damesta Posted August 18, 2018 Share Posted August 18, 2018 (edited) I have a newly rebuilt L28/e88. N42 dish piston block with early e88 head and internally lubricated l28 cam and oversized stainless valves. Motor runs great but after putting about 50 miles on it and getting the valve lash dialed in perfect it has developed a new noise, it is similar to a valve tick but deeper. Originally I was thinking exhaust leak or some chain slap against the guide but couldn't find anything wrong. This morning I finally tracked down the noise after spending about an hour stethescoping the entire engine while running and unfortunately it is coming from the head, it is 100% either the 4th, 5th or 6th cam lobe or corresponding valve, most likely the 5th lobe which is the intake valve on the 3rd cylinder. The noise is noticeably louder after the engine is fully warmed up but it does not get louder with rpms, after 1200-1500rpm the engine is loud enough to drown the noise out but it is very, very noticeable at idle now and sounds like its getting progressively louder to me at this point. Lash has been adjusted with the engine fully warmed up to .10i and .12e and triple checked, it is perfect. The only thing visually different about the 5th cam lobe is a little uneven corner wear, but wtching during rotation this wear does not contact the rocker lash pad, so I guess it was there prior to the rebuild...the other 4th and 6th lobes look normal. Anyone have any opinions, advice or ideas? Edited August 18, 2018 by damesta Quote Link to comment Share on other sites More sharing options...
Chickenman Posted August 18, 2018 Share Posted August 18, 2018 (edited) SOB... a long and detailed reply has just disappeared into thin air. WTF!! Short storey. Bad news. All Lobes in picture show metal to metal contact. Center lobe looks to be going flat. Pull the pan and check for metal particles. Cut the Oil filter apart and inspect it. I fear you are going to find many fine particles of iron from Camshaft wear. Likely suspects are a POS soft core ( CW? ). Cam appears to be made out of Pig Iron. Use only OEM Nissan cores. Find one on E-bay or forums. Find another Cam grinder and specify that they regrind your SUPPLIED OEM NISSAN core ( Put some identifying marks on it with an engraver ). Probably a combination of several factors. Lobes are showing metal to metal wear. That means that possibly not enough Cam break in Lube was used. Or none at all. Or oil you used did not have sufficient shear protection to prevent metal to metal contact. Energy Star rated oils ( generally the thinner weights below 10w-40 ) are not good on Vintage motors with Flat Tappet or sliding cam interfaces ( Buckets, Finger followers etc ) What valve springs are you using? What Oil weight and brand did you use for break-in? Even with a good core ( and it looks like you have a POS ) you must use copious amounts of Cam break-in lube, a dedicated high ZDDP break-in oil and then after breakin, a dedicated high ZDDP oil recommended for engines with Flat Tappet cams and particularly Higher Valve Spring pressures. API has finally admitted in the last 6 months ( after many, many years of pressure from the aftermarket companies ), that the the SM and SN API standards are NOT backwards compatible with older standards such as SH and SG. Something that has been true up until the reduction of ZDDP in the mid-2000's. Something that the High Performance industry and even GM has been telling the American Petroleum Industry since 2003. Basically the API flat out lied to consumers. Their test equipment and methods were NOT adequate to simulate the conditions that older high performance flat tappet engines required. new labeling should be coming out in 2019 or 2020 to reflect this. I don't have the sources available at my finger tips now. ( Google to find the info ) . But this is finally a vindication of sorts for what Hot Rodders and High Performance engine builder have known for over 10 years. The new SM and SN oils are Shite for " some " older engines. Edited August 18, 2018 by Chickenman Quote Link to comment Share on other sites More sharing options...
Chickenman Posted August 18, 2018 Share Posted August 18, 2018 Parkerizing of a reground Cam core is also very important to break-in procedure. Parkerizing involves the application of an outer coating that acts as a sponge for oil to be absorbed into the meatal, and also as a lubrication barrier to prevent brief metal to metal contact if something goes incorrect during the break in procedure. Unfortunately, certain States may have banned Parkerizing. I'm thinking California. Nitriding is also banned in some States. Best to check with your Cam regrinder to see if they Parkerize or Nitride process the cam. If not. Buy elsewhere. Some good info on Flat Tappet cam shaft requirements. Also applies to any finger follower design with a sliding interface. Such as Nissan L-series: http://www.enginebuildermag.com/2011/08/inside-flat-tappet-camshaft-andlifter-technology/ Quote Link to comment Share on other sites More sharing options...
damesta Posted August 18, 2018 Author Share Posted August 18, 2018 (edited) Let me re-phrase what I said about the cam as I shouldn't of said it was ground that way. This is not a reground cam, it is a stock L28 e30 cam that the machine shop lightly polished. What your seeing is not the metal to metal wear that it looks like, it is striations of assembly lube that can be wiped off...I thought the same thing first time I opened the vc. The only part of any lobe that shows any wear is the corner of the center lobe in the picture, and after watching it closely as it rotates that worn edge doesn't even contact the rocker lash pad, so I guess it was there prior to the rebuild. However, I believe I found the culprit, the rocker lash pad on that lobe is severely worn, very distinct line and dip in it. I'll ad some pictures. I swapped it out with the nicest used one I have and that got rid of about 80% of the sound I was hearing. I am hearing a little bit of tapping still but the concerning noise is completely gone, I believe the remaining noise is probably because the machine shop just polished my cam and rocker lash pads and then stuck them back on in no particular order. So now I know they are likely all mixed up and if one is this worn I'm sure quite a few others are pretty worn as well. Thinking I should probably just put all new rockers and guides on now since they are pretty cheap, any thoughts? Edited August 18, 2018 by damesta 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.