# Rocker Arms



## extinctmake (Feb 8, 2011)

I’ve been going through my small cache of Pontiac parts preparing for my engine build and I found a set of used Crane rocker arms, valve springs, poly lock rocker arm nuts, and screw-in rocker arms studs. These came from a 400 I acquired and sold many years back. 

I sold the #62 heads from the 400 to a guy who didn’t want these parts. He had some other valve train pieces he wanted to use. I kept the parts thinking they could be of some use. The cam that was with the engine was a Crane High Intensity series. I sold the cam and some other parts with it at a swap meet thinking it was too much for what I wanted for street use if/when I'd build my numbers-matching 389 for my '65 GTO.

Fast forward and I have all these rocker arms and related parts. I also have the original rocker arms to my 389. I looked at all of them and a small spot where the valve met the tip of the rocker arm was shiny. They didn't seem worse for wear.

I wonder. What wears out on a rocker arm under normal use? I’ve never had to replace one. Rebuilt a 350 Chevy for my old Nova 20-odd years back and we just used the existing rocker arms. 

I know most use a roller rocker and Comp Cams has a nice set for around $150. I realize many cam kits come with valve springs or a specific spring is required with some cams. I know this could be a case of a dollar waiting on a dime, but if these are good parts, why not use them? 

If my machinist says not to use them, then I may as well toss them in the scrap metal barrel. I see no point on keeping them if I won’t use them. If these are good, but don’t suit my engine, then I will just recycle them.

One more question about rocker arms: How can one tell a 1.50/1.52 rocker arm from a 1.65 rocker arm?


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## BearGFR (Aug 25, 2008)

Wear points are going to be where you might expect: rocker tip, pushrod cup, and fulcrum where it pivots on the stud. Without knowing the history (how old are they, how many miles do they have on them, what type/style/part number are they, how do they look overall) it's going to be very tough for anyone to make a good recommendation. 

How to tell the difference between 1.50's and 1.65's --- the difference will be in the distance from the fulcrum to the pushrod cup (the distance from the fulcrum to the valve tip will be the same on both). A 1.65's pushrod cup will be closer to the fulcrum than a 1.50's will be. You can try to measure one yourself if you're very careful. The trick is to correctly identify the 3 critical points: center of the fulcrum, center of the pushrod cup, center of the valve tip. Divide the distance from center-fulcrum to center-valve tip by the distance from center-fulcum to center-pushrod cup. That should get you either 1.50 or 1.65... but being off by even a very small amount can cause you to get a 'wrong' answer. 

Bear


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## PontiacJim (Dec 29, 2012)

Check out this article. You will see the difference in the placement of the pushrod hole found in the rocker arm near the bottom of the article. Pontiac V-8 Engines: Valvetrain Performance Guide 

The 1.65 rocker arm puts more stress on the rocker arm stud due to the change in position of the pushrod hole closer to the rocker arm cup. This additional stress can in some cases snap the rocker arm stud where it bottle necks - as *Bear* stated. The base of the stud is 7/16" and then "bottle necks" to the 3/8" threads with their 3/8" rocker arm nuts which get torqued into place. The screw-in studs do not "bottle neck" down to 3/8" and remain 7/16" sized on the threads and typically require an adjustable locking rocker arm nut. This is why IF using the 1.65's, you want to convert to aftermarket 7/16" screw-in studs as they are stronger.

If going to the 1.65 rockers, you also want to make sure that the pushrod does not bind or rub where the pushrod goes through the hole in the head. These are typically slotted longer (towards the intake side) to compensate for the pushrod being moved in closer to this contact point when the pushrod hole on the rocker arm is move inward toward the rocker arm cup. Depending on the cam lift, you may or may not need to do this, but consider this was done on the RA IV cam/heads it is something that needs to be checked even with the 068 cam if you go with 1.65 rockers.

1.65 rockers will open the valves quicker, slams them shut faster (ie pound the valves/seats), allows for more open time at higher lift, and can shift your power band higher in the RPM range (with the possible sacrifice of lower RPM performance). They can add a little more HP as they open the valves higher and change the cam's duration due to the quick opening, but why not simply get a cam that will give you the same lift as the 1.65 rockers, put less stress on the rocker arm studs, won't slam shut the valves, and need an adjustable polylock rocker arm nut?

If you are going big HP over stock, then there is an advantage. I feel the 1.5 ratio rockers are better suited for the street. They open the valves slightly slower which allows intake mixture velocity to build in the lower lift range which is what you want for a street car versus getting the valve open to max lift as quick as possible and at upper RPM's where max lift is better suited for a higher HP/race engine. The aftermarket Comp Cams stamped steel 1.52 rockers are good and have a closer 1.52 true ratio than the factory stamped pieces which are said to be closer to 1.48. If you want to upgrade from there, the roller tip 1.52's would be my choice with the 068 cam. 

Never used the roller tips, but have a set of the 1.65's from Comp Cams to try on my 455 build. But I will initially install the Comp Cams 1.52 stamped rockers that I already have to break in the engine and see how it performs. I however have a solid cam with .477" lift Intake & .501" lift exhaust, screw-in 7/16" studs, and have slotted the pushrod holes in the heads for the 1.65's. Adding the 1.65 will change my lift to .524" Intake & .551" Exhaust (to which my valve springs are capable of handling) and is where I really want to be plus it will shift my power band slightly higher up the RPM scale.

Again, where do you want to go with your build, what do you expect out of it, and at what price? The parts you have may or may not work with your build. You machinist can determine the spring pressures of the valve springs you have and see if they will work with your build and save you a few dollars. :thumbsup:


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## extinctmake (Feb 8, 2011)

Yeah guys, I think I will just chuck these rockers into the scrap metal bin. I don't want to mess something up because I tried to save a few bucks. I took some pictures of the rocker arms that I will post later, but why not get new stuff when completely rebuilding an engine? 

I did see Spotts offers a 068 cam ground to specs that mimmick a 068 cam using 1.65 rockers. Otherwise I am leaning towards a Melling 068 clone or the Summit 2801 cam depending whether my compression ratio and small carburetor will work with it. If not, then I will have to pick something else.

I will spend the money to convert to screw-in rocker arm studs. I am working with a 50 plus year old engine, so the press-in studs may not be as secure as they once were.

I don't have any problem with the prospect of using stock 1.5 ratio rocker arms. I just noticed the Comp Cams 1.5 or 1.52? roller rocker arms are about the same cost as the stock replacements. I am after a correct appearing restored engine that will operate on the gas and oil we are stuck using. It would be a bonus if it performed as well or even better than it did when it was new.

Hopefully this week I will receive word about the condition of my engine and a plan can be hatched to get this engine back into circulation.


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