# Weird tapping?



## I Need Meds (Feb 11, 2011)

Ok, heres my truck I bought it about a week ago and the guy told me it had no real problems just needed a tune up and an oil change its an '87 nissan hardbody 4x4 5 speed with a napz motor in it, after I drove it around for a few days (And changed the clutch slave cylinder) I started to her a slight knock in the higher rpms, sounded a bit like a bent rod but it has the ohc so no rods and its real faint, today I noticed that it also does it when I let off the gas a bit when its under load and when I took off on my way home it made a loud metal on metal grinding sound (I parked it after that) it still runs and the tap isn't there while it idles, I'm just not all that familiar with these motors (Mostly dealt with L18's in the older Datsuns) wanted to know if anyone might be able to throw me some suggestions or shed some light on this problem? and possibly an inexpensive fix for it. Also I'm looking for a tranny rebuild for the same truck or a cheap replacement tranny, Thank you for your time.


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## smj999smj (Jan 1, 2006)

Just because it's OHC has nothing to do with the rods. You could have a rod knock, but that's tough to determine on a forum level. I've seen those engine blow headgaskets between cylinders and cause a "knocking" noise. You also mention "tapping." This engine has mechanical valve tappets, so adjusting the valves would be in order. As far as the grinding noise, once again, tough to diagnose on a forum level unless you can provide a sound clip.


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## I Need Meds (Feb 11, 2011)

I will see if I can't get a sound clip from my phone tomorrow, and I was under the impression that if a vehicle has an ohc it doesn't have rods, I may be mistaken though.


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## jblakeslee (Nov 30, 2005)

You are confusing push rods and connecting rods.....OHC engines do not have push rods......which transfer cam motion to the rocker arms....in OHC cam engines one end of the rocker rides right on the cam lobes.....

Unless it is a Wenkel (rotary)....It does in fact have connecting rods.....which transfer motion from the crankshaft to the piston.....

Those connecting rods do have bearings, which could go bad and cause a rod knock.


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## I Need Meds (Feb 11, 2011)

Ok, I'll have to drop the oil pan later today, I have to go install a computer in a hyundai here soon, I'll keep you updated on the progress. Is there a way to tell if those bearings are any good by look?


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## jblakeslee (Nov 30, 2005)

I am not sure I would just jump right in and drop the pan....take a piece of rubber hose, and put one end to your ear, the other to the valve cover, listen......then try the same thing down at the oil pan....(carefully...engine should be running)....try to find out where the tapping is coming from before you just drop the pan.....check the timing cover also...

You mentioned the previous owner said it needed a oil change....Maybe it had been so long since the oil was changed that the gallery that feeds the rockers is blocked.....

could be several things.....but I would check pretty good before I spend the time dropping the pan.

Like previous posters have said....it is hard to figure out the cause of a noise via the internet......

To answer your question: Yes you will be able to see a bad bearing...it will look pitted, scratced, burn etc...but you will have to check each one probably.


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## I Need Meds (Feb 11, 2011)

Ok, I don't know why I didn't think of that sooner, right now I'm stuck on my wife's car, I usually use a 2 foot extension to check for knocks and what not, I haven't started on it just yet.


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## I Need Meds (Feb 11, 2011)

Ok, an update I have decided to part out most of the truck, the only things I am keeping from it is the chassis and the 4wd system due to me wanting a project car and I have enough cars to get me to and from, now I have another question I'm hoping someone can answer for me, I want to know the chassis length of this truck, its a single cab with a shortbed (6ft I believe) I want to drop a chev 350 motor in it and do a late 90's mustang with 4 door body around all of that which is why I want to know the length of the chassis to know if I have the room to build this beast.


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