Smoke out of breather catch tank?

[DesmoDork]

Perhaps someone could shed some light on this. 1600 Cross Flow rebuilt with big valves, forged pistons, new everything. Car would missfire when giving it full boot but ran great around town. Took it to chassis dyno and get the carbs jetted and they said the dizzy was suspect, the advance was not consistent. Changed it out to a new Pertronics unit and now revs happily all the way. Awesome.:cool:

However, a new issue has appeared.

1. When revving up to 5k range and holding it, the engine starts to lose power after about 5 seconds and smoke starts to come out the crankcase breather oil catch tank. It clears up in about 30 seconds. Very disconcerting. I'm hoping timing related. Maybe not enough advance? :p

Confused noob with enough info to be dangerous. :confused:

[Doug Liedblad]

Do you drop the RPM for the smoke to clear up or are you still holding it at > 5000 rpm?

Doug - not a Crossflow expert.

[GWise]

Is this while driving? Can you actually see the smoke out of the breather? Do you have the block breather (this is a little box under your carbs)

X-flow's do tend to give out oily fumes - if it's excessive, you may be seeing combustion gasses the crankcase. In this case, the engine needs rebuilding. - It's pretty normal to have some though. My crossflow does tend to put out a fair amount of oil into the catch tank and gives oily fumes.

This should explain a bit how engine breathing systems work. http://www.burtonpower.com/technical...er_system.aspx

I'm not sure what's causing your loss of power though.

[DesmoDork]

I have to back off for it to clear up. The smoke starts to come out the louvers and when I stopped and checked it and it was defiantely coming out the crankcase vent catch tank.

Thanks for the Burton link Doug. :) Very informative!

I advanced the timing. It is good around town but pings badly when you put the boot in. :sad: Now on full advance the timing mark lines up with the furthest left mark, which should be about 12 degress...I think.

[Doug Liedblad]

That was GWISE who posted the link.

He too has a crossflow and I am sure knows more than I.

Doug

[GWise]

I've never been much a fan of the way ford did things with the PCV valve. Do you wind up with a considerable amount of oil in your catch tank too?

I wonder if your PCV valve may be restricting airflow and causing a build up of pressure. One thing you may want to try is buying a new breather box. Otherwise, I feel that losing power may be unrelated.

Another thing you could do is drill and tap a couple holes in your rocker cover (if you have the ally one) to mount NPT to hose barb fitting. You'll run a hose from the PCV valve (you can delete the breather box in this case if you like) up to the crankcase and another down to the catch tank. You'll want to put these as high as possible (at least the one running to the catch tank) and make sure nothing interferes with moving pieces.

The timing mark is indeed the mark closest to 12". Have you checked where your mark is when the engine is at TDC?

Have you contacted Rich about this? He built your engine correct? He's a great guy who will go the extra mile. He probably knows more about the subject than I do.

Edit: Also, how full do you fill the crankcase? Do you tend to overfill it due to oil surge?

[DesmoDork]

I've never been much a fan of the way ford did things with the PCV valve. Do you wind up with a considerable amount of oil in your
Have you contacted Rich about this? He built your engine correct? He's a great guy who will go the extra mile. He probably knows more about the subject than I do.

I have been speaking to Richard, he is great and is always available for questions. It seems to be a combination of multiple issues and being able to track down the "most likely"...always challenging. His skills tend toward the assembly side, where someone else might lean toward the tuning side. I may try Huffaker Engineering. Jim is their cross flow guy and he had some thoughts on the distributor. I'm still going down the "timing issue" path...not sure but it is at least worth talking about....

I had not thought about the PCV valve....hmmm. Interesting. I don't get any oil in the catch tank.

[DesmoDork]

So it turns out there is detonation at high rpm and that is heating up the pistons and burning the oil on the underside of the piston. We can't seem to get rid of the issue no matter how we adjust the dizzy. The timing currently is at 30 degrees advance total at 2500 rpm and we checked TDC is at zero...

Not sure what is next. Maybe a beer

[slomove]

Not familiar with dizzies anymore but if it is already 30 degrees at 2500 how much more is it at 5000+ ? I suppose the inertia mechanism takes it out even further?

I am running with ECU the advance 30 degrees at WOT and full speed. Maybe you just have too much advance?

Other obvious question....is the fuel grade compatible with the compression of your engine?

Gert

[Doug Liedblad]

Small amounts of oil in the compression chamber will cause severe detonation as well. Generally reserved for diesels.

If the pistons are heating so much on the bottom, what shape are the tops in???

Doug and not a crossflow expert.

[sevenhead]

Your forged pistons may be providing a bit of insurance before something catastrophic happens. The cast pistons would not stand for much detonation. Detonation is usually a low speed/high load phenomenon. Since your troubles started after changing to the Pertronix that is where I would start. I don't believe the Pertronix unit is user adjustable. It is set at the factory and all you can do is change the static setting. To change the total advance and the advance curve you need to change the internal springs.
The advance curve may not suit your particular engine. Just as an aside, Formula Ford engines run 38-40 degrees total advance and they have 9.3:1 CR and run race gas.

Have you pulled the plugs to look for overheating? Are they the correct heat range?
How is your oil consumption?
What is the mileage on the rebuild and how was it broken in?
Were the carbs rejetted using the new disributor? What criteria was used for the changes?

I could go on and on but that's the trouble with long distance troubleshooting. I have a more questions than you probably have answers;)

Lee