Rocker Arm Question

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Fresh Air Inspector

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Hello All,

It has been awhile, lots of projects competing for my attention. Currently I'm working on assembling my 1988 318LA engine, this is a roller cam version but NOT a Magnum.

The engine has a Howard's cam (I - 220 degrees, 0.475 valve lift, E - 225 degrees, 0.500 valve lift, both @ 0.50, LSA 112 degrees), Hughes Engines roller lifters (HUG 5006), and Hughes Engines dual valve springs (HUG 1110P, coil w/beehive damper; 120 lb. closed, 300 lb. open). Although Howards recommended 140/145 lb. closed, 350/380 lb. open.

I'm struggling with what to do with the pushrods, rocker arms, rocker shaft and rocker shaft bolts. I don't believe these components will handle the valve spring load, especially the stock pushrods (6.777" length, 5/16" diameter, ?? wall thickness).

So, any feedback from those of you that have been there before. Looking forward to the feedback.
 
Don't use the factory rocker gear and change those springs. 50lbs to 80lbs is a hell of a difference in open pressure and you're going to risk valve float. The factory roller cam only ran to 4500 and this one will probably run to 5500.
 
I’ve been running the factory rockers and pushrods on a couple 360s. Factory set up hydraulic rollers with a comp cams 538, 541 224/230@ .050. Not sure of spring pressure anymore. One has aluminum heads one cast iron. Both see 6000 at times and have been together for over 6 years. I may be pushing it but it works
 
To both - many thanks for the feedback. I've contacted a company called PRW to see if they have a hollow pushrod with a length of 6.75", diameter of 5/16" and 5/16' ball ends.

Hello Duke5A,

Fully agree regarding the difference in closed pressure. I was delayed in picking up the heads from the machine shop and had given the shop both sets of spring pressures (Howards cam but Hughes lifters, springs and retainers - long story), but highlighted the ones from Howards (higher number). Unfortunately because I was delayed in picking up the heads the machinist couldn't remember what numbers he used. :-( Based on the other work he did, I will assume he went with the Howards numbers.

Hello 7177rr,

Interesting feedback. I would have thought that the pushrods would have been the weak point in your set up as I suspect your spring pressure is around the 350lb. range based on your cam specs? I figured the stock rocker shaft and rocker arms could handle seat pressures in that range.

Are your pushrods the same as the specs above? The aftermarket OE replacements are usually rated at a maximum of ~300lb. open pressure.

Thanks again for the feedback. Will update this thread when I have more info.
 
I was trying to look up the valve spring specs. No luck yet. The lifters, pushrods, rocker arms and the valley hold down are all factory parts. Again not sure what they are rated at. Been using factory set up since early 80’s. Flat tappet hydraulic (mopar purple shaft) .509 big block & small block.
 
Good question - hollow pushrods are needed for oiling the rockers on these engines since the oil travels up through the pushrod to lubricate the rocker arms.
 
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