Clackity clack in the motor...

[earth1]

Hey hey. For those of you that don't know, I have a lower mileage import engine that I swapped early in the spring. It's a stock VG30 besides the NISMO cams (which are really just modified JWT cams). I can't remember the specs off hand; if anyone needs them to help me diagnose, let me know.

The issue: Over time the engine has developed what I can best describe as a clacking sound. The sound is likely hapening at all RPMs but sometimes my new headers and exhaust overpower the sound, so it's hard to say. The clacking is definately worse when the RPMs drop fast; like when shifting or letting off the gas downhill. I have a lot of guesses but no real ideas.

It's probably not a tranny/clutch/pressure plate/throwout/flywheel issue cause it happens in/out of gear, but I could be wrong.

It sounds like it could be chatter from slack in the rocker arms. It is possible the rockers have worked loose. I suppose if there were (a) bad lifter the rocker would have some play in it throughout the cycle when the lifter doesn't come up right. Does anyone know what kind of sound a bad lifter would cause?

I will be pulling the valve covers off and if it's anything obvious like loose rockers I'll get it. If it's a lifter I guess it would help to konw before I start. If there are any ideas of how to diagnose further before I tear her apart let me know.

Something else. I found this on NPORA, it was written by an ozzie so I'm not sure what he means by cam pullys (?):

The things with cams is you need to know what the specs are, Also you need to adjust the timing using the 0.050" rule. This is the most important thing when installing new cams.

All machines have some backlash in them so it is very important to check the cam timing when you install them and you may need to use new multi key cam pulleys.

If you use the standard pulleys the timing may be out which can cause the cam to fall over not giving the desired performance.

[Ryan Gee]

Is it a lifter not pumping up... did you use some aftermarket units?

[earth1]

I just put new regular Nissan ones in; that's what NISMOparts told me to use. Do you think I should use something else? Is that the kind of sound you think a faulty lifter would make?

Maybe I should find one of those stethescope things to be sure it's a lifter...

[Ryan Gee]

I am just trying to think what would clack... no those lifters are perfect.

[Packman5280]

cam pully is just cam gears I imagine.

[JayRyan]

Mine's recently started clacking when I step on it...I think it's lifters.

[earth1]

I won't be getting to it until the weather turns, but I'll keep you posted. Probably just a lifter.

[Allen Cox]

Wow, sounds like a lifter issue, but could be a couple of things. When you just step on it, is that when the noise happens or is it all the time?

If it's when you step on it, then double check your timing. Also, it could be indicative of a broken exhaust manifold/leaking manifold gasket (which is the more likely of the problems, not timing).

If the exhaust is the issue, then the problem would be more prevalent when the engine is cold, and would lesson when it's warm, unless you were getting on it. Then back pressure would make the noise louder at that point.

Try this trick. When the engine is warmed up, put something over the exhaust tip, plugging the exhaust as completely as possible. Then listen for the noise. If the noise is from the exhaust side of things, it'll get louder. Doing this won't effect oil pressure, therefore, a lifter won't make a louder noise when you plug the exhaust.

[Ditchfinder]

I got a used jap engine and it had half the exhaust studs broken. I had to drill them out and install new ones. Alldata has a bulletin. but I think the other guys are correct its probably a lifter. I ran some ATF in my engine, about half quart for about 500miles real close to the oil change,and then started using mobil 1 10w30 in mine has all but gone away at start up.

[earth1]

I don't think it's an exhuast leak. I remember what my old motor sounded like with the leaks (but I forgot how much I hated that until you mentioned it). Hopefully I did away with that with the Thorleys and the 300 studs.

I should check the timing. After the swap I couldn't get it timed myself with the new cams good enough to pass emisions. So, I had a shop tune it and certify my emisions. It does still have an occasional backfire and runs a little rich sometimes, but I thought that was just the new cams.

Maybe I should have a more techy import shop look at it. I hate takin it to someone else though, I feel like most places don't want to deal with an older truck with special needs :).

[Ditchfinder]

I think some of us would help you, a mod day maybe??? why pay money? Ive got a timming light.and the factory service manual.You bring the beer and pizza.LOL

[Packman5280]

i have a manual and light as well, but I'm going to HI tomorrow for a little over a week.

[Allen Cox]

Who needs a manual? Take off the upper cover and verify the timing marks line up on the cam gears with the crank gear on #1. If that's correct, then let the engine warm up and check the engine's timing. Technically, disconnecting one of the TPS connectors will put her into base timing, but she's usually there anyways when she's all warmed up, nothing running (A/C, lights, etc.) and whatnot. Use the sticker under the hood for the timing for your truck, not the ESM.

[earth1]

Cool. Something I'm not sure of though; would aftermarket cams change the factory timing? I wouldn't think so, everything runs in the same # of revolutions right?

[Ditchfinder]

The cams should be about the same, probably a little more overlap and duration I would set it to the factory timming marks. start there.Make sure your on TDC #1 before you set your cams. I have done more than a few Honda performance cams and even with turbos the cam gears are only advance or decreased a few degrees.well at least until it makes it to the Dyno.

[Allen Cox]

I'd stick with the factory settings, unless a dyno is able to be used to get full potential out of them.

The backfiring has me a bit concerned though. The distributor is run off of the driver's side cam, so technically, the passenger's side could be off. There should be no reason that a backfiring should occur in your vehicle, ever.

I'd double check the physical cam timing. If you're not comfortable doing so, I can usually have a complete timing belt kit replaced in about 2 hours on that motor.

[earth1]

Thanks for the suggestions.

I guess I will go about the logical diagnosis. Check the timing; if that doesn't do it, get a look under the valve covers. I know everything was lined up when I put the new belt on in April, but I suppose it's possible the belt has since slipped a tooth.

I don't have a timing light and could use some help learning to check it right. I have family and guests to entertain for about the next 2 weeks but I'll be posting up to get a hand here soon. I have a decent sized garage but I'm willing to go anywhere to get help.

I have a maybe from Allen Cox and Ditchfinder? Ditchfinder, coming to Denver anytime soon? Pizza and beer is a definate. I can give a hand if you guys need help with anything too. Let me know if I can compensate in any other way...

[Packman5280]

i'll be back after the 2nd, gonna be working on the mustang in my garage the weekend of the 6th and 7th, checking timing too. you can come over here, or I can stop by your place and help sometime, just let me know.

[Ditchfinder]

Sure, I will hit the junk yards down and Denver on a weekend, and then come to you. I was joking about the pizza and beer maybe I can meet up with you and packman.I would not drive it is its back firing I didnt see that part,or at least only in necessity.

Quote:
I have a maybe from Allen Cox and Ditchfinder? Ditchfinder, coming to Denver anytime soon? Pizza and beer is a definate. I can give a hand if you guys need help with anything too. Let me know if I can compensate in any other way...