3500 swap questions

[IsaacHayes]

So the N/L body side mount will bolt up to the W body fenderwell???? Are you sure???? I don't see that happening. Or is the issue with the A/C mount and not the engine mount?

[3100 MPFI]

not the engine mount.

You know how the 3100 AC compressor is bolted on? 3 bolts? 2 are on top and one on the bottom.

They bolt straight into the block.

I mean the torque strut mount, not the side mount.

In the 1996 Grand Prix, that bracket is just the top section, and the AC compressor bolts go through the bottom 2 openings in the bracket.

if you search the n bodies, you will find that piece where the ac compressor goes through, but it will not have the upper part of the torque strut.

[IsaacHayes]

Ah ok I get it. Didn't know the GP could use that torq strut setup there. I thought they just had a rear bottom mount and the dogbones. Yeah my A/C mounts with an aluminum spacer on the top bolts only.

[3100 MPFI]

I will take a pic of the setup in my 1988.

The 3100 in the Grand Prix uses the motor mount below the harmonic balancer, and the 2 torque struts.

You kinda need the 2, but I honestly feel that if you replace the stock hydraulic motor mount with the solid rubber one, then you can get away with using only 1 of the torque struts.

There is no way to use the passenger side torque strut with the headers. Been there, done that. We thought we had found a way to do it, but I ended up cracking the boss on the front head.

This is what you get when you try to do things the WRONG WAY.

[PCGUY112887]

Where can I get a solid bottom motor mount? I have looked on at advanced and autozone, but they only sell the hydraulic oil-filled ones.

Also I don't quiet get what this nbody piece does. My compressor bolts straight to the block, it doesn't go through the whole "arm" thing for the upper mount that is in the way. If I put something from the nbody in between where my compressor bolts up and the block, what does that do aside from make the belt need to be longer?

I feel sick not knowing about this before I bought the headers... I try and try to research everything so I know what all has to be done, and as soon as I get everything I find something major wrong like this.

Would there be any way to chop the upper mount "arm" that is in the way to cut out he area that is in the way, then weld steel tubing to make the inside area for the headers bigger? It sounds like a job but I can't imagine the engine being OK with only 1 upper mount.

I guess I can't hack off the lower part of the 'arm' that is in the way and only use the upper part, can I? There is so much oil and crap I can't quite see where all of the bolts are, so I don't even know if there are any bolts in the upper area.

EDIT - Would there be some way to just add say 1" of steel under anywhere the mount mounts that connects to the engine, then modify the top dogbone or something? This way the entire mount is further away from the engine, but it would be deep enough to clear the headers (that is if they will fit in there height wise as well).

[PCGUY112887]

Also the cam position sensor has a small issue. On the 3100, the sensor is in the block and a wire just comes out. On the 3500, there is just a plug on the block and it doesn't look like it would come out easy. I tried to plug the harness into the plug on the 3500 and it is very close, right number of wires and everything, but it just slightly doesn't fit.

Do I just find a way to pull mine from the 3100 and put it in the 3500 in the same spot, or is there some adapter I can make?

[3100 MPFI]

I can't help with the cam sensor, but I can with the bracket.

First of all, I had to buy my solid mount from Napa. It is cheaper than the hydraulic, and you usually have to order it. When I bought mine, they did not want to sell it too me but after telling them that if I bought the hydraulic one, and it blew out, I was going to bust the windows out of their store, the ordered it for me.



First of all, that pic I posted? That shows what happens if you cut off the torque strut arm, and try to use it without the lower part of the bracket. That is why you will need to get this piece I am telling you about. I don't know how your AC compressor does, but mine goes straight into the block. Here are some pics to show what I am talking about.

This is the bracket in my 1996 Grand Prix (being swapped into my 1988 Cutlass Supreme. As you can see, it has the torque strut mount on top with 2 bolts under the torque strut, then there is 1 bolt that holds it to the block, then the 2 holes on the bottom are where the AC compressor bolts go into.



In this pic, the part that is circled, that is all that is in the skylark for a spacer. If you get that part then you will not have any issues with the belt, or the AC bolts not lining up. By using that spacer thing, you can leave the stock mount out, and just not have a passenger side torque strut. If your AC compressor does not go through the bracket like in the first pic, then you have something different.

[IsaacHayes]

Ah I see. Nothing to do with the N body motor mount. You're just saying get rid of that one dog bone. Yeah you need the N/L body compressor spacer. I have a spare one somewhere if you need it. Or just cut some hollow tube for spacers.

You may be ok without that one dogbone. If you could cut it and weld it to clear more that would work too.

[3100 MPFI]

I think it will be fine as long as you have the solid motor mount.

CLICK ME!!!!!

That should be the link to the napa solid motor mount. If that link does not work, it is napa part number BK 6121730, and cost $39.99. It says in the listing that it does NOT meet OEM specifications, but that is because it is solid, and not hydraulic. I did the search using 1995 Cutlass Supreme as the car.

The other thing you might want to do, and I was thinking about doing this when I had the headers, but I didn't, is replace the drivers side torque strut with an older poly mount that some of the car sites sells. I was going to do that, but at the time, I only needed one, and they came in pairs. I didn't get it, but it might also help keep the engine from moving too much without that second torque strut.

[PCGUY112887]

Humm... I get it now. I didn't realize the compressor bolts held in the bottom of the mount like that, and now I see the need for spacers or something.

How much does your engine move with only 1 and a solid mount? It may be OK but this engine will be making a good bit of power... I may need that other mount. Anyone any good at fabbing? Seems like if you cut the center portion that is in the way out, and welded to steel tubing to the outside of the mount that it may be OK. I have access to the stuff to do it, but I barely have any experience on a welder or even anything to cut through something this thick.

[3100 MPFI]

well, I drove it without a passenger torque strut for over 3 years. After the 3rd year, I finally broke the welds in the rear header (didn't have a flex joint in there, so it was only a matter of time).

My engine was making a decent ammount of power. My friend Lorenzo (gpse3400) thinks that it was a 14 second car, but I don't have proof of that (and I regret not getting back to the track to confirm it).

He thinks my 3100 was faster than his 3400, so it was making a decent ammount of power. I didn't have any issues with the passenger torque strut missing, and the only reason I put the stock bracket back in was becuase I removed the headers.

[PCGUY112887]

I want to ENSURE that I put my pushrods back correctly.

The big valves are intake, and the little valves are exhaust, correct?

[CNCguy]

I want to ENSURE that I put my pushrods back correctly.

The big valves are intake, and the little valves are exhaust, correct?

Correct and the long pushrods go to the exhaust valves which lean towards the exhast manifolds.

[PCGUY112887]

OK we have an update here!

Not the most progress, but I only get a few hours per evening... plus I work slow since I am always checking to ensure I did stuff right. I am also working mostly by myself so things go slower there.

I am attaching pictures of all of this.

First off we have my old 3100 manifolds vs my ported (by meee!) 3500 manifolds. Huge difference!

Then I have a picture of some springs. I got all of my new compcams springs on, however a few things shot off on some springs (damn you superdave for cursing me ) so we had to grab a retainer and 2 keepers off the 3100 I pulled out. Visually I could see no difference so I went ahead and used them. This should be OK, right?

And finally I have a pic of 2 sensors on the front of the 3500. On the 3100 a knock sensor and oil pressure sensor are here, so I will assume these are the same things. However neither of them are no where near compatible with the old harness, nor does it look like I can swap in my old sensors. What is to be done about this?

Also the coolant temp sensor in my head is a 2 wire sensor, when I thought it was going to be a 3. What should I do about this... just get a 3 wire sensor and put it in there, get a connector from a TPS sensor off a junk car and wire it up?

[3100 MPFI]

not sure about the sensors. I hae not seen the 3500 sensor. I did take a pic of the cut bracket I had on my 1988 Cutlass for the passenger torque strut. By using this, I cracked one of my mounting bosses. I do NOT recommend doing this.



And this is the AC compressor. As you can see, the 3 bolts go straight through, and go straight into the block.