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Author Topic:   rocker arms?
LUBEGUY07
Dirt Maniac

Total posts: 156
posted May 11, 2002 10:03 AM
at the races last night i was helping a friend with his car he had me look at his rocker arms they were off centered on the valves when they were openeing the valves. He runs a hydralic cam with 1.5 longslot rockers with guid plates, to me it looked like maybe he used they wrong length pushrods or maybe the valves werent set right. or is this ok and advice would be aperciated

Monster
Dirt Maniac

Total posts: 135
posted May 11, 2002 11:01 AM
By off-centered, do you mean from front to back, or side to side? Front=radiator end, rear=fuel cell end, side=driver or passenger.

LUBEGUY07
Dirt Maniac

Total posts: 156
posted May 11, 2002 11:44 AM
quote:
Originally posted by Monster:
By off-centered, do you mean from front to back, or side to side? Front=radiator end, rear=fuel cell end, side=driver or passenger.

they are off centered some front and some back

Monster
Dirt Maniac

Total posts: 135
posted May 12, 2002 10:12 AM
A lot of engine assemblers just bolt a set of guideplates on and get on with it, without any thought given to the alignment you speak of. The guideplates can be wiggled about to find the best possible alignment(good), they can be cut apart and aligned individually(better), or Isky makes a neat set that is already split, and has a tab that makes things easier(best). Once things are lined up properly, 10 minutes with a TIG welder(for the 2 piece plates) will give you a set of custom guideplates that will stay with those heads from now on. There are other causes for this, but most involve mistakes made in machining the heads and are not easily fixable. When you pick up a set of heads that are "Ready to bolt on", this procedure should always be looked after. The head guy will bolt everything on to the heads, but there is no way he can check this alignment, 'cause he doesn't have the rest of the engine. Like a lot of things, this becomes more critical as valve lift increases and the cam profile becomes more aggressive, but is good practice no matter what level you race at.

LUBEGUY07
Dirt Maniac

Total posts: 156
posted May 12, 2002 04:00 PM
so you think the guidplates are hitting the pushrods? or they could have messed up when they machined them for ***** in studs? thanks for the info monstor


LUBEGUY07
Dirt Maniac

Total posts: 156
posted May 12, 2002 08:03 PM
also he is using 1.5 longslot rockers and a low lift cam with around .470 lift will the longslots rocker hurt anything on a low lift cam?


Flatlander
Dirt Freak

Total posts: 310
posted May 12, 2002 10:12 PM
yes it could be the studs also it's fine to use the long slot rocker with a lower lift cam also one thing I would suggest is look at the spring seatsv and make sure they are sitting where they should be and fit properly however it does sound like a guide problem to meJMO

Monster
Dirt Maniac

Total posts: 135
posted May 13, 2002 09:58 AM
One purpose of the guideplates is to establish the rocker arm/valve tip alignment. When they are installed, the close tolerance slot that did the guiding before should be drilled out, so the only guiding is done by the plate. Hopefully, this was done. Due to manufacturing tolerances in all parts concerned, some(most) times, there is not perfect alignment. This is the point in the wiggling/cutting/welding ordeal. The best guiding is done by holding a pushrod in place as close to it's end as possible(just like a pool cue), and that is the reason for getting rid of the stock method, and also for stepped guideplates. And, no, long slot rockers won't hurt a thing. Remember, at 6000 rpm, each valve is opening and closing 25 times a second. It pays to be thorough.

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