Help: Pushrod length question
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Teching In
Joined: Mar 2006
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Help: Pushrod length question Working with a buddy on his LS1 Z28. Need some help with pushrod length. We did the procedure of turning the engine over by hand with an adjustable pushrod to get the correct length so that the tip is centered on the rocker's roller. but im affraid there wasnt enuf oil in the lifters etc when we did it cuz now it seems like the pushrods are too long (at least thats what i think).
Symptoms: it wont stay running at idle (it did the very first fire up momentarily) but it smooths out and runs fine at 2k rpm. cam is timed correctly. we even clayed the piston/valve after assembly and there was plenty of clearance. it is super rich down low. im thinking the valves arent closing soon enough or possibly hanging open ever so slightly. it backfires if you try to let it idle.
The valvetrain setup is as follows: 222/224 Cam .566 IN .568 EX spec on stock rockers, stock hydraullic roller lifters, moved up to 1.8:1 roller rockers (puts lift somewhere around .599 and .601 i think). pedestal mount roller rockers that are non-adjustable. we torqued them to spec. we put in bigger push-rods but i think we went too big. DART 205cc heads.
I dont remember what the stock push-rod length is (they are at his house otherwise i would measure). Should we stick with the stock push-rods? If my memory serves me correctly, we put in Comp Cams 7.425" push-rods. Are those too long? If so what do you recommend.
Thanks! Any help is greatly appreciated!
-Anthony
Symptoms: it wont stay running at idle (it did the very first fire up momentarily) but it smooths out and runs fine at 2k rpm. cam is timed correctly. we even clayed the piston/valve after assembly and there was plenty of clearance. it is super rich down low. im thinking the valves arent closing soon enough or possibly hanging open ever so slightly. it backfires if you try to let it idle.
The valvetrain setup is as follows: 222/224 Cam .566 IN .568 EX spec on stock rockers, stock hydraullic roller lifters, moved up to 1.8:1 roller rockers (puts lift somewhere around .599 and .601 i think). pedestal mount roller rockers that are non-adjustable. we torqued them to spec. we put in bigger push-rods but i think we went too big. DART 205cc heads.
I dont remember what the stock push-rod length is (they are at his house otherwise i would measure). Should we stick with the stock push-rods? If my memory serves me correctly, we put in Comp Cams 7.425" push-rods. Are those too long? If so what do you recommend.
Thanks! Any help is greatly appreciated!
-Anthony
Well stock length is 7.4"
I'm in the same exact boat as you right now and can NOT get a straight answer from ANYONE on this topic. Is it ok to pump up the lifter like that?? Crane cams will say NOT to do that, it's right on their website. Then Comp cams will say yes go ahead and do that.
SO basically, can someone finally post up somethign about the best way to check pushrod length>?? That would be great!!
Thanks Guys
I'm in the same exact boat as you right now and can NOT get a straight answer from ANYONE on this topic. Is it ok to pump up the lifter like that?? Crane cams will say NOT to do that, it's right on their website. Then Comp cams will say yes go ahead and do that.
SO basically, can someone finally post up somethign about the best way to check pushrod length>?? That would be great!!
Thanks Guys
Teching In
Joined: Sep 2005
Posts: 24
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I did a H/C swap on the Z06 recently. I ended up having to go with a shorter push rod due to the milled head and extra lift on the cam. I used the comp magnums 7.375. It actually measured out to 7.370, but 5 thousandths isn't going to kill me. How did you get a measurement from the adjustable pushrod? I ended up taping the thing, and taking it to a machine shop to check the length. Hope some of this helps.
Rob
Rob
If you havnt tuned for it, thats the likely culprit. You need to lean out the low RPMs and you need to increase the running airflow to keep the car idling. My guess would be tuning before a pushrod problem. Stock lifters can usually go atleast .060 in either direction before running out of adjustment.
Unmilled Dart heads will set up the same as stock. You should mount your rocker with the lifter on the base circle and then measure the pushrod length to just eat up the distance between the lifter and rocker. Then add your lifter preload to the measured length.
I agree, sounds like a tuning issue. Try a compression check, that will tell you whether you are hanging valves open. What is the LSA on the cam?
I agree, sounds like a tuning issue. Try a compression check, that will tell you whether you are hanging valves open. What is the LSA on the cam?
well now you got me concerned about my cam install that will happen next week. I got the comp cams 7.425 PR that will be going along with my Comp Cam XE-R 224/228 .581/.588 LSA 110+2 918 springs and TI retainers. will the PR length be fine with my setup???
Originally Posted by jlashley2001ss
well now you got me concerned about my cam install that will happen next week. I got the comp cams 7.425 PR that will be going along with my Comp Cam XE-R 224/228 .581/.588 LSA 110+2 918 springs and TI retainers. will the PR length be fine with my setup???
