Rocker-lifter issue

1965CS · Guru

Rocker-lifter issue

beaumontguru · Canadian Poncho Superstar!

Are the pushrod guide holes thru the head worn badly? Causing the pushrod to slop sideways. Or perhaps lifters sticking in the bores? Just a thought.

4SPEED427 · A Poncho Legend!

Can you give us any history on the engine? This a new combination, or been running it for a while and suddenly has issues?

No recent changes/alterations prior to this happening?

Engine was running fine, then suddenly this happened?

1965CS · Guru

I have been running the engine for several years, but always had some intermittent rocker noise. Also, I should have mentioned that before the second incident, new lifters and rods were put in and the cam is not that old and slightly higher lift than stock.

Inspection of the old lifters and rods, didn't see any abnormal wear.

-- Edited by 1965CS on Tuesday 12th of July 2022 03:57:21 PM

seventy2plus2 · Canadian Poncho Superstar!

something just popped into my head, as a buddy had a problem with his 70 454 breaking rocker arms. He'd put in a Comp Cams camshaft & springs, and the instructions say to use all Comp Cams components. His valve springs were too stiff, and the weak point was his stock rocker arms. I put the same camshaft in my car, but ensured to increase pushrod diameter from 5/16" to 3/8". I used complete Comp Cams valve train components, no problem.

However, I don't know if pushrod diameter is optional on small block chevies. I'd say moving up to the roller rockers was a good choice, maybe pushrods are the next step.

Prefectca · Poncho Master!

I have seen this before. The rocker arms dont have enough of a slot and are binding on the rocker studs at full lift. The weak point is the push rod. When the rocker arm cant go any further the push rod will fail.

Paul

1965CS · Guru

In doing some research, it seems that pushrods are available in .1 inch length differences, that is, mine are 7.8 inch so maybe a 7.9 would cure the problem? However, I have not found a source locally that has the different lengths, only the current 7.8.

seventy2plus2 · Canadian Poncho Superstar!

1965CS wrote:
In doing some research, it seems that pushrods are available in .1 inch length differences, that is, mine are 7.8 inch so maybe a 7.9 would cure the problem? However, I have not found a source locally that has the different lengths, only the current 7.8.

Here's a tool that can be used to ensure pushrod / rocker arm / valve stem geometry. Unless something has changed the geometry (shaved cylinder heads, taller valve stems) I don't think the geometry (and henceforth pushrod length) is the issue.

Proform 66789 Push Rod Length Checker, 3/8" studs. (tool for 7/16" studs is part # 66790)

pushrod checking tool.jpg

-- Edited by seventy2plus2 on Tuesday 12th of July 2022 11:43:46 PM

seventy2plus2 · Canadian Poncho Superstar!

Here's a video of a guy using that tool to check rocker arm geometry. You should be able to pick up the tool at Mopac in Calgary, probably about $20-25.

1965CS · Guru

seventy2plus2 wrote:
1965CS wrote:
In doing some research, it seems that pushrods are available in .1 inch length differences, that is, mine are 7.8 inch so maybe a 7.9 would cure the problem? However, I have not found a source locally that has the different lengths, only the current 7.8.
Here's a tool that can be used to ensure pushrod / rocker arm / valve stem geometry. Unless something has changed the geometry (shaved cylinder heads, taller valve stems) I don't think the geometry (and henceforth pushrod length) is the issue.
Proform 66789 Push Rod Length Checker, 3/8" studs. (tool for 7/16" studs is part # 66790)

-- Edited by seventy2plus2 on Tuesday 12th of July 2022 11:43:46 PM

I have seen this tool and the one that is an adjustable rod to measure the distance between lifters and rockers.

Prefectca · Poncho Master!

Back in the sixties the hi-perf 327 and the Camaro 302 had what were called long slot rocker arms due to the high lift camshafts. Installing the wrong type rocker arms resulted in the damage shown in your pictures.

seventy2plus2 · Canadian Poncho Superstar!

How did you ever make out with this Steve?

1965CS · Guru

seventy2plus2 wrote:
How did you ever make out with this Steve?

Been a very busy summer with other projects so far and still deciding on whether or not to bother fixing it. I may decide to replace the engine or just get rid of the car, but probably not this year.