LS3 crate motor exhaust manifold issue.

[cannonball55]

I bought a GM LS3 376ci 480hp crate motor. I also purchased a john's cars kit to install it with into my 73' 240z. The problem I'm running into is the exhaust manifold on the drivers side is dumping too close to the motor mount (right on top of the steering shaft). I thought about trying to buy a 98-01 camaro manifold but i got to looking and the exhaust ports are way smaller on the ls1 than on the ls3. I don't have the cash to buy a new set of headers to remedy this. (Taxes hurt this year) So i'm stuck trying to piece together stuff from junkyards atm. Anyone have any suggestions on a good flowing manifold that exits as far to the rear of the engine as possible? Mine atm exits under the third cylinder back and needs to be under the fourth. Been working on car for 6 months and almost finished only to be stumped here at the end by a manifold lol never fails.....

Any ideas would sure be appreciated.

 

Thanks,

Stewart

[BRAAP]

Just a heads up with OE exhaust manifolds.

I have been collecting various LSx parts, oil pans exhaust manifolds etc for my ’93 Nissan 300-ZX LSx conversion, (Oil pans, C-5 bat wing, Truck, GTO and F-bod, exhaust manus Truck, LS6 Vette, GTO, LS2 vette, and Caddy CTS-V).

I discovered the GTO manifolds, are really only worthwhile if you are satisfied with mild to mundane LSx performance. They are not a performance piece. The outlet ID is only 2”! The C-5 Vette and Truck have 2 ½” outlet ID,

 

At any rate, here are some pics...

 

 

 

[BRAAP]

Haven't installed an LSx in a S-30 car, but have been collecting exhaust manifolds for another V-8 Z project that has been scrapped. Still in the market for set of F-bod manifolds and possibly LS3 if they are much different than the LS2.

 

Here are some of those OE exhaust manifolds for those interested… I'll try to get pics of the rear dump truck manifolds today if time permits.

 

The C-5 LS1/6 manifold is a pretty nice looking piece for and OE Iron manifold. Primary diameters appear to be approx 1 5/8”- to possibly 1 ¾”? not quite round shaped, more oval shaped. All the merges are smooth and fluid, no steps inside. They are very close to equal length and in a true tri-Y design. Not sure the "Tri-Y" design in of itself has much benefit. Iron being less prone to exhaust leaks, though a little heavier than tubular steel. The interior walls are rough cast, not smooth like tubular steel headers.

 

 

 

 

This pic of the back side shows where the primaries and secondaries pair up in the casting.

 

This pic is looking up the collector. VERY difficult to make out in the picture, but you can just see the primary merge for the forward pair and the merge for the secondaries. The merges look nice and clean. VERY nice casting…

 

 

 

GTO manifolds, “smallish” 2” id header flange/dump;

 

 

 

 

 

Caddy CTS-V LS6 exhaust manifolds.

Interesting manifolds these are. The outlets are 2 different sizes. Driver side is 2 3/8” opening, passenger is 2 5/8”?!?! On the driver side, there is quite a bit of material in the casting around the header pipe flange to open up the one side that is fed by the front 3 cylinders therefore balancing the outlet dimension a bit.

It is clear that GM spent more time and attention on Vette exhaust manifolds.

Here be the pics, Cadillac CTS-V LS6 exhaust manifolds;

 

 

 

Parallax in the pic, actual measurement is 2 5/8" ID, not 2 9/16" as depicted

 

 

 

 

Vette C6, LS2 Exhaust manifolds…

Outlets are 2 3/8” for both, with a cool header flange gasket. Note the recess in the header pipe flange. Not sure if the Vette pipe flange will be needed or just a flat flange. They seem to be for the most part symmetrical like the other Vette manifolds.

 

 

 

Edited April 26, 2009 by BRAAP

[cannonball55]

Ones I have are the vette C6 ls2 listed above. They direct the exhaust right into the framerails on the 240z. Suppose I'll have to come up with some 98-2001 camaro ls1 manifolds. Those being the ones that John and johns cars based his kit after. Wonder if there are any cheap headers that would work... (150 bucks or less).

Thanks,

Stewart

[Dudeboy]

Can you post a picture ?If you know a good welder (or can do it yourself?)Get another set or driver side c6 exhaust manifold, you can cut them into two separate ports, and step them. You literally move the exhaust flange two ports rearward and weld in some more metal. I will get over to Jeff house this evening to see what he actually did with his, but I know he took another driver side c6 exhaust cut it in half, so that two front halves of the port are what you are left with (this is in a 78 280 if that matters).

[cannonball55]

Has anyone put together a list of headers that will work with the LS-series engines in the 240-280z cars? Would sure make a nice sticky post to have around.

Thanks,

Stewart

[Savage42]

Has anyone put together a list of headers that will work with the LS-series engines in the 240-280z cars? Would sure make a nice sticky post to have around.

Thanks,

Stewart

 

Makes for a short list, from what I've seen & heard.......JTR & JCI....that's about it.

[VinhZXT]

97-98 C5 headers can be easily modified to fit. Check my web site out for pictures.

[Savage42]

Wait! You said "modified"......so that means it's not a simple "bolt in", right?

[VinhZXT]

Wait! You said "modified"......so that means it's not a simple "bolt in", right?

 

I thought he knew none of the stock exhaust manifold will be bolt into a Z without modifications. This is why every body used the JTR headers or custom make their own.

[maichor]

I have another solution. You can just give your LS3 to me, you can have my LS1 with my custom ceramic coated headers.