At what point do stock stamped rocker become a risk?

[Lars]

About average how much lift can you run before it's a good idea to run adjustable rockers?

Thanks

 

[cavemanmoron]

I would say anything much more than .480 lift.

For cam selection, there are many opinions,
mine are,
what size engine? 2 bbl 4 bbl?
what rear gears are in the car?
are you going to be driving the car on the street, or drag racing?

Answer the questions Honestly, and you will get a
better performing cam choice, than if you just blindly
choose a too large cam.

You should also use the valve spring that are suggested for your cam choice.


Comp cams, has a great Free tech line.

http://compcams.com/


Edelbrock recommends adjustable rockers for the RPM cam,
for small block Mopar.

http://store.summitracing.com/partdetail.asp?part=EDL-7177&N=400065+115&autoview=sku

Basic Operating RPM Range: 1,500-6,500 RPM
Intake Duration at 050 inch Lift: 234
Exhaust Duration at 050 inch Lift: 244
Duration at 050 inch Lift: 234 int./244 exh.
Advertised Intake Duration: 308
Advertised Exhaust Duration: 318
Advertised Duration: 308 int./318 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.488 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.510 in.


Mopar Performance makes some good cams,
in my 318 i am using the Mopar # 4452759

Basic Operating RPM Range: 1,200-5,200 RPM
Intake Duration at 050 inch Lift: 221
Exhaust Duration at 050 inch Lift: 228
Duration at 050 inch Lift: 221 int./228 exh.
Advertised Intake Duration: 260
Advertised Exhaust Duration: 268
Advertised Duration: 260 int./268 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.430 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.450 in.

 

[AdamR]

The biggest problem with stock rockers is that they get thin wear the push rods sits. My 440 punched a hole threw a rocker with a cam with .500" of lift.

 

[Lars]

Well, I'm going to be putting my 360 in my 70. These are it's specs as it sits right now:

Stock replacement cast pistons .030
Summit cam .420 int .441 exh 262/272 advertised duration (matched springs also) this cam is in straight up
360 "J" heads, stock ports, stock valves
factory 4bbl dual plane intake

I had rebuilt this motor a while back for my truck, broke the rings in wrong, so it uses oil, gonna need a re-ring at least, only has about 40K on the machine work. Dart is a street/strip ride, 727 with 3000 stall (if I don't go stick), with 4.10's and a detroit locker. Sitting on 28" tall street tires right now, I want to get some 26" tall MT drag radials. No power steering or A/C parts on the car, I have no idea what it weighs. I was running desktop dyno and it looks like I'd gain more from getting the heads ported then a cam change at this point. Course I still have to get the engine in the car, and I haven't finished the engine bay yet.

 

[rumblefish360]

IMO, I'd spring for the MoPar HD vesrion to replace the factory parts. Like said above, I have seen stock rockers fail in that area. New HD parts will fix that promted like. I ran them fine with the .509 MP cam.

 

[mopar1962]

cave ,the 308 intake duration and 317 exhaust makes no sense whatsoever, I run around 308 int and 317 on a comp cam roller.that much duration with the given.050 duration and lift is a no go, I think u made a booboo regards

 

[mopar1962]

m.p. makes the thicker rockers

 

[duster340]

m.p. makes the thicker rockers

think it was moparmusclemagazine who took a good look at diferent rockers a few months ago and the found that all the stock or stockreplacement type rockers for bigblocks where just about the same regarding metalthicknes

 

[340sFastback]

Does anyone know if the MP stamped rockers are a true 1.5 ratio as opposed to the stock ones which are actually around 1.4 or so?