1970 LS5 Rocker Arms

[Allen N.]

I am restoring a 70 LS5 which currently has roller rockers and after market valve covers. Based on my research of this forum, I started looking for GM kit #12368085 containing 16 GM #3959182 rocker arms. It appears this kit has been discontinued. When I look for 3959182 rockers, I find they have been discontinued and replaced with 12675724. I am currently looking at buying the 3959182 rockers on ebay.

Anyone have a better recommendation or know anything about the 12675724 rockers?

Thanks,
Allen

[Jimmy G.]

Re: 1970 LS5 Rocker Arms

Aftermarket are better I have had to replace all my pushrods that were on my 72 as they wear and then oil will not flow. Opt for heavy duty as well --- originals are a little weak

[Michael H.]

Re: 1970 LS5 Rocker Arms

Look at Comp Cams as I used there rocker arms and pushrods and I've been very happy so far.

Mike

[Mark E.]

Re: 1970 LS5 Rocker Arms

I went through this three years ago with my LS5. I chose a Chevrolet Performance rocker arm kit which includes 16 arms, balls, nuts. About $100.

For push rods, I chose Crane Cams 13634-16. This is a set of of their stock 3/8" Chromemoly pushrods. About $140. I don't remember why I didn't go with GM... maybe not offered?

These are available from Summit, Jegs, and other reputable parts houses. It's risky buying mechanical parts from a vendor on eBay... it could be an Asian factory making counterfeit stuff.

If this is for a high performance street car, I have to push back a little on Jimmy's comments. OEM quality valve train parts are well engineered and up to the task. Maybe it's a different story when building a circle track engine running full throttle for hours at 8,000rpm. With that said, the 550+ HP L88 uses one-piece stamped rockers.

I thought about using roller tipped and roller bearing arms but glad I didn't. The one-piece stamped OEM arm is not only plenty strong, but simpler, and less expensive. Plus there's less risk of a one-piece part exploding scores of small bits into your engine if it fails.

[Joe L.]

Re: 1970 LS5 Rocker Arms

I thought about using roller tipped and roller bearing arms but glad I didn't. The one-piece stamped OEM arm is not only plenty strong, but simpler, and less expensive. Plus there's less risk of a one-piece part exploding scores of small bits into your engine if it fails.

Mark------


Then don't buy a car with any Gen III or newer small block. All have roller trunnion rocker arms.

[Joe L.]

Re: 1970 LS5 Rocker Arms

I am restoring a 70 LS5 which currently has roller rockers and after market valve covers. Based on my research of this forum, I started looking for GM kit #12368085 containing 16 GM #3959182 rocker arms. It appears this kit has been discontinued. When I look for 3959182 rockers, I find they have been discontinued and replaced with 12675724. I am currently looking at buying the 3959182 rockers on ebay.

Anyone have a better recommendation or know anything about the 12675724 rockers?

Thanks,
Allen

Allen-------


The 3959182 were not the rocker arms originally used for your application but they will work just fine.

I don't know (yet) anything about the GM #12675724.

[Mark E.]

Re: 1970 LS5 Rocker Arms

Mark------


Then don't buy a car with any Gen III or newer small block. All have roller trunnion rocker arms.

Touche.
As another example, the ZZ502 makes 508 HP, 580 lbs-ft of torque, has a 5800 rpm red line, and uses stamped rockers, P/N 12368082.

So stamped, one-piece rockers might also be adequate for a street LS5.

[Ray K.]

Re: 1970 LS5 Rocker Arms

Allen,

As Joe pointed out, the 3959182 rocker arms were not original to your car, but is a very good choice. I ran a set of these for several years on a 427 L-88 race engine with never an issue. Along with grooved balls #3899622 and 7/16 push rods. The 3/8 push rods should be good for street use.

Ray

[Joe L.]

Re: 1970 LS5 Rocker Arms

Touche.
As another example, the ZZ502 makes 508 HP, 580 lbs-ft of torque, has a 5800 rpm red line, and uses stamped rockers, P/N 12368082.

So stamped, one-piece rockers might also be adequate for a street LS5.

Mark-----

No doubt about it----the original stamped steel rockers are adequate. However, you don't think that GM used the roller trunnion rockers on Gen III and later small blocks because the stamped steel type would have been just as good, do you?

[Mark E.]

Re: 1970 LS5 Rocker Arms

Mark-----

No doubt about it----the original stamped steel rockers are adequate. However, you don't think that GM used the roller trunnion rockers on Gen III and later small blocks because the stamped steel type would have been just as good, do you?

Are stamped rockers "just as good" as rollers? Chevy's philosophy is the best design is the simplest, least expensive solution that meets performance (reliability, serviceability, manufacturability, affordability,...) targets. With this mental model, a "better" but unnecessary solution which adds cost or complexity is "not as good."

I don't know GM's reason for using a more expensive rocker in newer engines. But my guess is reliability was not the issue. Maybe rollers marginally improve fuel efficiency by reducing internal friction? Maybe GM set a new fuel economy target with the newer gen engines, which caused roller rockers to be the new best design choice.

And maybe Allen's performance targets are different for his big-block... rock solid reliability on the street, low cost, simple design, and no need to meet a CAFE target. Stamped rockers are a good choice for this.