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Old 04-01-2009, 09:20 PM
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Pushrod length???

71 350 bored .060. Installed Lunati bracket master cam #00017 .460 lift in. and ex. 1.5 rocker ratio, 224 degrees duration at .050 tappet lift 290 degree advertised duration. and a new set of RHS ProAction heads #12301-01, 2.020 intake, 1.600 exhaust valves. 23 degree valve angle valve length 5.011 (std. + .100)

Running into problems with pushrod length/rocker arms. in order to get the correct rocker arm geometry, the adjusting nut is only threaded halfway on to the stud. Almost as if the stud is not long enough. But the heads came with valves assembled, and rocker arm studs and guide plates came with the heads. where am I going wrong? Hard to explain, hope someone understands my situation. ANY help would be appreciated!

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Old 04-01-2009, 09:37 PM
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There are different length studs. With your +.100 valves, you may need longer studs. Measure yours according to this example from Crane. These are 1.680"
http://cranecams.com/?show=browsePar...umber=99156-16
I saw some on ebay that measured 1.910" on the same dimension as above "C" dimension.
Here's a 1.750" stud that uses the letter B for the same dimension....
http://www.northernautoparts.com/Pro...tModelId=17211
And a 1.900" from ARP...
http://www.northernautoparts.com/Pro...tModelId=17210

Last edited by techinspector1; 04-01-2009 at 09:48 PM.
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Old 04-01-2009, 10:43 PM
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What lifters and rockers?? is the installed spring height correct??
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Old 04-02-2009, 06:02 AM
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Lunati Micro-trol hydraulic flat tappet lifters #71817
Comp cams magnum steel roller tip rocker arms 1.52 ratio 3/8 stud #cca-1412
valves and springs were pre-assembled cannot find any info on spring height in paper work




If studs were to short, since everything cam together wouldn't the studs be to short for everyone that bought these heads? Or is there something in my setup that is causing this?
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Old 04-02-2009, 09:59 AM
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looking a little deeper

ok after doing a little more investigating and reading I was wrong. I think I am needed to go lower on the stud/shorter pushrod. in order to get the roller tip to ride on the center of the valve stem. right now I am almost at the very edge of the exhaust side of the valve stem, going up or longer pushrod will only push it out farther, correct? if i am doing this right and go lower/shorter pushrod then my rocker arm is rubbing against the valve spring, also can't get a socket in there to adjust the nut. but comp says rocker arms are supposed to clear spring up to 1.5 and mine are 1.46. Any insight or am I doing this all wrong?
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Old 04-02-2009, 10:59 AM
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I would start off by contacting the camshaft manufacturer, and the manufacturer of the rocker arms, and the manufacturer of the head. The camshaft manufacturer, is probably going to want you to use their rockers, likewise with the rocker manufacture is probably going to want you to use their cam. Try to get as much information from both as you can.
If they both basically agree on rocker arm geometry, do that.
Are the valves the correct length? Did they get installed at the correct depth? If the head you are using is locating the rocker arm pivot a different height off the deck, that will change things.

Last edited by DanielC; 04-02-2009 at 11:07 AM.
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Old 04-02-2009, 11:31 AM
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Quote:
Originally Posted by 71chevy
ok after doing a little more investigating and reading I was wrong. I think I am needed to go lower on the stud/shorter pushrod. in order to get the roller tip to ride on the center of the valve stem. right now I am almost at the very edge of the exhaust side of the valve stem, going up or longer pushrod will only push it out farther, correct? if i am doing this right and go lower/shorter pushrod then my rocker arm is rubbing against the valve spring, also can't get a socket in there to adjust the nut. but comp says rocker arms are supposed to clear spring up to 1.5 and mine are 1.46. Any insight or am I doing this all wrong?
Yep! your on it. The tip should be a centered as much as possible. However, what you should see is the roller will be slightly toward the intake side of the head when the lifter is on the base circle of the cam. As the lobe rises the lifter the roller should start to move outboard, toward the exhaust side. At mid lift the roller should be in the center of the stem's width. At full lift the contact point should move toward the exhaust side of the head.

There are often problems that you sight when setting up aftermarket heads. Clearance issue with the underside of the rocker and the retainer when using high lift cams are common and this is often exacerbated with aftermarket heads that move dimensions around from those of the OEM.

You need to do some measuring to be sure you know what the installed height of the stem and retainer is. As Techinspector pointed out there are slightly longer studs available. When you start mixing aftermarket parts you're on your own to get things to fit. While the advertisers like to make it sound simple, often it isn't.

Bogie
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Old 04-02-2009, 12:08 PM
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Make certain that the lifter is on the base of the cam. As mentioned before, at that point your roller should be making contact at a point on the valve stem which is about on the inboard 1/3 of the valve stem. Midway thru the valve lift the roller should be centered on the stem. With regard to interference with the rocker and the inboard side of the valve retainer/spring, sometimes it is necessary the use a lash cap on the tip of the valve stem to raise the rocker so it sits a bit higher off the retainer/stem. I dont remember if you said you had a push rod checker, if not, get one.

Last edited by 406 bug; 04-02-2009 at 12:15 PM.
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