Rock Arm Conundrum

[1967_Joe]

Rocker Arm Conundrum

I have a bad habit of over thinking things...like trying to decide on rocker arms...

On a 440 (30 bore) with eddy rpm performer heads and a comp cam hydraulic flat tappet cam (.545 valve lift and .364 lobe lift) 241/247 duration at .05" lift, grind XE285HL I'm thinking 1.5 ratio will do but that gets me to .546 lift, maybe 1.6?

Also, the rockers themselves...damn they are EXPENSIVE

Comp cams 1621-16 Pro Magnum Shaft Mount Rollers - $680
Proform extruded aluminum shaft mounted rollers - $230 (Price scares me)

Any other options that you guys have tried in similar builds? Are these overkill? This is a street motor, not track. I am very interested in your thoughts. What would you do? :icon_scratch:


Thanks in advance...

 

[snakeoil24]

Use the adjustable steel factory pieces aluminum are prone to fatigue. i fyou find a nice set of adjustables you can take them to a good machine shop and have them bronze bushed or send to tds machine and have a set that will last a long time.

 

[RustyRatRod]

Good luck finding the adjustable factory ones. Let me play devil's advocate for a minute. Why a hydraulic cam if you want to run adjustable rockers? This must be a mild build? If so, just use the factory non adjustable stamped rockers. They'll hold up just fine. Don't tell me it's because you want all the lift you can get. Really? Then you wouldda run a solid. Not trying to be smart here......you're in a difficult spot we all get it. GOOD rockers are not cheap. The stock factory non adjustable rockers are actually closer than you might think. I mean it IS after all a hydraulic cam. It will have limitations. So yes, you can tell I think adjustable rockers for a hydraulic cam is overkill........unless you've milled a lot of block and head off.

 

[benno440]

rusty is being a sour puss i have hyd cam with comp cams adjstable rockers, i wanted a nice street engine with lengetivity, plus the cost of a solid setup is ridiculous. plus i bought the heads as a kit that came with the rockers.

i have heard hughes engines makes some good adjustable roickers for a decent price

 

[coloradodave]

I agree with Rusty. On a STREET motor the stock rockers are fine, within the parameters he stated. Put the money into something that will make a difference.

 

[Meep-Meep]

Here are my thoughts. First off you have a cam that probably requires the use of dual valve springs and a seat pressure of 120 lbs or better. Right there is reason enough for me to NOT use the factory rockers and push rods. The factory stuff is good and proven, but on stock springs - or springs that don't exceed 90 lbs on the seat. I personally like to overkill the valve train because I think at high RPM the pushrod can act like a spring and not translate the cam profile accurately to the valve. Or in other words the stock valve train might go into a harmonic. Interesting comment about the fatigue factor of the aluminum rockers. However, the more spring pressure and higher cycles the greater the fatigue. Keep the cam profile and springs mild and the aluminum rockers will probably live for a long time.

 

[MikeyT]

I like the 1.5 roller ones ones from Mancini, they are restamped Harland Sharp ones. Stay away from proform.. Projunk in my book. I guess if you are going to build it up well, why cheap out on rockers.

Good luck, sounds awesome!
Mike

 

[Jeremiah]

www.hughesengines.com They are nice and middle of the road price wise. If you ever decide to step up to a solid roller you will be set. Lots of things factor into what you want to run for rocker arm ratio when it comes to increasing the effective duration, etc. What is the compression, torque converter, rear gear ratio, weight of car, exhaust system (manifolds, headers, etc) and what kind of fuel do you plan on running.

 

[RustyRatRod]

rusty is being a sour puss..........

Not at all. He has eddy aluminum heads and wants to run a mild hydraulic cam with 10.1 compression. The whole premise behind aluminum heads is to be an improvement over iron. Running only 10.1 compression with a .540 lift hydraulic cam isn't an improvement over an iron headed motor. You can do that all day long with iron heads. Just changing the heads to aluminum garners little to no advantage.

On the other hand, if you take full advantage of aluminum heads and use them as they were intended, (ported and .600 plus lift) then you can exceed 11.1 compression on pump gas and have 650 plus HP. It's Joe's money. If he wants to build a mild aluminum headed motor, then he certainly can. But he will be leaving much power on the table not using the parts as fully intended.

 

[451Mopar]

That is a pretty healthy hydraulic cam. The stock rocker arms may fail at the pushrod cup. I have seen several where the pushrods broke through the stock rockers. The Mopar Performance replacement rockers are a bit thicker. Hughes has nice adjustable rockers. I would use 1.6:1 ratio, but check the heads for pushrod clearance when changing the rocker ratios. Depending on the valve springs used, seat pressures mat be around 135 to 150, and open pressures around 375 to 400 pounds.