crank case evacuation? help

[dbmx66]

im going to be racing this on a regular basis.

it will see some street.

will i have problem with a high performance engine with a crank case evac system on the street?

[Super73]

Just make sure to use a check ball style breather with baffle. Run the tube to the headers.

[custom70]

I use this setup on my Camaro, which is primarly a street car. It seems to work good, I have not had any problems with it and do not have to worry about oil on the valve covers.

[nxtruck]

I run this same system on my truck. In order for it to work to it's potential, the exhaust system should be as low a restriction as possible. On my truck, my system will pull around 1" or so at idle and lower rpms, but at WOT and 4000 rpms on up, it will pull upwards of 5".
BTW, it's a good idea to replace the check valves that screw onto the header-mounted nipples once a year as maintenance. You shouldn't have any trouble with this system as long as you're running either no exhaust or a free-flowing exhaust system.

[dbmx66]

my muffle are going to have tubing welded through, and after the full length headers there is gonna be about 2.5 feet of pipe. is that free flowing enough?

[nxtruck]

Originally Posted by dbmx66

my muffle are going to have tubing welded through, and after the full length headers there is gonna be about 2.5 feet of pipe. is that free flowing enough?

What size exhaust tubing and collectors are you using? And what muffler are you using? IMO, if you use a good muffler, there wouldn't be much of a reason to weld pipe through them. A good, straight-thru muffler like a Dynomax or Magnaflow in the correct size wouldn't need this to be efficient.

[dbmx66]

idk for muffler yet, but there 3 inch collectors, but im looking into buy custom ones with a 3.5 inch, and its a small block btw.

[nxtruck]

IMO, if you've got 3" collectors to work with, then run a couple feet of 3" exhaust, then a good 3" muffler, and then another foot or so of straight tailpipe. This will be about as low restriction as you can get and still run mufflers. It may be a little loud in the cab, however.

[Super73]

Say I was running the pictured set up but:

Open headers at the track
3" necked down to 2.5 then through turbo mufflers for the street.

Would that be a problem?

[nxtruck]

Shaun,
I can't say for sure if the 3" - 2 1/2" transition would have a negative affect on the evac system, as I've only experimented with a 3 1/2" - 3 1/2" collector/exhaust setup. It'd be easy enough to try, however, and if it didn't work, you could always cap the collector nipples.

[Marv D]

One more thing to be cautious of,, the cheep Mr Gasket type breathers are a total POS and leak like a sieve. What vacuum your building with the exhaust flow sucks raw air from all the leaks of the breather and evacuates very little. They leak where the tube goes into the top 1/2 of the breather case, and the top 1/2, bottom 1/2 pinch seam is usually anything but air tight! The best ones I've seen were the regular ol Mopar breathers. There was a guy on evilbay for a while that was taking the stock mopar breathers and chroming them. They were pretty cheap as i remember,, like $9 each.

Another cool litle deal I found, Jeggs sells a kit to insert the tube into the exhaust / header pipe that has the right angle, bevel and ,, is threaded on one end for the normal 1/2" NPT for the A.I.R. valve, but the weld in bung and other end of this pipe is the same as a Bosch 02 sensor. Which you can get plugs for if you ever decide to dump the header evec system, OR, your 02 sensor already has a bung if you ever decide to data log A/F.

I had lots of space issues to get a evac system in the 66 but heres a shot of the exhaust system while everything was under construction. I put the evac tube in right after the cone reducing the 4" collector to 3" pipe. (all that hardware crap dumping in from the top). Just fired this pig last night (without the gushing oil leak) so haven't really seen how much vacuum it pulls. If it's enough to evacuate the slobbering small block i'm happy.

http://www.small-block-chevy.com/ima.../exhaust10.JPG

[nxtruck]

I should've posted this also: what Marv's sayin' about those cheap Mr. Gasket breathers is dead-on. They're junk, plain and simple. If you use a Moroso kit, those breathers work well, at least in my experience. You can buy 'em seperately from Jegs or Summit.
Also, the Moroso kit comes with nipples that have an angle cut groove cut into the one side of them. These type nipples seem to work better than the ones w/o the groove, at least in my experiences with them. I have tried them both and had better results with the grooved nipples.
Marv, I'd be curious to know how your system works, once you get everything up and running.

