Replace LA1 with LX9?

[PAimp00]

I"m thinking of replacing the slappy, tired 3400 in my "00 Impala with a 04-06 LX9 (3500) as they're cheaper and easy to find currently. What issues would I run into? My concerns are:
Throttle body swap? Or, swap upper LA1 intake onto LX9 LIM with some porting? Will existing PCM deal with small increase in displacement? Will RDB trans bolt up, if not, is it only a flex plate change? Will cam and crank sensors swap, or utilize LX9 sensors and change harness connector? Will exhaust manifold(s) need to be changed? At $475 for a 25K motor with warranty including labor, it's an interesting proposition.

[bszopi]

http://60degreev6.com/forum/f96/span-style-color-span-style-color-0000ff-3500-t36647

[PAimp00]

Thanks. Not a lot of help overall. The biggest issues on that thread is A/C and PS. They will probably have bigger problems with sensors and electronics. About all it helps me on is the UIM to LIM question. Other than what I mentioned previously, I know the rest of the differences should be easily resolved. I guess I really need crank/cam sensor info. They would be the largest hurdle, if the trans bolts up.

[bszopi]

You will need the external crank trigger from WOT-tech. Easily resolved, but that a big pricetag which may make that cheaper 3500 seem not so cheap compared to a 3400. Mounts would be another thing as well. Here is a more recent (and shorter) thread discussing it: http://60degreev6.com/forum/f96/3500...-i-read-t41330

[IsaacHayes]

Swap parts from the 3400 such as timing cover if needed, fuel rail, UIM (or adapt the 3500 one, it makes more power, not too hard to do), and external crank trigger.

The rest are A/c mount issue, etc. It's possible but does have a few "snags" to get around.

[PAimp00]

Interestingly, WOT-Tech says the stock 3500 UIM doesn't flow as well as the 3400's. I'd probably stick with the 3400 manifold. The buck and a half pricetag on the external crank trigger removes a lot of motivation, but if I end up with a modest HP increase, I may still do it. Now, what about the cam sensor, the exhaust manifolds and the PCM? Also, is the crank bolt pattern the same?

[Superdave]

I swapped my 3400 out for a 3500 last year, best upgrade ever!

for the cam sensor, you should be able to either use the 3500's sensor or drop in the one from the 3400. the output the same signal to the PCM.

the 3500 exhaust manifolds flow better but you can just re-use the 3400 ones so that you don't have to build a new crossover pipe and all that.

the crank pattern is the same, and the 3500 UIM flows much better than the 3400 one after like 5-10 minutes of porting. 3400 owners have even bolted on stock 3500 plenums and reported gains. It's a much better design.

Forced_firebird still might be selling adapter flanges which let you use the 65mm TB from the 3.5 Olds on a 3500 UIM, more info Here: http://www.v6z24.com/jbodyforum/65mm...p-t102558.html


Keep in mind you also have the option of bolting the 3500 heads, UIM and plenum onto your 3400. Toss in a decent cam and some 3.4 RWD pistons and you'll have a real screamer.

[IsaacHayes]

The ports on the 3500 plenum are slightly smaller than 3400 ones, just do a quick gasket match its super easy. (wasn't for me, but my air tank could barely turn my air grinder for 7secs). I gasket matched my 3500 plenum, and 3400 LIM ports. The 3400 had less to remove than the 3500 so yeah I can see why it would flow less stock, but keep in mind there is more to it than flow and I'm betting even unported it makes more power than a 3400 upper. My 3100 loves the combo

[Barry]

Its a pretty easy swap.

Ac will work by enlarging the compressor holes, and using 3 washers on the bottom bolt, or trim the top spacer to bring it flush to the block.

The back bosses by the tranny bracket is the most complicated part of the swap. They need to me modified. The hardest part is finding reference points on both of the blocks so you can compare them and make the changes you need to make.

IIRC the 3500 bosses are the same angle(30*, parralel to the heads) as the 3400. I had to move mine in .257 inches If I remember correctly. They are also up too high. I made a custom bracket to compensate. Slotting the holes isn't my style.