Broken rocker arms on 304 V8???

[Ian Johnston]

Anyone had trouble with rocker arms on 5lt motors? Daughters VT Clubby broke 2 coming up to Adelaide yesterday. I fixed it today
with a couple of 2nd hand ones, but need to fix it properly.
I think it may have too much valve spring pressure.(been rebuilt to 355 stroker)

[vq rat]

how much lift has the cam got push rod length could be wrong, stock rockers?? was the heads shaved or block decked??

[Morton]

Most big cammed motors really need roller rockers.

[ari666]

did it break the rocker arm? or that bridge joining the two rockers? a mate used to snap that bridge often, he put a couple of shims in under it and it stopped breaking after that.

if it broke the actual rocker, you got problems.

[Ian Johnston]

Its only a mild torque cam(roller cam) No block/head decking done.
Broke actual rocker arm, not the alloy bridge.
It has stiffer valve springs, and I am guessing they are too strong for the standard rockers.
Looks like rollers on there way.

[VR38]

Were they worn out old arms fitted that failed or new/good condition ones?

[ari666]

mate any chance of a pic? how do you mean "broke" you mean bent, snapped, or chewed through?

those puppies are pressed steel. snapping one would have to be a catastrophic fail. either the rocker was a POS or something serious going on with the valve. does the valve open and close?


edit* just re-read: you broke TWO???? mate. as far as "worn out old ones" my impala is running with the rockers it was born with in 66' they are not really something that wears out. i mean they wear around the two friction points,

this engine got triple springs in it or something?

[VR38]

Three, they wear on the three friction points.
I have seen quite a few holden pressed steel rockers punch thru the pushrod cap etc from high wear.

[delcowizzid]

yeah my guess is punched the rod throgh the rocker and split it in half happens a lot

[Ian Johnston]

Been having trouble with my internet, so slow reply. This is actually the 3rd rocker issue. 1st was a punched hole,which we just put down to one
of those things, and now 2 broken ones.
They didnt break thru the pushrod holes, was halfway between pushrod, and bridge mount.
It has tripple valve springs, which I think is causing the problem.
Going to get rollers put on 2morro if possible. Was coming to Adelaide for a tune, so will get it all done together.
And, they were brand new factory rockers.

[ari666]

It has tripple valve springs, which I think is causing the problem.

LOL. ya THINK?

[Ian Johnston]

All fixed now. Got a set of Yella Terra rollers fitted.

[immortality]

Mild torque cam with triple valve springs..... doesn't sound like a good combination. I'd look at getting the correct springs for the cam and save the valve train from all that excessive load.

Don't suppose you have the spec's for those bad boys

[Ian Johnston]

Talked to the engine man the other day, and he said the springs dont have excessive seat pressure, just bigger diameter to stop binding with the extra cam lift. Heads have been modified to acomodate the springs, and different valve stem seals.

[immortality]

your fortunate that it's a roller cam, a mild flat tappet cam wouldn't like the heavy springs. Do you know the cam specs?

[Ian Johnston]

No, sorry, I dont know the specs. Its a Wade grind, thats all I know. Was ground for torque, not top end power.