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Old 12-15-2011, 08:12 AM
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Rocker arm suggestions for Pontiac 400

Stamped? Roller Tipped? Full Roller Rockers?

Mild street build with Lunati 262/268 camshaft & hydraulic lifters....

Thanks....

Mike

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Old 12-15-2011, 11:41 AM
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Mike,

If you wish to maintain the stock rocker geometry, you can use the stock rockers and the tapered nuts, along with the 'bottleneck" studs (stock), and torque the nuts to 20 lbs. That cam appears similar to the Comp XE262H (that's the one we use for these builds). I KNOW it's okay with the stock stuff. Measure the base circle and compare it to the old "stock" cam. If it's the same (within .010", anyway), you're good to go.

If you want a little more performance, Comp Magnums (roller tip, "premium") are excellent. While there's a slight reduction in parasitic loss, the "real" gains come from the rocker being more accurate than stampings, keeping valve train geometry "the same" across all cylinders. These rockers will require the use of "adjustable" nuts (at minimum). It's recommended to upgrade the studs to full-length 7/16" if you're changing rockers. Stock BBC studs suffice. The Magnum rockers come with the 3/8 AND 7/16 "crimp" nuts.

Based on how Pontiac heads flow, I would recommend sticking with the 1.5:1 ratio (Magnums are listed as 1.52:1, close enough...).

Jim
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Old 12-15-2011, 12:30 PM
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Quote:
Originally Posted by MJS69
Stamped? Roller Tipped? Full Roller Rockers?

Mild street build with Lunati 262/268 camshaft & hydraulic lifters....

Thanks....

Mike
Mike,
I ran Crane (Gold) 1.5:1 with a gross lift of .480", then .520", for years. After I went to race only, I bought an engine with a roller cam that had Harland Sharp 1.65:1 rockers. I have since switched to T&D shaft rockers in both of my Pontiac engines, but if I were still using stud mounted rockers, I think I would either use Crane Gold or H.S., although I have heard favorable comments about Scorpion rockers. The roller tip rockers are probably less expensive and more reliable, than aluminum full rollers, so that might be a good alternative for you.
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Old 12-15-2011, 12:52 PM
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Quote:
Originally Posted by MJS69
Stamped? Roller Tipped? Full Roller Rockers?

Mild street build with Lunati 262/268 camshaft & hydraulic lifters....

Thanks....

Mike
Just a word on using net lash/bottleneck studs. If you use the stock stamped rockers and nuts that are torqued to 20 ft/lb, the preload needs to be carefully checked. Changes in the base circle, head gasket thickness, any milling done to the heads or block, etc. can effect the hydraulic lifter preload.

A better solution is to bite the bullet and use an aftermarket rocker, straight studs and polylocs as mentioned above. Be sure to check the valve train geometry before you buy pushrods. The stock p-rods might be fine but always better to check to be sure. If you can afford full roller (fulcrum and tip) rockers, by all means- do it. Harland Sharp are the only Pontiac roller rockers I have used and they work fine.

If you ever consider 1.65 ratio rockers, be aware that the pushrod hole in the head may need to be opened up towards the stud to give enough clearance. Better in your case to keep the stock ratio (or the 1.52 Comp), IMHO.
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Old 12-15-2011, 01:54 PM
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Thanks for the replies...

The heads are bare castings, so I'll be getting all new everything....The cam I'm getting is a bit higher lift than many of the comparible grinds I've looked at, so I'll be sticking with a 1:5 ratio.

Question on the Magnum roller tipped rockers...I can replace the crimp nut they come with with a set of adjustible polylocks, right? Or can I use them "as-is" out of the box? When switching to 7/16" straight screw in studs, am I going to run into possible rocker slot interference with a lift of .489?

Thanks...

Mike
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Old 12-15-2011, 02:28 PM
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Anytime you change from a stock spec cam, you need to change to an adjustable valve train. You may or may not have rocker clearance problems, but always check! Be sure to check valve to piston clearance, also.
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Old 12-15-2011, 04:18 PM
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thanks for the replies everybody...I plan on checking the valve clearance and pushrod length...

I've been looking at parts for this build for some time now, and the three rocker arms I generally have in mind are the comp magnums, the harland sharpes and the scorpions...leaning more towards the comp magnums becasue they are steel and the decent price.

I'd love to get the Crower steel roller rockers, but then I just have to cut that money out of some other area of my engine budget, and I'm suffering from serious "mission creep" here...what started as a $3500 build is now rapidly approaching the $5K mark...
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