Well, I think I've really done it this time. Went out for a drive yesterday, and came back on a tow-truck. (sigh) Started out normally, car was running perfect as always. Good temp, good OP, running excellent. Got about 150 miles out and noticed that the oil-pressure guage was acting a little bit weird. This is a car that has ALWAYS had great OP, when running at 45mph or above, guage at 60PSI, and never below 30PSI at idle. (5w-30 synth) Well, the guage was bouncing around some. Not bad, just kinda bouncing between 60 and 45psi at 70mph. Car seem to be running fine, not hot, no smoke, not missing or anything. Well, I pulled into a gas station to see what was up, I though I might have blown a gasket or something and was loosing oil. That's when I noticed a kinda strange tapping noise. NOT valve noise, but kinda a plasticy ticking noise. I pulled the hood open and checked the oil and it was FULL. Hmmm... Can't see any smoke, leaks, the coolant level was fine, nothing wrong that I could see. Noise seemed to maybe be coming from the vicinity of the top of the firewall area. Started it up, it was running fine, just making that funny light tapping/ticking noise. Not fuel injectors, not valves, and it was coming and going. It was varying with engine speed. Ok, so I threw a couple of extra quarts of oil in the trunk and turned around. Well, about 20 miles later, it suddenly started getting REALLY loud. And the noise was synced to the bouncing of the pressure guage. BIG Uh-Oh! I dove off at the nearest exit, and pulled into another gas station. NOW it sounds like ball-bearings banging around in a dryer! But, I STILL have OP, about 20psi at idle. Threw the hood open again, and now it sounds like the top of the engine. NOT the bottom, and the thing is it really didn't sound or feel like it was coming from valve covers or anything. And the noise is alternating between loud and non-existent, with some very ominous squeaking/moaning sounds thrown in for good measure. Called a mechanic (Walsenburg CO on a saturday afternoon, you can imagine) and he came out and looked at it. He basically said that it wasn't the bottom end, but that something was really wrong and the only way to tell would be to start taking it apart, which he couldn't do before monday. Ok, so I call a tow-truck and $350 later, we are back in Colorado Springs. None of the shops are open here naturally either. So what on earth is wrong with it?

Car is a 1987 IROC-Z L98, TPI, 700-r4. Oil RELIGIOUSLY changed with synthetic, engine has 140k, and never been into. Nothing has been done to the car in 2 months, which was the last oil change. It started out fine, no noise, no issues at all. I'd have guessed an oil pump, but chevy oil pumps almost NEVER fail, and the OP was never at 0. Driving it as the noise got loud, the engine was running just fine, smooth and easy, no missing, plenty of torque etc. I've checked the oil THREE TIMES, it's full and clean. But it seems pretty obvious that the top of the engine is not getting oiled. What did I do, and where do I start, and how bad is it?

Thanks in Advance!!!

 

If it still makes good power and the exhaust is clear, no excessive blowby, it may just be the top bushing in the distributor/dist drive gear has bit the dust.
That will make the OP bounce and the "plastic" ticking sound.

 

Would the ticking progress to banging? it IS the original distributor...

 

Supervisor42 may be onto something (and I'd like to get some of it).

The noise may be related to a worn distributor, or the distributor may be a manifestation of the real problem. It's an '87, so cam walk is probably not an issue since the retainer plates seldom fail. The distributor axial play, radial play, gear wear pattern, and oil pump drive shaft may tell a story.

If it were not a TPI, I'd be tempted to pull the intake after a close inspection of the distributor, but pulling a TPI intake is a bit more of a chore. You may end up doing that anyway, but I'd at least mark the distributor position and pull it for a quick look, and get a good look down the hole with a flashlight.

On the up-side, since oil pressure never fell off completely, I would agree with the initial assessment of the Walsenburg mechanic that damage to the bottom end is less likely. Given the mileage of the engine, coupled with the fact that you're a synthetic junkie like me, I'd doubt that there is serious damage to the bottom end or pistons/rods due to a lubrication failure. If there is any damage, it's more likely a side effect of whatever failed first.

After the distributor, I'd be a little suspicious of the timing chain and sprockets. And, as always, one thing leads to another. If you decide that you DO have to pull the intake, and DO have to pull the timing chain, it would almost be a shame not to replace the cam. Did you put a new roller cam on your holiday wish list? Perhaps your car did. If you go that far, it might also be prudent to plan ahead and have your original injectors checked and cleaned, since they have been in service for 20 years and 140K miles.

Ho! Ho! Ho!

 

I would LOVE for supervisor42 to be on to something! That would be a relatively easy fix! (as opposed to an engine rebuild!) About a year ago, just to be safe, we did the timing chain and gears and water pump. And about 2002 we had the injectors serviced. 2 years ago did the EGR because the intake manifold gasket failed, and as long as it was down that far... (it's AMAZING how much original stuff is on this car!) We didn't do the cam, and I hadn't touched the distributor, because I was playing by the "if it ain't broke, don't fix it" engineers maxim. Also, with an older car, seems the more stuff you pull off, the more OTHER stuff breaks! But I think the 1st thing I'm gonna do now, is pull the distributor. I think you guys are right, that sounds like the place to start! The noise really did seem to be coming from the top back part of the engine. And yeah, pulling the TPI is a PITA, but if I did damage something, it may come to that.

Thanks SO much for your help! Any other brainstorms, please post!

 

Got that distributor out yet?

 

Ho-Ho-Ho! Vader ur FUNNY! It's 32 degrees out and snowing. Plus, getting parts today would be IMPOSSIBLE.

