Exhaust Manifold Differences

[BlueGTS]

I am adding some custom 3" mufflers in my side sills and I was thinking about changing my exhaust manifold out to at the same time to ones from a later model Gen II. In doing this I will have to purchase a reducer from my 3" muffler to my exhaust manifold collector. My question is: do non-cast manifolds have larger diameter collector than the one on my stock 96GTS? What is the diameter of the newer Gen II collectors? 2.25"?

 

[Ron]

Your only benefit to move from cast to tubular GENII manifolds is a 20 lbs weight savings. No horsepower gain at all.

You will need new flex pipes as the cast have bolted flanges and the tubular have band clamps. Same diameter flex pipe on each. You will also need new header bolts as the tubular flanges are thinner. You will also notice hotter side sills. The cast manifolds seem to act as somewhat of a heat sink.

Save your money and effort and either stay stock or go to real headers.

 

[BlueGTS]

Thanks Ron, I am about to order my mufflers today and want to buy some reducers so it can mate to my stock collector. From what you are saying, if I get a complete exhaust manifold setup including cats, from a newer Gen II it will work with whatever I buy today. Is the stock collector 2.25 or 2.5”? Thanks,

 

[FlyBryViper]

My stock collectors/elbows were 2.5" on my 01. The adapters I got from Jon B. at partsrack.com fit perfect, even though the high-flow cats were 3"
I have a set of 01 tubular headers for sale, but they don't do a lot except weigh less than the cast manifolds.

 

[BlueGTS]

Ron, thanks for the information I did not even notice that I needed new bolts until you mentioned it. I will pick up all new header bolts and new gaskets. For some reason my car has non-metal gaskets which do not look like they should be re-used.

I picked up the headers at the right price so I am going to put them on. Each one weighs 13 pounds more than the tubular type so that is some savings. Looking at them they do not look any less restrictive, as a matter of fact the collector looks more restrictive because of its 90-degree bend. Taking them off was very quick and easy and I did not even have to jack up the car. If I remembered your comment about the bolts and had picked up a few gaskets it would have be done in a few hours.

 

[FlyBryViper]

Get the heat shields too? You will need them or the fire-proof sleeve for your sparkplug wires. Also, the heat shields direct some of the heat down, out of the engine compartment.

 

[Tom F&L GoR]

FWIW, when I swapped my Gen 1 to Gen 2 manifolds, I reused the Gen 1 shields. If you're moderately careful, the old ones stay in good shape and are molded around the new manifolds easily. It's one of those things where you use a little more effort than you want to, but they aren't as fragile as you think.

 

[FlyBryViper]

I hacked and bent and cut my Gen.II heat shields to fit over my Jet Hot coated Archer Racing headers. Makes it look slmost like stock, coated headers.

 

[opnwide]

FWIW, I'd stick to 2 1/2" muffs if you're keeping the stock ex manifolds. Going to a 3" pipe will slow down ex velocity and may lose a few hp. Sound will also be louder with a 3" exhaust. 3" exhaust should only be used with headers.

 

[BlueGTS]

I have both sets of heat shields but I will try to bend my 96’s to fit over the newer manifolds, as they look a bit better.

opnwide, I understand the theory behind what you are saying but I think most people see an increase in HP with just a catback versus the stock 2.5" exhaust. Either way, I am prepping my car for the Roe install. I don't think a SCed car would like the stock exhaust much.