Engine replacement

[dickaccoun]

I had a 1990 Buick Reatta convertible with 134,000 miles. It sounds like I have a wrist pin knocking. I'm thinking about replacing the motor. Does anyone know which one would be the easiest match

[Jim]

You would want to use any GM '89 or '90. '88s were the same engine but had 3800 embossed in the air plenum and the '89-90s did not so it would be obvious that you had an '88 engine in your '90. The '91s had a completely different intake system.

I have bought a couple of Reattas for parts that had a knock in the engine and it turned out to be a bad harmonic balancer. ( crankshaft pulley )

[dickaccoun]

Jim: thanks for the information, as the motor warms up the noise seems to diminish, which makes me think it has something to do with expansion of internal parts. We changed the main and rod bearings, but made no difference. I don't want to keep throwing money at, but I will ask my mechanic to take a look.

Thanks Dick

[Vincent Vega]

Did the mechanic mic or plastigage the bearings? What made him decide to replace main & rod bearings? "Nope, that's not it. Next up, wrist pins or new engine." Sounds like he wants a new boat. Get a second opinion.

[harry yarnell]

Jim's right; a bad harmonic balancer will sound just like a rod or bearing knock.

[BillNC]

This may also apply to the 3.8 engine. On 3 other different type engines I had, they produced a rattle when cold, especially loud on a very cold morning. The noise was more pronounced under load and the noise faded considerably after warm up. The 3 engines had excessive piston to cylinder wall clearance. The pistons have a greater expansion rate than the cylinder. On two different 4 stroke motorcycle engines I had, had worn wristpins and the rattle didn't really change at all with temperature seeming to even worsen slightly when warm. On a Chevy engine I had it would rattle loudly for the first few seconds after start up then become a slight rattle and worsen a little after a being totally warmed up. This one I never took apart but I think it was a rod bearing since the startup rattle was extreme before initial oil pressure build up and after warm up the oil would become thinner. Others may or may not of had different results.

[Vincent Vega]

There is also an internal balancer shaft in the 3800 engine. Another possible source of noise. The FSM on Reatta.net will show the balancer shaft location and R&R procedures.