lifter bleed off ??'s/pushrod length ??'s
04-22-2008, 03:40 AM
#1
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lifter bleed off ??'s/pushrod length ??'s So here's my dilema; I have checked my pushrod length with my checker tool, and found that if I did it right I need 7.530 lenght pushrods. That seems a little long to me, so I come to the guru board for some advice.
I am using some GM MLS gaskets with compressed thickness of .058 as they advertised, Livernois heads 243 castings, stock rockers and lifters for now (Caddy Lifters waiting to go in), 7.40 hardened pushrods, Comp Cams blower grind of 226/234 with .598/.599 lift on 117 LSA. With the rockers torqued to 22lbft and checked multiple times, and no tension on the springs I can easily spin the pushrods with my fingers. I checked the wear pattern on the valve stem, and it's a hair off center to the short side. When I torque the rockers down to spec they get tight and no side to side movement is there for the first 15 seconds, then the lifters bleed off and there is quite a bit of side to side movement. So here's my first ?; how much bleed off is normal with the engine off and cool. I turned the checker tool out retorquing the rockers each time until I got no bleed off even after 60 seconds. The measurement I got from that was 7.460 approximately, so I figured the .070 preload in and got the 7.530. Did I check it right? Am I correct on my calculations? Each turn on the checker tool is = to .050 right?
I know that the rods are too short from looking at the wear pattern and that's probably the biggest reason for the loud ticking I get beyond the normal sewing machine noise, after the engine warms up, but it didn't look like it was almost a whole tenth off. How many out there are running that big a pushrod and what lift is the cam?
I am using some GM MLS gaskets with compressed thickness of .058 as they advertised, Livernois heads 243 castings, stock rockers and lifters for now (Caddy Lifters waiting to go in), 7.40 hardened pushrods, Comp Cams blower grind of 226/234 with .598/.599 lift on 117 LSA. With the rockers torqued to 22lbft and checked multiple times, and no tension on the springs I can easily spin the pushrods with my fingers. I checked the wear pattern on the valve stem, and it's a hair off center to the short side. When I torque the rockers down to spec they get tight and no side to side movement is there for the first 15 seconds, then the lifters bleed off and there is quite a bit of side to side movement. So here's my first ?; how much bleed off is normal with the engine off and cool. I turned the checker tool out retorquing the rockers each time until I got no bleed off even after 60 seconds. The measurement I got from that was 7.460 approximately, so I figured the .070 preload in and got the 7.530. Did I check it right? Am I correct on my calculations? Each turn on the checker tool is = to .050 right?
I know that the rods are too short from looking at the wear pattern and that's probably the biggest reason for the loud ticking I get beyond the normal sewing machine noise, after the engine warms up, but it didn't look like it was almost a whole tenth off. How many out there are running that big a pushrod and what lift is the cam?
04-22-2008, 06:14 AM
#2
Pushrod length has no affect on the wipe pattern of the rocker, the only way to change the wipe pattern is to shim the rockers.
To check pushrod length, you set the lifter you are checking on the cam base circle (TDC) and then adjust the pushrod until you get zero lash, then add preload to the length to obtain a final number.
Here are more details: Link
To check pushrod length, you set the lifter you are checking on the cam base circle (TDC) and then adjust the pushrod until you get zero lash, then add preload to the length to obtain a final number.
Here are more details: Link
