6.0 LS swap header fitment issues

[72-k20-burb]

Hi folks,

long time reader, first post.

I bought a 72 k20 suburban a few months back, and have proceeded to tear out the old power plant and put in a low mile l96 (6.0). I got the old np205 on the back still and it's in the stock mounting location.

I'm using the dirty dingo 4x4 crossmember kit with clamshell mounts.

The stock manifolds on the 6.0 did not work, and I just bought THY-323Y-C doug thorleys and they wont work. Ah!

I checked throley and summit, both sites make it seem like they should fit. Is everyone using slider mounts to move the motor back? I'm hoping to avoid that so the trans and drive shafts all stay in stock locations.

Are there other headers I should get that will clear? I checked the thorley 324s and they have the same fitment listed online. At $650 a pop I don't want to cut these up to make them fit unless absolutely required.

Thanks!

[mongocanfly]

Welcome....
I got sucked into that "they should fit" thing...I wound up using headers for a hummer...but I would never recommend anyone do this...it took a ton of modifying to make it work...if I was doing it over I would probably use LS3 manifolds...I think those would work..and it being a K series will make it even more difficult to dodge driveshaft,axle and such

[72-k20-burb]

The LS3 exhaust manifolds look pretty darn close to the ones that came on the l96. Do they hug tighter than other manifolds?

Dirty dingo has 1302LS1-C Schoenfeld headers that supposedly work for 4x4, however they won't call me back after a few voicemails. I already spent enough money there I would have hoped for better service.

I read a few people here used Speed engineering, they have a note that says no 4x4..

Getting custom exhaust made seems simple enough to clear the 4x4 transfer case if I can first clear the frame... I'd really rather not cut or modify like you said.

[mongocanfly]

I'm not sure what the L96 mani looks like...
Here's the diff between a 5.3 and a LS3 mani...the 5.3s stick out from the engine about 3/4" more than the LS3

[CJM72]

We should trade! I have a set of THY-324Y-C headers that fit inside the frame rails fine, but basically were rubbing on the firewall on the driver's side. If you have clearance in that area, these might work for you. Too bad we weren't closer, or I'd let you try to fit them. I could have just hammered a dent in the firewall, but I didn't want to do that. Almost bought the 323y's as I've seen others fit them just fine.

https://boston.craigslist.org/sob/pt...719481365.html

[CJM72]

For the record, I have the same Dirty Dingo crossmember with a 6.0 and a 4l65e adapted to the np205. Left the NP205 in the stock location, but I have a k5. It's too bad, these headers tuck up nicely, cleared the frame, spring shackles, and look great.

[mongocanfly]

CJM.....So the LS3 manis fit ok?..

[72-k20-burb]

Thanks for the comparison Greg, I'll upload a picture of the l96 ones for future reference.

Originally Posted by CJM72

For the record, I have the same Dirty Dingo crossmember with a 6.0 and a 4l65e adapted to the np205. Left the NP205 in the stock location, but I have a k5. It's too bad, these headers tuck up nicely, cleared the frame, spring shackles, and look great.

Is the k5 front frame geometry any different from the c10/k20 etc?

What 6.0 do you have and what headers did you end up using? I've heard these 323s fit with the LQ9/4s so that's why I bought them hoping it would be the same for the l96 6.0.

The photo from your craigslist ad makes it look like your motor sits pretty similar to mine. I'm tempted to send mine back to summit now and get those 324s. I only went with the 323s over the 324s because of the 1-7/8 sizes primaries.

[mongocanfly]

I've also got a set of manis off my LQ9 and they are the same as the ones from the 5.3

[CJM72]

Originally Posted by mongocanfly

CJM.....So the LS3 manis fit ok?..

Yup, fit great. I have them bolted in there now! Just would like to have headers.

[CJM72]

Originally Posted by 72-k20-burb

Thanks for the comparison Greg, I'll upload a picture of the l96 ones for future reference.



Is the k5 front frame geometry any different from the c10/k20 etc?

What 6.0 do you have and what headers did you end up using? I've heard these 323s fit with the LQ9/4s so that's why I bought them hoping it would be the same for the l96 6.0.

The photo from your craigslist ad makes it look like your motor sits pretty similar to mine. I'm tempted to send mine back to summit now and get those 324s. I only went with the 323s over the 324s because of the 1-7/8 sizes primaries.

Looking at the pictures in my thread, the cross member and motor location look identical. I believe the 4x4 trucks all have same frame geometry up front. You can see where mine driver's header was touching the firewall. Couldn't even slide a piece of paper in there!

