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1990 turbo grand prix help pleease


tgp1990

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Hello, I have recently purchased a 1990 Pontiac turbo grand prix with 130xxx miles on it and almost completely rust free. I had the top of the motor completely rebuilt (heads,gaskets,seals,ect.) and was running around ten pounds of boost just fine for about 4 months until here recently I noticed a very slight oil leak coming from my back valve cover. I checked my oil consistintely waiting to get in the shop and two days later while running it a little hard it started a decently loud knock. Thankfully I was near home so, I went straight there and shut it down and haven't started it since. The mechanic who worked on it with me before said it was probably a rod knock. So, I'm trying to get any and all advice and suggestions I can get on what to do. This car is rare and my baby so please anything that can help would be great and I'll answer all questions or anything. Thank you for your time.

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Your problem is this.......

 

you did all that refreshing work to the top end and you decided to forsake the bottom end,

 

after 130,000 miles it would have been a good idea to open up the bottom as well and mic up all of the main & rod journals to make sure they were in acceptable condition and if not do what is necessary to safeguard the bottom end before you tightened up the top end. 

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That's what I was feeling. I was told by the person who did the top end that the bottom would be ok but, having the valve cover leak caused a sudden shortage of oil and it all added up. What I'm wondering now is where to go from here. I have done a fair share of research on the car and love it inside and out, I have now invested almost 3k in the car for rebuild, lots of oem/aftermarket parts, new turbo, powdercoating the engine ect. Within 3 miles of the knock starting I shut the car off and can very faintly see some metal specks in the oil. I want to know prices for repair in shop and at home if possible(decent bit of car/hands on expierience), value of the car if fixed and if not (ie. Parts) and just any general advice I can get.

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I see,

 

you were not responsible for this *error* in judgement,

 

you have a couple of choices.......to do a proper repair to the block ...it would mean a complete boring/honing, fresh slugs, turn the crank, resize the rods, inspect the cam, fresh cam bearings, fresh oil pump, fresh timing chain & gears,

 

or if you want to do this on the cheap........pull the crank, get it turned, fresh bottom end bearings (obviously you have to clearance check them during assembly), install a fresh oil pump, install fresh timing chain & gears  and reassemble the engine and this should be enough to keep the bottom end from grenading.

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In my opinion, if you're not knowledgeable on what one needs to know so as to do this work, and you don't have the necessary tools on hand then you'll need to approach someone nearby who does who could assist you or you will have to rely on a machine shop to do the work,

 

*and note that I said machine shop, not a general garage*

 

if there is a machine shop in your area go and inquire as to what they would charge you to do either just the machine work (you do the disassemble and send in the crank, and of course you'll reassemble) or the entire job.

 

More than likely you'll have to pull the engine and send it in to them if they are willing to do the entire job. Understand that you won't get any sort of warranty on this method of job seeing as it is not a complete rebuild.

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Jasper isn't going to get you an LG5.  You'll get an LH0.  It's not worth it.  Are you sure it's a rod knock?  Do you have a decent set of tools, jack stands?  It's no picnic, but i's possible to remove the oil pan from the bottom of the motor.  If you feel you can do that, pull it off.  Give each rod a wiggle.  There should be very slight movement parallel with the crankshaft, and none perpendicular to the crankshaft.  

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Got the car on stands and started taking the pan off. And recomendations on how to hoist the engine and get the mount out of the way? I saw a thread about using a 4×4 and a couple 2×4s to make a hoist and wasn't sure. Thanks.

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I would just pull the motor if it's got a rod knock. you won't be able to remove the pan without removing the subframe first. probably best to pull it out the top with a cherry picker in my opinion

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I can't say with any certainty because I only have 3800s, but if I were to remove that bracket I would 1) remove the bottom bracket bolts

2) jack the engine up with a large piece of wood on the oil pan to spread the load.

3) chain the engine tightly to a hunk of 4×4 across the engine bay from the right strut tower to the core support

4) remove the engine to bracket bolts (which are hard to reach) and lower the engine slowly and hope the chain is tight enough to give some clearance to pull the pan.

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Ok, I appreciate all the advice and has given me a lot for what to do. After a long past couple days I now have the oil pan off. I put the car on stands, took the wheels off,took the mount and mount bracket off(fun), jacked the the engine up via tranny with a board, took off the oil filter and adapter, the sensor, the starter and a couple other things in the way. After jacking the engine up a litle higher I was barely able to wiggle the pan out. There was a little bit of metal debris in the pan along with very fine shaving in the oil at the bottom of the pan. Looking up in the motor now the first two wiggle as should, the second two don't and the last two do. So, I'm positive now it's a rod bearing and need some help on where to go. I have gotten all pricing on main and rod bearing kits along with the crank if need be. I'll post pictures soon.

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You will need a crank kit.  Don't bother with Rock Auto for that.  It's cheaper to get it at AutoZone.   You'll need to pull the motor out to change the crank.  Pic will be helpful.  Take the caps off the rods to check the bearings.  Keep them in the right order and position to assure they go back on exactly as they came off.

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A crank kit is by far the easiest and least expensive solution.  But it depends on what happened in there.  You may need to get your rods machined, too.

 

Either way, the 3500 is a ton more work and much more pricey.

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