Hot weather issues

[Sixracer]

I have been doing some work on the Silicone flaps that seal the baffels to the cowl. O-300D in a 1961 172B I have sealed up all leakage in the back baffel. Plug wire holes- lines, ect.... I also sealed the case to back baffel clearances with silicone. I used Permatax Ultra gray. I bought some sheet silicone rubber and am cutting out wider, better fitting, flaps to seal the cowl to the engine baffels. I'm of the opinion that the top chamber needs to be sealed better to cool the cylinders. If they stay cool the oil that migrates through them will not get as hot. In our race engines the oil temp is directly related to cylinder temps. I question those "blast tubes". One of mine just points to, nothing in the lower cowl area and the one on the left side of the engine points to the area where the temp probe fits in the case. I'm thinking this give a fales oil temp. I might do a little testing by stopping up the blast tubes with rubber stoppers and make a few T&G's and then remove the stoppers. A before and after of the oil temp might be interesting. More info after I finish the job friday night and do a little pattern work on Sunday. Thought.....I've been wondering if one or both of those "Blast Tubes" shouldn't be pointed to the area of the Generator to keep it cool... ???

[edbooth]

I question those "blast tubes".

As noted in past responses, and frequently discussed by past club patriarch's, the conclusion has been that the blast tubes main function was to help cool the oil temp sensor.

[jrenwick]

Both of the oil cooling tubes should be pointed at the area where the temperature probe is; that's where Cessna put them. I think it's a myth that those tubes only cool the probe. All of the oil passes through a narrow place in the wall of the accessory case at that point, and it's an ideal place to put additional cooling. The probe is cooled because the oil around it is being cooled.

My last 170 had two oil temperature probes. One was the original one, and the second was an EI digital gauge with the probe mounted in an Oberg oil filter. They both produced consistent readings, although if they were off by a few degrees I wouldn't have known it because the original gauge doesn't have numbers on it. But judging by the position of the needle with respect to the red line, I'd say any differences were negligible. Those tubes actually help cool the oil, not "just the probe."

[HA]

somebody, long before my time with this airplane, made the screw holes on the blast tube flanges into slots so that you can turn them a bit to aim them better. I've always figured the tubes were a poor man's oil cooler, just like the hole and baffling in the front of the cowl to send air across the sump.

[Sixracer]

Thanks, guys. That is very good info for me. It tells me I have both blast tubes not loctaed correctly. the left side is off a little, but the right side is just "out in the empty space" I guess I should have done a search of blast tubes in this forum before posing a question. .. sorry, new guy mistake. One note as to the mounting of the tubes. Mine have slots in them, too, but they look factory. Very nicely machined if done after Cessna assy/MFg. I have a F&M filter kit to install. Guess I had better study those blast tube locations real good. Thinking about the location of my blast tubes I might need to see if they were relocated for a F&M filter kit. Hummm!! Someone might have removed it (F&M) and not put the tubes back in their stock location. I did notice some different attchement fasteners on the left and right blast tube mounts. Interesting. Might have found some of my heating concerns with out touching those baffels.
Thanks, for the info. It is appreciated and I will use it wisely.
Adg

[Sixracer]

Well here is the scoop on my blast tubes. Left side is installed correctly, pointing as stated in the thread.
The rt side was pointing out into the wide open space of the lower cowl. When I removed it I noticed some witness marks from another set of screws put in the slots. When I rotated it to line up with those old screw marks the tube was laying near the rear of the case beside the big nut for the sump screen. Go figure... installed wrong.
Thanks guys for the help. If I hadn't been told which direction to go with it I would have been stumbling around trying to figure it out... Good info. Thanks.
Adg

[GAHorn]

Adding to previous comments/observations: Don't forget to check your exhaust system for hot gases blowing onto your pushrod tube/housings from leaky joints, clamps, and flange-gaskets. Those are return-pathways for oil draining from the rocker-boxes to the sump...and hot exhaust blowing on them increases oil temperatures.