[vertigto]

Which would be your preference on a mild 400 rebuild (@400 hp) with a HFT cam (Ultradyne 221/230 @ .50" , 112 LSA, .454 lift w/ 1.5 rockers)??

Stock stamped or roller tip and why?

[PontiacJim1959]

Originally Posted by vertigto

Which would be your preference on a mild 400 rebuild (@400 hp) with a HFT cam (Ultradyne 221/230 @ .50" , 112 LSA, .454 lift w/ 1.5 rockers)??

Stock stamped or roller tip and why?

In my opinion, at that level, it's just a matter of price and ego to say "I have roller tip rockers." I would go with the aftermarket stamped steel rockers with the 1.5 ratio and long slot hole at the rocker ball fulcrum. I used these on my last 400CI build with the Comp Cams XE274 cam without issue.

https://www.summitracing.com/parts/c...6/make/pontiac

On my present 455 build I did go with roller tip rockers, just because. I have both the 1.5 and 1.65 just to play with, but I am not budget constrained. On the 400CI build, I was, so thus the stamped rockers.

[KEN CROCIE]

Prefer? Harland Sharp or Crane Gold.
Get by with ? Stock stamped steel. With only .048" more lift than stock, OEM rockers are fine. Aftermarket stamped steel are more problematic.

[mgarblik]

With the cam you describe, I would use stock stamped steel rocker arms. Stamped steel with a roller nose, especially if made offshore, give you 16 more potential areas of catastrophic failure when a roller fails. The factory went with the stock design because it was cheap and durable.

[1968GTO421]

Originally Posted by mgarblik

With the cam you describe, I would use stock stamped steel rocker arms. Stamped steel with a roller nose, especially if made offshore, give you 16 more potential areas of catastrophic failure when a roller fails. The factory went with the stock design because it was cheap and durable.

Would you consider stock stamped steel rockers for a cam with I-.489" lift, E-.504" lift (1.5 ratio) to be OK or look at Harland Sharps instead?

Thanks

[KEN CROCIE]

RA4had .520" lift.

[Schurkey]

When it was me, I wanted the 1.65 ratio on a mild cam. The only practical way to do that was with Comp roller-tip rockers, cause I couldn't source plain stamped 1.65s.

I had to grind the livin' piss out of the pushrod holes in the heads to get clearance at all valve lifts. I was NOT happy; this was in direct contradiction to what I'd read about pushrod clearance. I even had to grind the slots deeper into the pushrod guideplates to fix the binding.

Was it worth it? Father in Law hardly drove that car, then sold it. I should have used stamped-steel 1.5 rockers and saved myself a day's worth of grinding.

[Holeshot71]

Does anyone know how much lift a stock 1.5 stamped steel rocker arm can handle?

[Cliff R]

Rocker arms are metal parts that pivot and transfer movement. It's been proven that roller designs add very little if any power based solely on their design, but they do have more accurate ratios than typical stamped steel parts so there may be something waiting for you there. They also come with additional weight, even lighter aluminum designs and some flex to go with them.

Some stamped steel rockers aren't nearly as strong as others, Ken sort of nudged a little in that direction above and I'm not overly fond of the grooved rocker balls some show up with. Good in theory but you loose some surface area and they tend to allow more leak path down the studs instead of flowing more oil out over the ends of the rockers to get atomized for lubrication and spring cooling.

The only real lift limitations with a stamped steel rocker arm is binding at the pivot on the studs, so make sure the slots or elongated if/as needed if you determine more running room is required........Cliff

[Skip Fix]

When I built the 400 in the 81 TA I found GOOD stamped steel are almost as expensive as Harland Sharp.

[Formulajones]

Skip is correct. When I built the 400 for PS, roller rockers aren't allowed. The problem I had with them is that literally none of them are the advertised ratio they are supposed to be. I went through more OEM sets than I can count trying to get a complete set of 16 that at least measured the same and as close to 1.5 that I could find.
I finally gave up that time consuming battle and bought a new set of quality stamped steel rockers that all measured pretty darn close to 1.5, and ended up spending close to what a set of Harland Sharps cost at that time.
For most people doing a basic build it wouldn't matter.

Then after blowing the bottom out of an OEM stamped rocker on another engine that only had 115 lbs seat pressure on a mild hydraulic flat tappet I kind of shy away from them now.

[KEN CROCIE]

Cliff and others: I'll expand on the "nudge".
In the 70s and 80s H-O sold "high lift rocker arm kits" consisting of GM 1.65 rockers with choice of lock nuts and rocker arm balls. The price from GM seemed to go up every month. I sourced an aftermarket 1.65 rocker and I didn't have to take the 11/32" pushrod, rocker ball, and nut, as it was packaged from GM. I bought these newly sourced rocker arms (USA made) in 1000 lots. I started getting calls from customers about broken rockers! I rigged up a test fixture to strength test the new rockers against the factory units. My friends machine shop had a hyd. press that measured in tons. The new rockers would fail at 3/4 to 1-1/2 ton . Failure location was random. Some times the pushrod seat would blow through, or the ball area would crack or blow through. The factory rocker would consistently fail at 3 tons and the cracks would be evenly distributed all across the rocker. There were no blow through failures. (done--I just made a long story short!)

