kelleyperformance Posted February 1, 2007 Report Share Posted February 1, 2007 well when i installed my forged bottom end, heads, and cam, i used the 1.8 crane rocker arm kit. got a bigger cam, so i decided to put the stockers back on. well there is no compression, the starter just spins freely. my guess is the valves wont close. so my question is: i switched to the LS2 heads (242 casting, i think) from the truck castings. they are milled to 64.5cc chambers. is it possible that the milled heads arent liking the stock rockers, due to less surface, causing the valves not to shut? i need some sugestions ASAP. thanks Quote Link to comment Share on other sites More sharing options...
misterp Posted February 1, 2007 Report Share Posted February 1, 2007 Pushrods too long? Quote Link to comment Share on other sites More sharing options...
04CHASE Posted February 1, 2007 Report Share Posted February 1, 2007 did you check your pushrod legnth, did you use new ones are something different ? that could be the problem . Quote Link to comment Share on other sites More sharing options...
kelleyperformance Posted February 1, 2007 Author Report Share Posted February 1, 2007 no, everything is stock now. i removed all parts of the crane kit, and reinstalled the GM guideplate on each side, then the stock pushrods, then the rockers...... Quote Link to comment Share on other sites More sharing options...
Quik Posted February 1, 2007 Report Share Posted February 1, 2007 did you think you oculd of bent some valves? shouldnt even of thought of using 1.8 rockers. a 243 head a 6.0 isnt much to worry. i ran that setup with 3 different cams all using stock length PRs and didnt have your issue. sounds like valves are bent Quote Link to comment Share on other sites More sharing options...
misterp Posted February 1, 2007 Report Share Posted February 1, 2007 (edited) Get an air-hold fitting, hook up compressed air to the chamber and rotate the engine to TDC; you will hear/feel the air escaping either from the intake valve (air will come out backwards out of the throttle body) or exhaust valve (air exiting out the exhaust system), or both. Ideally the cylinder should not leak at all, although there will be a little blowby heard around the rings into the crankcase (this is normal). Mr. P. Edited February 1, 2007 by misterp (see edit history) Quote Link to comment Share on other sites More sharing options...
kelleyperformance Posted February 1, 2007 Author Report Share Posted February 1, 2007 valves cant be bent, truck ran fine into the shop. installed them all by hand, and very carefully. pushrods are all new, stock pushrods. something is really odd here. mr.p: did the compression test. like 6 cylanders valves are open. i feel really lousy today, so i dont feel like messing with it. i should know whats up as soon as i take the coilpacks and vc back off. Quote Link to comment Share on other sites More sharing options...
kelleyperformance Posted February 1, 2007 Author Report Share Posted February 1, 2007 valves cant be bent, truck ran fine into the shop. installed them all by hand, and very carefully. pushrods are all new, stock pushrods. something is really odd here. mr.p: did the compression test. like 6 cylanders valves are open. i feel really lousy today, so i dont feel like messing with it. i should know whats up as soon as i take the coilpacks and vc back off. Quote Link to comment Share on other sites More sharing options...
kelleyperformance Posted February 1, 2007 Author Report Share Posted February 1, 2007 valves cant be bent, truck ran fine into the shop. installed them all by hand, and very carefully. pushrods are all new, stock pushrods. something is really odd here. mr.p: did the compression test. like 6 cylanders valves are open. i feel really lousy today, so i dont feel like messing with it. i should know whats up as soon as i take the coilpacks and vc back off. Quote Link to comment Share on other sites More sharing options...
kelleyperformance Posted February 1, 2007 Author Report Share Posted February 1, 2007 valves cant be bent, truck ran fine into the shop. installed them all by hand, and very carefully. pushrods are all new, stock pushrods. something is really odd here. mr.p: did the compression test. like 6 cylanders valves are open. i feel really lousy today, so i dont feel like messing with it. i should know whats up as soon as i take the coilpacks and vc back off. Quote Link to comment Share on other sites More sharing options...
packjh Posted February 2, 2007 Report Share Posted February 2, 2007 sounds like a broken record or a really lousy skipping cd Quote Link to comment Share on other sites More sharing options...
misterp Posted February 2, 2007 Report Share Posted February 2, 2007 valves cant be bent, truck ran fine into the shop. installed them all by hand, and very carefully. pushrods are all new, stock pushrods. something is really odd here. mr.p: did the compression test. like 6 cylanders valves are open. i feel really lousy today, so i dont feel like messing with it. i should know whats up as soon as i take the coilpacks and vc back off. Maybe the heads you installed have been shaved enough that you need shorter pushrods? I hear you about the feeling miserable... Quote Link to comment Share on other sites More sharing options...
kelleyperformance Posted February 2, 2007 Author Report Share Posted February 2, 2007 sorry about the quadurple posts stupid cell phone always does stuff like that. mr p thats what i was thinking, its really the only logical explanation. everything seems to be working right under the VCs. if they were too long, the valves would lift open but never close all the way..... causing my loss of compression Quote Link to comment Share on other sites More sharing options...
misterp Posted February 2, 2007 Report Share Posted February 2, 2007 (edited) sorry about the quadurple posts stupid cell phone always does stuff like that. mr p thats what i was thinking, its really the only logical explanation. everything seems to be working right under the VCs. if they were too long, the valves would lift open but never close all the way..... causing my loss of compression Well there is one other option, it like never happens but: the cam could be defective, cut from the wrong base circle, but I seriously doubt it. It's probably the pushrods. Check this before you rip it all apart - get the valve cover off, and your eyeball down near the front valvestem so you can closely watch the roller-tip "roll" across the tip of the valvestem as it cycles through it's motion. On a correctly adjusted valvetrain the tip should be observed moving from the inside edge of the stem, across the center, to the outside edge and back. My guess is that you will see your rocker arm tips moving from the center of the stem to the very outside and back to the center again (the inside of the stem never sees any wear). Another check - with the cylinder at TDC firing position, you should be able to twist the pushrods, and also be able to bottom them into the lifter about another 0.04" - 0.07". If you cannot twist the pushrod and/or the lifter plunger is bottomed in the lifter body then your valve lash is way too tight, and the only way to fix that on a stock Gen-III is with custom length pushrods. Mr. P. Edited February 2, 2007 by misterp (see edit history) Quote Link to comment Share on other sites More sharing options...
misterp Posted February 2, 2007 Report Share Posted February 2, 2007 I just drew a pic to illustrate my point - When blueprinting valvetrains you want the tip of the rocker arm to be centered on the valvestem; we would dye the tops of the valvestems with machinist's blue dye (a Sharpie will work), assemble the rocker arms & torque to spec, spin the motor through a few revs, then take the rocker arms off to view the wear pattern and verify that our valvetrain geometry was spot-on. Don't forget that you also want the plunger in the hydraulic lifter to be 1/2-way down into its body. Mr. P. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.