PCV and valve cover info needed |
Post Reply |
Author | |
78mustang
Newbie Joined: April-27-2006 Location: United States Status: Offline Points: 9 |
Post Options
Thanks(0)
Posted: April-30-2006 at 7:35pm |
1978 Commander 302 CCW w/ aftermarket (sleezy chrome) valve covers on my boat. On one side I have a PCV going into the flame arrestor (probably needs manifold (not ported) vacuum?) and the other side has a valve cover breather, one of the filtered kind. Sumabich stinks like buring oil and there is blowby coming out of the breather. I run the blower a LOT and I want to square this away.
Can somebody please tell me what goes where? A pic of the appropriate configuration would be much appreciated. I'll be installing a new distributor Wed or Thu and want to fix this at the same time. thanks, /s/sMTM |
|
79nautique
Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872 |
Post Options
Thanks(0)
|
there should be a port on the base of the carb (depending on the brand) or the spacer plate under the carb for the pvc. It is the cause of the smell and the blow-by, if you don't have a spacer plate and it's a holley get one.
|
|
David F
Platinum Member Joined: June-11-2004 Location: United States Status: Offline Points: 1770 |
Post Options
Thanks(0)
|
...and the breather goes to the spark arrestor.
|
|
78mustang
Newbie Joined: April-27-2006 Location: United States Status: Offline Points: 9 |
Post Options
Thanks(0)
|
Edelbrock marine carb, no vacuum port on spacer. I put a barb on the intake where a plug was, just aft of carb and plumbed a PCV valve to that barb. Other valve cover has an elbow plumbed to flame arrestor.
I don't grasp how I have not introduced a huge vacuum leak into the whole program via manifold vacuum to PCV valve. It's been a long time since my wrench turning days but it seems as I now have a nice 3/8" vacuum leak. |
|
jameski
Senior Member Joined: May-18-2004 Location: United States Status: Offline Points: 368 |
Post Options
Thanks(0)
|
You are basically correct; you HAVE introduce a big vacuum leak, but that is the correct way to plumb it.
Now, you will need to do some idle adjustments to your carb and possibly your timing also. |
|
David F
Platinum Member Joined: June-11-2004 Location: United States Status: Offline Points: 1770 |
Post Options
Thanks(0)
|
78mustang. Be carefull. If you used a vacuum source from anywhere other than just below the carburetor then you risk leaning out one cylinder.
|
|
78mustang
Newbie Joined: April-27-2006 Location: United States Status: Offline Points: 9 |
Post Options
Thanks(0)
|
Oh I will surely be re-visiting the timing just after I stab the new distributor. I'll carry the vacuum gauge and tach and timing light down to the lift and tweak away. And a can of carb cleaner and a shade tree stethescope (peice of fuel line stuck to ear) to check for vacuum leaks around the new plumbing.
I'll go take a look at the "donor" motor on my engine stand and see where the vacuum port goes in the intake. It's a common port that drives brake booster and vacuum accumulator cannister on automotive apps. Leaning out a cyl SHOULD not be a prob. I was reading and researching and the PCV valve lets about 3 cfm through @ idle and around double that at cruise. With that said -- it's small vacuum leak and it is controlled, I assume that won't degrade idle nor driveablity. Unlike a bad gasket, cracked vacuum line or such. |
|
79nautique
Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872 |
Post Options
Thanks(0)
|
it makes no difference which one you use it's going to have the same effect, being correctly plumbed.
|
|
jameski
Senior Member Joined: May-18-2004 Location: United States Status: Offline Points: 368 |
Post Options
Thanks(0)
|
Reminds me of the old days... We had a '56 Plymoth Belvedere (I think it was a 383). One valve cover had a sealed oil filler cap, the other had a 1" steel pipe that vented onto the ground.
No vacuum leaks on that baby! |
|
JEFF KOSTIS
Gold Member Joined: April-19-2005 Location: United States Status: Offline Points: 817 |
Post Options
Thanks(0)
|
The 74 OMC 225 (Chevy 307) doesnt have a PCV, instead, 90 degree elbows are used on each valve cover that run via a hose to the flame arrestor. The 76 PCM (Ford 302) has the PCV. Can you figure??
Also, the PCV valve is in fact a valve that closes at high vacuum (idle) and opens at low vacuum(WOT). At idle it still sucks a little, but this is how it regulates the air into the intake. If its not working properly, one symtom is you will have major idle issues. Jeff... |
|
abolton
Groupie Joined: September-07-2005 Location: United States Status: Offline Points: 81 |
Post Options
Thanks(0)
|
Ok I am having idle issues. I just put on some killer Ford racing valve covers and a Edlbrock performer manifold and a rebuilt 4160 Ford blue carb on my 78SN. It looks sweet, I did not re-use my PVC valve, but I did plum the breather vent to the carb spacer plate at the rear. My idle won't hold under 1200 rpm and I can't think that my carb guy screwed up the float adjustment. Do you that not having the PVC valve there is causing my idle problems, or do I go after the float adj?
|
|
ABE
|
|
79nautique
Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872 |
Post Options
Thanks(0)
|
the float will not cause a high idle your problem is you have created a hugh vaccum leak by plumbing the breather to the spacer plate, remove the breather install a PCV valve and plumb it to the carb spacer problem solve. then you will have to go back and readjust the carb since you've messed with it chasing the wrong problem.
|
|
abolton
Groupie Joined: September-07-2005 Location: United States Status: Offline Points: 81 |
Post Options
Thanks(0)
|
Ok re-installed the PVC valve and re-adjusted the carb screws back. Still won't hold idle under 1200. Looking for other leaks tonight, I'll keep ya posted...
|
|
ABE
|
|
79nautique
Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872 |
Post Options
Thanks(0)
|
have you tried adjusting the idle screw? have you tried removing the throttle cable from the carb to make sure it's adjusted correctly and not pulling the carb of the base idle curcuit? Disconnect the throttle cable at the carb and then make your adjustments to the carb.
post a picture of your engine so we can see how you have thing plumbed, use photobuck.com to post the picture and the tree looking icon above the message window. |
|
abolton
Groupie Joined: September-07-2005 Location: United States Status: Offline Points: 81 |
Post Options
Thanks(0)
|
PVC was the problem idle is fixed now I have to go after the same hesitation problem out of the hole I had last year b4 I had the carb rebuilt.
|
|
ABE
|
|
79nautique
Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872 |
Post Options
Thanks(0)
|
adjust the accel pump and that should take care of it.
|
|
abolton
Groupie Joined: September-07-2005 Location: United States Status: Offline Points: 81 |
Post Options
Thanks(0)
|
Still had problems so it went back to the carb guy, after talking with him, he realized I did not have a exhaust heat riser tube. Da so that is where he said my vac leak is, he pluged it and I pick it up Sat. Car guys don't have a clue about boats.
|
|
ABE
|
|
Post Reply | |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |