Thread: Hello everyone, new member, engine swap question

Hey everyone, I recently bought a 98 Grand Prix GT. I've always been a GM guy, my first car was a 91 Grand Prix SE and I loved the hell out of that thing. Sold it when it rotted out, bought a few chevies, and currently own a Corsica. I found a 98 Grand Prix on craigslist, and after a few days of texting/calling the guy to take a look at it, I finally made arrangements to look at it. After a 30 minute drive, the guy texts me when I'm 5 minutes from his house and says "Oh, by the way, it's got a slight engine knock". F***.......


Well, I wasn't about to turn around and go back, he was only asking 1500 for the car with 160k on it, but the pictures showed almost no rust, which is rare for a wisconsin car over 15 years old. I showed up and gave the car a walk around, needs tires and some slight surface rust repair on the rear quarters. Then I started it up, and it ran GREAT. sounded smooth, no rattles, no knocks. Revved it up to 2500 RPM (I know, I know, don't do that on a cold engine, blah blah blah) and I heard a noise which I was pretty sure was piston slap - a higher pitch rattle. Ok, I can live with that, piston slap doesn't always mean the death of the engine....

Took it around the block a few times, steers straight, rides fantastic, that rattling isn't happening at less than 2500 RPM. I go back to the guy's house, and I offer him 800 for the car. He says yes, signs the title and I'm on my way. I start driving home, and guess what? It starts knocking. Uh oh.

So, here I am, with an 800 dollar car with a knocking engine. I sourced a new engine from a local salvage yard, for 300 dollars and a 6 month warranty. I was planning on just rebuilding the bottom end of the engine, but when I pulled the drain plug and metal sparkles came out with the oil, I decided against that - if there's metal in the pan, there's metal everywhere else in the engine too.

So, sorry for the long-winded story, if you made it this far, I just have two questions.

Number one: Since I am going to be swapping the engine, is there anything else I should tackle while it's out of the car? I'm planning on unbolting from the TC and removing the engine only, while leaving the trans in the car. I'm going to degrease the subframe and replace a few squishy hoses while I'm in there, but is there any parts which would/should be replaced that are easier to get to with the engine out, especially at 160k miles?

Number two: Do you think I overpaid for the car? Is it worth putting an engine into, or should I just cut my losses and try to sell it for what I bought it for, or part it out? Haven't signed the title yet, so that option is still available.

I really like the car, it's got just about every option except the sunroof, and everything (EVERYTHING) works, with the exception of the engine.

Thanks for reading, I look forward to your opinions.

Nope, not supercharging. I'm on a budget, and can't afford to buy the S/C engine (600) plus the PCM and exhaust and all of the other goodies to go along with it. Just planning on a direct swap for the same engine.

I think you did ok. Throw an engine in it (after replacing all the gaskets) and call it good. I bought my GP out of a junkyard needing an engine and rocker panels for $400 so I think you did fine.

I would also toss in front and rear main seals and an oil pan gasket....check to make sure timing cover and rear crank case housing gaskets aren't leaking while you are there. Some guys say to forget that stuff, but, every time I try to cut a corner, it bites me in the buttocks.

Originally Posted by TwiztdWun

I would also toss in front and rear main seals and an oil pan gasket....check to make sure timing cover and rear crank case housing gaskets aren't leaking while you are there. Some guys say to forget that stuff, but, every time I try to cut a corner, it bites me in the buttocks.

I will definitely be replacing any gaskets that appear to be leaking, and I'm going to degrease the new engine and clean it up before putting it in. However, I'm on limited funds (I'm trying to keep this engine swap under $500 including the engine, otherwise it might take me until next payday, and dad wants his garage back lol) so replacing an oil pan gasket and main seals would be an added expense I can't really afford at the moment. I guess I'll have to see how the engine looks when I get it, if there's any damp spots on the engine I'll just have to replace the gaskets that appear to be leaking. Oil pan gaskets are pretty damn hard to replace in-vehicle on the 3800 lol.

Originally Posted by Below Average Joe

Understood. I would just do what I said and I forgot to check the upper intake around the TB. They tend to break since they are plastic and fail and cause your engine to hydro-lock. Read this thread from Bill on how to fix that issue permanently......

http://www.grandprixforums.net/threa...w-to-Mod-a-LIM

I checked out that post, that's extremely helpful and I might have to look in to doing that with the new engine - although, as stated above, I'm on a budget and somewhat limited with time - If possible, this all needs to be done by this weekend.

http://www.rockauto.com/catalog/more...039&cc=1317103 - This style gasket?

http://www.dormanproducts.com/mobile...997&make=BUICK - This coolant elbow?

Thanks for all the advice. You guys are incredibly helpful, most other forums it's at least a few hours before I get a reply, and the info is usually less-than-helpful.

Wasn't aware my car had a MAF sensor, I didn't see one under the hood - I believe it's a MAP/IAT setup, but I could be wrong.

Will definitely clean the TB and I may have to swap out intake manifolds, the new engine is from a different model car (but still a 3800 series II)

Anyone else have tips/advice on what should be replaced? Other parts outside of the engine are included in my question - should I do anything to the brakes, power steering, are there upgrades that should be done to the trans, maybe replacing bushings or hard to reach parts? Thanks again.

Maf is on the throttle body, the flat sensor on the top

Just completed an engine swap myself and had to turn around and swap out some sensors, i have sensolocation lol

Check for sludge on the bottom inside the oil pan, it can clog the oil pump intake after a few minutes of running time and then restrict oil to the rest of the engine, hence the knock.