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SVO 302 Valve adjustment
I have just put on some GTX40 alum heads. When I got them they had the rocker arms loose and unadjusted. These are the stamped steel bolt down type with a fulcrum and fulcrum guide. The engine is a B51 302 with a B303 cam in it. Thats a Hyd roller type cam.
My question is. How do you adjust these rockers for lifter preload? I tried calling Ford motorsport and was told to turn the locking nut 1/2 turn past the point that you have 0 valve lash at TDC on each cylinder. The problem is these are bolt down rockers and have no locking nuts. If you don't tighten up the hold down bolt the rocker will lossen up to the point that it stops working the valve up and down with dammage to follow. So do I need to shim them or something? I'm a new member so I'll thank you all in advance and say Hello at the same time. Howard Jones |
Howard:
Welcome to the site! Verify that the rockers you have are intended to be used with these heads. If so : It sounds like rockers you have are non- adjustable (like most OEM Ford), they utilize "sleds" that align the rockers and allow the rockers a point to to pivot on (instead of roller bearings) when the sleds are tightened down to the heads. All things considered there is usually enough allowable adjustment in the lifters to arrive at "0" lash once they are tightened down and oil pressure is initially achieved. This is assuming that the valve to piston clearance has been verified so they will not hit each other, pushrods are the correct length and neither the heads or the block surfaces have had excess amounts of material removed. Tighten them down as you cycle through the firing order and you should be ok. Initially there will probably be some "clicking" in the valvetrain when it is first started untill the lifters presurize. Good luck Rick |
Thanks Rick,
The rockers and all the valve train parts are oem ford parts that were orginal parts on each motor and are intented to be used with these motors, 320hp b51 y303 heads and 345hp b51 x303 heads. I simply swaped a set of y303 heads off the motor and put on x303 heads from another SVO 302 motor. This should have been a no brainer head swap. I used the pushrods that were orginally in the motor and left the rockers on the heads, x303, that they came with. Everything else valves, springs, etc. either were original with the motor or the heads. My motor has less than 1000 miles on it and the heads have something like 5000 miles on them. Both motors worked fine before disasembly. The engine runs ok now, after I torqued down the rockers to 25 pounds, thats a guess on torque value, but it sounds like maybe one valve/ rocker is noisey. louder under load, goes away when I take my foot off it and coast. Could this be a flat lifter? |
Can you isolate which lifter/cylinder it is? Has it had enough time to "pump up"?
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I believe it is #5 cylinder. I have found out that these type rockers are not adjustable like solids with a adjustment nut and jam nut. Lifter preload can be changed with shims or milling the head at the pedestal for the rocker.
I think I am going to change over to roller rockers from craincams. They are adjustable for lash (lifter preload) like the solid lifters. Thanks |
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