I6 258 owners: how many Pcv valves do you use? - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 03-22-2001, 09:06 PM
Posts: n/a
I6 258 owners: how many Pcv valves do you use?

I know this has been brought before, at least the pro's and con's about the number of PCV valves to run on a 258 I6. But I'm curious how many of you are useing two?? . For example, I'm only using one which is in the forward grommet hole (closest to the radiator) and I'm running a breather cap (normally used on a older Ford 6 cyclinder.) in the back. The reason why I'm asking is, I have seen a few I6's that have two PCV's hooked up. In talking about this about it with some friends, a couple of them mentioned that 2 was a normal setup. Anyone know if thats correct? I dont think it is, but I dont for sure.

1. If you are currently using two PCV' valves, How are they setup?
When I dropped the 258 I6 in I'm using now, before I changed the setup, the motor came with two PCV valves, The forward PCV had a vacuum line that went to the bottom of the air cleaner. The rear PCV linked in at the manifold, next to the EGR valve. I drove it like that for awhile but started finding a lot of "blowby" into the air cleaner, not to mention some slight dieseling.

Now that I shifted to one PCV valve and the breather cap, my motor likes the arrangement a lot better....but it hasnt eliminated the "blowby" persay.

2. If you are only using one PCV valve,,,what did you do to eliminate the 2nd valve, and how are you running your vacuum lines?
I'm curious about this, because I dont really like the idea of a breather cap,,,and I'd like to find a better setup. However, until I do...I'll keep the cap.
It certainly helps my six's performance.

Any info you fellows could share would be appreciated....thanks

Sponsored Links
post #2 of (permalink) Old 03-22-2001, 09:14 PM
Join Date: Jan 2000
Posts: 573
Thanks: 0
Thanked 0 Times in 0 Posts
Re: I6 258 owners: how many Pcv valves do you use?

I run one, and it's in the back grommet in the valve cover. The front grommet I run a line to the air filter assembly. It used to go to one of those little filter thingys on the inside of the filter housing, but since I switched to a K&N it just runs to the 3/4" nipple in the bottom of the lower housing. I tried eliminating the one to the air filter and got oil all over everywhere. It must need the bit of vacuum that's provided somehow.


greencj7 is offline  
post #3 of (permalink) Old 03-22-2001, 09:45 PM
Posts: n/a
Re: I6 258 owners: how many Pcv valves do you use?

Hmm....guess I've never heard about the possibility of running two different PCV valves. Isn't this board great...learn something new all the time [img]/wwwthreads_images/icons/smile.gif[/img]. My current setup has the PCV in the front grommet of the valve cover, with a chrome breather cap occupying the rear-most grommet.


Sponsored Links
post #4 of (permalink) Old 03-22-2001, 10:51 PM
Posts: n/a
Re: I6 258 owners: how many Pcv valves do you use?

I never thought about it before... I have only one that run from the front to the air filter assembly. Need to check where the hose in the back runs to... I'll get back to you guys with this one, now I'm really curious...


Rusty beat-up old junker with many problems.
post #5 of (permalink) Old 03-23-2001, 12:01 AM
Join Date: Jan 2001
Location: GA, USA
Posts: 773
Thanks: 0
Thanked 0 Times in 0 Posts
Re: I6 258 owners: how many Pcv valves do you use?

I've only seen one on any 258s. I think the standard setup is for the PCV to be in the front grommet and in the rear grommet a line to the air cleaner. I'm not sure about this, but doesen't the air moving through PCV hose pull air through the valve and then through the rear line from the air cleaner.


BMB is offline  
post #6 of (permalink) Old 03-23-2001, 12:20 AM
Join Date: Aug 2000
Posts: 455
Thanks: 0
Thanked 0 Times in 0 Posts
Re: I6 258 owners: how many Pcv valves do you use?

In the front hole I have the PCV valve and in the back hole I have a hose that runs to the air cleaner on my Weber.

My Jeep is a work in progress, Happy Trails
Woodsrider is offline  
post #7 of (permalink) Old 03-23-2001, 12:55 AM
Join Date: Oct 2000
Posts: 418
Thanks: 0
Thanked 0 Times in 0 Posts
Re: I6 258 owners: how many Pcv valves do you use?

hey green cj when you switched to a k&n filter did you change the air cleaner assembly or just put a k/n in the factory cleaner housing? I want to put an open 12 or 14" cleaner on my 258 but not sure what to get?

JeepinDoberman is offline  
post #8 of (permalink) Old 03-23-2001, 12:59 AM
Join Date: Sep 1999
Posts: 873
Thanks: 0
Thanked 1 Time in 1 Post
Re: I6 258 owners: how many Pcv valves do you use?

Here's the way i think it is supposed to work. The FRONT grommet contains the pcv valve with a hose that goes to the base of the carb. The REAR Grommet is supposed to have a plastic elbow connected to a vacuum hose that goes to the air cleaner.

The hose coming from the air cleaner to the rear grommet is supposed to be for fresh air to be drawn into the crankcase. The PCV valve on the front of the valve cover is a one way check valve that only allows crankcase gasses to be sucked out.
I would think that if you have two PCV valves, then you have two one-way check valves that allow gasses to escape, but not fresh air to be drawn in. I don't know if that is a bad thing or not, but it doesn't fit with the original design of the system.
I use the PCV valve in the front and a breather in the back. I get a little oil residue on my valve cover, but not enough to worry about. If everything in your engine is working properly, very little oil should come out of the breather.

Hope this was helpful.

Dan 84 CJ-7,Weber,HEI. 95 ZJ,V8. http://netnow.micron.net/~wdohrn/
Dan 84 CJ-7 is offline  
post #9 of (permalink) Old 03-23-2001, 02:25 PM
Posts: n/a
Re: I6 258 owners: how many Pcv valves do you use?

Dan84 has it right. Front is PCV, back is for fresh air to go into the valve cover. The reason for the blow-by is too many fumes and pressure from them in the valve cover. This is often caused by bad rings. Putting a PCV on the back grommet with the blow-by would just suck oil into the carb, same as keeping it hooked up to the air cleaner. The cap is a good idea until the source of the blow-by is found and corrected.

'88 Sahara, 4.2, auto.
post #10 of (permalink) Old 03-23-2001, 02:39 PM
Posts: n/a
Re: I6 258 owners: how many Pcv valves do you use?

I am running stock setup on an 88 Wrangler 258 with BBD carb . The front valve cover hole /grommet has the PCV valve with a vac hose that connects to intake manifold vac to draw off the crankcase vapors and burn them in the cylinders. The rear hole/ grommet has a hose connected to the air cleaner / breather filter . This is to allow filtered air from the air box to enter the valve cover and permit thereby permit fresh air circulation/input as polluted air is pulled away from the front PCV hole. Unfortunately, I am suffering from oil blowby back into the air box which is choking both the tiny air breather filter and the large air box filter . I recently tried a product called Lucas Brand Oil Stabilizer in the crankcase. It resembles a thick , heavy weight oil which took forever to pour into the crankcase valve cover. I am not sure if it is helping reduce the oil blowby somewhat as it claims to do . My local auto parts guy suggested it at $6 for one quart. I also tried Restore Brand to reduce oil blowby . Don't think that helped at all. I am trying to avoid a rebuild.

Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome