GM Sm Blk Rockers

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ProPower engines
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GM Sm Blk Rockers

Postby ProPower engines » Tue Aug 22, 2017 11:44 am

Hey guys
Who sells the best stock appearing rockers for sm blk 350 style heads??
These will be used for a limited race application but tired of push rods coming through the rocker body.
100# seat 300 open spring pressures. geometry is dead on but keep wasting rockers. Am currently using an SBI stock replacement type with push rod guide plates.
These can be long slot rockers either 1.5 or 1.6 ratio but I am looking for real world experience with recommended brand names regarding durability as I have not built anything using stock rockers for many many years


Suggestions welcome and greatly appreciated
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Re: GM Sm Blk Rockers

Postby engineguyBill » Tue Aug 22, 2017 12:20 pm

Elgin has good quality stock-type SBC rockers with long slot that hold up very well. BUT if your pushrods are breaking through the rocker arms, you have an oiling problem. Without oil being delivered to the rocker arm, through the pushrods, any rocker arm will fail.
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Re: GM Sm Blk Rockers

Postby pamotorman » Tue Aug 22, 2017 2:27 pm

also make sure you put cam break in moly kote on the push rod tips and rocker ball for start up .

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Re: GM Sm Blk Rockers

Postby Newold1 » Tue Aug 22, 2017 4:55 pm

Make sure the push rods you are using have the correct ends on them for the stock type rockers as a mismatch here can waste rockers and push rods really fast. If you visit the websites for push rod makers like Trend, Smith Brothers and Manton you will see how many different sizes and radius the ends can come in and if they are not matched to the rocker arm push rod cup the two will EAT EACH OTHER! :shock:

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Re: GM Sm Blk Rockers

Postby KnightEngines » Tue Aug 22, 2017 6:18 pm

I went through this years ago with holden speedway engines, we'd punch the pushrods through the rockers pretty regular, tried a couple of different brands of stock replacement arms & none were any better.
In the end we discovered 1970's vintage factory arms were the best - made back before everything was made by the lowest bidder.
So every engine that came in that got aftermarket rockers I put the originals in a box & when it was time to build one of the speedway things I'd dig through the box & find 16 without too much wear, reface the tips & use them.
Had very few failures with old factory arms.

The other trick we used before we discovered the factory arms were better was to fire up the MIG & run a short bead of weld across the back of the pushrod cup. I don't want to think about what that did to the shape of the cup, but we'd coat the pushrod ends in moly lube & never had a failure :shock:

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Re: GM Sm Blk Rockers

Postby pamotorman » Tue Aug 22, 2017 6:54 pm

when they cut back on the number of strikes to save time to form the rocker arms the problem started.

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Re: GM Sm Blk Rockers

Postby Walter R. Malik » Tue Aug 22, 2017 7:08 pm

Sometimes, putting a small "flat" on the end of the pushrod tip, (I would use a valve grinder butt facer), about .150" in diameter would help a bunch; allowing a small volume of oil to remain between the pushrod tip and the rocker arm socket.
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Re: GM Sm Blk Rockers

Postby pamotorman » Tue Aug 22, 2017 7:31 pm

Walter R. Malik wrote:Sometimes, putting a small "flat" on the end of the pushrod tip, (I would use a valve grinder butt facer), about .150" in diameter would help a bunch; allowing a small volume of oil to remain between the pushrod tip and the rocker arm socket.

stock small block chevy HP push rods had a recessed area around the oil hole. of you installed the push rod upside you lose this feature so check your push rods before you install them.

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Re: GM Sm Blk Rockers

Postby Carnut1 » Tue Aug 22, 2017 8:04 pm

When I had problems popping rockers, bending pushrods and snapping 3/8" studs turns out I had valve spring surge issue.

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Re: GM Sm Blk Rockers

Postby rfast racing » Tue Aug 22, 2017 8:18 pm

Back in the day when we had too run stock type rocker arms in ct engines we used crane nitro carb rocker arms w kool nuts and oil baffles we also took a pushrod in a drill w/moly on the ball and lapped it in the pushrod slot with great success they are available in 1.5 and 1.6 ratios

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Re: GM Sm Blk Rockers

Postby MadBill » Tue Aug 22, 2017 8:45 pm

Wouldn't you be better off to use valve grinding paste? (assuming a check with layout blue showed a less-than-complete contact zone)
Also, if an exhaust rocker fails, it's best to put the new rocker on the intake and move the old one to the exhaust.
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Re: GM Sm Blk Rockers

Postby Krooser » Tue Aug 22, 2017 9:30 pm

Wow.... there's a lifetime of knowledge in those posts...
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Postby dwilliams » Tue Aug 22, 2017 10:20 pm

The pushrod end and cup are highly loaded; oil flowing through the little hole in the rocker helps keep them cool.

If you look at a worn factory rocker, up in the cup, you can see a dark ring around the hole; there's a sort of nipple-shaped relief so that the hole in the pushrod doesn't have to line up precisely with the hole.

Some aftermarket rockers don't have the relief, so while they theoretically have more bearing area, they don't let as much oil pass.

Also, the holes in the pushrods and the holes in the rockers are "timed"; with a small stock cam you're supposed to get a tiny amount of oil through almost all the time, and a good squirt when the holes in the pushrod and rocker line up. With a large cam and aftermarket parts it's possible for the holes to be so out of time they never quite line up.

You might also try testing some old stock rockers vs. the new aftermarket ones with a small file on the top of the cup. The new rockers should be at *least* as hard to file as the stock ones.. If not, that would indicate a heat treat problem.

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Re: GM Sm Blk Rockers

Postby ProPower engines » Sun Aug 27, 2017 1:35 am

I tried the elgin rockers and they had the same issue as the SBI rockers.

We found many years back the GM rockers that had the "O" on the tip were by far the most durable and never broke through the push rod area as well.
I had 3 rockers break on the dyno after break in of the cam but I did look at every aspect mentioned for durability and longevity but they still let go.
They have tons of oil and the slots do not bottom on the rocker. The push rod fits well that is after checking a few sets of them.
Most rockers as mentioned show creases around the push rod cup area that the old GM rockers do not.

Has anyone tried the Crane nitro carb stock type rockers??
Crane claims they will be fine with the pressures being run so I may give them a try. [-o<
They look better made they any shiney stock rocker looked at this last week

Thanks for the suggestions

Any more please feel free

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Re: GM Sm Blk Rockers

Postby In-Tech » Sun Aug 27, 2017 3:00 am

I wish I could help, like most of us, I quit stamped rockers about the first cam change back ~ '82 lol.

Which Elgin's did you use, was it these RK-840N "Nitro-Carbided"? The picture looks different than the Crane but could be as simple as not the picture of the product. Description says: Elgin Nitro-Carbided Long Slot Rockers
The "original" manufacturer of stock style race rockers! 3-5 times greater resistance to wear, fatigue, and fracture in high stress areas. Eliminates pushrod cup and fulcrum failures. Precision die formed for the most accurate ratios of any stamped steel rocker. Long-slot design and comes complete with oil-groove pivot balls and adjusting nuts. For race applications where rules require stock type rockers. This includes oval track, plus NHRA and IHRA "Stock Class" categories where stock-type rockers are required.
http://www.competitionproducts.com/Elgi ... aJ3k7ghNS4

The cranes are pretty expensive so I would hope they are stronger but the description is almost word for word to the Elgin. The pic looks like a rail type rocker though. :?
https://www.summitracing.com/parts/crn- ... /chevrolet

Everything else I found looked like junk proform chinese crap for stock builds.
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