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Finished up a refresh on a Rocket 350. Valve job, cam, rockers, lifters, springs, intake, carb, pushrods basically the entire top end.
So we adjusted the valves and everything ran great after break in.
Started smoking out the exhaust pretty heavily. Couldn’t find any tell tale signs.
Removed the pcv valve and it almost immediately stopped. Ran it around the block and it’s never run better. Put the pcv back on and it started smoking halfway down the street.
It was a new pcv so I don’t think it’s bad. My friend says to just run it with two breathers.
I’m not opposed to that but I didn’t want to do that and overlook whatever’s causing it to smoke. Plus I figured it’d make a mess under the hood didn’t want to be huffing in fumes at a light.
I don’t think it’s a stuck valve or bad rings etc. as it ran great with the pcv off.
In that case your PCV valve is too restricting. Think about this. No PCV valve = no smoke, w/ PCV valve = smoke. Did you hook up a vacuum gauge to validate the vacuum?
No I didn't hook up a gauge. I can do that tomorrow morning and double check. Pretty sure its pulling a vacuum I don't think it would smoke if it wasn't.
With the PCV valve REMOVED from the valve cover but ATTACHED to the carburetor vacuum hose, validate vacuum after the PCV valve. Are you pulling a vacuum THROUGH the PCV valve?
Okay, I'll do that first thing in morning and confirm this.
With the PCV valve REMOVED from the valve cover but ATTACHED to the carburetor vacuum hose, validate vacuum after the PCV valve. Are you pulling a vacuum THROUGH the PCV valve?
Just texted my friend. He said that's the first thing he did. Definitely pulling vacuum through the valve.
You don’t think it would smoke if it wasn’t pulling a vacuum is counter to what the vacuum applied to the PCV valve is supposed to do. You need to pull a vacuum through the PCV valve and into the carburetor. It sounds like you are NOT pulling a vacuum. Sometimes there is a piece of metal in PCV valves when shipped - don’t ask me why, to keep the screen from falling out? Anyways, a bunch of vendors sell various PCV valve replacements. Make certain the PCV valve is not closed off for some reason. New stuff does not equate to a proper working product. Poor products do occur.
I'll double check that but my buddy said it was definitely pulling a vacuum. I think I'll buy a new one and just compare it. See if I'm getting the same results.Maybe its just not working as good as it should.
Well, if that’s the case, rather than removing the PCV valve, keep the PCV valve inserted into the valve cover and just remove the vacuum hose from the carburetor. The effect should be the same as removing the PCV valve. Does it smoke or not smoke in this configuration?
Okay that's a good idea. I should have thought of that.
What valve covers does the engine have?
Do those valve covers have the baffle under the PCV valve?
Just wondering if there is oil being sucked into the PCV due to a baffle issue.
They're taller Edlebrock covers. Had to go with taller covers to fit the rocker studs for Harland rockers. There is a baffle but its a much smaller baffle than stock covers.
Once you establish it is in fact the PCV thats causing the smoke, try swapping it to the other valve cover and see if maybe it would be out of the oil path.
Just wondering if there is oil being sucked into the PCV due to a baffle issue.
Kenneth is on the case!
This sounds like you have an inadequate PCV baffle. One possibility for remediation is to stuff the existing (small baffle) with coarse steel wool. In this case you must fabricate a screen that will enclose the steel wool to prevent it migrating.
Another possibility is to use the standard Olds valve cover breather and adapt the PCV to pull through that breather. That way you will have the steel wool already encapsulated.
Okay. Got started this morning and first thing I noticed was that the baffles are different on each valve cover. I had it in the one up top and I’m going to move it to the bottom one and see how that goes. I’m thinking the wider baffle may help.
I got sidetracked with adjusting the valves. I’m still not where I want to be so it’ll be the weekend before I can get back on it and take a closer look at the pcv issue.
I did buy a new pcv and there is more vacuum being pulled through the new one vs the old. So definitely the old one has some kind of minor obstruction.
Last edited by CoastalRyan; February 10th, 2021 at 05:27 PM.
I fixed it. A few of the other forums I'm on are set up so you can copy an image off your phone and paste in your reply. Didn't know I couldn't do that here.
Thanks for that. Looks interesting. It’ll be a few days before I get back on it but if switching the covers and using a new pcv doesn’t work I’ll look at going that route.
I was wondering/ thinking about the PVC vacuum location as it relates to even and equal cylinder AF ratios.
if the PVC draws from the large full vacuum port on the carb, or efi, then i assume all the cylinders have the same influence from the PCV system.
But if the vacuum is drawn from a single runner, or back part of the intake, can thar mean that the AF mixture into that individual cylinder, or group of cylinders, is different and leaner than the other cylinders?
Thank
February 9th, 2021, 05:51 PM
