3500 swap questions

[Superdave]

the 3100/3400 cover will bolt onto the 3500 fine, altho i don't know why you'd change the 3500 one out. I used a 3400 timing cover gasket on my 3500 cover.


I don't use the 24x crank sensor or the cam sensor, just the 7x external trigger. Mine idles really rough but that's not the sensor's fault


Yes, the 3400/3100 pump will mount to the 3500 timing cover. I have one from a '95 Beretta on my 3500. Just some other notes, i'm using a 2.8 alternator bracket with the stock alternator for my car, a 2002 3400 fuel rail, '98 FPR and multech 1 injectors. I'm also using the stock 3500 MAP sensor, stock 3.1 OPSU and knock sensor.


*also, i figured out a way around grinding the TB neck for FPR clearance. I'll post up pics tonight of my modified FPR. It clears the 3500 neck w/o problems.



in all reality the 3500 swap isn't much different than a 3400 swap, just a few things like the block mounting bosses are slightly different and the CTS setup. You can drill and tap the rear head larger to accept the newer 3 wire sensor if that's what you need. I have a 2 wire in each head (one for the gauge and one for the computer/fan).

The 24x sensor has nothing to do with SFI. SFI is controlled by the cam sensor. The 24x sensor has to do with having a more accurate timing at low RPMs in order to allow for a smoother idle at those RPMs (below 3k).

Funny, my old 3.1 idled much smoother than my current 3100.

The 3500 front cover still has the three bolt holes for the power steering pump. It just has an additional threaded bolt hole for the idler.

[bszopi]

The 24x sensor has nothing to do with SFI. SFI is controlled by the cam sensor. The 24x sensor has to do with having a more accurate timing at low RPMs in order to allow for a smoother idle at those RPMs (below 3k).

[IsaacHayes]

Superdave doesn't have a SFI car, so he doesn't need the 24x sensor. Not sure if he swapped timing covers for the accessories or not?

24x sensor is a 2nd crank sensor us SFI guys have and you still need the 7x for spark. The timing cover is the thing on the end that all the pulleys and stuff bolt on to, and is also the water pump housing. Swapping over the 3100 cover and all the accessories solves the problems you are worried about.

I figure the cost of head gaskets and intake gaskets/etc is about the same as the external trigger setup.... I haven't done the math but you end up with a whole new engine...

[PCGUY112887]

Well I'd need to get a 3400 vs the stock 3100 to use the heads from the 3500... by the time I do that I might as well just use the whole 3500. Since it's newer, it should take to boost better if I so chose to do so. Plus it has those fancy oil squirters.

This is a huge learning experience for me which is why I want to do it on a project car so I have as much time as I need. I've learned lots about engines over the past year or so but I still lack information, which is why I ask here.

[ProjectMM]

insted of doing all that work, what about doing a 3500 head swap, and lower intake? if it's even possible? it would save alot of work and would give a grate topend increase.

I've been looking into this for my car, sense i live in california and a turbo or supercharger would fly for somg!

[PCGUY112887]

Excuse me for my ignorance but I don't quite know what you guys are talking about.

I'm not even sure where the timing cover is. And the crank pulley with the 24x sensor? Would swapping these over do the same thing as buying the external crank trigger from the store here, or are these 2 totally different things/issues with this swap?

As far as the PS pump goes, since there isn't one on the 3500 are the holes to even mount one still there? Would a different belt size be needed after adding it?

[CNCguy]

The 3100 cover should bolt on fine but I have never tried it before. I make billet front covers for the 60V6s and they are interchangeable with 3100, 3400, LX9, LZ4 & LZ9. Perhaps Superdave would know for sure since he just finished his swap.

[IsaacHayes]

Yes things are interchangable. Use your power steering pump :P

Honestly the AC looks just like my 94 3100. I'm betting you could get yours to bolt up or figure something out.


Re-use the 3100 existing fuel rail, injectors, FPR, knock sensor(might be the same if the 3100 is OBDII), alt, a/c, powersteering, etc. You can bolt up your old exhaust manifolds but the 3500 stuff flows better so if you can use that and get it welded up to a downpipe then you'd be doing a lot better.

Main thing I'd be concerned about is if you can swap the 3100 timing cover over, you'll need to along with the crank pulley so you have the 24x sensor for idle and low rpm stability. Anyone know for SURE that you can do this?

[PCGUY112887]

Oh I didn't know things were interchangable.

What does it do for power steering? Are there still normal lines I can hookup my steering to?

You would retain your alternator, and starter anyway, at least teh alternator, since the 3500 alt probably wouldn't firt the chassis right, just like the genII J-body guys, starter I beleive is teh same between 3400 and 3500, including late 3100. The Water pump is also the same, and should be swapped out for a new one anyway, when installing a new engine. The 3500 doesn't use a power steering pump anyway.

I'd still be considering the 3500 if I were in your position.

[PCGUY112887]

Well turns out all of the 3500's around here come with no accessories (water pump, PS pump, alt, starter, etc).

Almost seems not worth it trying to go with a 3500 and seems better to go with the stock 3100 in the project car and do whatever to it.

Question number 1... evil piston slap... what exactly causes it and what would be required to do to solve it?

Question number 2... who has experience with what company with custom pistons for a 3100?

[IsaacHayes]

a 3400 plenum solves the TB adapter and vacuum line issues. Bolts right up to the 3500 LIM and everything on your 3100 bolts right to it like stock.

A 3500 plenum is nice (power wise), but requires grinding the TB neck for FPR clearance, taping the IAC/Evap port and putting a 1/4 NPT nipple there for vacuum for the FPR and transmission modulator. Running a vacuum line to the stock MAP, or use the 3500 MAP and splice the wiring connector on there. And of course a TB adapter. If you search for "3500 plenum checklist" or something it you'll find my thread on what's all needed. You could always do it later when you had time to get back some more power and just use a 3400 plenum for now.

Go to the yard and look at the 3500. See what it looks like and if your compressor will bolt up. From the picture of the 3500 i've seen it looks JUST LIKE my 94 compressor bolt holes. The lines hook up different, but that doesn't matter just bolt yours on....


2 up top with a spacer, one below. Just like mine.

I think maybe the people with compressor bolt issues are the gen2 mpfi swappers that use their old R12 compressors.... Maybe that's the deal?

Do the 3500, you'll have nice power NA and you can get a DHP and get it running well. Then later down the road swap on the 3500 plenum and get a 65mm throttle body for more power, or turbo it. If you turbo though your trans won't last too long with that power. So maybe just a hot 3500 NA powerplant is the best compromise.

[PCGUY112887]

I figured 3400/turbo for cost, however 3400's around here are more expensive than 3500's. I found 4 3500's for $550, but all 3400's with many more miles are $700-$800... then I would have to add the cost of doing some things to it like LIM, worry if anything else is going to leak since it has 50k already on it, etc.

With the 3500 I again have costs, external crank trigger, TB adapter and TB, then the worry of the AC.

As far as turbo vs NA, that comes down to cost vs power.

Ugh decisions decisions... I like the 3500 the AC is my main worry since I have no idea if it will adapt or if the old compressor will bolt to the block, etc.

[IsaacHayes]

Depends what your goals are, and your resources (welder, etc).

If going N/A, the 3500 is a great choice.

If going for power/cost, 3400 and turbo it. But remember your auto may not like that.

My A/C compressor leaks from the housing seam. Defrost worked just fine this winter. Ever since I fixed the firewall from leaking when it rained, I don't get a foggy windshield anymore.

Likely you could adapt the 3500 compressor maybe? I don't know if the lines bolt up differently or if the 3500 lines would fit your engine bay? Or make a bracket to adapt your 3100 compressor? From the pic it looks like the top 2 bolts would bolt up and are the same as my compressor....