merc3065

It's always quietly knocked on startup for about 20-30 seconds before it would go away (i just thought it was to do with cold engine/oil)

Heres the story from the start.
Bought the car at 48000 miles, had problems to start with, the RPMs were fluctuating like mad. So had it safetied after I got the car home, all that problem was to fix was plugs, wires and new cap&rotor. Had some exhaust work done on it, the main pipe was split along the weld seam from the cat to the muffler, new tires all around, new rear break pads and everything was good. So then the back end starts makin noise and the engine keeps flooding itself(even before the tune up it did it). So I run 2 bottles of injector cleaner and solve the flooding problem. Changed the rear end oil, came out greenish black, added the diff additive, changed the oil no more noises from the back end. Had to recenter the rear sway bar as it had slipped on the rear axle (dont know how it slipped). Replaced the old bushings on the sway bar as well. Figured good idea while I had it off.

Now for the big problem, on thursday(17th jun) mornin after I start it up and head to work, I notice that the oil pressure has dropped dramatically when at idle in gear (2-3psi if that). I think nothing of it because when i drove around it would go right up to 28-35psi, until I get home and the thing starts knockin away.

Thinking theres something wrong(gee I wonder why) I hook up the laptop and the ALDL cable. No knock counts, nothin outta the ordinary except that the engine is still making knocking noises. So today on saturday, I take if for an oil change and when they restart it the thing sounds really loud as it knocks away. Im still runnin the ALDL and still no knock counts. I take it to my mechanic and he starts stickin a screw driver in the lower end of the bottom pulley wheels and finds theres a lot of play at lowest one in the front. After pulling the plugs to cylinder 1 and 2 (one at a time of course), he's pretty sure its cylinder 1 thats causing the knocking.

He's told me its more likely the main bearing that is either worn, spun or the crankshaft is worn down in addition to the rest of the bearing problems.

With the low oil pressure and the gauge going whacky with the knocking noise, would this be safe to say he's bang on the money? I do run the car hard and he said that its very likely i've ran it too hard for the age of the components (1988 trans am L98 and yes ive had it over 5000 rpm during drag races). He told me I can drive it as is just to keep the RPMs lower than 2100 and it could last for years without any problem. I personally want to have the car running at 100%.

What im wanting to know is how much will the average lower end rebuild cost, and if its worth while fixing it with OEM parts or at the same time its all apart upgrading the internals to forged or better quality parts (if there is such a thing)
-OR- going to a new engine altogether like a rebuilt L98 or a new stock LS1 or LT1 crate motor.

Any input would be greatly appreciated as I don't wanna have miss out on track fun with the summer months just starting. Money is not an issue but saving money is always appreciated when it comes to big ticket items like this.

Vader

Merc,

What viscosity oil are you using? What kind of filter is installed? Does the drained oil appear exceptionally dirty? Have you verified the oil pressure reading with a mechanical gauge?

If the oil is light, and is very dirty when drained, you may want to try a flush with ATF, then switch to a higher viscosity synthetic. It may be too late if mechanical damage has already been done, but if you have a simple oil starvation problem at a bearing, a cleanup and heavier oil may help. You don't have much to lose. I've quieted main and rod bearing noises in more than a few sludged engines with a flush. The fact that the #1 cylinder is the offender also raises the possibility of oil starvation to the front bearings - farthest from the oil pump.

As for the load being too great for the age ("he said that its very likely i've ran it too hard for the age of the components") that is a complete fallacy. Component age has little to do with it. Mileage and wear are the big variables. At 50K miles, there should be little wear unless there has been neglect or abuse.

Beyond that, I doubt that anyone will be able to answer your questions better than the guy who removes the oil pan an checks the bearings and journals. Forged parts will wear just as fast as cast, and aren't necessary at stock power levels. Personally, I'd build a spare engine and have it ready for a swap, and nurse the car along until then. Of course, how you build that spare is an entirely different matter, and that may indeed need forged internals if you intend to produce significantly higher power levels.

The fact that there may be some axial play in the crank is not serious unless it is greater than 0.020". There is an allowable design tolerance for crankshaft end play of 0.003-0.009", and I've seen otherwise decent running SBC engines with over 0.020" of axial (end) play.

merc3065

The oil weight im using is 10w30 mobil 1 synthetic. I just use an off the shelf oil filter made by Fram.

The guy who drained the oil hadn't seen oil that dirty before so I can only assume that the engine inside is very dirty. When I first got the car, the thing had problems with the plugs being fould by a flooding engine(stuck injectors). Im not positive, but wouldn't excessive amounts of build up and left over gas not being fired cause sludge build up inside the engine?

I've been suggested to on a local board to my area, that perhaps a 383 could be the way to go if I have to start replacing parts on the current engine.

How do you use ATF to flush the engine? I dont understand how oils work in order to see how the ATF will work. What kinda effects would flushing it with ATF do to the engine? Im thinking you run it for a few miles just to get it worked in before draining it and then adding a 20w50 synthetic oil, mechanic suggested this, or a low pressure high volume oil pump with the same weight of oil and you'll never have a problem with oil starvation.

Is it safe to run the car as it stands? He suggested keeping it below 2500rpm. Or should I drain the 10w30 and get a heavier weight oil in order to keep it happy until I can get it fixed?

Vader

The Mobil 1 is a good choice. You can continue to use that, or switch to 15W50 synthetic for the warmer months to help maintain a bit more oil pressure - but not just yet. However, the Fram filter may not be such a good choice for several reasons, but I'll touch on that in a little more detail later.

Oil pressure is relatively insignificant if there is no oil flow to the bearings. That is what I am questioning in your situation, and what might possibly be helped by a flush.

