7 degree valve locks recessed for lash cap?

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wyrmrider
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Re: 7 degree valve locks recessed for lash cap?

Post by wyrmrider »

you most likely know this but there are stock rockers that area round 1.42 and there are stock rockers that are really 1.5
getting the lash caps on ,open a valve to half lift and put an old stem seal on it with a screw clamp to hold it half open
put on a rocker with the head upside down so it fits on the ball and adjust the rocker stud nut till you get 90 degrees from the top of the lash cap to the center of the rocker ball circle
put the head on the block with a used gasket and rotate the cam to half lift with a dial indicator
now we have the valve at half lift and the cam lobe at half lift and the rocker ball height set for rocker arm tangtent with the valve stem at half lift
measure for pushrod with an adjustable pushrod
order pushrods
you will have to let the pushrod/ rocker angle be whatever it turns out to be

is this a cam or cam lift limited class motor?
you would not think about backseting your rocker studs and using 1.7 big block or 1.65 Pontiac rockers would you? :)
jetmech727
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Re: 7 degree valve locks recessed for lash cap?

Post by jetmech727 »

wyrmrider wrote:you most likely know this but there are stock rockers that area round 1.42 and there are stock rockers that are really 1.5
getting the lash caps on ,open a valve to half lift and put an old stem seal on it with a screw clamp to hold it half open
put on a rocker with the head upside down so it fits on the ball and adjust the rocker stud nut till you get 90 degrees from the top of the lash cap to the center of the rocker ball circle
put the head on the block with a used gasket and rotate the cam to half lift with a dial indicator
now we have the valve at half lift and the cam lobe at half lift and the rocker ball height set for rocker arm tangtent with the valve stem at half lift
measure for pushrod with an adjustable pushrod
order pushrods
you will have to let the pushrod/ rocker angle be whatever it turns out to be

is this a cam or cam lift limited class motor?
you would not think about backseting your rocker studs and using 1.7 big block or 1.65 Pontiac rockers would you? :)

Yes I have considered using the big block rockers. The drawings are out there to relocate the studs and it looks like a very interesting fun project. The fact of the matter is I need 450 reliable hp and a car with a well balanced set up. The cars must be 3200 Lb at the end of the race and an 8 inch wheel on dirt so we are a bit tire limited. The project you speak of has peaked my interest and i might try it sometime but just not enough hours in the day right now.
wyrmrider
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Re: 7 degree valve locks recessed for lash cap?

Post by wyrmrider »

I hope you at least have the hours to get your geometry right
if you want to jerk the valve off the seat faster you can use 1/3 lift for the tangent
maximum leverage is obviously where the rocker is perpendicular to the valve
but it also closes quicker and the action when open is that there is more side thrust so BVVC that the rocker stays on the valve tip- lash caps help here too can help with valve float as valve accelerations are lower when cam is going over the nose
works on cam limited setups and others where you want more flow earlier in the piston moving down cycle
having the rocker ball low has the side thrust with the valve closed where it has more leverage on the guide- not usually a good thing- can also have earlier valve float as acceleration is maxed when valve further open
If I have a head for a motor that say had stock 400 valve lift and I increased it to .500 I could make the stem .050 longer and have the closed angle up and the open angle down stay the same keeping the pushrod length and rocker ball height stock
(insert your numbers and see what you come up with)( if base circle has not changed, valves not sunk, etc. On SBC I install a lot of .100 long valves...are they legal in your class?
sometimes I do not understand the rule bodies- by the time you buy the 1.5 optimized heavy duty heat treated "stock" rockers you could have bought a set of roller rockers- penny wise and pound foolish
who wants to end the day with a pushrod poked through the rocker seat
restricting oil will generate heat and lead to the above- find a way to get the oil back to the pan and supply enough to your valvetrain to keep it cool and lubed
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