96GPSE Posted November 24, 2010 Report Share Posted November 24, 2010 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) Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted November 24, 2010 Report Share Posted November 24, 2010 (edited) 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 Quote Link to comment Share on other sites More sharing options...
96GPSE Posted November 24, 2010 Author Report Share Posted November 24, 2010 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? Quote Link to comment Share on other sites More sharing options...
Crazy K Posted November 24, 2010 Report Share Posted November 24, 2010 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. Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted November 24, 2010 Report Share Posted November 24, 2010 The runners are different. I put a 3400 gasket on a 3500 head and it didn't seal. Quote Link to comment Share on other sites More sharing options...
BXX Posted November 24, 2010 Report Share Posted November 24, 2010 Why use the 3400 UIM??? Just makes no sense to me.. And whats the problem with using RTV in place of the end seals?? Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted November 25, 2010 Report Share Posted November 25, 2010 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. Quote Link to comment Share on other sites More sharing options...
96GPSE Posted November 25, 2010 Author Report Share Posted November 25, 2010 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. Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted November 26, 2010 Report Share Posted November 26, 2010 I used RTV in the corners of the gasket anyway. I recommend you do the same! Quote Link to comment Share on other sites More sharing options...
visitor Posted November 26, 2010 Report Share Posted November 26, 2010 Do you get a decent power boost by doing the top swap? Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted November 26, 2010 Report Share Posted November 26, 2010 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. Quote Link to comment Share on other sites More sharing options...
1QUICKHATCH Posted December 11, 2010 Report Share Posted December 11, 2010 any updates? I am thinking of installing my 3500 from my Alero. Quote Link to comment Share on other sites More sharing options...
96GPSE Posted December 13, 2010 Author Report Share Posted December 13, 2010 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. Quote Link to comment Share on other sites More sharing options...
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