The Stovebolt Site Forums The Shop Area Engine Shop Poor crankcase ventilation - Update #2

What are the symptoms of poor ventilation? What effect would it have on engine performance?

Thanks

"Poor ventilation", as in, the crankcase is sealed (no open connection to the atmosphere)?
Oil all over the place, every gasket leaks, smoke pours out of the dipstick tube.
If the case is ventilated but the pressure is still high, it's probably time for new rings.

Poor as in current draft tube possibly clogged. How would it effect performance?
New points, plugs, cap, wires, coil. Checked and adjusted timing.
Truck runs well till a couple miles down the road at 45 MPH. Then it seems to bog down, cant maintain speed. Oil pressure and temp remains good. Have to baby it back home.

That's not a ventilation problem- - - -it's a clogged exhaust system. Try loosening the exhaust pipe flange at the manifold 1/2" or so and do a test drive. Another symptom will be an inability to maintain good intake manifold vacuum at steady throttle cruise.
Jerry

A quick look at the butterfly in the exhaust manifold might be in order. It should move and open when warm. Take a look at the Manifold Heat Valve.
http://chevy.oldcarmanualproject.com/shop/1955truck2/55ctsm0620.htm

Thanks for the suggestions. I will check it out and report back.

Also it this doesn't work, check float level setting in carb as well. Best of luck

Loosened exhaust pipe at manifold. No apparent change. Actually cut off muffler to eliminate that as a possibility. Turns out it was a straight through muffler with baffles/louvers lining the tube. It was clear. Rechecked spark plug gaps as my son-in-law did those. They were set between .04 and .045. Set to .035. Adjusted the jet on the carb 1/2 turn out. Took it for a drive. Still starts bogging down after a couple miles at 45 mph. Sounds like some of the cylinders aren't firing. It seems to run fine just driving around the neighborhood.
The butterfly is stuck in the closed position to the intake.
Any ideas appreciated.

Thank you

That, " The butterfly is stuck in the closed position to the intake." is what you need to address. Try this post for ideas and tips: https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=850512
Some good stuff. The engine can not breath with the butterfly closed. So it warms up and goes bad. When that is working, it warms up(good for gas mileage, and drive-ability), then opens(good for continued performance). There are other posts as well. Use the search function for more.

Found the problem. The butterfly is loose on the shaft and just hangs partially open all the time.
It was not welded to the shaft, looks like the shaft just slipped through the middle to be held by the metal folded over the shaft. I would like to just secure it in place in the proper position for a warm engine. It doesn't normally get that cold here in Central Texas, and I wouldn't be driving it then anyway. Is it possible to drill through cast iron and just secure it with a screw? Any other ideas?

Just want to say how much I appreciate all the help.

Thanks again.
Jeff