Ford Mustang Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
42 Posts
Discussion Starter #1
I have a 1970 302 block with a 1985 rotating assembly and cylinder heads. We were trying to lash the valves but I cannot get the rockers tight enough so that the pushrods stop moving. The hydraulic lifters always seem to bleed out and then give it enough room to spin the pushrods again. The bolts on the rockers are all the way down and cannot go any tighter. I am also having several issues with the motor running(lack of performance, really smooth idle(mid cam), backfiring, ect.) and I am becoming convinced that my pushrods are too short. Does anyone agree with this diagnosis and/or know the length of pushrods that should be used in this application? Thanks Nathan
 

·
Registered
Joined
·
73 Posts
Did it ever run good at all? not totaly sure but you may have worn the lobes off the cam. if you have adjusted it several times and have them tightened down, and are now at the end of the threads for tightening. I have had this happen before it sounds identical runs ok set the lash drive it starts to run bad backfiring reset the lash and it repeats. Not ruling out pushrod length but it could be deeper. It only took three runs to totaly wipe the lobes off my cam. good luck hope this helped
 

·
Registered
Joined
·
396 Posts
Certainly sounds like short pushrods. You shouldn't bleed down either though.

The roller tip should ride in the middle of the valve stem.
 

·
Registered
Joined
·
42 Posts
Discussion Starter #4
no, it hasnt ever really been run good. Its a brand new motor and ive only gone around the block a couple times barely above idle due to the issue of backfiring under pressure being in gear. i was also concered at first of wiping the cam but the rockers have always been tightened down while leaving the pushrods loose enough to turn. Also, I changed the oil and filter after a neutral break in which resulted in perfect, clean, metal free oil. So, assuming I am right, which i try not to do, and the cam has not been stripped, should i look to my pushrods next? Thanks
 

·
Registered
Joined
·
25 Posts
nothing wrong with the push rods turning as the motor is running, youre just looking for no noise coming from the rocker arm,pushrod area. wes
 

·
Registered
Joined
·
396 Posts
I have a 1970 302 block with a 1985 rotating assembly and cylinder heads. We were trying to lash the valves but I cannot get the rockers tight enough so that the pushrods stop moving. The hydraulic lifters always seem to bleed out and then give it enough room to spin the pushrods again. The bolts on the rockers are all the way down and cannot go any tighter. I am also having several issues with the motor running(lack of performance, really smooth idle(mid cam), backfiring, ect.) and I am becoming convinced that my pushrods are too short. Does anyone agree with this diagnosis and/or know the length of pushrods that should be used in this application? Thanks Nathan
Back to your original question. The length of your pushrods depends on your heads, head gaskets, lifters, etc. Anyone that gives you a pat answer on length is guessing at best. Best to check length by using the blue dye method--make sure they ride in the middle of the valve.

When checking lash, get the oil pressure up to pump up the lifter, don't over tighten, slowly tighten so the lifter doesn't bleed out.

Keep in mind, it shouldn't bleed out. Mine used to bleed out cause I had WAY too high spring force in the heads and blew them out, that is how I know. The only way I could set them is as I mention above. They would work, but it ran like crap at low RPM and until oil pressure built.
 
1 - 9 of 9 Posts
Top