Differences in 95 and 96 engines

[davidw]

So, I've spent the morning searching and I think all I've done is confused myself. So, at the risk of being told to "search again" I thought I'd ask what should be a simple question. I have a 96 Monte and after rebuilding the top end a couple years ago and last summer the tranny, I now have a dull, hammering noise which sounds like the bottom end coming apart. I found a guy locally that has a rebuilt 3.4 long block that he wants out of his shop but isn't certain if it is a 96-97 or earlier. If I'm reading the posts I've found correctly, if it is 95 or earlier I can simply use the upper and lower intake manifold and plenum from my car, correct? But then am I also correct that the 96-97 have a second knock sensor? I assume that is going to be an issue along with the EGR valve? Please help, I'm ready to leave this car in Chicago with the keys in it!

david

[Dave96z34]

Sadly you couldn't pay me to take a 91-95 engine my recommendation is find a 96-97 you will have less problems. They are actually not to hard to come by but idtrack down the source of the sound for sure it could be your tranny again.

[davidw]

Thanks for the reply Dave. The more research I have done the more I agree with you. I'm inclined now to simply pull the engine and have it rebuilt. But the best engine shop in the area are the one's that did the heads, which have also developed a ticking noise, so I'm wary to have them do the complete rebuild.

I'm 99% certain it's the bottom end. Car in park, slowly wind up the engine, the dull hammering get's louder and the speed increases as the rpm's go up. Interesting that at a certain point it quiets down. It's actually loudest right off of idle.

That said, in the back of my mind I'm also considering finding a donor car with a 3.8, having it rebuilt, and swapping the wiring harness and computer. As much as I love the 3.4, she has done me wrong one too many times.

[RedZMonte]

I had a 92 and have a 95. never had a problem with the motors. You will need to swap your heads and top end. IIRC the 91+ DOHC blocks are interchangeable. the 1996 had 2 knock sensors in the block so if its not a 96-7 then you will need to find a place for the front knock sensor. I have a 96 harness on my car and used a spare port on the block for the front knock sensor. but i wouldnt be affraid to use a 91-5 block. the compression was a tad lower on the pre-96's but not a large ammount.

S

[Dave96z34]

I was saying for the hasel of switching heads and relocating a knock sensor id rather just find a 96-97 and be done.

[RedZMonte]

you don't have to swap the heads over, but the '96-7 top end does flow better. if you want to just install a complete engine then you will need a 1994+ for your harness/ecu to work. (1994+ have a few things on them that the older ones dont, cam position sensor and what not)

S