Anyone using Doug Thorley 323Y-C headers?

[OKGMC4]

I see most people get the 324Y-C headers that are 1 5/8 primary and 3" collector but they make a 1 7/8 primary with a 3" collector under part number 323Y-C. Seems like most of the LS engines (LS1, LS2, etc.) like the bigger pipes so it would make sense that a 6.0 or modified 5.3 (cam and ported heads) would work well with these. Any thoughts? I'd really like to see how they fit in the frame.

[chevyguy_72]

Originally Posted by OKGMC4

I see most people get the 324Y-C headers that are 1 5/8 primary and 3" collector but they make a 1 7/8 primary with a 3" collector under part number 323Y-C. Seems like most of the LS engines (LS1, LS2, etc.) like the bigger pipes so it would make sense that a 6.0 or modified 5.3 (cam and ported heads) would work well with these. Any thoughts? I'd really like to see how they fit in the frame.

I have them... don't have any closeup pics of the frame but you can pretty much see... they are currently on a 6.2 stock 72 frame no mods at all... I have the CPP sheet metal stands and the dirty dingo sliders...
You will prob want to use a CTSV or other low profile oil pan as the truck version hangs down below the cross member...

[66LSx]

I used the 324Y vs. the 323Y or 322Y to keep the exhaust above the frame rails....

323 and 322 come down at an angle toward teh ground... 324 levels out....

322/323 pointing toward the ground:


324 levels out at exit (sorry big)

[68GMCCustom]

so the headers with the larger 1 7/8" primary tubes are shorter then the headers with the 1 5/8" tubes?

[66LSx]

Originally Posted by 68GMCCustom

so the headers with the larger 1 7/8" primary tubes are shorter then the headers with the 1 5/8" tubes?

shorter... dunno.... but they do exit at an angle....

at an angle I don't think you could recover without going below the frame rails.
Here is the 322/323 exit angle




if your not planning on bagging it... its really a wash.

Here is how I got to run my exhaust... up over the trans x member with the 1-5/8" 324's...

[OKGMC4]

I did some more looking and I just ordered the 323yc for several reasons. Hookers are way more money. Hedmans can be had for a decent sum but they require either special or 73-87 motor mounts and I just bought my ebay adapter plates and new 69 style mounts. The Thorley headers seem to have a thicker flange than most at 3/8 inch. They also have a thicker pipe than most at 14 gauge. You can use the stock dipstick tube with these.

I decided that my desire for all out flow with 1 7/8 primaries outweighed having full length with 1 5/8. Do some research and you'll see that many many LS headers don't even offer 1 5/8 as an option. These engines like the big pipes.

I had planned on using my 6 cylinder brackets and moving the engine WAY back. You can do that with the 324yc but the bends are different with the larger headers. Doesn't look like these will clear so I will use my V8 brackets instead. Will try the rear holes first and see what happens. I still think the point of interference will be the passenger side firewall. That's OK. I wanted the engine back but I may also have clearance issues with the engine and coil covers that I ordered from BH custom designs so it may have to stay a little forward. I can also redrill the adapter plates and move the mounts a bit. Should be interesting but the covers won't be here till next week and JEGS says the headers won't ship until 4-21-14 so it will will be a while before I know what hits and what fits.

[OKGMC4]

Some pics of a truck with the 324y-c and 6 cylinder mounts.

[OKGMC4]

The rear pipe is where I think I'll have issues with the 323yc. This truck has the brackets in the front holes and it looks a little close. If you look at the pics of the 1 5/8 version on the truck above it actually looks like the driver side will hit first.

[Hart_Rod]

Originally Posted by OKGMC4

I did some more looking and I just ordered the 323yc for several reasons. Hookers are way more money. Hedmans can be had for a decent sum but they require either special or 73-87 motor mounts and I just bought my ebay adapter plates and new 69 style mounts. The Thorley headers seem to have a thicker flange than most at 3/8 inch. They also have a thicker pipe than most at 14 gauge. You can use the stock dipstick tube with these.

I decided that my desire for all out flow with 1 7/8 primaries outweighed having full length with 1 5/8. Do some research and you'll see that many many LS headers don't even offer 1 5/8 as an option. These engines like the big pipes.

I had planned on using my 6 cylinder brackets and moving the engine WAY back. You can do that with the 324yc but the bends are different with the larger headers. Doesn't look like these will clear so I will use my V8 brackets instead. Will try the rear holes first and see what happens. I still think the point of interference will be the passenger side firewall. That's OK. I wanted the engine back but I may also have clearance issues with the engine and coil covers that I ordered from BH custom designs so it may have to stay a little forward. I can also redrill the adapter plates and move the mounts a bit. Should be interesting but the covers won't be here till next week and JEGS says the headers won't ship until 4-21-14 so it will will be a while before I know what hits and what fits.

I'm using 323Ys on my LS3 with a 1900 Maggie. I've got the engine as far back as it will go with CPP engine stands and Dirty Dingo slider mounts. No problems with clearance.

[trkfrk]

Great choice with the Doug Thorley's. They seem to be a really quality built header. Show us pics when you get yours installed. I installed the 324Y-C's and really happy how well they fit.

[trkfrk]

Pic 2

[Billett]

I run the 1-7/8s. I did a bit of reading around the old interwebs and honestly, if you plan on staying stock or mild the 1-5/8s are a much better fit. You may gain some top end power with the larger primaries but you lose a ton under the entire curve.

[OKGMC4]

I've heard that about losing bottom end power but if you believe what this CarCraft article says, it looks like there is very little difference in reality. According to the article there was very little change from vette manifolds to 1 5/8, 1 3/4, or even 1 7/8 headers. Of course that is on a bone stock LS1. So, it may stand to reason that an LS with ported heads and some cam may see more gain...but at the same time it didn't see any real loss under the curve.

http://www.carcraft.com/techarticles...e_header_test/

I pan on doing cnc ported heads and a Lingenfelter cam and don't want to feel like I left any on the table with this engine. My 56 is all stock and has the vette manifolds and I know it runs well, but the power is lacking IMHO. I am amazed how many people see the 5.3 in there and say "wow, I bet it's fast!" and internally I'm shaking my head. I want my 69 to outrun my 56 with one arm tied behind it's back when it's done. It will have more engine, more gear, more stall, and bigger exhaust. Can't go wrong with that recipe, can I?

[bigwheel6]

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