Looking at exhaust upgrades...

[andrewlandon67]

And I'm mostly looking at either the CB or Berg 1 1/2 inch heater box merged systems, but I'm not 100% sure if I should do it. My motor is a 1914, 40x35.5 heads, W120 cam, 1.25 rockers, 44 IDFs, 8.9:1 compression. Would going with that be a good idea or a waste of time? Right now, with stock boxes and a cheap Empi header, it has a really hard time doing anything above 5500 RPM, and as far as I can tune it, the exhaust seems like it'd be the biggest culprit. Also, if it matters, my car spends most of it's time between 5000 and 6000 feet in elevation. Any words of advice?

[Zach Gomulka]

Exact same specs as the 1915 I built for my buddy's car, except he's running IDA's (IDA's are overkill, your 44's are perfect). I used a 1 1/2" header and a 2 1/4" A-1 Dynomax, has no problem pulling to 7k. A standard header is defintiely holding you back, upgrade that then mess with the jetting. You have 36mm vents?

[Jim Ratto]

Your current exhaust is too restrictive for a good, tuned, big-valve 1641.

Like Zach said, a 1-1/2" merged is ideal for your setup. Your engine will take on a whole new urgency with the right exhaust on it. Seriously, maybe 15+ hp

I cannot say enough good things about the CSP 42mm I put on my 94 x 78, it replaced a no-name small-flange 1-3/4" traditional merged with big turbo muffler. It runs better and cooler, and the engine response at high rpm is so much more pronounced.

Here:  http://cal-look.no/lounge/index.php/topic,25742.0.html

Have fun

Jim

[andrewlandon67]

Right on, thanks guys! 1 1/2 seems like the way to go, especially since I would like to keep heater boxes. Jim, after reading through that thread I can't help but ask if you'd say there's a big difference in drive/tune-ability between a traditional merged system, and a Sidewinder style system?

[andrewlandon67]

And yes Zach, I believe my venturies are 36 mm. I've been attempting to tune my jets, but I really want to wait to hook my buddies wideband up until I get everything else as good as I can.

[andrewlandon67]

One last stupid question, for anyone still reading. Will I need to go richer or leaner than my current jetting for the larger exhaust? Right now, my jets are 140 main, 200 AC on F11 emulsion tubes, and the engine seems to be pretty happy with it, but I'm assuming once I step up to a less-restrictive exhaust, I'll need to go back through the jetting.

[Zach Gomulka]

You probably will have to re-jet. Make one change at a time, install the exhaust and see what the a/f ratio does before messing with jets.

[andrewlandon67]

That makes sense... Thanks for the advice, man!