JCan Posted January 14, 2013 Author Share Posted January 14, 2013 Update. I reduced the valve gap to 0.006/0.008" intake/Exhaust. and restarted the engine with no change. Next, I removed the cam followers and lash pads. I noticed the lash pads I removed completely flat on the bottom (as opposed to the stock lash pads which have rather long walls and seem to cuddle the valve. I also noted the lash pads (top side) did not have the groove on either side and the cam follower wore two small lines on either side of the middle of the lash pad. The lash pads measured 0.155" thick. see pictures: Left pictures are the stock lash pads right pictures are the isky lash pads that were installed on my head. Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted January 14, 2013 Share Posted January 14, 2013 take a pic off the rocker tip for me please Quote Link to comment Share on other sites More sharing options...
JCan Posted January 14, 2013 Author Share Posted January 14, 2013 Seems like the rocker arms are only touching the lash pads at the sides... right? Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted January 14, 2013 Share Posted January 14, 2013 Yes there not flat , i would have them re surffaced , its not dear get isky to do them or any cam shop , id say your valve clearance is not what you think as the rocker only has point contact , have them done and it will be quiet Quote Link to comment Share on other sites More sharing options...
Lazeum Posted January 14, 2013 Share Posted January 14, 2013 Pete, What could have caused such wear? Resurfacing the rocker would also get rid of the hardened layer in contact with pads, wouldn't it? I might have the same issue. I've noticed valve lash on my engine are very sensitive, lash changes to some extent according to cam position while it should not change. Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted January 14, 2013 Share Posted January 14, 2013 There is no hard layer the pad is hard all the way thru , every time you fit a new cam you need to redo the rocker or the cam will wear badly , i know many dont but thats just bad work , We have them done on every engine , and yes it is hard to set tappets if there is a bad surface , Quote Link to comment Share on other sites More sharing options...
Lazeum Posted January 14, 2013 Share Posted January 14, 2013 The rockers on my head were new but maybe not the lash pads... Is there any hard layer on rocker tips as well on contact patch area with lash pads? Regarding reason, could a too tight lash between cam & rocker cause this defect? Quote Link to comment Share on other sites More sharing options...
JCan Posted January 15, 2013 Author Share Posted January 15, 2013 Update! I took the rocker arms to the head builder and showed him the tappet wear and the matching rocker arm wear. He was of the opinion that this was not the problem but did grind the rocker arms so that they would naturally touch the center of the lash pad instead of the edges as shown above. (picture of modified rocker arm, orig rocker arm, and lash pads -attached). We're pealing the onion here... First steps, reinstall cam lash pads and rocker arms. Blue (sharpie marker on the pad where the rocker arm comes in contact with the cam) rocker arms and check each rocker arm / cam surface to ensure the arm is properly mating to the cam. While I am doing this be sure to check the rocker arm is pushing the valve in the proper place. Next, with the engine cold, gap both intake and exhaust valves at 0.008" Next, start the engine, let it warm up, turn it off and regap intake and exhaust valves at 0.008 intake and 0.010 exhaust Start engine and see if it is quieter. If I still have a problem, I have located an old valve cover and I am going to cut the top off, mount it to the head and run the engine to see if I can tell which valve is making the tapping noise. Next steps if the noise persists, is to swap my beautifully rebuilt P90 head with squish to a N42 head ... sigh... Jim Quote Link to comment Share on other sites More sharing options...
Lazeum Posted January 15, 2013 Share Posted January 15, 2013 have you also done something on lash pads with regrinded rockers or did you keep them the way they are with the recess? Quote Link to comment Share on other sites More sharing options...
Xnke Posted January 15, 2013 Share Posted January 15, 2013 Any lash pad thicker than 0.120" is usually a flat-bottom lash pad. That's completely normal. Does the tapping sound track crank speed, cam speed, or valve speed? Quote Link to comment Share on other sites More sharing options...
JCan Posted January 15, 2013 Author Share Posted January 15, 2013 Lazeum - I am using the same lash pads. Xnke - I believe the ticking noise is at the valve speed. If it continues, I plan to determine which valve it is by cutting the top off the valve cover. More to come! Jim Quote Link to comment Share on other sites More sharing options...
