383 240z Posted September 23, 2001 Share Posted September 23, 2001 I popped the cover on a friends 3.1L turbo today for a valve adj.and noticed a few irregularities. 1) no wear at all on the base circle 2) unequal wear on the ramps and nose 3)a small amount on scoring (enough to catch a fingernail)on several of the noses. This worries me the cam and engine are new. I know the breakin procedure was followed and this thing only has about 1500-2000 miles on it! Any ideas on what went wrong? I know the first oil pump was bad (damned Mellings) but we found that out before the engine was fired (we spun the pump with a drill before firing it ) I'll try to contact the cam grinder on monday just thought I'd run it by you guys first. Keith Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 23, 2001 Share Posted September 23, 2001 This can happen for several reasons. What oiling system did the cam use (internal or external)? Were the rockers replaced with the cam? Is the wipe pattern on the rocker pads completely on the pads? What do the rocker pads look like? Are they scored or pitted? Are all of the lobes damaged, or just a few? If just a few, which ones? Quote Link to comment Share on other sites More sharing options...
383 240z Posted September 23, 2001 Author Share Posted September 23, 2001 #1 oiling system How do I tell? I'm a v8 guy working on a friends car. #2 yes the lash pads were replaced with the cam #3 I'll have to pull the cam to check get back to you one that one (I did not notice any irregularities) #4 I did not feel any thing on the lash pads with the feeler gauge #5 just a few mostly intake lobes. thanks for the help Maybe this is the time to buy a cam that is matched to the turbo and head what mods should be done to the oiling system? which is better internal or external? Keith Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 23, 2001 Share Posted September 23, 2001 As Tim mentioned in his Query, if the cam and the "lash pads" (or however nissan wants to refer to lifters) were not both replaced, a cam will score easily during initial break-in. You say break-in was adhered to, was the RPM kept fairly high when it was first fired (like 2K rpm's?). Cam lobes get wiped out if the revs are down and the oil pressure isn't kept up a bit during first start. Please forgive if I'm telling you stuff you already know, not knowing all the members, its hard to remember what everyone's experience is with cars. Where do you go from here? New cam and followers (lifters, lash pads whatever) and of course making sure the oil is getting to the top end properly. Hope you find the culpruit. Cheers, Lone Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 23, 2001 Share Posted September 23, 2001 The externally oiled cams have a spraybar that is attached to and gets it's oil from the cam towers. An internally oiled cam does not use the spraybar. They are hollow and have oil holes in each lobe that apply the oil. Which is better? For most applications, it doesn't make much difference, so long as both the cam and head are setup for the same system (i.e., don't use a solid cam without a spraybar). Some people swear by using the spraybar with an internally oiled cam, and this has been the subject of much debate. Many have used this setup with no problems, but I still think it's risky. My reasoning is that there is a restrictor built into the block that limits the amount of oil flow to the head. If this is not removed, then the limited supply of oil will now be split between the cam and the spraybar. This will lower the oil pressure in both, and it's quite possible that you'll actually end up with LESS oil actually getting to the cam lobes (if the pressure is too low, the oil from the spraybar won't actually reach the cam). Also, if you remove the restrictor, you will most likely alleviate this problem, but that restrictor was there in order to keep as much oil pressure as possible at the crank main bearings. If you don't have a ton of experience with L-series engines, I'd stay away from such a setup. Quote Link to comment Share on other sites More sharing options...
383 240z Posted September 24, 2001 Author Share Posted September 24, 2001 A hole in each lobe? I'did not see that during the valve adj. but ther is also nothing over the cam that I could see spraying oil on to the cam I did notice holes on the cam towers though I have a few spare l-series motors laying about I'll pop the covers off and look for the differences. Lone no prob on questions me on the basics. I'm trained on just about every marque of german and british cars.(that was my paycheck for a long time) but I am also well versed on american v-8's(my hobby since I was a kid) the lash pad term is from Jaguar(old habits die hard) I'll ask the tuner shop about the 2k rpm break in that first fired the motor. They installed the TEC-II and insisted on starting it. Oh well now the fun starts picking a new lobe profile!!! Keith Quote Link to comment Share on other sites More sharing options...
Guest Tom Scala Posted September 24, 2001 Share Posted September 24, 2001 If there is noticable wear on the cam it might be good to check the main & rod bearings as alot of times the debris will end up there. Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 24, 2001 Share Posted September 24, 2001 quote: Originally posted by 383 240z: A hole in each lobe? I'did not see that during the valve adj. but ther is also nothing over the cam that I could see spraying oil on to the cam I did notice holes on the cam towers though If there are uncovered holes on the side of the cam towers (passenger side, assuming it's left hand drive), that is most likely your problem. If your head was originally equipped with a spraybar, and no longer has one, these holes MUST be sealed off, and you MUST use an internally oiled cam. The holes (assuming I'm reading your post correctly) are the oil supply for the spraybar - if they are not sealed, then they are just pi$$ing the oil out the side of the cam towers, and very little (if any) oil is going to the cam. Motorsport Auto sells blockoff plates for these hole for about $4, BTW... Quote Link to comment Share on other sites More sharing options...
383 240z Posted September 24, 2001 Author Share Posted September 24, 2001 So this spray bar is attached to the head? I checked the oil diagram in several manuals and I see the bar in thoses but not on this engine thanks for all the help Any suggestions on who to contact about a lobe profile for a stroked 3.1L turbo motor?? Keith Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 26, 2001 Share Posted September 26, 2001 I think Z people are the best, this is my car keith is talking about. He called me last night to tell me the possible bad news. I hope this get solved. Building this car has been a dream come true. Thank you everyone. Quote Link to comment Share on other sites More sharing options...
Guest scca Posted September 26, 2001 Share Posted September 26, 2001 you will likely need a new cam. oh and you dont need to ALWAYS replace rockers with new cams. FYI REBELLO uses "seasoned" rockers on the race motors. i've seen brand new cams eat new rockers within 1000 miles of new. so sometimes its just a metallurgy thing. this was on properly setup cams with new lashpads and all the geometry correctly done. the rockers and cam just didnt like each other i've had the most luck with using perfect used rockers on a new cam, dont use ones with a small flat spot.... and it seems that the larger the cam profile the more common this problem can be Quote Link to comment Share on other sites More sharing options...
383 240z Posted September 29, 2001 Author Share Posted September 29, 2001 Well I talked to the engine builder and he said tell me what you want and I'll buy the cam!!!! Now All I have to do is pick a cam anybody want to put in their $.02 worth?? it is a 3.1L p78 head with a T-03/04 turbo and EFI. Thanks again Keith 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.