod rubbing head.

I've used the 1318 rockers & 24733 rods on several engines (some vortec, some LB4/L35).....none with a geometry issue.

[/my experience]
 
jwaller

jwaller

Evil Genius/SyTy Guru
Re: Pushrod rubbing head.

you are going to have to enlarge the holes in the heads you shouldn't be getting any noise from that though. you need at least 5/8 of a turn of preload.
 
S

Syclone #1721

I LOVE 4UM SUPERSTARS
Re: Pushrod rubbing head.

Also, def preload the lifters....no need to do it running...the nice thing about hydraulics is they have room for error especially the GM hydraulic rollers.....just put the cylinder you are going to adjust to TDC and then take the valves to zero lash and give them 3/4 to 1 full turn. Bolt the valve covers back on and drive it like you stole it.:tup:
 
Richard Le

Richard Le

New member
Re: Pushrod rubbing head.

However, if you are using COMP 875 lifters, then they require only 0 - 1/8 turn of preload after zero lash per instructions for best performance.
 
Quickstop [UK]

Quickstop [UK]

Combating adversyty.
Re: Pushrod rubbing head.

Richard Le said:
However, if you are using COMP 875 lifters, then they require only 0 - 1/8 turn of preload after zero lash per instructions for best performance.
Click to expand...

Where does it say that?

I am running those and never heard that advice. I did read the 875s are noisier though but I have 2 deg of knock and that's it. Not tuned it yet though but am very attentive to the lash issue.

I did 3/4 turn after 0 lash....
 
BoostedSUV

BoostedSUV

Active member
Re: Pushrod rubbing head.

Syclone #1721 said:
Its the 1.6 rockers doin this...they move pushrod closer to the rocker stud.....solutions are enlarge pushrod holes....or just use 1.5s.....go with the 1.5s...the gain if any isnt worth the hassle.
Click to expand...

X2. Put the 1.5s on it and be done it with it. With the 1.6s you will need to enlarge the push rod boses. I too learned this the hardway.
 
Richard Le

Richard Le

New member
Re: Pushrod rubbing head.

Quickstop [UK] said:
Where does it say that?

I am running those and never heard that advice. I did read the 875s are noisier though but I have 2 deg of knock and that's it. Not tuned it yet though but am very attentive to the lash issue.

I did 3/4 turn after 0 lash....
Click to expand...
Directly from the instruction manual that came with the lifters: http://www.comp.com/Technical/Instructions/Files/COMP4-115.pdf

"The following instructions cover the correct guidelines for installing COMP Cams® Pro Magnum™ Hydraulic Lifters. All Pro Magnum Lifters™ require an adjustable valve train for proper operation. Through various testing we have discovered that lifter preload should be set between zero and 1/8 of a turn for optimal performance."

Setting them too tight and you run the risk of damaging the lifters or hanging the exhaust valves open. According to COMP Cams, excessive pre-load will cause rough idling and low manifold vacuum, and can even lead to severe engine damage. Mine are quiet at 1/8 turn preload. You will find tons of info on the 875 lifters if you Google "875 lifters preload".
 
You must log in or register to reply here.
Top