Hello everyone, Happy holidays. Getting ready for this engine swap, I just took the engine out of my 69 coupe. Its a 80 or 81 350 that was put in before I bought the car. Tomorrow I start to detail the engine compartment. Any suggestions are appreciated. The ZZ4 is still in the crate. I would like to put headers on with a 2 1/2" exhaust system out the back, does anyone know if this can be done? I know that 2 1/2" pipes are for big block but will fit on the car. Can I install them on a 350 with headers or is this not necessary? Thanks for any info. Steve

2.5" exhaust is fine.. alot of guys here use it on an SB..

the one thing you want to watch out for is make sure you get the right headers..

use small tube headers for low end power.. use large tube for a high end hp..

using large tube kills your torque somewhat as it reduces your exhaust scavenging and renders your valve overlap almost useless.

using large tube kills your torque somewhat as it reduces your exhaust scavenging and renders your valve overlap almost useless

ZooooooMMMMM over my head!!!!

I just want to put 2.5"'s on my smb with ceramic 2" headers using the connecting flange at the header tube collector, very cool sound going through the gears with 2.5" pipes, deeper I think. Will the change in torque be noticeable?

MIkey and his beast (project)

I have the Chevy HO Engine, very similiar to ZZ4 but 20 hp less, I have Hooker Super Competition Headers from Summitt Racing and 2 1/2" SS Exhaust from Mid America. I put the headers on after the engine swap and exhaust change. The thing I notice with the headers is the throttle is more responsive. Didn't notice any torque difference with headers. Now the new engine livened things up a bit. I am planning a 700R4 transmission swap for the torque increase off the line.

The super comp headers will bolt right to the 2.5" exhaust? I'd like to stay away from any welding if I can. No problem with engine compartment clearances, spark plug access or any thing like that? Also, what kind of mufflers do you use? Thank you everyone for your input. Steve

A picture

You give Summitt the pipe diameter and the headers come with an adapter that bolts. Flange to flange. However, I doubt if you will find pipes that fit the headers without modification (I could be wrong here?). Mine didn't, had to be cut. For that matter the pipes had to be cut to install with the original manifold. I bought Mid America's Turbo mufflers - 304 SS. I went with all stainless exhaust for longiviety....don't want to screw with that job again. The headers fit great in the engine compartment. The advice I got on Headers is don't skimp on quality to save money (pipe gage). It will cost in the long run (poor fit).

Welding is almost a must with any exhaust, unless you want to have tons of u-clamps every where. even then they might leak. I used mid america's 2.5" chambered dual exhaust for header applications. I asembled it and had to do some cutting and even made my own balancer tube. I had it all clamped up just so it will last till i get it to the muffler shop so they can weld it all together for me. later I added flowmaster 50's to lower the noise further due to neighbors whining.

Steam,

I installed a ZZ430 with sidepipes. The clearance from the collector to the road can be a problem. Sidepipes eliminate this problem, but you end up with hot pipes when you exit. I do some autocross and lowering the car means a lot to me. Hope this helps.

Mike, what Ben is saying is easily put.

Install large tube headers for high engine speed power. But you will lose low rpm power and torque.

Install small tube headers for much better low rpm power and torque, but you won't get quite as much on the high rpm end, as you would with the larger headers.

Most of our small blocks will work better with the small tube headers. It's better off the line, and works better for most of our drive lines. BUT if you are a strickly high rpm guy, say with a high stall speed converter or a high rpm launch with a clutch, and a higher numerical rear end ratio, the large tube will make you happy.

The very agressive motor build ups will usually have the higher numerical ratio rear, and higher launch rpms.

The 2 1/2 inch exhaust pipes work well with any of our cars. Many of the stock ones will do fine with 2 or 2 1/4 inch. But the larger pipe usually sounds a bit better.