LS to TH350

[Jstock85]

Ready to drop a gen3 vortec in 85 c10. Turbo 350 is already in the truck. I know I'll need the spacer plate and the longer bolts but can anyone who has done this before tell me if I'll need a new flexplate and starter as well? I'll be reusing the stock converter and the stock starter that came with the engine for now.

Thanks!

[davepl]

I've never done an automatic LS, but with the manuals you face the dilemma where the flywheel face depth is 0.400 more shallow than the classic block, so I got a specialized flywheel that was that much thicker.

Maybe the spacer plate you refer to takes up that difference? I'm in for the solution because I'm curious!

[Jstock85]

Yeah I'm definitely sure the spacer makes that up. I'm not sure if a new flexplate and starter is necessary. In all the research I've done I haven't heard a definite yes or no on those

[Tomahawk30]

I just installed a 2003 5.3l from a Silverado in my 79 Silverado, and the easiest way to do it is to buy the hub adapter and use the stock LS flexplate. Then you just use standard torque converter bolts. The only thing you may have to do is open the mounting holes up a little on the flexplate. I didn't have to on mine because it'd already been mated to a TH400 when I bought it. You may also have to trim outer ear on the th350 depending on which exhaust manifolds / headers you use. I used the cheap headers they sell on ebay for swaps and had to trim the passenger side slightly.

https://www.amazon.com/Torque-Conver...4P4QWQ6WEVZZN6

[Tomahawk30]

Here's a good video explaining it:

https://www.youtube.com/watch?v=8wpaqjiQXYI

[Jstock85]

I'll check that out. Thanks!

[aruss99]

I have a th400 but the process should be the same. I used a spacer and stock ls flexplate. I had to open up the holes a little bit to get the 3 bolt torque converter on, but other than that, it bolted right up. I reused the factory starter. 2 of the holes on the engine/ transmission don't line up, so don't be concerned about that when you begin to fasten the two together

[suburban99]

Working on swapping a LQ4 6.0 into my 72 K10. Stock LS starter is fine. My flex plate was the flat version and all I had to do was enlarge the bolt holes...4L80E has 6 bolts and the TH350 has 3. My tranny is in stock position and it is a tight fit to firewall, but so was the HEI distributor. I did not want the hassle of adjusting the drive shafts as mine is a 4x4, so I went with stock position. Fired mine up last weekend just to see if it would run and it ran great.

[Jstock85]

Originally Posted by suburban99

Working on swapping a LQ4 6.0 into my 72 K10. Stock LS starter is fine. My flex plate was the flat version and all I had to do was enlarge the bolt holes...4L80E has 6 bolts and the TH350 has 3. My tranny is in stock position and it is a tight fit to firewall, but so was the HEI distributor. I did not want the hassle of adjusting the drive shafts as mine is a 4x4, so I went with stock position. Fired mine up last weekend just to see if it would run and it ran great.

My trans is tight to the hump also. Im hoping it won't have to be moved either. That's good news on the starter and the flex plate. Less parts to replace. I am a bit concerned on the bolts lining up. Other guys have mentioned that also. I was under the impression that the bell housing patterns were the same which is what allows LS series engines to mate to older style GM transmissions. I guess ill have to get in there and see for myself!!

[mongocanfly]

bellhousing to engine dowel and bolt pattern is the same..except for one bolt..its a non issue..be sure to use 2 dowels..
I think he's referring to the number of torque convertor bolts..6 instead of 3

[suburban99]

Originally Posted by mongocanfly

bellhousing to engine dowel and bolt pattern is the same..except for one bolt..its a non issue..be sure to use 2 dowels..
I think he's referring to the number of torque convertor bolts..6 instead of 3

Yes the torque convertor bolts are what I am referring to.

[Jstock85]

I have one last question. Do any of you guys know what years of flex plates are interchangeable? For example, I went to a couple local junk yards this weekend and saw a lot of vehicles with the flex plate still in. The motor had been pulled or the trans pulled. I can't imaging GM making several different flex plates. My engine came off a 2000 silverado 1500. Anyone know what years I can pull from and still get what i need?

[Tomahawk30]

I can't say for sure, but I believe the flexplate from any 4l60e engine should work with the sleeve to mate to the th350. I've never read about any differences from year to year on the flexplate, though admittedly I've never had a reason to research that specifically.

[19Hoosierdaddies68]

Originally Posted by suburban99

Working on swapping a LQ4 6.0 into my 72 K10. Stock LS starter is fine. My flex plate was the flat version and all I had to do was enlarge the bolt holes...4L80E has 6 bolts and the TH350 has 3. My tranny is in stock position and it is a tight fit to firewall, but so was the HEI distributor. I did not want the hassle of adjusting the drive shafts as mine is a 4x4, so I went with stock position. Fired mine up last weekend just to see if it would run and it ran great.

Hello Suburban99, pulling you post from the dead. I'm swapping a 2002 5.3 into a 71 K5. Using my T350. Went with Dirty Dingo mounts. Now hitting the firewall and coming up about 1" or so short of mounting to the T350. Sounds like our setups are similar. Did you have to trim valve covers or anything to get it to set back further? Seems my passenger side valve cover back coil pack mount it hanging me up. Any thoughts on where I am off? TIA.

[Rust-O-Matic]

Originally Posted by suburban99

Working on swapping a LQ4 6.0 into my 72 K10. Stock LS starter is fine. My flex plate was the flat version and all I had to do was enlarge the bolt holes...4L80E has 6 bolts and the TH350 has 3. My tranny is in stock position and it is a tight fit to firewall, but so was the HEI distributor. I did not want the hassle of adjusting the drive shafts as mine is a 4x4, so I went with stock position. Fired mine up last weekend just to see if it would run and it ran great.

I know this thread is old, but could you tell me which engine mounts you used to keep the trans in the stock location? I'm entertaining doing the same on an '84. Thanks!

[mongocanfly]

I'll throw this in, on mine I used the ol Ebay adapter plates, the ones that locate the rear of the LS engine in the same location as the ol sbc...the clam shells bolt to them, and it sits right in there.
Then your trans and driveshaft stay in their original location

[Rust-O-Matic]

Originally Posted by mongocanfly

I'll throw this in, on mine I used the ol Ebay adapter plates, the ones that locate the rear of the LS engine in the same location as the ol sbc...the clam shells bolt to them, and it sits right in there.
Then your trans and driveshaft stay in their original location

Ok, thanks. I presume you're talking about the plain jane version that's just a flat plate with two sets of holes in it (one set for the ls block, one set for the clamshell). I noticed some have 3 sets holes for position adjustment, and some others have slotted holes.

There's so many options, it's hard to tell which ones are going to put the rear of the engine in the stock location. What you describe sounds like it should work for me though.

[mongocanfly]

Yeah, mine have just one set of holes..