ok guys
i thought that i blew just the heads but it turns out that the block is cracked too. dad says that we can not go to a bigger motor (ie 355 or 90*v6) 3.4 swap is out of the question too. the question is, will the 3.1 short block for a 90-92 f-body work in my 89 camaro with a 2.8 in it? dad says something about the "knock sensor" is in the wrong posistion. i thought that these motors were identical except for stroke and a stronger crank area in the 3.1. i am trying to convince him in as little words as possible that the 3.1 and the 2.8 parts are totally interchangable. am i wrong? i need help, he's ordering the parts monday and i need to know before then if there is any difference. thanks guys

 

You dad is right on the Knock sensor.
The 2.8's do not have a knock sensor (atleast as far as I know they didn't) that was special to the 3.1

The 3.1 Engines used a little different technology too, they used the MAP (manifold Air pressure senor) instead of the MAF (Mass air flow sensor). But if you just put the 3.1 under the 2.8 FI system this should have no affect on it (or so I think).

As far as the engine. The 3.1 is just the next step from the 2.8, so putting one in the place of your 2.8 should require minimal effort. As you can just used the same FI on the 2.8, and place the 3.1 underneath it all (sort of like what Ked did with the 3.4 swap)

Infact look up Keds article 3.4 boogie.
Read it.
Even though this is a 3.1 the same idea applies.
Put both engines side by side, and duplicate the original 2.8 look.

 

What exactly is the knock sensor? something to do with timing or something? is the sensor in the block or in the heads, cause dad said something about it being in the heads, if i use the 2.8 heads, would i have a problem. basically i wanna run a bigger stroke 2.8 block, right? or am i completey wrong in my thinking? i am going to run all of the stuff off of my existing 2.8 from the heads up.

 

TTT

I'll let the experts sort things out for you.

But I think your basic idea will work. I am 99% sure that everything heads up should work.

 

Bummer to hear about the motor! I don't see any problem with just changing the block out. The heads are the same between motors, though. Is there a reason you want to change the heads? I'm not familiar with the knock sensor's location on the 3.1, but if it is in the heads, then you could do one of two things. You could leave the knock sensor where it is, unconnected, so it fills the hole- there's nowhere to hook it into a 2.8 MPFI harness. Or, you could remove the knock sensor, and put a pipe plug in it's place. Either way, it won't affect the motor. Like Joe_L said, the reason there was a knock sensor on the 3.1 was because the MPFI also changed. But you can run a 2.8 MPFI system on a 3.1 block, no problem.

Another difference between 85-89 MPFI and 90-92 MPFI? 85-89 MAF MPFI used a 9th injector, the cold start injector, also called a cold start valve. This is located in the back of the intake manifold, near the base of the distributor, and has a thin fuel line running from the top of the fuel rail to it. The 90-92 MAP MPFI doesn't have the cold start injector. There's no hole in the top of the fuel rail. Not sure if a hole exists in the intake manifold.

But none of that matters; it's not particular to the 3.1 block, but it's particular to the 90-92 MAP MPFI system. Since you're using a 85-89 MAF MPFI system on a 3.1 block, you don't have to worry about cold start injectors or knock sensors. I hope that made some sense.

 

makes compelete sense tomp. the heads i will be useing are brand new 2.8 heads, right out of the box. i purchased them to put on my 2.8 but when i started the car and still had air being pumped into the coolant system, a crazy rise in engine temperature, and a misquito fog like smoke coming out of the exhaust, i new that the block had to be at least warped, if not cracked. i know that lots of people have made these motors last way more than180k but i heard that the majority of them fail around 90-110k. i jut turn 90,600 about two days before we declared it "broke". i guess the next question is will napa (or whoever i go to to get my shortblock) except my 2.8 as a core, plan on calling them tomorrow. thanks again for the advice.

 

Right on Tom. I need knew we needed someones expertise in here.
I completely forgot about the Cold start valve. That could be his biggest problem.