The fact that you are now using a synthetic (which tends to clean engines quite well) may have helped to loosen some of those accumulated deposits. Indeed, the mechanic's description of the condition of the drained oil would indicate that there was significant contamination, and the synthetic was in fact loosening it if not clearing it up.

What I am envisioning is the clogging of oil passages in the case and crank caused by neglect, contamination, and the resultant sludge formation. If there are significant deposits of sludge in the engine, some of that sludge may break loose and lodge in the oil galleries to some of the bearings. If these galleries are completely clogged or at least partially restricted, the restriction could prevent an adequate volume of oil to those bearings. That oil starvation can easily cause bearing knock and eventual engine destruction.

The unfortunate part is that if the contamination was loosened and not caught in the filter, it may have lodged in galleries. Since Fram filters tend to have some of the smallest filter element surface areas available, it could have easily been clogged very quickly and gone into a bypass mode in a rather short time, sending unfiltered oil (carrying sludge) through your engine. This could also account for some loss of oil pressure, since the bypass valves in the filters and blocks typically require a 10 PSIG differential pressure to open. Again, Fram filters seem to be among the worst at flowing bypass oil volume.

Automatic Transmission Fluid is an oil. It also has a high concentration of detergent additives fo help keep surfaces clean and particles in suspension. You can use this to your advantage in a dirty engine. Drain the oil and remove the filter. Fill the crankcase with AFT to the proper level and install a new filter. Start and warm the engine fully without driving the vehicle..ATF is a very low viscosity oil, and may not lubricate adequately under load, so using it while driving is not recommended. The fact that the detergents are likey to loosen more deposits is another reason to refrain from operating the engine under any kind of load from driving. Once the coolant is at full operating temperature, slowly vary the RPM of the engine between idle and about 2,000 RPM. Maintain the 2,000 RPM rate for 20-30 seconds, then allow the engine to idle for a while. Perform the RPM variation several times to splash and distribute oil everywhere in the engine. After about 20-30 minutes of running, shut off the engine and drain the oil immediately - while it is still very hot. The surge of hot, thin oil from the sump drain should help flush out any larger particles of sludge that may be in the sump. Allow all the oil and sludge to drain for as long as necessary. Remove the filter and install a new one. Refill with a good quality mineral oil, like Mobil 0 10W30. Avoid any of the higher viscosity range oils, like 5W30, 20W50 or 10W40, or any oils sold as "high mileage" or "Truck/SUV" oils. They contain excessive additives which will only create MORE sludge.

If at any time during the ATF flush/run the noise becomes significantly worse, stop the engine and drain the oil, remove the filter, and refill with the correct oil.

You will be changing your oil again in a short time, perhaps a week or less, so plan on acquiring all the necessary supplies of oil and filters. I'd suggest using a Champion, NAPA, Hastings, or AC filter instead of the Fram. The AC, Champion Labs, and other mentioned filters typically have a larger filter medium surface area, and can trap more particles before clogging and forcing the oi to bypass the filter. You should plan on changing oil and filters more frequently until the oil remains clean for at least 1,000 mile intervals. For this, you may want to use mineral oil and avoid wasting the synthetic at such short intervals. Until the oil remains clear for at least 1,000 miles, you should limit the load on the engine both in peak RPM and acceleration loading. Take it easy until the oil stays clean, which will be an indication that the amount of sludge in the crankcase is more normal. Once the oil remains relatively clean (not black) for a 1.000 mile interval, you can and should switch back to synthetic for normal change intervals. Try not to switch back to Fram filters, however. That includes any of their clones sold under different names. If you don't change your own oil, and frequent a quick-lube establishment that uses Fram or Pennzoil filters, find another lube service or take your own filters for them to install. If they argue, go elsewhere or give them my email addy.

I would definitely do something to address the problem. Ignoring it will not make it go away. What I suggest may not solve the problems(s), and may be a waste of some oil, filters, and a little of your time. However, it may also alleviate some of the problem if not solve it. As I mentioned, I've done this in the past and been successful, and also had it do nothing to help. But short of removing the engine for inspection and repair, it is such an insignificant "waste" of oil, filters, and time that it is worth the effort, in my opinion. It may do nothing, or it may get you back on the road. At the very least, the engine will be cleaner when you remove it for repair. .

matty boy

hey... i seem to have the EXACT same issue as you did merc. Only difference is mine only knocks when its at full operating temperature and underload. What ended up being the issue? Did vader's suggestion get rid of your knock? Im hoping its not a main or rod bearing on my car as its a 91 tpi convertible with only 53k miles. Im looking for anything to try before i have to pull the motor and do a full rebuild Also planning on going to a delco filter, and get rid of the fram, also gonna run some 5 40 synthetic (hoping for better hot temperatures) Any other ideas out there?

urbanhunter44

iTrader: (3)

holy thread resurrection lol

Edwardgp

InfernalVortex

iTrader: (4)

If its bearings knocking then no amount of fancy oil and filters is gonna fix it. You'll need to pull that sucker out. Beyond that, it may be a cracked flexplate. look into that.

https://www.thirdgen.org/forums/post...398-post3.html

Guess he had to get it rebuilt.

merc3065

Yep, ressurrection from 8 years ago...wow...

Everything that Vader said was true. neglect caused sludge build up. My use of synthetic oil loosened all the goop and it bunged up the front 2 mains which caused them to grind into a silvery mess due to lack of oil.

Required full rebuild, no amount of fancy oil additives or filters or synthetic oils will fix this issue.

Rebuild time! At least the guy knows how to search!