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Rocker arm ???

General engine tech -- Drag Racing to Circle Track

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88bluestar
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Rocker arm ???

Post by 88bluestar » Fri May 22, 2020 7:30 pm

Main question is how much lift will stamped steel rocker arms withstand?... roller tip helps?
With the 3/8” stud and no girdle rule is there a max lift to consider as well?
Any suggestion to make the most of these rules?

Max 360 cubic inches with a 1% error. Compression of 10.0 or less with no error.
Stock-type stamped rocker arms or stamped steel, roller tip rockers allowed.
Screw-in rocker amt studs are allowed. 3/8-inch studs only with guide plates. No stud girdles of
any kind,
Poly locks are okay.
Must have cast iron two-barrel intake. No acid dipping and no pressure porting. The depth of the
plenum will be measured with a deep side of 3.950 inches maximum and short side of 2.030 inches. We expect to see an unmodified runner to the back of the divider, with ribs that stand up 0.150 inch. Caliper will be used to measure bores and depth. Unaltered marine cast iron two-barrel intake will be allowed with Vortec heads. The Rochester carb may only be used on the OEM two- barrel intake manifold. You can be disqualified or asked to race with a different manifold. The aluminum manifolds allowed are: GM Edelbrock# 2101,2701 or 2716 Weiand# 7547 0r 7547-1 Ford. Edelbrock# 2121, 2171 or 2665 Chrysler. Edelbrock# 2176 Weiand# 7545. These manifolds may use a 1” adapter.
If intake is found to be illegal, driver will lose all prize money for that night and points for that season.
Flat tappet cam shafts only. No roller lifters.
Aluminum water pumps and pulleys are allowed.
Aftermarket power steering pumps are allowed.
Must have cast iron cylinder heads, original valve angle and location. Valve springs: 1.250-inch
maximum diameter; .195-inch wire, steel retainers, five full coils.
Any distributor type ignition allowed. No crank trigger or magnetos allowed. No timing retard
control allowed. Must use a rev limiter with a 7,000 RPM chip. Chip must be out of reach of driver.
Crank shaft, cam gear and balancer must weigh a minimum of 50 pounds. Must install a 1-inch
pipe plug to inspect crank shaft or remove pan.
No titanium anywhere.
Tachometer may be claimed for $300 by promoter and drivers finishing on lead lap.
No tri-y headers.

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BOOT
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Re: Rocker arm ???

Post by BOOT » Fri May 22, 2020 8:18 pm

88bluestar wrote:
Fri May 22, 2020 7:30 pm

Tachometer may be claimed for $300 by promoter and drivers finishing on lead lap.
I'm not a circle track guy so I'll assume people are hiding junk inside the tach or converting it to do something else?

Several old threads on here bout stamped rockers. Are you allowed oil sprayer valve covers?
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Re: Rocker arm ???

Post by rustbucket79 » Fri May 22, 2020 11:35 pm

Cast iron 2 bbl intake must be used.

Further down, allowed aluminum intakes allowed?!?!?

Long slot stamped rockers will support more lift than what a proper duration cam will provide. The Crane Cool Nuts (poly locks) are a worthy investment, along with quality studs.

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Re: Rocker arm ???

Post by modok » Sat May 23, 2020 12:18 am

BOOT wrote:
Fri May 22, 2020 8:18 pm
88bluestar wrote:
Fri May 22, 2020 7:30 pm

Tachometer may be claimed for $300 by promoter and drivers finishing on lead lap.
I'm not a circle track guy so I'll assume people are hiding junk inside the tach or converting it to do something else?
Perhaps traction control

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Re: Rocker arm ???

Post by Krooser » Sat May 23, 2020 8:29 am

A long slot rocker seems to do ok at .525 or so... Lots of guys around here running under those.

The fancy roller tips make a guy feel good but they do little to nothing for performance and do wear and break. Those " cyrogenic" treated rockers are a waste, too, IMHO.

Use a decent long slot rocker and you'll be golden....bring a couple spares for race nite.

So many tracks have these useless IMCA engine rules. Reminds me of many of our "lockdown" virus rules. Some make sense...others???
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Re: Rocker arm ???

Post by Krooser » Sat May 23, 2020 8:29 am

A long slot rocker seems to do ok at .525 or so... Lots of guys around here running under those.

The fancy roller tips make a guy feel good but they do little to nothing for performance and do wear and break. Those " cyrogenic" treated rockers are a waste, too, IMHO.

Use a decent long slot rocker and you'll be golden....bring a couple spares for race nite.

So many tracks have these useless IMCA engine rules. Reminds me of many of our "lockdown" virus rules. Some make sense...others???
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jed
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Re: Rocker arm ???

Post by jed » Sat May 23, 2020 9:37 am

just rember that with a die grinder and a stone you can clean up the rocker arm slot and make it longer.

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Re: Rocker arm ???