[DWilbur]

The DD engine mounts don't work with LS 4X4 swap. The issue is the mounts set the engine 1-1/2" lower that 2 wheel drive LS swap. In the end I modified my Dough Thorley Headers had to rework the front header tubes on both sides to clear the frame so they fit.

[72-k20-burb]

Originally Posted by DWilbur

The DD engine mounts don't work with LS 4X4 swap. The issue is the mounts set the engine 1-1/2" lower that 2 wheel drive LS swap. In the end I modified my Dough Thorley Headers had to rework the front header tubes on both sides to clear the frame so they fit.

Interesting. Do you mean the sliding DD mounts?

I bought their 4x4 mount and crossmember kit, so far everything fits great. Except the headers..

I'm halfway through an exchange with summit so I'll post when I get the new ones and test fitment.

[Clyde65]

Just curious but maybe a shortie header would work. I have the Sanderson CSLS1 and although my truck is a 2wd and a 65, I would think they will fit. Just a thought.

[DWilbur]

Originally Posted by Clyde65

Just curious but maybe a shortie header would work. I have the Sanderson CSLS1 and although my truck is a 2wd and a 65, I would think they will fit. Just a thought.

The shorties should work. I have a set of Headman shorties that I tried but they are about the same as stock exhaust manifolds. I did not like the way they dump strait down if they dumped at an angle they would work better for my truck.

[72-k20-burb]

Originally Posted by DWilbur

The shorties should work. I have a set of Headman shorties that I tried but they are about the same as stock exhaust manifolds. I did not like the way they dump strait down if they dumped at an angle they would work better for my truck.

looking at the picture the no1 primary looks like it takes the same turn as the others I've tried. I went to a c10 gathering an a lot of people there had headers that all fit ok, but none of them were 4x4 LS swaps.

The stock manifolds on the l96 will only require a small modification to fit, but I'd really like to get some longer headers on there.

Right now I have a 6l90 on and the np205 sits in it's stock location so all drivetrain is the same. Would be nice to keep from moving anything. Finding the right exhaust seems simpler/cheaper than making new transmission mounts or new drive shafts.

[DWilbur]

Here is picture of the Dough Thorley Headers I had to modify to fit. Both front tubes is the issue they hit the frame. now they clear by 3/8"

[72-k20-burb]

Originally Posted by DWilbur

Here is picture of the Dough Thorley Headers I had to modify to fit. Both front tubes is the issue they hit the frame. now they clear by 3/8"

Are those the 323s or 324s?

[Slippy]

I used the Speed Engineering ls swap headers on my K5 Blazer 4x4. Worked great. Only issue is the spark plug wires on the drivers side will have to be changed to the msd flexible boot type.. they were around $169 shipped on eBay..nice thick flanges and look great.

[72-k20-burb]

Originally Posted by Slippy

I used the Speed Engineering ls swap headers on my K5 Blazer 4x4. Worked great. Only issue is the spark plug wires on the drivers side will have to be changed to the msd flexible boot type.. they were around $169 shipped on eBay..nice thick flanges and look great.

Those look good. I looked at speed engineering a bit, everything I found on their website says no 4x4.

What motor mounts / crossmember are you using?

[72-k20-burb]

So I got the DT 323's exchanged for the 324s and they fit. mostly.

Passenger clears, drivers side had to shave a tiny bit.

[Slippy]

I’m using the pacific fab crossmember and mounts.

Originally Posted by 72-k20-burb

Those look good. I looked at speed engineering a bit, everything I found on their website says no 4x4.

What motor mounts / crossmember are you using?

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[72-k20-burb]

[QUOTE=Slippy;8377748]I’m using the pacific fab crossmember and mounts.

Your clearence makes me jealous. I was kind of stuck on using long tubes for some reason. I think the LS3 manifolds was a good back up option, good to know about speed engineering too.

[Slippy]

[QUOTE=72-k20-burb;8377901]

Originally Posted by Slippy

I’m using the pacific fab crossmember and mounts.

Your clearence makes me jealous. I was kind of stuck on using long tubes for some reason. I think the LS3 manifolds was a good back up option, good to know about speed engineering too.

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[tim3834089]

Originally Posted by CJM72

We should trade! I have a set of THY-324Y-C headers that fit inside the frame rails fine, but basically were rubbing on the firewall on the driver's side. If you have clearance in that area, these might work for you. Too bad we weren't closer, or I'd let you try to fit them. I could have just hammered a dent in the firewall, but I didn't want to do that. Almost bought the 323y's as I've seen others fit them just fine.

https://boston.craigslist.org/sob/pt...719481365.html

I have a set of 323y I’d like to trade for 324y.
They are new and never ran. Headers only
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