Speaking of parts, what replacement distributor would you recommend? There seem to be DOZENS of them.....

 

So, you're saying that the temperature is above average, and there's a little snow. The hood should keep the snow off your back. Besides, all you might need to repair the distributor is a washer or two.

 

Well, drat. It's not the distributor, and it's not the oil pump. This is beginning to sound like maybe I really did spin a bearing or something.... The noise is now sounding more and more like the piston mating with the head...

 

Spun the #7 rod bearing... So, it's time for a new engine! Now all I gotta decide is what I'm going to do to it.

 

Well ****. (rhymes with quit) It was worth checking out anyway.
~chanting~... stroker...stroker...stroker...

 

Yeah, the 383 stroker tempts me. But this is also a road car. I take all my long trips in her. So the zz4 tempts me, and rebuilding the original engine tempts me too.

Top priorities
reliability
power
efficiency

Yeah, I know they don't go together, necessarily, but I always loved the L98, for it's torque where you need it, the 25mpg you got on the highway, and (until now!) the fact that it's never broke. The intake and exhaust AND rear end are BONE STOCK. I've got the feeling if I did the stroker, that would ALL have to change. The 700-r4 is rebuilt to take some power, so I think it would be ok. I'm guessing in ascending order:

.10 over bore on original with new heads, cam, possibly crank.
zz4 - which would almost certainly need total new exhaust.
383 stroker, which will need EVERYTHING.

Any suggestions, please let me know! I am working with a budget, so the sky is NOT the limit!

 

Or, check the rod and crank, throw a bearing in it and drive it.

 

How bad is the carnage? A crank kit/rotating assembly may be the easy solution to the bottom end. The rest is up to you.

 

Well the head on one side would have to be replaced (kinda banged up on the drivers side) And the piston, and possibly some crank damage (didn't take it down that far) On an engine with 140k, there are 7 OTHER rod bearings just waiting to fail! So it's basically time for an engine, I'd been wanting to maybe do that anyway. But the plan was for next SPRING. (shrug) Don't drive it very much this time of year anyway, but I'll miss it until I get it running again!

 

Brand new GM L31 roller shortblocks at SDPC or Sumiit for $1499.00.

 

or the long block for $2500
or the zz4 for $4000

Yup, it's a dilema! Still looking for the best combination of power, reliability and efficiency, for around $4k.

 

Top priorities
reliability
power
efficiency
LS1.

 

Does your engine sound like mine? Here's a short vid of the engine running:

http://www.caledonweb.com/cars/91r7u_knock.wmv

I figure in my case it's alower rod bearing gone bad and the piston is contacting the head or a valve. The engine is a 350. I plan to rebuild the original 305 and put it back in the car to make the car original.

 

That sounds too slow to be a crank knock to me. It sounds like a broken valve spring to me. Or a cracked/burnt valve. It sounds like it is once every 2 rounds, not every round of the crank.

 

So, how did we determine that a rod bearing has spun, if we didn't take it down that far? And what is this head damage you are indicating? Have you pulled a head?

 

Whaaaaa.......if the piston is contacting the head or valve it ain't gonna make that sound fer long before it coughs! I highly doubt you have any piston to anything contact..... I think you have a valvetrain problem....broken spring/rocker arm....bent pushrod.....it runs with a shake so I'm sure your down a cylinder.....pull a valve cover and look

 

From my experience with synthetics.....if the car is new and broke in...they work fine....if the engine has a few miles on it(over 50k) and is several years old....then keep running the dino oils.....years ago I had switched to synthetic in my 88 camaro...it had 64k on it...after 6k running the synthetic I spun two rod bearings....I replaced all the bearings(rods and mains) and switched back to havoline 10-40 and its been running fine ever since. and have heard other similar stories...thats back when I dealt with auto parts.

 

This is another option, a remanufactured L98 long block with a warranty at $1276.00 http://www.rebuilt-auto-engines.com/...53106281121.d7 However, I have never dealt with them nor do I know how good they are. I'd think it would be the way to go for you

 

I'll look at this first (supervisor42 said the same) before pulling the engine. I felt that the noise was too loud and the shake too severe for it to be a topend issue but I'd much prefer if you guys were correct.

 

If you yank the plug wire on the suspected cyl the rod knock will go away.
I imagine he did it that way. ?

-- Joe

 

If you end up doing the whole engine I would think real hard about rebuilding the engine in there now. Sounds like a pretty nice original car and also sounds like you take excellent care of it. Some day these original L98 cars will start to increase in value and having the correct engine might affect it's value in another 10 years. Or crate engine and keep the original. This is all asuming it is a fairly stock car in nice original condition.

 

OK, so I popped off the rocker covers and discovered that the the nut on the #6 exh valve had loosened almost to the point of coming right off.

After tightening it back down and putting everyhting back together the engine runs fine without the nasty knock.

Thanks to supervisor42 and Rob Wade for offering up the solution. Saved me a bunch of work.

I did find out that the engine has 96 Vortec heads on it that have been drilled to take the stock TPI base and that the engine is an older 350 casting (3970010).

 

I would recommend pulling the covers one more time and replacing the nut. If it backed off, it will not hold. Check the "roll off" torque on all the others. If any can be loosened with 1 hand on a 3/8" ratchet (pinky on the extension), I wouldn't consider them "trustworthy".

 

Thanks, that sounds like a good idea. The car is parked for the winter so I have a few things I plan on doing to it.

 

Good deal.....Superviser 42 is dead on. Get a new set of locknuts on that puppy before spring. Sounds like the ones you have now have s--t the bed.