[Sirrotica]

I remember reading that the OEM Pontiac rockers went through some type of cyanide hardening process. I imagine that GM was/is one of the only manufacturers that could afford that type of process, due to dealing with the liability of a poison such as cyanide. Doubtful any of the aftermarket manufacturers could stand that expense, and used inferior processes.

Cyanide hardening: translation a process of introducing carbon and nitrogen into the surface of steel by heating it to a suitable temperature in a molten bath of sodium cyanide, or a mixture of sodium and potassium cyanide, diluted with sodium carbonate and quenching in oil or water.

I remember trying a set on Manley 1.65 rockers that failed soon after they were installed on a 72 455 HO engine. The ball pulled through the rocker arm. Upon examination they were all failing in the same way. I suspect the failure was because of the absence of the cyanide process.

I've never owned a set of roller rockers, and have used GM rockers on all my Pontiac builds, race engines and street engines. I realize that they aren't as accurate as a roller rocker in ratio, but they're damn tough, and will take a ton of abuse even after being run on the street for many thousands of miles in street duty.

[Tim Corcoran]

Sirroica
Sorry if I am hijacking the post from the OP. Thank you for the info on the factory stamped rockers. Have you ever used them on a mild roller cam and what is the max lift you have used with them? Thanks.

[Jay S]

I would be curious about Sirrioca’a answer on what he has ran also.

We have ran and built some race car engines in the “no roller rocker rule class’s. With the right profile you can go pretty high on the lift, . 570 ish. That is racing though with low expectations on the rocker life. I have a coupe street engines that are .540-.550 with the stock rockers. But it depends on the profile A LOT.

As far as I know all the roller tipped rockers are rated at 1.52, and IRC the 1.5 stock rockers generally run 1.46-1.48. If you watch the geometry closely a shorter push rod on the stock 1.5 rockers get the ratio back closer to 1.5. The ra4 rockers I have used have the pushrod out further from the fulcrum than the roller tipped 1.65s. You have to grind a TON to get a roller tipped 1.65 compcams or a 1.65 PRW to clear the pushrod past .5” lift. The RA 4 melling are more doable, they run closer to 1.6 than 1.65.

The other thing that kills the stock rocker is the spring pressure over the nose of the cam. We ran solid flat tappets and solid rollers with stock 1.5 rockers in Pontiacs for circle track racing. After about 350 lbs over the nose the life gets noticeably shorter. For us 320 has been ok on the street most of the time. We are up around .550” with the RA4 style melling on limit driven street engines. The aggressive solid rollers and solid flat tappets we ran with high spring rates the lift was just over .5”.

At .45 lift I think you could run about what ever style rocker you wanted. Probably the stock 1.5s are as good as any.

[77 TRASHCAN]

What was the name of the Pontiac engineer, that essentially invented the stamped rocker?

[Rocky Rotella]

Originally Posted by 77 TRASHCAN

What was the name of the Pontiac engineer, that essentially invented the stamped rocker?

Clayton Leach!

[John Milner]

I’m running a cam that is advertised as a .510 lift with 1.5 rockers in my 428. I’m running 1.65 ram air iv rockers which I believe makes the lift around .560. I didn’t have any interference. The slot on my factory 1.65 iv rockers measured the same as some stock 1.5’s.

[Sirrotica]

Originally Posted by Tim Corcoran

Sirroica
Sorry if I am hijacking the post from the OP. Thank you for the info on the factory stamped rockers. Have you ever used them on a mild roller cam and what is the max lift you have used with them? Thanks.

Yes, I have used them with a mechanical roller cam, it really wasn't mild though, adv duration was 320 degrees, and lift was .525. That was with 1.5 ratio arms , which is what I ran. Back in the 70s they used to go by advertised duration mostly, not @.050, so I couldn't tell you what the lift @.050 was, but it was radical because it made the 400 it was in run like a SBC, even with 3.90 gears in a 65 GTO I would routinely shift it at 6500 because it didn't have much power unless you wound it up. This cam at the time was the largest roller cam listed in Crower's catalogue.

I bought the cam second hand, the guy I bought it from said it was in a Pontiac powered rail dragster in the 60s, so it was big for the time. I did have to open up the slots because they contacted the studs.

After I scattered that engine (keeper split and a valve head went through the engine breaking piston and rod) there was some slight damage to one of the lobes, so I sent it back to Crower and had it repaired, and reground for something a little more streetable. The lift was down to .480 and the advertised duration was 284, still fairly radical but much more streetable than the original grind was. Zero rocker arm problems with either grind

Hopefully that helps you out.............