TimZ Posted January 15, 2013 Share Posted January 15, 2013 Lazeum - I am using the same lash pads. Xnke - I believe the ticking noise is at the valve speed. If it continues, I plan to determine which valve it is by cutting the top off the valve cover. More to come! Jim Didn't you say that the sound did _not_ get louder when you lifted the valve cover? Quote Link to comment Share on other sites More sharing options...
JCan Posted January 15, 2013 Author Share Posted January 15, 2013 I think there are two sounds. One is the valve trane ( I will gap it hot this time) the second is a violent tapping which seems to come from the back side of the valve cover. When I lifted the valve cover while engine was running the noise did not change. This time during assembly I'll pay very close attention to rocker arms and will check gap as a function of angle. Quote Link to comment Share on other sites More sharing options...
JCan Posted January 15, 2013 Author Share Posted January 15, 2013 Good news! Car is working!!! little to no head noise! Alright, what caused the issue. Rocker arm to cam gap was not correct. Why? Remember the lash pad marks? one on each side of the lash pad with nothing touching the center of the pad. What would happen if the planes defined by the cam lobe/rocker arm was not parallel with the lash pad/rocker arm plane? If the rocker arm was soft, it would cause the rocker arm to twist until the two planes are parallel? I believe this was my problem. Once I had the portion of the rocker arm that touches the lash pad ground down do that it touches the lash pad on one spot and in the center of the lash pad, I could accurately adjust the valves. (note: during adjustment prior, the rocker arms seemed to rock, now they are steady) I re-assembled the head, and was careful to gap the exhaust/intake at 0.010"/0.008" respectively. Started the car, and warmed up the engine (the engine was a bit quieter, however it was still loud). once the fan kicked on, I turned off the engine and re-gapped the valves. Started the engine and WOW it is running quietly now! YEA! Thanks very much for everyone who took the time to help me on this thread.!!! Jim Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted January 16, 2013 Share Posted January 16, 2013 Good to hear , it worked out Quote Link to comment Share on other sites More sharing options...
JCan Posted January 16, 2013 Author Share Posted January 16, 2013 PMC raceengines (pete?) You were right! You know, prior to grinding my rocker arms I could not adjust the cam/rocker gap properly... Now that the rocker only touches the lash pad/valve interface in one spot, it is so easy to adjust the gap.! This engine is a monster! I think I may have gone a little bit too far with the cam I chose (280 degree duration) with SU carbs. Idle at 700 rpm seems difficult to achieve and the exhaust is a bit loud... No matter, the car is running and I am very happy! Thanks again for your help! Jim Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted January 16, 2013 Share Posted January 16, 2013 Realy you should have them done propley the serface needs to be very smoth or you get nasty wear on the cam and lash cap , if you look very close you will see the the pad that rubs on the cam is hollow in the middle and will have a line in it this makes it very hard to set tappets spot on , and also the lift cerve will not be constant , ,, so remember new cam have the rockers done as well. All cam shops can re serface rockers , we pay $12 per rocker to have them done and the new again . Quote Link to comment Share on other sites More sharing options...
JCan Posted January 16, 2013 Author Share Posted January 16, 2013 Pete - I had valley head service do the lash cap side of the rockers and did not touch the rocker to cam interface (it looked pretty good). They did spend a lot of time with the valves and cam geometry. The guys didn't think that the rockers needed any work and that is why they didn't touch them. In general they are pretty competent guys! At least that is my illusion... lets not burst my bubble now! Grin.... Quote Link to comment Share on other sites More sharing options...
Xnke Posted January 17, 2013 Share Posted January 17, 2013 They *think*...are those rocker arms resurfaced on both the lash pad surface AND the cam lobe surface?? New cam, resurface the cam-lobe surface...lash pads that are cut without the side reliefs need resurfaced lash-pad faces. Yeah, the 280* cams sound pretty nice, and the one I have idles best at about 900RPM. Quote Link to comment Share on other sites More sharing options...
JCan Posted January 17, 2013 Author Share Posted January 17, 2013 Grrr. Were using su carbs. I think I might be able to idle at 900 rpm. But it will take all the finesse I can muster. Exhaust is loud. Thinking about adding glass-packs in addition to the dynomax turbo muffler ( the most quiet muffler they sell ) Quote Link to comment Share on other sites More sharing options...
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