rocker arm geometry

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o1heavy

1974 dart sport
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heres my problem (putting together a mild 360)
when checking the valve tip to rocker arm tip center
the roller are just about to roll off the tip the valve

i've heard this could be a problem with a large lift,but alittle surprised that i got this issue
running a mopar 292-509 cam and 340x heads
running a 1.6 on the exhuast and a 1.5 on the intake
the 1.5 ratio's are the problem not the 1.6
can someone school me
and how to fix this

thanks for any help
 
I assume were talking LA heads?? What brand rockers? I used some cheap ones once that had bad geometry. Are the valve stems all the same height (or real close)? If so it has to be the rockers are off.
 
Were the heads milled? Usually on older builds,most people mill the heads fron.020 to .080.Then order adj.pushrods/different length pushrods.Check it out.Call Hughes/Comp cams,and order a adjustable pushrod. They(or here)can walk you through it.
 
I agree, the installed valve height has to be identical on these mopar heads due to the stationary rocker shaft configuration.

You only have a couple of options to change the valve geometry on these heads. You can either raise or lower the valve stem height (grind the valve stem to shorten, mill the valve seats deeper to raise), or you can raise or lower the rocker shaft (raise with shims, lower by milling the shaft cradles).

There's another option I've never personally used... you can install lash caps on top of the valve stems to raise the valve height. Some valve spring keepers will interfere with these and may need to be milled.

You can also switch rocker assemblies. They all seem to be different. I ended up trying several sets and finally found that Harland Sharps were right on for my setup (408 with 6777 Eddy's).

The rocker contact point should start inboard of the center of the valve stem, and as the valve opens the contact point (scrub angle) will will move outboard, crossing the center of the valve stem, and end up equidistant to the outboard side at max valve lift. To complicate matters, the rocker-to-valve stem angle should be 90 degrees at mid valve lift.

Google it and be prepared to become an expert. You may want to consider having an expert help if you're unfamiliar with it. Whatever you do, get it right before you finish the motor... dont' go half axx or you'll end up doing it all over again.
 
Were the heads milled? Usually on older builds,most people mill the heads fron.020 to .080.Then order adj.pushrods/different length pushrods.Check it out.Call Hughes/Comp cams,and order a adjustable pushrod. They(or here)can walk you through it.

If we're talking about a rocker shaft setup such as a LA, B, or RB engine uses pushrod length has no bearing on valve tip geometry which is the problem the OP says he has. The only things that affect valve tip geometry is valve stem height, rocker fulcrum height, and the rocker arms themselves.
 
I'm no expert on subject but wouldn't it be hard to get it correct when using both 1.5 and 1.6 ratio rockers? Seems like it would be impossible to set up for both to have correct roller tip pattern unless setting valves at different heights for the two different ratio rockers.
 
340xheads

using mopar performance roller rockers
thinking of going with all 1.6's or trying another set of rockers

this set up ran for for a very long time on my previous engine
just never check it
thanks for the help guys


man so close to getting it back together ,
 
I'm no expert on subject but wouldn't it be hard to get it correct when using both 1.5 and 1.6 ratio rockers? Seems like it would be impossible to set up for both to have correct roller tip pattern unless setting valves at different heights for the two different ratio rockers.

If the rocker arms are designed correctly they'll have proper geometry no matter what ratio they are. The valve stem height should not need to be varied from the stock height for different ratio rockers.
 
this set up ran for for a very long time on my previous engine
just never check it
thanks for the help guys


man so close to getting it back together ,

That's the way it goes. Sometimes you never know how things are until you pull it apart, unless it's excessively noisy. It was also on X heads that I ran into the problem with bad geometry using cheap rockers. Mine was pretty noisy so I knew their was something wrong and when I got it apart I found the rockers were running nearly off the valve stem tip.

I also tried using a set of lash caps like 64valiantconv mentioned to correct the issue. It did help a lot but I wasn't satisfied and bought a set of Harland sharps and they were dead on. In fact every time I've used Harland's they were dead on. Not cheap but they're sure a lot less hassle.
 
Ratio changes are on the pushrod side of the rocker. No difference on the valve tip side for any ratio. If these are cheaper arms, and if a straight edge laid over the tops of the valve stems show them all at an equal height, then it's either the arms or the valve job. Pushrods mean nothing to a shaft system geometry, as noted.
 
use a marker or dykem and then run it over to check the marks.

Is it to the exh side of the head or intake/valley side of head?

inf it's toward the intake/valley...just buy some shims to raise the shafts some, that alsobring the roller toward the valve tip more.

if it's the other way...you need to cut the stem heights down, or figure an offset rocker shaft 'more work'...but I have seen the holes drilled offset and stands ground a lil to move the shaft away.....a picture in a book.
 
not true fishey
the rdius of the roller must be compensated for by raising the shafts
and
the only wys to move to center of the valve once the above is accomplished are rockers with a different ar length or move the shafts back

go to the b3 racing industries web site and read all 4 tech articles

"Years ago, the 90's, I worked for Rick Herrick. Rick's shop was in Ft. Lauderdale right down from Harvey Cranes old shop. In the early days Rick made a bunch of stuff for Harvey and other cam companies. One day it cam up about the pattern on the valve tip and valve guide wear. His reply was "Harvey and I proved 3 years ago if the sweep is no wider than .060" then its within 2/3's of the middle of the valve you will not wear out the guides. If it is centered and .070, it will wear the guide out."
Chris Straub

so true but early crane rockers were all wrong so he sold them as "quick lift"
 
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Just sayin'

xscuseless.gif
 
Leave it to Wrym to correct people on a 9 year old thread....
:rofl:Hey Wrym, was B3 here 9 years ago?
LOL Newbie Don Jones started the ball rolling . Interesting, A member since 2008 and only 2 posts.
 
lot of people find these old threads with search
there were lots of threads 0 and 5 years ago on this topic
seems ,like it just keeps coming around
 
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