valve clearance ?

[dodge71demon]

383 with 906 heads I clayed the pistons for pushrod length do I want the same clearance for the intake and exhaust valves which would require different length pushrods would be longer on exhaust or use the same length as the intake I have around .175 clearance using 8.50 intake and stock 8.55 exhaust I dyed the stems and the rocker pattern is good cam is 477/480 or would going with the longer exhaust pushrod cause the valve to open to much for good operation I'm asking because the factory used the same pushrods for a reason

 

[famous bob]

383 with 906 heads I clayed the pistons for pushrod length do I want the same clearance for the intake and exhaust valves which would require different length pushrods would be longer on exhaust or use the same length as the intake I have around .175 clearance using 8.50 intake and stock 8.55 exhaust I dyed the stems and the rocker pattern is good cam is 477/480 or would going with the longer exhaust pushrod cause the valve to open to much for good operation I'm asking because the factory used the same pushrods for a reason

hydrolic cam ?

 

[dodge71demon]

hydrolic cam ?

yes and stock rockers

 

[IQ52]

Are we talking about piston to valve clearance? You don't need the same piston to valve clearance on the intake and exhaust, you need enough piston to valve clearance, approximately .080" intake and .100" exhaust.

Pushrod length will effect hydraulic lifter preload but shouldn't effect piston to valve clearance. I don't think pushrod length will effect piston to valve clearance on a hydraulic lifter unless the lifter loses contact with the cam lobe on the closing ramp (what I call valve float). Then the lifter pumps up and holds the valve open, decreasing piston to valve clearance during the overlap phase (where piston to valve clearance is critical). Less preload (shorter pushrods in this case), less pump up. It's why adjustable rockers on hydraulic cams are valuable. If you back the preload down to zero, the lifter can't pump up as much as it's basically pumped up from the start. Some people deliberately preload the hydraulic lifter so much the hydraulic system nearly bottoms out, limits the hydraulic travel in the lifter, and does much the same thing as zero preload.

 

[69 Cuda 440]

Are we talking about piston to valve clearance? You don't need the same piston to valve clearance on the intake and exhaust, you need enough piston to valve clearance, approximately .080" intake and .100" exhaust.

Pushrod length will effect hydraulic lifter preload but shouldn't effect piston to valve clearance. I don't think pushrod length will effect piston to valve clearance on a hydraulic lifter unless the lifter loses contact with the cam lobe on the closing ramp (what I call valve float). Then the lifter pumps up and holds the valve open, decreasing piston to valve clearance during the overlap phase (where piston to valve clearance is critical). Less preload (shorter pushrods in this case), less pump up. It's why adjustable rockers on hydraulic cams are valuable. If you back the preload down to zero, the lifter can't pump up as much as it's basically pumped up from the start. Some people deliberately preload the hydraulic lifter so much the hydraulic system nearly bottoms out, limits the hydraulic travel in the lifter, and does much the same thing as zero preload.

Excellent Information 'IQ52'