Gulp and O2 bung locations

[wrench459]

Is there a place in the exhaust where both can serve there function?
Old school says to place the gulp valve at 45 degrees(180 from ground) at the start of the collector.
New school wants to locate the oxygen sensor further back into the collector atleast 90 degrees from ground level. Just some thinging about some possible conflicts for when I ditch the carb.

[wrench459]

Number three on the link http://i250.photobucket.com/albums/g.../gulpvalve.jpg
That's the only name I've ever heard it called.(gulp)
My problem is will the crankcase vapors upset the O2 sensor located further down stream?

[hrcollinsjr]

Originally Posted by wrench459 My problem is will the crankcase vapors upset the O2 sensor located further down stream?

I would think so, but what do I know? Will it really make that much difference if you put the valve downstream of the 02 sensor?

Dan, the pan evac systems as we know them may be old school. While trying to find another name for your "gulp valve" I ran across a few more things I didn't know.

Why do race cars run a vacuum pump? Where it all began, at least in the NHRA Sportsman ranks, was with the introduction of mufflers to the racing class. Once the cars started running mufflers traditional pan evacuation systems (pan-evacs) no longer worked properly.

One way is that as the crank spins in a partial vacuum, less air density means less resistance to rotation. The proper amount of vacuum will improve ring seal. C&S research indicates you can have too much. About 10” to 14” of vacuum at 7000 RPM yields the highest power gains.

I don't know if you've researched these options or not but if you haven't you may want to.

Harold

[RallyBob]

You can run a pan evac system with mufflers. We installed quite a few on Subaru drag cars, the trick was to drill a hole into the pipe, and hold the evac tube in place with the engine at a set rpm while on a lift. Then pivot the tube slowly and at some poiint you'll find the 'sweet spot' where the exhaust created the highest vacuum on the evac tube. You'll want a few degrees off from this angle, as too much vacuum means you'll over-draw the crankcase and oil down the track (blackflag!).

Bob