Thread: 04 GTP Rod Knock

Hello new guy. Welp.... if the engine is knocking already....you're kinda F'd man. No oil, no "rod bolts" are going to fix that. By rod bolts I think you mean head studs? Or do you mean entirely new push rods? All the experts on here (I'm only a wannabe expert) will tell ya that once the engine knocks, that's it. You need a new (used) engine. Re-building these engines isn't really an option because rebuilt 3800 engines tend to last 500-3,000 miles and then they go BOOM again.

You can re-use the oil pan bolts, but you need to either take the entire engine out, or you need to remove the sub-frame from the bottom and suspend the engine from above. The sub-frame blocks access to a few of the bolts making the job impossible to do without removal or suspension.

And torque specs for wheels? Lol. Just tighten the lug nuts till you can't anymore. Done.

you would be a 100% better off buying a used engine and slapping it in there.

now the used engine dont have to be a 04 up either. or even a sc engine. being you have a set of heads that hopefully are good still.

so if you end up with a na engine, you can strip it to a short block, clean it up all nice, do new main seals, rear cover gasket, timing cover gasket, re use the old heads, new head gaskets of course. then put your al pan on if you have one and your lim blower and tb. whala you just did a top swap.

if you get a na engine you'll need to swap the flex plate too, the tc bolts pattern is not the same. so you'll need to use the old l32 plate.

i tell you all this cause ppl seem to think a l32 or l67 are worth gold, and theres less to be had these days. the na engine you can find for $3-400 or so most of the time.


this is what i engine up doing, bu while i had the heads in hand i ported them, added a fsic, 2.8 pulley, rockers, meth and race car lol not really but its cool.

Most likely, the crank is scored and will need to be replaced. You are way better off finding a junkyard motor and swapping it in. But since that isn't an option, it won't cost much to try.

Connecting rod bolts torque spec is 20ft lbs plus 50°. They are torque to yield and only recommended to be used once. That being said, I've reused them without problems. Arp rod bolts require the rod to be resized, so don't use those.

As for bearing size, I would get new stock bearings or just one size smaller. You really need to measure it though to be sure.

Don't go in expecting this to work. Most likely it won't. But you may get lucky.

Scottydoggs- Sounds like a different motor is my best option, but I still wouldn't be able to perform a swap with my current tools. A different engine is affordable, the price for a mechanic to change it is not. Thank you for your wisdom my man.

GTPpower- Thank you for the help, should be interesting if the sub frame has to come out. I will steer clear of ARP and re-use what's on it, that would've been a bummer if I had gotten those lol. I might call a GMC dealer and have them pull the size of the bearings for me since I'm not able to find them online (or I could just measure them you're right). Thanks for the torque, we'll see how it goes. I think it should be fun as there's nothing to loose at this point. Will update on the progress.

On your 04 you'll have a steel oil pan which is harder to work with than the 05+ aluminum ones. To get your oil pan off, you'll want an 18mm ratcheting wrench or you will hate life fighting that bracket. You'll also need to either chain the motor up like I do in my transmission swap how to thread or a hoist/engine support bracket. After that it'll be 20 10mm bolts that hold the pan up. The oil pan gasket is an automatic, if you choose to do it then get one.

From personal experience I can tell you 200 miles was how long mine lasted after I dicked with the bearings. Personally... and I'm being 100% honest as if you were my best friend, I would not suggest doing bearings. You'd save money junking it. Now if you want to do an engine swap, check out the how to thread by me and you'll see that overall it's pretty straight forward. You'll need only a couple more tools than you would doing the bearings. I've had feedback from people who had hardly changed their oil before following the how to and they said it was simple. These 3800's are about the easiest swap out there.

i got a hoist from harbor freight for like 140. engine stands are like 50. other then that you can get by pretty well with a small 30 piece socket set.

most rental places rent hoists and stands, but its gonna cost ya almost as much as buying and owning it. you can always resell it on cl if you dont want to keep it.

ive already used the hoist twice. i unbolt it all and put it back in its box and store it flat. this one does fold up and stand for storage, but i lack the room for that even lol

Originally Posted by BigFudge23

Sorry if I'm using the wrong terminology, I believe the rod bolts are what connect the cap to the connecting rod. And that's what my mechanic said, I would assume he (and you) are right in saying that motor is done for but if I'm able to get it to run for a few thousand (or hundred) more miles then we can ditch it and find something else, I don't think I can lower the value of the car by trying. I've been able to find a supplier that could ship the same motor w/90k miles for almost $500 even, however, I really am limited with tools and would not be able to perform a motor swap (as much as I would love to). I haven't actually gone underneath to see what is needed or if I can even access anything so thank you for the heads up. This would definitely make things more difficult. Thank you kind sir for the advice, I really appreciate it!

