- May 20, 2011
- Reaction score
In response to some of the questions posed in the CCV catch can thread I went looking for this information which is too good not to share here.
Here is a relatively cheap way I found to build your own Ford blow-by measurement tool.
Here is the actual Ford tool that connects to the engine as well as the magnehelic gauge, in the Ford gauge bar, that reads the pressure.
It is basically just an open pipe that connects to the oil fill hole in the valve cover. On the top end of the tool is a .40" diameter hole and on the side is a fitting to connect a hose that goes to the pressure gauge.
The cost of the Ford stand pipe and adapter that connects it to the engine is over $100. I couldn't justify that so, I built my own out of an old Ford oil fill cap and some PVC pipe. The first step was to take apart the oil fill cap and drill out the bottom part that screws into the valve cover. This hole needs to be larger than .40". I found that 1 1/4" PVC pipe fits nicely into an existing groove in the oil fill cap. After cutting the pipe to ±6.0" in length, I drilled and tapped an 1/8" pipe thread hole into the side of the pipe. I then installed an 1/8" pipe to hose barb fitting that will connect to the pressure gauge hose. Once that was done, I cleaned the cap really well and glued the piece of pipe into the groove in the cap using super glue. The last piece is the cap for the pipe with the required .40" hole drilled in it. I found the magnehelic gauge on eBay for under $20. There was a pretty wide selection with quite a few available when I bought mine. Another option would be to build your own u-tube manometer. http://www.komar.org/faq/manometer/
If you go the magnehelic gauge route, it will have four 1/8" female pipe thread ports in it. Two for high pressure and two for low pressure. One of each will be on the side of the gauge and the other set is on the back. You want to plug one of the high and one of the low pressure ports. Then connect the hose fitting to the remaining high pressure port while leaving the remaining low pressure port open to atmosphere. You can connect to either the side or back high pressure port - whichever works better for your setup.
To test blow-by, ensure engine is fully warmed up and plug or pinch off the CCV. Hold engine at near WOT in park and take the blow-by reading. Results will be in inches of water column. Less than 4" of H2O is a pass for the 7.3.
I didn't glue the cap onto the pipe of mine as I wanted to also use this setup to measure how much restriction my CCV mod was causing. I can do this by installing a cap with no hole in it onto the pipe and then run the pressure hose into the cab to monitor crankcase pressure while driving (with the CCV open). Another reason to not glue the cap on is that I think the 6.0 requires a smaller orifice than the .40" used on the 7.3. Having two caps, one for each engine, would allow the tool to easily be used on both engines. Also, the pressures we are talking about here are so small that I don't think there is any danger of the caps ever blowing off. It takes 27" of H2O to reach 1 psig.
I had a PM request for more pictures of this, so I thought I'd add them here.
This shows the back of the magnehelic gauge and what to do with all the different holes.
Are you asking for the crankcase pressure differences between the CCV routed to the intake, in the stock configuration, vs an open road draft tube out the bottom of the truck?
Assuming yes, I essentially saw the pressure cut in half by removing the CCV from the intake. It's been a while, but it went from something like .4" H2O to .2" H2O.
I had installed a CCV catch can identical to this one when I first bought the truck. It basically routes the CCV gases into a large diameter pipe filled with kitchen scrubber pads and then routes it back into the intake in the stock location. I still had some oil getting past the scrubber pads and into the intake and this is what led to my building this tool - I figured I had excessive blowby. Anyway, with this CCV catch can installed and a closed cap (one without a hole drilled in it) installed on the blowby tool I measured a max crankcase pressure of around .4" H2O.
I then removed all the scrubber pads, essentially returning the CCV to stock, and measured .4" H2O again.
Next, I pulled the inlet hose off the CCV catch can and left it hang out the bottom of the truck right behind the transfer case. I measured .2" of H2O and the truck seemed to run noticeably better. That's where I still have it today.
That .2" H2O drop in pressure is equal to .007psi. I wouldn't think that would make a difference, but it did on mine.
Also, I'm sure this all depends on how much engine blowby is present to begin with. Mine is 2.5" H2O.
so the top of the pipe should have a hole in it?
Correct, .40" diameter for the 7.3.