Windshield Wiper Tee

Bob_C · Post by **Bob_C** » Wed Jan 11, 2006 8:43 pm

Quick question. I was reading something about M38s having a .040 restrictor in the windshield wiper / distributor tee right below the exhaust manifold. Does the same apply for the M38A1 / F-Head? I havent ran my engine under load or anything yet, just let it idle for a few moments about once a week to keep the oil on the parts -- and havent noticed anything happening, even when I push the throttle a little bit. I only have a standard tee there.

What is the purpose of it as well?

Forgive my questions, I'm not 100% up on distributor mechanics.

BobW · Post by **BobW** » Wed Jan 11, 2006 9:06 pm

The A1 should also have the special restrictor fitting in the Tee. It lets a small amount of air circulate through the distributor. Without the restriction too much air will circulate and it becomes a vacuum leak. A vacuum leak usually shows up as low speed/idle problem.

Bob_C · Post by **Bob_C** » Wed Jan 11, 2006 10:12 pm

Thanks Bob.

Havent seen any signs of that. But I will definitally put it on. I remember reading something about buying a tee then drilling it out. What was this product number again?

Much thanks,
Bob

BobW · Post by **BobW** » Thu Jan 12, 2006 5:09 pm

This is what it looks like on the M38. The A1 will have different shaped lines but otherwise it's the same. The distributor line screws into the special fitting on the left. The wiper hose goes to the line on top.

The restriction is not in the wiper Tee. It is in a special connector that screws into the tee before the distributor line. It is hard to find in the parts book because there are some omissions. The best place to look is TM 9-8015-1, Engine and Clutch, 1954. Pp 151 "The 3/16 inch special connector is used in the distributor vent line to restrict the distributor vent line to 0.040 inch." The illustration on pp 150 shows the special connector as part C. The arrow doesn't exactly go to the connnector but it's close. The part number is "Connector, 3/16", inv flared tube, special - WO-802265". In the parts book (ORD9 SNL G758 sept 1951) this connector is missing from the illustration in group 0304.5 but the part is listed on pp 87. The parts description doesn't say anything about it being a special fitting. The following link shows how to make up the special fitting.
http://www.cj3a.info/sibling/m38vent/vent3.htm

The wiper tee is not exactly a normal tee fitting. It is in group 2202 with the wipers. Part number 178910 is "TEE, flared tube, inverted, 1/4 tube, 1/8 female pipe side (distributor vent tube)". The two ends are 1/4 inverted flare fittings for the vacuum line from the vacuum pump and the line that goes to the wipers. The center fitting is 1/8" pipe thread so it requires the special fitting to adapt it (and restrict it) to 3/16" inverted flare for the distributor line. This tee is a Weatherhead fitting number 652x4, 1/4 tube 1/8 pipe Female Branch Tee.

The A1 vent system is very similar to the M38 vent system. I posted the M38 underwater ventilation system article on my new web site here
http://www.cj3a.info/sibling/m38vent/vent.htm

Post by **wesk** » Thu Jan 12, 2006 7:40 pm

Hey Bob did you solo in that 150?

Bob_C · Post by **Bob_C** » Thu Jan 12, 2006 8:39 pm

Hey Wes,

I most certainly did!

I started working towards my pilots license in July-ish of 2004, when I was 15. Then, on my 16th birthday, August 18, 04, I soloed with about 8 hours of instruction. Did a couple of cross countrys during the remainder of the summer. School started and stuff, so every couple of weeks, I would go up just to poke a hole in the sky for an hour or two. By the time school let out, I only had 25 hours or so.

July of 2005 I started really working at it again. I knocked out all of the requirements pretty quickly. Infact, I was just squeaking by. I had basically the minimum hours for everything.

Got my written out of the way in July too. Wasn't as bad as I thouht it would be, but I hate the "legal-speak" the FAA writes everything in.

Then, on August 17th, 05 -- my 17th birthday, I had my checkride. The examiner was a good guy, I liked him. He was not a power hungry schmuck like some of them can be. He was very detailed oriented though. After about only an hour - hour and a half of the oral part of the test, I preflighted the airplane and we went off. An hour later, we landed and told me congrats -- and I got my Private Pilot VFR Certificate! I had only 41 hours before I went for my checkride, just made it over the 40hour minimum.

Haven't gone flying a whole lot recntly. I try to go up every three weeks or so. But with me trying to funnel my money towards my M38A1 project, and with 100LL AVGAS being so darn expensive (plus the $65/hour for flying), I find it hard to go up any more than that.

I would have a little more incentive if one of my friends were brave enough to go up with me

. Or at least, if their parents had enough trust to let them go up with me.

---
Bob, thanks for the info! The fitting not being listed as a .040 restrictor in the parts book is probably why I didnt notice it first time around, as I bought all the fittings looking at it.

Post by **wesk** » Fri Jan 13, 2006 7:50 am

I know whay you mean. I solo'd in a 150 but I actually learned to fly in a C-170 (little wheel in the back). Finding both time and money now-a-days is tough. Keep at it though. In MHO there isn't much else in life that equals that great feeling you have up there when you're all alone with the main man!