I've rebuilt two of these engine's that are both still on the road, so first off, it's possible. The one in my car is rolling on 8,000+miles. Do I recommend it to the average person looking to "get a few more miles"? No. I rebuild mine with a very experienced machine shop behind me, and even after spending $1500 rebuilding it, I cut one corner and didn't replace the valve guides, and now I'm going to have to pull the heads again to fix it.

The following information is not from me, but my machinist who has 30+years in the business of rebuilding engines. I know you've probably seen a couple youtube videos by slightly disingenuous folks who never actually show you what happens 500 miles after it's "rebuilt". You would think that your solid engine will always stay exactly like it was factory and the bearings must be the only thing wrong. That thinking couldn't be farther from the truth. As your engine ages, two main things happen to the rotating assembly. The crankshaft, bearings, and connecting rod wear, and the connecting rods stretch. Though you can't really see it with the naked eye, the connecting rods actually start to become more and more oval rather than round. Even on a perfectly healthy engine, you cannot simply remove the connecting rods and throw in new bearings for this reason. In order to actually fix it, the machine shop grinds the portion between the cap and connecting rod to bring it back "into round", then you can replace the bearing, if and only if the crankshaft is within clearance and not damaged.

Now, I've been talking a lot on clearance, so why is it important? Well, lots of reasons, but namely oil pressure. If your clearances are too big, you get low oil pressure, the various surfaces are allowed to touch and they grind together and heat up and eventually seize together and break. By just replacing the bearings without correcting for the wear in your engine and bringing these clearances back into tolerance, your engine WILL fail, and soon.

Also, when your engine "knocks", you're really hearing the connecting rods bang downward across this excess clearance over and over, and most likely if there's even any bearing left, the crankshaft has been damaged, most likely beyond repair. Your bearings also have the likelyhood of spinning, in which they are supposed to remain stationary since one bearing has an oil feed hole, but they break loose and spin around, causing massive damage to the crankshaft.

Around here, on half off days, you can get a good engine for $100-200 from the junkyard. It can be a chore the first time, but it's also fun and rewarding, and you don't need any crazy tools, just basic hand tools. The only real "special" tool you need to do an engine swap is a lift, which you can either rent, or it's $150 at harbor freight (cheaper if you check craigslist).

Normally I preface with "I'm not telling you what to do", but here I am. You WILL waste your time and money on just replacing the bearings, and I can tell you, replacing them in the car is just as hard as installing a new engine. Aslo, the rod bolts are 100% torque to yield, which means that they are one use ONLY. They also cost most what your used engine hoist would. Save your time and money, replace that engine.

Sorry I had to be harsh, but it's the truth. Replacing an engine is not the hardest thing in the world and bill-boost has some great writeups that take you step by step, and we're all here to lend a hand should you have any questions.

another possibility is to ask if someone is in your area and can help with the location to swap. I've met many members by helping our or providing a location.

Scottydoggs, another really good guy... I met because he was in an apartment and didn't feel up to doing his transmission. He drove more hours than day than the swap took. Poor guy... you should have seen his face when I tried to dash plant him.

this could be one of them times you test the limits of your apt buildings limits for BS. some places if your in your parking spot working they dont care, other wont let you change a flat tire.

i also have the curse of apt life. seen a guy who lives here do a engine and tranny swap in the stop and shop parking lot across the st. it sat parked for months then was in tear down mode for 2 weeks. leaked a load of oil all over where theres a stain 20 foot long still today. no one said a damn thing to this guy. i was kinda amazed.

ive got a friend with a large driveway who lets me do work on my car there. did the engine swap. the last tranny swap. everything really, hub last week lol