Exhaust cut outs, yeah or neah?

[Guest zfan]

I have been toying with putting cutouts on my sbc 240Z. Has anyone run the ones like they sell in Summit? If so does the lack of back pressure from running an open exhaust kill the sbc's performance.

 

I'm trying to get into the 11's

 

Mike

[Mike kZ]

I bought those but haven't installed them yet. When I had my car on the dyno we could tell the my exhaust system was chokeing my engine.

[Guest 73TPIZ]

zfan,

 

I'm running a cutout made from a four cylinder throttle body i had laying around. i just made a plate from 1/8" to bolt the TB to, merged the duals into one behind the axle, and welded that to the plate. i activate it with a lawn mower throttle cable run up to the trans tunnel beside the drivers seat. When closed the duals run into a 2 in/1 out muffler and is super quiet but very restrictive. I ran a pass at Reynolds last week with it closed and was 4 tenths slower.

 

i thought heat would be a factor but i've been running it for a year and no probs. you just have to pop it open a little when you first start the car or the heat will swell it and make it stick closed.

 

Future plans would be 2 TB's on 3" duals when i go more cubes so theres no restriction at all. Just a 305 motor now so 1 is prob ok. I've heard FI motors need some back pressure so may leave it as is.

 

I could send some pics if interested. Take Care.

[Guest Aaron]

I can speak from experience that Charles' exhaust cutout makes a huge difference on the posterior dyno.