Post by BigBro74 » Sat May 23, 2020 10:31 am

You actually seem to have quite a bit of room to work-
I have questions- it says Rochester with stock intake only- what carb are you to run with all the better listed aluminum intakes (which I would run)?? Does it get a Holley 2bbl on those? (It doesn’t say)
You can use 1.6 ratio stamped rockers it looks like , and there are no rules against it, or solid lifters.

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Re: Rocker arm ???

Post by dannobee » Sat May 23, 2020 10:43 am

BOOT wrote:
Fri May 22, 2020 8:18 pm
I'm not a circle track guy so I'll assume people are hiding junk inside the tach or converting it to do something else?
Traction control. But it's just as easy to have it hidden inside the MSD box (or any other box with a rev limiter). They use the same technology that your newer daily driver uses to check for a misfire, except they kill the timing instead of flashing the check engine light. The good ones use an adaptive learn and "know" when the crank speed delta exceeds the "normal" predicted speed and adjusts the timing accordingly. Often in less than one crank rotation.

I'm with Krooser on this one. I don't miss the days of touring and going to different tracks with goofy one time rules that were track specific. One that comes to mind was something like "Jo-Bob Nelson's engine has been deemed legal until it blows up or the end of the 2018 season." Or claimer rules. At least they changed most of the rules so that you'd have to be in the top 5 in order to claim another guy's engine. We always contended that most of the cheating was going on in the back of the pack, not the front.

Max valve lift that I've personally ran on stock rockers was about 0.550". Bigger than that and the pushrod would push through the cup and stay there (rocker on a stick). Bring spares of both.

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Re: Rocker arm ???

Post by dannobee » Sat May 23, 2020 10:49 am

BigBro74 wrote:
Sat May 23, 2020 10:31 am
You actually seem to have quite a bit of room to work-
I have questions- it says Rochester with stock intake only- what carb are you to run with all the better listed aluminum intakes (which I would run)?? Does it get a Holley 2bbl on those? (It doesn’t say)
You can use 1.6 ratio stamped rockers it looks like , and there are no rules against it, or solid lifters.
Holley 4412

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Re: Rocker arm ???

Post by 88bluestar » Sat May 23, 2020 5:55 pm

4412 carb is what I’ll be using. 2701 or the vortec equivalent if I find EQ350C or use Small runner Vortec bowtie heads. Already discussed cam, lifter and requirement on valvesprings with Mike Jones. Just trying to get advice on the strongest stamped rocker arms with a roller which he suggested with the added intake lift. The ignition boxes are inspected quite often and sent to MSD for legality.

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Re: Rocker arm ???

Post by marvingvx » Sat May 23, 2020 6:19 pm

Just had a recent experience with roller tip rockers (customer supplied). The engine should have turned 7000 put on the dyno hit a wall about 5400 power peaked about 4,900. Was no other obvious reasons everything appeared to be right, replaced with full roller rockers on it and I hit 6900 before it started falling off. Speculations between me and two other builders in my shop was The Rocker somehow became unstable rocking on the pivoting ball. Didn't do any more in-depth analyzation but I will be extremely resistant next time a customer wants me to install roller tip rockers. 355 class rules engine

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Re: Rocker arm ???

Post by novafornow » Sat May 23, 2020 7:03 pm

It has been a very long time, but I think that I was able to run around .540” gross. As stated you will break them. You must fab up an oil improvement. If I remember, I tacked diverters to the rocker to send oil directly to the ball.

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Re: Rocker arm ???

Post by Walter R. Malik » Sun May 24, 2020 8:17 am

Krooser wrote:
Sat May 23, 2020 8:29 am
A long slot rocker seems to do ok at .525 or so... Lots of guys around here running under those.

The fancy roller tips make a guy feel good but they do little to nothing for performance and do wear and break. Those " cyrogenic" treated rockers are a waste, too, IMHO.

Use a decent long slot rocker and you'll be golden....bring a couple spares for race nite.

So many tracks have these useless IMCA engine rules. Reminds me of many of our "lockdown" virus rules. Some make sense...others???
YES ... the roller tips help save the valve guide wear but, are heavier at the tip and won't rev as high.
You can grind regular slot 1.6/1 ratio rockers to have a longer slot then have them nitrided afterward and they don't seem to wear much at all.
Don't restrict the oil in the lifter galleries or use restrictor pushrods; the pushrod cups in the rockers NEED that extra oil.

We have run as much as .580" valve lift using a 3/8" stud but, with a girdle; NET, after lash.

Definitely run one of the legal aluminum intakes. The #7547 Weiand would be my choice.
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Re: Rocker arm ???

Post by 88bluestar » Sun May 24, 2020 8:03 pm

Walter, are you saying it makes better sense not use the roller tip type? I would likely be hitting the 7,000 pill at the end of the straight depending on gearing. .585 lift on the intake is likely what I'll be at.

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