3500 top swap

[96GPSE]

I'm just buttoning up my 3500 top swap and I have one concern. On the 3500 GM has the orange gaskets that go between the intake and block (where you'd normally put RTV only for a 3400/3100). The 3500 LIM is dimensioned differently to accommodate this somewhat thick orange gasket.

My question is for anyone that's done the 3500 top swap, how did you seal this up and how is it holding up?

 

(3500 top swap going on the 3400 in my GP)

[Jonpro03]

I had to buy the 3500 gaskets. They weren't cheap either.

 

If you are using the 3400 heads than you have to use a 3400 LIM but a 3500 UIM will bolt on to it. If you are using the 3500 heads, you need to buy the 3500 LIM gaskets. They are not the same as the 3400 LIM gaskets believe me I tried that.

Edited November 24, 2010 by Jonpro03

[96GPSE]

I have: 3400 block, 3500 heads, 3500 lim, and 3400 UIM. I used the 3500 LIM gasket set which came with the orange gaskets for the lim valley, but there are no holes in the 3400 block to retain the gasket.

 

What was your setup, Jonpro?

[Crazy K]

I have: 3400 block, 3500 heads, 3500 lim, and 3400 UIM. I used the 3500 LIM gasket set which came with the orange gaskets for the lim valley, but there are no holes in the 3400 block to retain the gasket.

 

What was your setup, Jonpro?

 

i think this was solved by someone drilling those pilot holes in their engine on 60degreev6... or.. ASK BRIAN P? he may have been the one who did this.

[Jonpro03]

The runners are different. I put a 3400 gasket on a 3500 head and it didn't seal.

[BXX]

Why use the 3400 UIM???

 

Just makes no sense to me..

 

 

And whats the problem with using RTV in place of the end seals??

[Jonpro03]

I'm sure he's using the 3400 UIM because he didn't want to (or couldn't) buy the TB adapter. You cannot use RTV on a 3500 LIM because it is too large of a gap to fill. GM shaved the LIM back a little to install a thick rubber gasket instead of using RTV.

 

I use a 3500 block/heads/LIM/and lp3100 UIM with 56mm tb.

 

I would just cut the tabs off of the orange valley gaskets.

[96GPSE]

I dry fitted the LIM with the tabs on the orange gasket cut off...it seemed really sketchy. The gasket wanted to move all over the place. I think I'm going to use some RTV to hold the valley gasket in place, let it dry, then install the LIM. Thanks guys.

[Jonpro03]

I used RTV in the corners of the gasket anyway. I recommend you do the same!

[visitor]

Do you get a decent power boost by doing the top swap?

[Jonpro03]

You get the best boost in power if you change to the 3500 heads. They are the best flowing heads for our motors. If you do a head swap, use the 3100 gaskets and you'll get a higher compression ratio. Or just swap in a 3500 motor all together. Stock, it has ~200hp 220tq.

[1QUICKHATCH]

any updates? I am thinking of installing my 3500 from my Alero.

[96GPSE]

I positioned the valley gaskets on the block after cutting the tabs off. I made some wire "clips" to hold the valley gasket in place while the RTV between the valley gasket and LIM gasket dried - they didn't want to stay put without something holding them in place. I then added a bit more to the corners and installed the LIM. Been running for a while now, no signs of leaks from this area.

Also the power increase is quite noticeable. I drove my GP with the stock 3100 for 110k miles, then dropped in a 3400 last year which was OK, but the 3500 top swap provided the most noticeable power increase.

Also I had to re-shape the coolant tube attached to the LIM - there was the slightest amount of interference between that and the UIM right were it makes the 90 degree turn down into the thermostat area. I just flattened it out a bit to make it fit.