[dbmx66]

what about the jegs brand evac kit?


http://www.jegs.com/i/JEGS/555/52210/10002/-1

[nxtruck]

Personally, I would pass on that kit and just buy the Moroso kit. It already has the good breathers and nipples.

[Wild83C10]

I also have the Moroso setup and it seems to work. At idle if you pull the tube or breather out you can put a piece of paper up to it and it will hold it there with the suction.

Super73, I beleive the 3 down to 2.5" should actually work better as that type of setup should help with scavaging and with exhaust velocity.

[dbmx66]

just order the moroso kit.

[nxtruck]

Good choice. Be sure to follow the directions as to proper angle of the collector nipples. You don't necessarily have to place the nipples on the tops of the collectors like they tell you, but putting them just past the merge in the collector seems to be an important step. I put the nipples in the sides of my collectors because of space limitations and they work just fine like that.

[dbmx66]

do they have to be exactly at the collector or can they be in my actual exhaust tube, like right behing the header? or wont it work right?

[nxtruck]

Opinions vary on this. In my case, mine are located right where the primaries merge into the collector, but I've seen where others have put them in the actual pipe, like in Marv's pic above. I can only tell you what worked for me. It may take some experimentation on your part to achieve the desired results. Hopefully what I've shared with you will get you headed in the right direction.

[Marv D]

It works MUCH MUCH better to put the nipple as close to the primary tubes in the collector as you can like Chris is telling you. My mess is simply a test to see if it will work back that far, and because I had such space limitations. Eventually I will be datalogging and the 02 sensors will go there, and 'eventually' I'm sure this will have a vacuum pump. So like I said, this is just a test for now. It pulls only 2" of vacuum at 1300rpm idle sitting in the shop with a nice cool engine and exhaust system. That's pretty ineffective. Compare to nearly 6" I had with the Nova and fenderwell headers before it went to a pump.

I think we had this talk here,, maybe over on the ElCamino board... not sure. As exhaust gasses travel down the exhaust tube they cool. As it cools,,, it contracts, and looses velocity. That's why you can go from a 1-5/8" header tube,,, and 4 primaries into a 3-1/2" collector, to a 2-1/2" exhaust pipe and muffler. Think of it this way... coming out of the chamber the exhaust temps are upwards of 1300°,, by the time it reaches the back bumper you can stick your hand over the tail pipe and not pull back a bloody sttump that is char-broiled medium well. As the gasses cools, it looses velocity BIG TIME. It's loosing a lot of heat, and a lot of velocity in a very short time / pipe. So like Chris is saying... closer to the merge in the collector, the better velocity and vacuum your going to see. And that's what it's all about. Creating a vacuum to PULL the gasses out of the crankcase.

[Super73]

Originally Posted by Marv D

As the gasses cools, it looses velocity BIG TIME. It's loosing a lot of heat, and a lot of velocity in a very short time / pipe.

Little off topic here, but sort of still on, this is one of the issues a lot of people feel rear mount turbos have. Instead of using the hot gasses/velocity to spool the turbo, they relly on a little more back pressure to spin the turbo. One reason why front mounts are argued to be superior.

[dbmx66]

im just gonna weld them right into the collector. right after the primaries merge.

about the whole heat of the exhaust thing, i was planning on header wrapping the headers. doesnt that keep the heat in? there fore wouldnt it help with the evac system even more?

i dont know if that makes sense, just kinda brainstorming.

[Marv D]

DBM,, check with prople who have had wrapped headers. I've seen two sets and both were rusted dramatically . Apparently the wrap holds any moisture it may find (from washing the motor, to splash from the waterbox) and it really does a number on the headers. But that may just be the luck of the few sets I've seen wrapped. I'd rather see them coated inside and out than the wrap.

[dbmx66]

well mine are already cermanic coated heddmens.

but i didnt know if the wrap would help at all.

[69trk]

would this evac system help keep my nitrous big block plugs cleaner? Right now all i have is breathers. Also, will it help with oil loss...