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Old 02-22-2007, 12:54 PM
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Should I change rocker arm ratio?

I have a mild 350 in my 76 4x4 Blazer. I think the rocker arms may be stock components and when I did a cam swap I noticed that they were well worn.

I planning on getting some stamped roller tipped rockers to replace the og's. What would be gained or lost from going one step higher on the ratio?

I am running 9-9.5:1 CR, 041 64cc 2.02 heads, flat top pistons, Comp Xtreme 4x4 cam (210/218 @ .05, .447/.462 Lift, 111*LSA) top end kit, Summit Long Tubes (1.5" Primaries), true 2.5" dual exhaust, Edelbrock EPS intake, Holley Truck Averger 670, MSD HEI ingition.

Does anybody think I will have clearance issues? How will it effect the power range? I'll bet fuel milage will go down.

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Old 02-22-2007, 02:02 PM
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Quote:
Originally Posted by 70bird
I have a mild 350 in my 76 4x4 Blazer. I think the rocker arms may be stock components and when I did a cam swap I noticed that they were well worn.

I planning on getting some stamped roller tipped rockers to replace the og's. What would be gained or lost from going one step higher on the ratio?

I am running 9-9.5:1 CR, 041 64cc 2.02 heads, flat top pistons, Comp Xtreme 4x4 cam (210/218 @ .05, .447/.462 Lift, 111*LSA) top end kit, Summit Long Tubes (1.5" Primaries), true 2.5" dual exhaust, Edelbrock EPS intake, Holley Truck Averger 670, MSD HEI ingition.

Does anybody think I will have clearance issues? How will it effect the power range? I'll bet fuel milage will go down.
First, I didn't know anybody made stamped roller tip rockers. Give me a reference so I can see them, please.
I suggest you look at CompCams steel roller tips with ball fulcrums.

Second, 1.6 rockers will increase the lift 6.7% across the board (even more with your worn stock rockers), which means more torque.
Fuel consumption should not be effected.

Third, .493 lift should not be a problem, but you should talk to CompCams about their rockers and clearances.
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Old 02-22-2007, 02:10 PM
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X, I believe the roller tipper with a ball fulcrum is what he's referring to.

Anyway, one thing to look at is the pushrod slots. I believe the pushrod slots in 041 heads aren't long enough to use a 1.6 rocker. When the cam is on it's base circle the pushrods will rub on one end of the slot. They can be opened up but if you did you would need to account for all the shavings created from the cutting. It's something you really shouldn't do with the heads on.
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Old 02-22-2007, 02:13 PM
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Also depends on how many RPM's you're going to spin, although with that cam it doesn't look like above 5500-6 grand. Higher ratio rockers will increase the speed at which your valves move, because they'll be traveling a greater distance in the same amount of time.

Comps will not guarantee your clearance. They never do. The only thing they'll tell you over the phone is "measure your clearances, I won't venture a guess." Any time you change something that is what they recommend. Its a bit conservative (as are their cam recommendations, but I digress) but its the safe bet. If you measured before then use that as a reference. Most of the time I keep my clay.

Also remember that with parts expanding due to heat and the valves moving with momentum (which is great now as I mentioned before), lift is always just a hair more when the motor is running than it is when you're just cranking it over with clay in the chambers. Furthermore, your oil pump probably has a bit more hydraulic pressure in the lifters.

Always be safe, nobody can tell you what your clearances are but you and an instrument.

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Old 02-22-2007, 02:20 PM
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Quote:
Originally Posted by xntrik
First, I didn't know anybody made stamped roller tip rockers. Give me a reference so I can see them, please.
He may be talking about the ones from Summit Racing:
They are Summit brand...Part# SUM-141507/ Price: $89.95
That's the 1.6 ratio. They look pretty good to me.....Probably limited clearance for (larger) aftermarket springs. But hey, they have roller tips. We have a 350 in the shop, with double-hump heads, and it has 1.65 Crane rockers. It didn't need anything. Something with the heads, maybe? I'm a Mopar man, so I don't really know.......
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Old 02-22-2007, 06:28 PM
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Cool, thanks.
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Old 02-23-2007, 12:17 AM
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Those are the exact rockers I am considering.

I do seem to recall the pushrod slot being pretty small. The old pushrods had wear marks on them from rubbing the head. Nothing major. I replaced the pushrods when I did the cam change b/c 3 of the tips were busted. The pressure held them together for who knows how long.

Maybe I'll pull the heads to elongate the slots and check the clearances. I've always been curious how close things are in the cylinders.

Where would I get the clay? I've never seen it at a parts store. And how much is needed to check valve clearances? 1/4"....1/8" layer on top of the piston?

The springs are 1.254 dia. I'm assuming that is a close to stock diameter. The springs came with the cam kit.

As far as rpm's go, it rarely sees above 5K. Usually only when I'm smoking the kid's in their rice burners. I'm sure they hate having an old, 5200 lb+, lifted 4x4 get up to 80+ before they do.

What about cylinder pressure? I've never checked the pressure but would it increase substantially? And what's an upper limit for cylinder pressure for pump premium? I'm sure I can do a search and find a couple threads about that.
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Old 02-23-2007, 01:23 AM
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1.6 Rockers

Check my adds just listed a set today,selling off my Chevy parts as I sold the chevy for new project,( NEW) $85 including shipping see add for pics.
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